Dissertations / Theses: 'Sediments lacustres'

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Tosal, Alcobé Aixa. "Modelització paleoclimàtica del límit Eocè–Oligocè a Catalunya a partir de l’anàlisi CLAMP." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668462.

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Aquesta tesi té com a objectiu modelitzar el paleoclima del trànsit Eocè−Oligocè de la Conca de l’Ebre i conèixer com aquest canvi afectà a la flora local. Aquesta caracterització paleoclimàtica s’ha obtingut a partir de l’estudi de les fulles de dicotiledònies de les localitats de Sarral (Priabonià terminal) i Cervera (Rupelià inferior) mitjançant CLAMP (Climate Leaf Analysis Multivariate Program). Per altra banda, per tal de poder caracteritzar els canvis florístics entre ambdues localitats, s’ha estudiat la seva taxonomia, tafonomia i paleoecologia així com la sedimentologia dels dipòsits que inclouen les associacions fòssils. S’han descrit setanta-cinc espècies de magnoliòpsides una de les quals, Rhus asymmetrica, és nova. La descripció s’ha basat en criteris moderns prenent en consideració caràcters com la nervadura terciària i detalls del marge foliar, fet que ha permès definir el polimorfisme intraespecífic d’algunes espècies. Tot i així en el futur caldrà revisar la taxonomia d’aquestes espècies comparant-les amb especies similars d’altres localitats europees contemporànies i amb les fulles d’espècies actuals afins. Des del punt de vista paleoambiental les flores de les dues localitats estudiades s’estructuraven en biomes similars encara que de composició força diferent. Aquestes diferències han permès caracteritzar els canvis en la distribució de la vegetació, que van tenir lloc entre el Priabonià i el Rupelià a la Conca de l’Ebre. L’exemple més evident fa referència a la vegetació que ocupava la zona adjacent a la comunitat del bosc de ribera amb un accés indirecte de les seves restes als rius i al llac. En el Priabonià de Sarral aquest bioma estava dominat per Tetraclinis, formant una bosquina oberta de cupressàcies. En canvi, al Rupelià de Cervera les plantes que creixien darrera del bosc de ribera eren principalment Daphnogene, Laurophyllum, Myrica faya i M. oligocenica i formaven petites laurisilves. Un altre bioma que mostra diferències notables entre les dues localitats estudiades fa referència a la part més allunyada dels llacs que estaria caracteritzada per una vegetació de tipus sabana. Aquest bioma mostrà una biodiversitat relativament baixa durant el Priabonià de Sarral, on estaria dominat per vuit espècies de fabals, Zizyphus zizyphoides i Pinus. Pel contrari, la comunitat equivalent en el Rupelià de Cervera estaria dominada per catorze espècies de fabals i set espècies d’altres grups taxonòmics tals com Rhamnus aizoon, Rhus asymmetrica i espècies afins com Toxicodendron. L’anàlisi CLAMP de les flores estudiades a la Conca de l’Ebre mostra una tendència climàtica cap a un refredament i un augment de l’estacionalitat entre l’Eocè superior i l’Oligocè inferior, que concorda amb la tendència global observada a l’hemisferi nord. Tanmateix, també assenyala que la pluviometria era més elevada a l’Oligocè de Cervera que al Priabonià de Sarral, fet que seria l’oposat de la tendència generalment acceptada vers un augment de l’aridesa al sud d’Europa durant aquest període. Aquests resultats reflectirien un canvi climàtic més complex del què s’havia documenatat fins ara. L’anàlisi de fàcies aporta dades clau per interpretar els resultats de la modelització mitjançant CLAMP. En aquest sentit, la flora de Sarral es trobaria en els períodes secs d’una seqüència de somització lacustre interpretada com a moments de màxima precessió. Per altra banda, la flora rupeliana de Cervera reflectiria els estadis humits dels cicles sedimentaris de somització lacustre, que correspondrien als cicles orbitals de precessió mínima. Aquestes condicions climàtiques específiques de cada localitat permeten comprendre els canvis en la composició i la distribució de la vegetació detectats per l’estudi paleoecològic. Per exemple, la temperatura elevada i la pluviometria baixa del Priabonià de Sarral haurien afavorit les plantes adaptades a bosquines obertes i de tipus sabana dominades per les fabals o Tetraclinis. Alhora, aquelles espècies amb un requeriment hídric més elevat, com les lauràcies, s’haurien vist obligades a créixer en zones relativament més humides, concretament al bosc de ribera. En canvi, les condicions ambientals amb una temperatura més moderada i una pluviometria més alta en el Rupelià de Cervera haurien permès el desenvolupament de moltes altres famílies de plantes al costat de les fabals, especialment les anacardiàcies. L’increment de la pluviometria a l’Oligocè de Cervera hauria beneficiat que els llorers s’expandissin fora del bosc de ribera formant petites comunitats de laurisilva. La combinació dels estudis sedimentològics, tafonòmics, paleoecològics i paleoclimàtics ha permès comprendre les interaccions entre el clima i la vegetació durant el trànsit Eocè−Oligocè a la Conca de l’Ebre. La sobreimposició de cicles climàtics d’ordre menor (cicles orbitals de precessió) en els cicles d’ordre major (cicles d’excentricitat) produiria un canvi climàtic no lineal. Els paràmetres pluviomètrics fluctuants van condicionar enormement l’evolució de les comunitats vegetals i probablement es trobarien en l’origen d’una vegetació resistent a aquestes variacions, com és la flora Mediterrània.

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Heras, i. Cisa F. Xavier de las (Francesc Xavier). "Geoquímica orgànica de conques lacustres fòssils." Doctoral thesis, Universitat de Barcelona, 1989. http://hdl.handle.net/10803/2823.

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La memòria té dos apartats diferenciats. Al primer es caracteritzen des del punt de vista estructural bio-marcadors (o fòssils moleculars) com ara hidrocarburs alifàtics, alicílics i aromàtics, compostos oxigenats (alcohols, aldehids, cetones, àcids mono i dicarboxílics i hidroàcids) i sofrats (tiolans, tians, benziotofens i alquitiofens).

Alguns d'aquests biomarcadors es descriuen per primer cop com a cetoalcohols, alcandiols i hidroxiàcids substituïts en posicions centrals de la cadena i derivats dels àcids dicarboxílics. També es descriuen per primer cop, derivats tiofènics i tiolànics d'hidrocarburs hopànics.

En el segon capítol s'utilitzen els biomarcadors identificats, per a la caracterització de les aportacions predominants de matèria orgànica dins de les unitats lacustres de la regió nord-oriental de la Península Ibèrica: Campins (Oligocè Superior), Rubielos de Mora i Ribesalbes (Miocè Mitjà), Libros i Cerdanya (Miocè Superior).

A més, s'han reconegut a les conques diversos ambients deposicionals: anòxic, òxic, hipersalí i les seves transicions.

Finalment, s'han descrit noves etapes en els processos de diagènesi de triterpanoïdes d'orígen continental; esteroïdes i isoprenoïdes, així com de la fosfatogènesi.
La memoria tiene dos apartados diferenciados: en el primero se caracterizan desde el punto de vista estructural biomarcadores (o fósiles moleculares) tales como hidrocarburos alifáticos, alicílicos y aromáticos, compuestos oxigenados (alcoholes, aldehidos, cetonas, ácidos mono y dicarboxilicos e hidroxiacidos) y azufrados (tiolanos, tianos, benzotiofenos y alquiltiofenos).

Algunos de estos biomarcadores se describen por primera vez como cetoalcoholes, alcandioles e hidroxiácidos sustituidos en posiciones centrales de la cadena y derivados de los ácidos dicarboxílicos. También se describen por primera vez, derivados tiofénicos y tiolánicos de hidrocarburos hopánicos.

En el segundo capitulo se utilizan los biomarcadores identificados, para la caracterización de los aportes predominantes de materia orgánica dentro de las unidades lacustres de la región nororiental de la Península Ibérica: Campins (Oligoceno Superior), Rubielos de Mora y Ribesalbes (Mioceno Medio), Libros y Cerdanya (Mioceno Superior).

Además, se han reconocido en las cuencas distintos ambientes deposicionales: anóxico, óxico, hipersalino y sus transiciones.

Finalmente, se han descrito nuevas etapas en los procesos de diagénesis de triterpanoides de origen continental; esteroides e isoprenoides, así como de la fosfatogénesis.

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Serieyssol, Karen. "Les diatomees des sediments lacustres d'age miocene superieur d'andance et rochessauve (ardeche). Paleoecologie et biostratigraphie." Paris 6, 1993. http://www.theses.fr/1993PA066581.

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Ce travail est une contribution a la connaissance des diatomees fossiles du massif central francais, du point vue systematique, paleoecologique et biostratigraphique. Deux series volcano-sedimentaires, la montagne d'andance et la structure de rochessauve, sont etudiees. Ces deux series, deposees dans des crateres d'explosion de type maar, sont situees sur le flan oriental du massif central en bordure nord-est du plateau du coiron. Dans le premier chapitre, les deux series analysees sont replacees dans leur contexte geographique et geologique. La sequence stratigraphique de la montagne d'andance et celle de la structure de rochessauve sont presentees. La montagne d'andance contient deux niveaux a diatomees, l'argile blanc-grisatre et la diatomite, tandis que la structure de rochessauve a trois niveaux, l'argile a diatomees, le niveau sedimentaire a diatomees situe dans la serie des breches intermediaires, et la diatomite. La diatomite de la montagne d'andance est datee par radiometrique en 8,3 et 6. 7 m. A. Et par des mammiferes mn 11 ; les basaltes qui couvrent les sediments de rochessauve sont datees entre 8. 0 et 6. 4 m. A. Et les mammiferes trouves dans la diatomite correspondent a la zone, mn 12. Le deuxieme chapitre est consacre aux methodes de travail et d'analyses. Les caracteres ecologiques des milieux deduits des diatomees sont discutes. Un inventaire systematique des diatomees observees dans les deux sites etudies est donne avec des remarques ecologiques pour chaque espece. L'analyse en composantes principales et une classification hierarchique des echantillons ont ete utilisees pour etablir des correlations entre differents sondages realise dans a andance et determiner quatre biozones dans la diatomite. Dans le troisieme chapitre, la biostratigraphie et la paleoecologie des differentes sections de la montagne d'andance sont discutees. Le quatrieme chapitre traite de la biostratigraphie, de la paleoecologie, et de la correlation des differentes coupes de la structure de rochessauve. La plupart des changements d'associations sont a attribuer a des fluctuations des conditions de milieu ou a un changement dans le rapport precipitation/evaporation. L'etude systematique des especes a interet biostratigraphique est realisee dans le cinquieme chapitre. Les especes a large repartition paleogeographique sont cyclotella iris brun et heribaud et ses varietes, cyclotella andancensis ehrlich, fragilaria zeilleri heribaud et sa variete elliptica gasse, et melosira undulata (ehr. ) kutzing ; les especes a repartition paleogeographique restreinte sont cyclotella perforata heribaud, cyclotella multipunctata nov. Sp. , cyclotella manguini ehrlich, mesodictyon gasseae nov. Sp. , mesodictyon ( ?) pygmaeus nov. Comb. , stephanodiscus radiata nov. Sp. , stephanodiscus dispar nov. Comb. Dans le dernier chapitre, une biostratigraphie preliminaire des diatomees d'eau douce est proposee pour le massif central ; celle-ci est comparee aux donnees obtenues d'autres regions du monde. Une analyse cladistique est faite sur les cyclotella et cyclostephanos du miocene et du pliocene. Six groupes d'especes sont identifies. La separation de cyclotella et de cyclostephanos est proposee. Certaines idees sur l'evolution des genres cyclotella et cyclostephanos sont presentees

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Delvalle, David. "Geochemical and mineralogical analysis of stream and lake sediments from a tropical watershed (Panama canal watershed) /." Heidelberg : [Ruprecht-Karls-Universität], 1989. http://catalogue.bnf.fr/ark:/12148/cb37428731k.

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Alves, Raquel Araujo. "A paisagem na Região Leste de Roraima, Município de Bonfim: aspectos fisiográficos, morfológicos, granulométricos e mineralógicos dos ambientes lacustres." Universidade Federal de Roraima, 2016. http://www.bdtd.ufrr.br/tde_busca/arquivo.php?codArquivo=392.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O município de Bonfim localizado a nordeste do estado de Roraima é caracterizado por apresentar sequências de serras, morros, colinas ravinadas e colinas com vales encaixados, além de elevações residuais que se destacam numa extensa superfície aplainada, somada à formação dos solos arenosos e o alto índice de precipitação que contribuem para ocorrência de ambiente lacustre. A presente pesquisa propôs analisar a paisagem através dos aspectos geomorfológicos, para o entendimento do ambiente lacustre na área de expansão urbana da cidade de Bonfim. Para tanto, fez-se necessário levantamento bibliográfico, cartográfico e de sensores remotos, atividades de campo com intuito de identificar e descrever os compartimentos e unidades geomorfológicas. Também foram realizadas análises das características morfológicas, granulométricas, mineralógicas e química pontual dos sedimentos lacustres. Os resultados demonstraram que a paisagem da região de Bonfim é representada por modelados de dissecação representados por: Patamares em Crista Estruturado, Maciço Somital Convexo, Morros Residuais Estruturados, Morros e Colinas Escalonadas com Vales Abertos e Colinas Dissecadas Abertas. Interligados aos Plainos Erosivos, Superfície de Aplainamento e Plaino Aluvial ao longo das drenagens. Os ambientes lacustres, feições significativas nessa paisagem, ocorrem com predominância da morfologia circular/oval e em menor proporção alongados, compostos e dentríticos. Muitos apresentam regime intermitente a exemplo, do Lago do Italiano em contraste com o sistema perene representado pelo Lago do Bicho. São densamente colonizados por macrófitas aquáticas, como ciperáceas das quais se distribuem conforme as variações de profundidades destes. Os sedimentos/solos são predominantemente arenosos, com grãos angulosos a subangulosos. São compostos essencialmente de quartzo e secundariamente de caulinita, além de goethita e muscovita. A composição química destaca altas concentrações de SiO2, Fe2O3 e Al2O3, afirmando os minerais encontrados nesses sedimentos. Os ambientes lacustres têm sido submetidos à intensa pressão antrópica, representada pela ocupação desordenada que levou a problemas como: lançamentos de efluentes domésticos e descarte de resíduos sólidos. Portanto, é necessária devida atenção aos processos que ocorrem nesses ambientes, pois estes contribuem para compreensão da dinâmica de transformação da paisagem especialmente quando associados ao crescimento urbano desordenado.
The district of Bonfim located northeast of the state of Roraima is characterized in that sequences of mountains, hills, ravines hills and hills with deep valleys, as well as residual elevations that stand out in a large flat surface, in addition to the formation of sandy soils and high precipitation index contribute to the occurrence of lacustrine environment. This study proposed to analyze the landscape through the geomorphological aspects to understand the lacustrine environment in the urban expansion area of the city of Bonfim. Therefore, it was necessary literature, mapping and remote sensing, field activities in order to identify and describe the compartments and geomorphological units. Analysis of morphological, granulometrics, mineralogical and chemical point of soil / lake sediments were also held. The results showed that the landscape of Bonfim region is represented by modeled dissecting represented by: Landings in Structured Crista, Massif Somite Convex, Residual Hills Structured, Hills and Hills Staggerd to Opened Valleys and Opened Dissected Hills, linked to Erosive Plains, Plain Surface and Alluvial Plain along the drainages. The lacustrine environments, significant features in this landscape, occur with predominantly circular and oval morphology and elongated in lower proportion, compounds and dendritic. A lot of them has intermittent regimen example, the Italian Lake in contrast to the perennial system represented by the Bicho Lake. They are densely colonized by aquatic weeds such as sedges which are distributed according to variations of these depths. The sediments / soils are predominantly sandy, with angular grains sub angular. They are composed mainly of quartz and kaolinite secondarily, and goethite and muscovite. The chemical composition highlights high concentrations of SiO2, Fe2O3 and Al2O3, stating the minerals found in these sediments. The lacustrine environments have been subjected to intense anthropic pressure, represented by the disorderly occupation which led to problems such as releases of domestic sewage and solid waste disposal. Therefore, it is necessary attention to the processes that occur in these environments because they contribute to understanding the dynamics of the transformation of the landscape especially when combined with urban sprawl.

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SABER, ABDEL-ILAH. "Application de la spectrofluorimetrie shpol'skii a l'analyse quantitative des h. A. P. Dans les sediments lacustres et dans les sediments et organismes marins." Chambéry, 1990. http://www.theses.fr/1990CHAMS009.

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L'etude de l'impact des hydrocarbures, et plus particulierement des hydrocarbures aromatiques policycliques (hap) sur notre environnement, necessite la mise au point de techniques avancees pour la mise de ces polluants non reglementes. La presence des hap dans l'environnement aquatique (lacustre et marin) a pour origines anthropogeniques, essentiellement les retombees atmospheriques, les rejets d'eaux usees industrielles et domestiques, le ruissellement des eaux pluviales sur les reseaux routiers, les rejets accidentels et les naufrages des petroliers. Le manuscrit concerne une application de la spectrofluorimetrie haute resolution basse temperature a l'analyse quantitative d'hap dans les sediments lacustres et sediments et organismes marins: caracteristiques principales de la chaine analytique informatisee necessitant des conditions de selectivite, de sensibilite et de rapidite d'exploitation, indispensables a l'analyse en routine de traces d'hydrocarbures; etude de correlation entre la distribution des hap dans les sediments lacustres (lac d'aiguebelette) et celle observee dans les emissions vehiculaires ponderees a partir de l'image precise du parc automobile francais; etude des profils de concentrations et des distributions des hap dans les sediments et organismes marins (baie de koweit)

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BERREKHIS, ABDELHAFID. "Caracterisation des constituants de la matiere organique des sediments lacustres jurassiens. Contribution a une differenciation des lacs." Besançon, 1997. http://www.theses.fr/1997BESA2074.

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Des etudes realisees sur des sediments de nombreux lacs jurassiens, a matrice calcaire. Elles portent sur la matiere organique. Nous nous sommes particulierement interesses a la fraction acidosoluble extraite a ph 1. 5 a l'aide de hcl 3n a 20% kci et nous avons cherche a quantifier globalement les acides amines puis a identifier les plus abondants d'entre eux. Que ce soit pour le dosage global, par colorimetrie ou pour leur identification par clhp, nous avons rencontre des difficultes dues a une forte teneur en calcium dans nos echantillons. Nous traitons ici du role du calcium sur les deux methodes analytiques, de son elimination et comparons les resultats des deux methodes. Nous avons recherche les relations possibles entre les teneurs en acides amines extraits et l'origine ainsi que la nature des apports et les conditions de transformation de ceux-ci.

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BENK, ADDOUR ABDELFATTAH. "Changements hydrologiques et climatiques dans le moyen-atlas marocain, chronologie, mineralogie, geochimie isotopique et elementaire des sediments lacustres de tigalmamine." Paris 11, 1993. http://www.theses.fr/1993PA112488.

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Ce travail est une contribution a la comprehension des conditions hydro climatiques dans le moyen atlas marocain (lacs tigalmamine, 3254#7 n 521#7 e 1600m mas1) depuis environ 18000 abp, trois sondages ont ete etudies. Le premier abord est reserve a la sedimentation. Deux facies sedimentaires marquent ces milieux: 1) facies de bas niveau lacustre caracterise par une forte production de calcite authigenique 2) facies de haut niveau lacustre avec une fraction detritique fine importante. La deuxieme partie est consacree a la geochimie isotopique. Les resultats obtenus sur les 2 sondages amont, revelent des forts degres d'erosion et d'alteration avant 8,5 kabp. Le sondage aval est moins marque par le detritisme. La troisieme partie retrace les caracteristiques chimiques, thermiques et bathymetriques des eaux du lac a partir des rapports (sr/ca) et (mg/ca) de la calcite des ostracodes et par le comptage des gyrogonites des charophytes. Les resultats ont revele: 3 periodes de bas niveau interpretees comme arides (7. 6-6. 8, 5 4. 5, 3-2. 5 et 2. 3 kabp une phase d'instabilite limnologique (10. 5 -8. 5 kabp), - 3 phases de haut niveau lacustre: 6. 8-5, 4. 5-3 et de 1. 7 kabp a l'actuel. Il est interessant de constater que les periodes arides que nous avons recenses, sont a attribuer a un desequilibre du systeme ocean-atmosphere-continent

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Pérez, Cano Jordi. "Barremian charophytes from the Maestrat Basin: taxonomy, palaeoecology, palaeobiogeography and biostratigraphy." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/673634.

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This thesis is focused on the taxonomical, biogeographical, palaeoecological and biostratigraphical characterization of the Barremian charophytes of the Maestrat Basin (Eastern Iberian Chain, Spain). Thirty-four charophyte taxa, including fructifications and thalli, which belong to the three families that co-existed during the Early Cretaceous, i.e., the Porocharaceae, the Characeae and the Clavatoraceae, were identified in two Barremian sections (Fredes and Herbers-Mas de Petxí). Twenty-six of them correspond to clavatoracean utricles, including Clavator grovesii var. jiuquanensis, which is herein firstly reported in the Iberian Chain. Similar clavatoracean richness is not found elsewhere, showing the importance of the Maestrat Basin as a hotspot for the clavatoracean species-richness during Barremian. New characters found in the clavatoracean utricles and thalli improved the knowledge on this important, mainly Cretaceous, family. The Echinochara lazarii utricle was reinterpreted as bilaterally symmetrical, rather than triradiated. This type of symmetry was previously unknown within genus Echinochara and in the whole subfamily Atopocharoidae, leading to a taxonomic emendation of this genus. This species was found attached to the thallus Charaxis spicatus allowing the reconstruction of the Echinochara whole-plant. The cortication of this thallus was reviewed and a new type of cortication, called double triplostichous cortication, was described. A second important result was the characterization of a gradualistic evolutionary lineage in Clavator calcitrapus. This lineage includes two anagenetic varieties, C. calcitrapus var. jiangluoensis and C. calcitrapus var. calcitrapus, linked by all possible intermediary morphotypes. This lineage has important biogeographic implications since the oldest variety had a subcosmopolitan range, while the second was endemic to Iberia. Finally, a previously unknown centripetal calcification pattern was found in the internodal cell of genus Munieria. This type of calcification is reminiscent of the one observed in the clavatoroid gyrogonites, providing further support to the hypothesis that this thallus belonged to the Clavatoraceae. The expanded sedimentary record of the Herbers-Mas de Petxí section and the abundance and diversity of charophyte remains found, provided a unique context, at least at European scale, to study the palaeoecology of charophyte species and the evolution of charophyte floras through the Barremian. Three sedimentary units, named from base to top Cantaperdius, Artoles and Morella formations, were analysed. Within these lithostratigraphic units, five charophyte associations were distinguished. 1) A charophyte association developed in freshwater lakes with low clastic input was found in the lower part of the Cantaperdius Formation and was mainly composed of Atopochara trivolvis var. triquetra, Clavator harrisii, Ascidiella stellata, and A. triquetra. Besides, Hemiclavator-rich populations were locally dominant. 2) An association characteristic of freshwater lakes with high clastic input mainly composed of Echinochara lazarii, Globator maillardii var. trochiliscoides, A. trivolvis var. triquetra, C. harrisii, Hemiclavator neimongolensis var. neimongolensis, and occasionally also Clavator calcitrapus. This association is mostly found in the upper part of the Cantaperdius Formation. 3) Porochara maestratica populations mainly thrived in low-clastic-influenced brackish settings; while 4) E. lazarii preferably thrived in clastic-influenced brackish settings. Both these brackish settings where abundant in the Artoles Formation. 5) The charophyte association developed in lakes formed in coastal mudflat to floodplain settings was mainly constituted by E. lazarii, A. trivolvis var. triquetra and var. trivolvis, and C. harrisii var. harrisii and var. reyi. This association is found in the Morella Formation. The environmental distribution of the associations recognized depended on the salinity, the clastic influence, and the depth. A new Barremian–early Aptian charophyte biostratigraphy is proposed. Two biozonations, European and Eurasian, were distinguished and correlated. Furthermore, these biozones were calibrated to the Geological Time Scale by means of strontium-isotope stratigraphy, enabling their correlation with the coeval marine realm. The European biostratigraphy is formed by two partial range biozones (characterized by the First Appearance Data, FAD), of index species that were endemic from the Western Tethyan Archipelago (extant Europe and North Africa): (1) Globator maillardii var. trochiliscoides (early Barremian) and (2) Ascidiella cruciata-Pseudoglobator paucibracteatus. The base of this latter biozone was calibrated with an oyster shell sample with an 87Sr/86Sr ratio of 0.707482, translating to a late early Barremian age, giving a total timespan of late early Barremian–early Aptian for this biozone. The Eurasian biozone is composed of three partial range biozones. (1) Atopochara trivolvis var. triquetra biozone is almost equivalent to the G. maillardii var. trochiliscoides biozone. (2) Hemiclavator neimongolensis var. neimongolensis biozone, which was calibrated with an oyster shell whose 87Sr/86Sr ratio is 0.707481 (late early Barremian). (3) The next biozone is defined by the FAD of Clavator grovesii var. jiuquanensis. Its base was dated with an oyster shell gathered 24.5 m below the FAD of the index species and its 87Sr/86Sr ratio is 0.707489 (late early Barremian). The FAD of C. grovesii var. corrugatus defines the next biozone. The biozonation described herein is intended to facilitate the correlation between different basins of the western Tethys, and between non-marine basins in whole Eurasia.
Aquesta tesi es focalitza en la caracterització taxonòmica, biogeogràfica, paleoecològica i biostratigràfica dels caròfits barremians de la conca del Maestrat (Cadena Ibèrica). Dels 34 taxons identificats, pertanyents a tres famílies que coexistiren durant el Cretaci Inferior (Porocharaceae, Characeae i Clavatoraceae) 26 pertanyen a utricles de clavatoràcies. Aquesta diversitat és única a escala mundial i mostra que el Maestrat fou un punt calent de biodiversitat d’aquesta família. Des del punt de vista morfològic s’ha mostrat que l’utricle d’Echinochara lazarii tenia una simetria bilateral, en comptes de presentar la simetrial triradial descrita originalment pel gènere. A més s’ha pogut reconstruir de la planta sencera d’ i Echinochara gràcies a haver descobert la connexió anatòmica entre Echinochara lazarii i el tal·lus descrit prèviament com Charaxis spicatus. Aquesta planta presentava una corticació desconeguda fins ara, que s’ha anomenat triplòstica doble. S’ha descrit també un nou llinatge evolutiu dins les clavatoràcies, format per dues varietats anagenètiques dins l’espècie de Clavator calcitrapus, que és de gran interès en paleobiogeografia i biostratigrafia. Finalment, la descripció d’una calcificació centrípeta als entrenusos del tal·lus de Munieria (un fòssil que ha estat motiu de controvèrsia respecte a la seva afinitat taxonòmica), dóna suport a la hipòtesi de que pertanyia a una clavatoràcia. L’estudi paleoecològic ha permès distingir diferents associacions de caròfits: 1) L’associació característica de llacs d’aigua dolça amb poca influència clàstica on predominava Atopochara trivolvis var. triquetra, Clavator harrisii, Ascidiella stellata i A. triquetra. 2) Una associació de llacs d’aigua dolça amb molta influència clàstica, dominada per Echinochara lazarii, Globator maillardii var. trochiliscoides, A. trivolvis var. triquetra, C. harrisii, Hemiclavator neimongolensis var. neimongolensis. 3) Porochara maestratica dominava als ambients salabrosos amb poca influència clàstica, mentre que 4) E. lazarii dominava ambients salabrosos amb més influència clàstica. 5) L’associació característica de basses i aiguamolls de fangars i planes d’inundació incloïa E. lazarii, A. trivolvis var. triquetra i C. harrisii. Es revisa la biostratigrafia dels caròfits del Barremià–Aptià inferior amb dues biozonacions, una per l’àmbit de l’Arxipèlag Cretaci de la Tetis (Europa, nord d’Àfrica i Orient mitjà) i una segona d’àmbit eurasiàtic. La primera biozonació està composta per dues biozones, les espècies índex de les quals eren endèmiques de l'arxipèlag: (1) Globator maillardii var. trochiliscoides (Barremià inferior) i (2) Ascidiella cruciata-Pseudoglobator paucibracteatus. La base d’aquesta última s’ha calibrat amb l’escala del temps geològic mitjançant uns valor d’ 87Sr/86Sr de 0,707482 (Barremià inferior terminal) obtinguts en una valva d’ostreid. Aquesta biozona inclou l’interval Barremià inferior terminal–Aptià inferior. La biozonació euroasiàtica conté tres biozones, les espècies índex de les quals estan presents a tota Euràsia. (1) La biozona Atopochara trivolvis var. triquetra té una edat de Barremià inferior. (2) La base de la biozona H. neimongolensis var. neimongolensis fou calibrada amb l’escala del temps geològic mitjançant una mostra d’ostreid que va proporcionar un valor de l’ 87Sr/86Sr de 0,7074781 (Barremià inferior superior). (3) La biozona Clavator grovesii var. jiuquanensis s’ha calibrat calibrat amb l’escala del temps geològic mitjançant una mostra d’ostreid que va proporcionar uns valors d’ 87Sr/86Sr de 0,707489 (Barremià superior inferior). Aquesta nova proposta biostratigràfica es preveu que faciliti la correlació entre les conques del Tetis i entre les conques continentals d’Euràsia.

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Guillemot, Typhaine. "Réponses sédimentaires et moléculaires des remplissages lacustres groenlandais aux changements climatiques holocènes et à l'évolution des pratiques agropastorales." Thesis, Besançon, 2015. http://www.theses.fr/2015BESA2034/document.

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Dans le cadre du changement climatique global, mieux comprendre les interactions Hommes/Environnement/Climat au sud-ouest du Groenland est aujourd’hui un enjeu majeur pour développer des stratégies d’adaptation tout en préservant au mieux les écosystèmes. Pour cela, une approche rétrospective a été réalisée sur trois séquences lacustres retraçant l’histoire paléo-environnementale sur les 5000 derniers millénaires. Le lac d’Igaliku (N61°00’22’’, O45°26’28’’), situé à 2 km de la capitale épiscopale médiévale au cœur de la région agricole groenlandaise, a une sédimentation principalement influencée par les activités anthropiques. Un inventaire moléculaire complet a été réalisé sur cette séquence pour caractériser les dynamiques agropastorales passées et leurs impacts sur les écosystèmes. Les biomarqueurs fécaux identifié ont notamment permis de mettre en évidence deux phases agropastorales majeures (la période d’occupation viking et la période récente) séparées par le Petit Âge Glaciaire (PAG), pratiquant un élevage prédominant d’ovins. Les biomarqueurs moléculaires de végétation (n-alcanes, acétates de triterpényles) couplées à des données palynologiques montrent une réduction du couvert arbustif au cours de ces deux phases. Par ailleurs, les biomarqueurs d’érosion des sols (TTHCs) couplées aux données sédimentaires indiquent une érosion drastique qu’autour des années 1980 lors de la création de parcelles de fourrage par labour mécanisé. De même, ce n’est que sur le dernier siècle qu’une altération de l’état trophique du lac d’Igaliku associée à des pratiques de fertilisation des parcelles de fourrage est observée avec une augmentation des chaines courtes d’n-alcanes et plus particulièrement des diatomées mésotrophes. Les lacs de Qallimiut (N60°43’27’’, O45°23’12’’) et de Little Kangerluluup (N60°38’32’’, O45°38’11’’), situés en contexte faiblement anthropisé, sont alimentés par des tributaires à forte variabilité hydrologique. Ils correspondent à des systèmes sédimentaires dominés par des apports clastiques sous contrôle climatique dominant. Afin d’améliorer la résolution spatiale et temporelle des changements climatiques holocènes dans cette région, une étude sédimentaire multi-paramètre a été réalisée sur ces deux sites. Des analyses pétrophysiques, granulométriques, minéralogiques et géochimiques ont mis en évidence des niveaux de crues fréquents au cours des épisodes froids et humides comme la transition Milieu/Fin de l’Holocène (ca. 2500 BC), la transition Sub-boréal/Sub-atlantique (ca. 700 BC) et le PAG (entre ca. 1300 AD et ca. 1900 AD), synchrones à des périodes de minimas solaires. Ces épisodes de détériorations climatiques ont particulièrement influencé les sociétés humaines successives installées dès ca. 2500 BC au Groenland. Un maximum de fréquence de crues et une baisse drastique des températures sont notamment enregistrés pendant le PAG, indiquant qu’il s’agit de l’épisode le plus froid enregistré au sud du Groenland au cours de la seconde moitié de l’Holocène, responsable en grande partie de l’abandon de ces terres par les agriculteurs vikings au milieu du XVème siècle
In the current context of global change, understanding the interactions between Human/Environment/Climate is necessary to develop adaptive strategies and preserve ecosystems. A retrospective approach is therefore realized in three lacustrine cores to reconstruct the paleo-environmental history during the last five millennia. Lake Igaliku (N61°00’22’’, W45°26’28’’), located at 2km from the medieval episcopal cathedral in the historical farming center, has a sedimentation mainly driven by anthropogenic activities. A complete molecular inventory has been made on this sequence to characterize past agropastoral dynamics and their impacts on south Greenlandic ecosystems. The identified fecal biomarkers revealed two agropastoral phases, during the Norse settlement and recently, separated by the Little Ice Age (LIA) and mainly characterized by sheep breeding. Vegetation molecular biomarkers (n-alkanes, triterpenyl acetates) and palynological data showed a reduction of trees and shrubs cover during these two periods especially. Erosion biomarkers (TTHCs) and sedimentological data identified only one drastic erosion in the 1980s synchronous with the mechanized creation of fodder parcels. Moreover, an eutrophication of the lake waters was recorded with short chain length n-alkanes and mesotrophic diatoms. Lake Qallimiut (N60°43’27’’, W45°23’12’’) and Little Kangerluluup (N60°38’32’’, W45°38’11’’), less impacted by anthropogenic activities, are fed by major streams influenced by hydrological variations. Their sedimentation is therefore mainly driven by climate changes. To improve the temporal and spatial resolution of climate changes during the Holocene, a multi-proxy sedimentological study was made on these two sites. Petrophysical, mineralogical and geochemical analyses have identified flood events especially occurring during cooler and wetter periods such as the Middle to Late Holocene transition (ca. 2500 BC), the Sub-boreal/Sub-atlantic transition (ca. 700 BC) and the LIA (between ca. AD 1300 et ca. AD 1900). These climate pejorations have impacted local human societies. For example, during the LIA, a maximum of flood events and drop of temperatures are recorded, partly responsible of the Norse demise

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Stetten, Lucie. "Spéciation et mobilité de l'uranium dans des sols et des sédiments lacustres en aval d'anciens sites miniers." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS249.

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L’objectif de ce travail de thèse était d’améliorer les connaissances sur le comportement géochimique et la mobilité de l’uranium (U) dans des sédiments lacustres et des sols enrichis en U, dont les conditions réductrices sont à priori propices à son piégeage. Des analyses de spectroscopie d’absorption des rayons X et de microscopie électronique à balayage combinées à des analyses géochimiques ont été mises en œuvre. Pour les sédiments lacustres, la réduction progressive de U(VI) en U(IV) sous l’interface eau-sédiment est mise en évidence. Les données de spéciation et la modélisation géochimique suggèrent un contrôle important de la réduction par le Fe(II) issu de la diagenèse précoce, au travers de la réduction microbienne du Fe(III) structural des argiles. Pour les sols, une réduction brutale de U(VI) est observée, contrôlée par le niveau de saturation en eau. Pour les deux sites étudiés, des complexes mononucléaires adsorbés de U(IV) et des minéraux phosphatés de U(IV) ont été mis en évidence. Pour l’étude des sols, une redistribution de U au niveau du front redox, via la dissolution oxydative des minéraux phosphatés de U(IV) suivie de la complexation de U(VI) à la matière organique du sol est suggérée. Des incubations de sol ont permis de confirmer ces mécanismes de redistribution. Ces travaux appellent à considérer les phases de U(IV) non-cristallines et les minéraux phosphatés de U(IV) comme espèces contrôlant la solubilité de l’uranium dans les environnements contaminés. Il apparaît donc nécessaire de prendre en compte ces formes chimiques pour modéliser la mobilité de l’uranium dans ces systèmes et permettre une gestion adéquate de ces environnements contaminés
Uranium scavenging in soils and sediments located downstream from former U mines is expected to naturally limit uranium dispersion in downstream waterways. However, uranium mobility in such contaminated sites may depend on the identity of U traps as well as the geochemical conditions. The aim of this thesis was to improve our knowledge on the geochemical behavior and the mobility of uranium in U contaminated lacustrine sediments and wetland soils, whose reducing conditions is expected to mitigate uranium mobility because U(IV) species are less soluble than U(VI) ones. X-ray absorption spectroscopy and scanning electron microscopy analyzes combined with geochemical analyzes were carried out. In U contaminated lake sediments, we show that indirect reduction of U(VI) by Fe(II) associated to clay minerals may be a major diagenetic process responsible for the scavenging of uranium. For organic-rich weltand soils, we show a sharp uranium redox boundary mainly controlled by the water-table. For both sites, U(IV) mononuclear species and U(IV)-phosphate minerals were identified as the major species controlling uranium solubility, while uraninite is virtually absent. For the highly U-contaminated wetland soil, we suggest a major uranium redistribution via the oxidative dissolution of U(IV)-minerals followed by U(VI) organic matter complexation. Soil incubation experiments have confirmed these redistribution mechanisms and suggest different geochemical behaviors for lermontovite (U(PO4)(OH)•H2O) and ningyoite (CaU(PO4)2•2H2O). These experiments also highlight the role of organic matter in the control of uranium mobility, favoring the remobilization of U(IV) organic complexes under reducing conditions. Altogether, our results call for the need to consider both non-uraninite U(IV) minerals and mononuclear U(IV) complexes in such anoxic environments as major species controlling uranium solubility

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De, Wever Alexis. "Étude de la biominéralisation de carbonates intracellulaires et de silicates de magnésium hydratés dans des environnements lacustres alcalins." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS480.pdf.

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Les stromatolites sont des roches organo-sédimentaires laminées composées de carbonates de Ca et/ou Mg mais également de silicates de Mg dans certains cas. Les processus impliqués dans leur formation restent encore mal compris. L’objectif central de cette thèse est de mieux comprendre les processus géochimiques et géomicrobiologiques permettant de favoriser ou au contraire de défavoriser la formation des carbonates et silicates de magnésium dans les environnements lacustres alcalins mexicains. Deux axes principaux ont été développés. Le premier axe s’est focalisé sur les analyses de souches formant des carbonates de calcium amorphes (ACC) intracellulaire (ACC+) ou non. Une grande diversité de souches de cyanobactéries a été analysée pour leur capacité à incorporer le Ca. De plus, l’impact des alcalino-terreux sur la croissance de certaines de ces souches a été déterminé. A partir de cette étude, nous avons mis en évidence que les souches de cyanobactérie ACC+ incorporent plus de Ca que les autres et qu’elles le stockent principalement dans les inclusions d’ACC et dans les polyphosphates (polyP). De plus, nous avons déterminé que les souches ACC+ ont relativement plus besoin de Ca pour leur croissance et certaines d’entre elles sont capables de substituer le Ca par du Sr et Ba. Nous proposons que les inclusions d’ACC 1) peuvent servir de ballasts, 2) peuvent tamponner le pH intracellulaire et équilibrer la formation d'hydroxyde par conversion de HCO3 en CO2 lors de la fixation du carbone et 3) alternativement, ils peuvent servir de forme de stockage de carbone inorganique disponible pour les cellules sur des périodes limitées en C. De plus, les polyP pourraient être impliqués dans le stockage de Ca. Plus largement, les cyanobactéries ACC+ pourraient favoriser la dissolution de carbonate de Ca et par extension celle des stromatolites. Le second axe s’est intéressé à l’étude de la formation de silicates de magnésium dans les sédiments et mésocosmes analogues de 3 lacs alcalins mexicains mais également par des expériences de biominéralisation. Les analyses minéralogiques et chimiques des silicates de magnésium ont été couplées aux caractérisations géochimiques des solutions. L’étude des sédiments a montré la formation de deux smectites, l’une pauvre et l’autre riche en Al et également de smectite ferrugineuse ou sans forte teneur en Fe. Plusieurs interprétations ont été proposées quant à leur formation : 1) la dissolution conjointe d’hydromagnésite et des frustules de silice biogénique, 2) elle est héritée de la colonne d’eau, 3) est liée à l’altération des feldspaths dans les sédiments et 4) à la biominéralisation dans la colonne d’eau. Il a également été montré qu’une souche de cyanobactéries est capable d’induire la précipitation de silicates de magnésium en milieu non tamponné. Dans les mésocosme des lacs alcalins, la formation de silicate de Mg serait directement liée à la composition minéralogique des microbialites, et possiblement des diatomées permettant l’apport de Si dans la solution et localement dans le biofilm, et est biologiquement influencée par les EPS des communautés microbiennes
Stromatolites are laminated organo-sedimentary rocks composed of Ca and/or Mg carbonates but also Mg-silicates in some cases. The processes involved in their formation are still poorly understood. The main goal of this thesis was to better understand the geochemical and geomicrobiological processes that favor the formation or dissolution of carbonates and Mg-silicates in Mexican alkaline lacustrine environments. Two main axes have been developed. The first axis focused on the study of 52 cyanobacterial strains, some forming ACC intracellular, others not forming ACC. The strains were analyzed for their ability to incorporate Ca. The impact of alkaline earth elements on the growth of some of the strains was determined. In this study we have shown that ACC+ cyanobacterial strains incorporate more Ca than others and they store this Ca strongly in ACC and in polyP. In addition, we determined that ACC+ strains need more Ca for their growth and some of them are capable to substitute Ca by Sr and Ba for this purpose. We propose that ACC inclusions 1) can serve as ballasts, 2) can buffer intracellular pH and balance the formation of HCO3 conversion hydroxide to CO2 during carbon fixation and 3) available inorganic carbon storage for carbon dioxide. In addition, polyP could be involved in Ca storage. More broadly, ACC+ cyanobacteria have contributed to the dissolution of calcium carbonate and by extension stromatolites. The second axis focused on the study of Mg-silicate formation in sediments and mesocosms of 3 Mexican alkaline lakes but also in laboratory experiments. Mineralogical and chemical analyzes of magnesium silicates have been coupled with geochemical characterization of the solutions. The study of sediments showed the formation of an Al-low and an Al-rich stevensite-like phase and of ferrous or non-ferrous saponite-like. Several interpretations have been proposed regarding their formation: 1) dissolution of hydromagnesite and biogenic silica frustules, 2) it is inherited from the water column, 3) it is related to the alteration of feldspaths within sediments and 4) biomineralization in the water column. It has also been shown that a cyanobacterial strain was able to induce precipitation of magnesium silicates in an unbuffered medium. Mg-silicate formation in mesocosms from alkaline lakes is thought to be directly related to the mineralogical composition of microbialites, and possibly diatoms that allow Si to be introduced into the solution and locally into the biofilm and is biologically influenced by microbial community EPS

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RIBEIRO, ANDREZA P. "Determinacao de metais pesados e outros elementos de interesse em sedimentos lacustres da Estacao de Tratamento de Esgoto de Barueri, Sao Paulo, por ativacao neutronica." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11026.

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Made available in DSpace on 2014-10-09T12:47:06Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:10:34Z (GMT). No. of bitstreams: 1 08284.pdf: 5015226 bytes, checksum: 6a231582a7866a2856a41c83a5877c9b (MD5)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:00/00546-3

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Stupar, Yohana Vanesa. "Trends and rates of mercury and arsenic in sediments accumulated in the last 80 years in the climatic-sensitive Mar Chiquita system, Central Argentina." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00920306.

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In South America and especially in Argentina, the behaviour of mercury (Hg) and arsenic (As) mainly in sediments remains poorly understood. The Mar Chiquita system and more particularly the Laguna del Plata with its associated Suquía River basin is used here as a case study to identify the dynamic of these two trace elements. Their distribution in space and time are studied in relation with the anthropic presence and the hydrological conditions that importantly changed in the last century.The methodology consisted first to study the spatial distribution of mercury and arsenic thanks to the analysis of water and sediments taken all along the Suquía River and Laguna del Plata. Secondly, the sampling and study of a sediment core taken in Laguna del Plata allowed to evaluate variations of Hg and As with time.The implementation of selective extractions allowed to better identify Hg and As bearing phases. The global interpretation of the results and the support of satellites images revealed the important role played by climate changes and hydrological variations in the control of mercury and arsenic behaviour within the Mar Chiquita system. The combination of these different approaches revealed that the dynamic of mercury and arsenic shows contrast behaviour. Hg concentrations are low when the climate conditions are dry and lake-level is low. They are mainly associated to sulphurs carried by the Suquía River. The augmentation in regional precipitations produced higher runoff, rise in the lake-level and an increment in Hg accumulations. In this period Hg is mainly associated to the organic matter. As instead is contributed to the lake in solution and by the influence of winds from the loessic Chaco Pampean Plain in drier periods. As is associated to reactive Fe and Mn oxyhydroxides throughout the core. High concentrations in the bottom of the core are also associated to sulphides while in the middle and upper part As concentrations are as well associated with carbonates.

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Blanchet, François. "Etude géomécanique de glissements de terrain dans les argiles glacio-lacustres de la vallée du Drac." Phd thesis, Grenoble 1, 1988. http://www.theses.fr/1988GRE10117.

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Nous avons etudie un glissement de terrain affectant le lotissement du mas d'avignonet, situe sur la rive gauche de la retenue du monteynard. Une campagne de reconnaissance in situ comportant sondages, releves geologiques, indices de mouvement, mesures inclinimetriques, topographiques et piezometriques nous a permis de mettre en evidence plusieurs surfaces de deformations. On propose des mecanismes probables de rupture de ces glissements; on definit leur geometrie et on evalue les valeurs residuelles des caracteristiques mecaniques a la rupture des argiles litees, formation a l'origine de nombreuses instabilites dans la region. On analyse la stabilite du lotissement ainsi que le role des seismes sur la stabilite a long terme du versant

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Canuto, Fabiana Alves Bezerra. "Fracionamento químico de fósforo em testemunho de sedimento do Reservatório Macela, Itabaiana-Sergipe." Pós-Graduação em Química, 2013. https://ri.ufs.br/handle/riufs/6083.

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This work concerns the fractionation of phosphorus present in sediments from the Macela Reservoir, located in the city of Itabaiana (Sergipe State, Brazil). Two sediment cores were obtained, each to a depth of approximately 30 cm, which were divided into 5 cm sections. The analytical method employed a Standards, Measurements, and Testing (SMT) protocol, in which the phosphorus was split into the fractions: total (PT), inorganic (PI), organic (PO), non-apatite (PNAP), and apatite (PAP). The technique was validated in terms of the limits of detection (DL) and quantification (QL) for each fraction. No significant contamination was observed. The accuracy was in the range 99-101%, and the relative standard deviation (RSD) was better than 2%. The measured phosphorus concentrations were in the ranges 441.60-1335.47 µg g-1 (PT), 409.54-1209.86 µg g-1 (PI), and 21.35-195.87 µg g-1 (PO). For the inorganic forms, the concentrations of PNAP and PAP were in the ranges 106.82-541.09 µg g-1 and 238.56-698.01 µg g-1, respectively. The concentrations of the phosphorus fractions were highest in Core 2. The contents of Fe, Al, Ca, and Corg were 3.45-4.95%, 4.85-7.73%, 1.02-1.89%, and 1.88-8.55%, respectively. Correlation analysis using the Spearman test identified iron and aluminum as the most important controlling factors for P in the sediments studied. The application of principal components analysis (PCA) and hierarchical clustering analysis (HCA) to the measured parameters divided the sediment samples into two groups, according to their similarities. This was also confirmed using analysis of variance (ANOVA, p<0.05).
Neste trabalho foi realizado o fracionamento do fósforo em sedimentos do Reservatório Macela, localizado na cidade de Itabaiana, Sergipe, Brasil. Foram tomados dois testemunhos com profundidade de aproximadamente 30 cm cada, que foram seccionados de 5 cm em 5 cm. O método analítico utilizado foi o Protocolo desenvolvido pelo Standards, Measurements and Testing (SMT), que fracionou o fósforo nos sedimentos em total (PT), inorgânico (PI), orgânico (PO), não apatita (PNAP) e apatita (PAP). A validação da metodologia foi verificada através dos valores de limite de detecção (LD) e de limite de quantificação (LQ) para PT, PI, PO, PNAP e PAP, onde se observou que não houve contaminação significativa. A exatidão do método foi conferida através dos valores de concordância variando 99 a 101% e o desvio padrão relativo (RSD) foi melhor que 2%. A concentração de P variaram entre 441,60 e 1335,47 µg g-1 para PT, entre 409,54 e 1209,86 µg g-1 para PI e entre 21,35 e 195,87 µg g-1 para Po. Para as formas inorgânicas o valor das concentrações de PNAP variou de 106,82 e 541,09 µg g-1 e de PAP variou de 238,56 a 698,01 µg g-1. As concentrações das frações de fósforo nos sedimentos analisados foram maiores no testemunho II. Os conteúdos de Fe, Al, Ca e Corg variaram de 3,45 a 4,95 %, de 4,85 a 7,73 %, de 1,02 a 1,89 % e de 1,88 a 8,55 %. A matriz de correlação de Sperman identificou o ferro e o alumínio como os fatores controladores mais importantes dos P nos sedimentos analisados. A análise de componentes principais (PCA) e analise de agrupamento hierárquico (HCA), aplicada aos parâmetros medidos, dividiu as amostras de sedimentos em dois grupos, de acordo com suas similaridades. Esta tendência foi confirmada pela análise de variância (ANOVA, p< 0,05).

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Mbusnum, Gweth Kevin. "Evaluation of hydrophobic organic contaminants in two aquatic environmments of Cental Africa, Cameroon : lake Barombi Mbo and the Wouri estuary mangrove." Thesis, Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0266.

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Les Polluants Organiques Persistants (POPs) sont des composés hautement toxiques, persistants dans l’environnement, une capacité de transport à grande distance et accumulation sur les phases riches en matière organique. Compte tenu de la vulnérabilité des écosystèmes aquatiques aux pollutions et la rareté des données sur les POPs en Afrique, cette thèse examine les niveaux de Pesticides organochlorés (POCs), Polychlorobyphelyes (PCBs) et Hydrocarbures polyaromatiques (HAPs) dans le bassin versant du Lac Barombi (LBW) et la Mangrove estuaire du Wouri (MEW). Dans le LBW, les POCs détectés étaient, l’endosulfan, l‘hexachlorocyclohexanes (HCHs), le dieldrine and l’aldrine. Aucun OCPs n’a été détecté dans les eaux et les plus fréquemment détectés étaient les HCHs avec des teneurs plus élevées dans les sols par rapport au sédiments (ruisseaux et Lac). Le ratio α/γ-HCH ont indiqué l’utilisation récente du lindane (γ-HCH). La présence des OCPs a été attribué à l’agriculture et la pêche. Les teneurs en PAHs étaient plus élevées dans les sédiments lacustres que les autres échantillons. Les sources pyrolytiques de HAPs étaient dominantes plus spécifiquement la combustion d’herbes, du bois ou le charbon. Les recommandations pour la qualité des sédiments (SQGs) un faible risque de toxicité sur les organismes aquatiques. Dans les MEW, les teneurs en HAPs dans les sédiments étaient 10 fois plus élevés que les PCBs et Pesticides Chlorés (PCLs). Les PCLs les plus abondant étaient l’endosulfan, l’alachlor, l’heptachlor, le lindane (γ-HCH) et le DDT pour lesquels les métabolites indiquent une utilisation récente. La contribution des HAPs pyrolytiques était dominante
Persistent Organic Pollutants (POPs) are compounds that are highly toxic to living organisms, persistent in the environment, undergo long distance transport and accumulate in organic-rich phases (sediments and fatty tissues). Given the vulnerability of aquatic ecosystems to pollution and scarcity of data on POPs in Africa and, this thesis examines the level of Organochlorinated Pesticides (OCPs), Polychlorobiphenyls (PCBs) and Polyaromatic hydrocarbons (PAHs) in the Lake Barombi Watershed (LBW) and Wouri Estuary Mangrove (WEM) in Cameroon. In LBW, OCPs detected were endosulfan, hexachlorocyclohexanes (HCHs), dieldrin and aldrin. No OCPs were detected in water and the most frequently detected were HCHs with higher levels in soil than sediments (stream and lake). The α/γ-HCH ratio indicated recent use of lindane. The presence of OCPs is attributed to agriculture and fishing. PAH levels were higher in lake sediments than other samples. Pyrolytic sources of PAHs were predominant specifically combustion of grass, wood or coal. Sediment Quality Guidelines (SQGs) indicated low ecological risks to aquatic life. In the WEM, PAHs levels in sediments were more abundant than Chlorinated Pesticides (CLPs) and PCBs. The most abundant CLPs were endosulfan, alachlor, heptachlor, lindane (γ-HCH) and DDT for which metabolites pattern revealed recent use. PAHs ratios showed a predominant pyrolytic input. The presence of POPs in the WEM is mainly attributed to disease vector control (malaria), municipal waste dumps, industrial emissions and effluents, open burning of wastes, petroleum exploitation and harbour activities. SQGs implied low to moderate predictive biological toxicity

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Legrand, Benjamin. "Caractérisation des proliférations nostocaléennes anciennes et futures via les akinètes présents dans les sédiments." Thesis, Université Clermont Auvergne‎ (2017-2020), 2017. http://www.theses.fr/2017CLFAC109/document.

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Les akinètes sont des cellules de résistance produites par les cyanobactéries de l’ordre des Nostocales. Issues de la différenciation de cellules végétatives, les akinètes sont capables de persister en surface des sédiments pendant la période hivernale puis de germer au printemps pour recoloniser la colonne d’eau. Le suivi des populations pélagiques et benthiques effectué pendant deux années sur le lac d’Aydat a montré que les akinètes présents à la surface des sédiments sont représentatifs de la diversité et de l’abondance, des proliférations nostocaléennes passées. Leur capacité à persister dans les sédiments sur de longues échelles de temps a permis de mettre en évidence la présence de cyanobactéries il y a plusieurs milliers d’années. La présence récurrente d’akinètes dans les sédiments jusqu’à la période actuelle indique la persistance d’un niveau trophique élevé sur l’ensemble de l’histoire de ce lac. Parallèlement, le potentiel toxique des akinètes, étudié via la détection des gènes anaC et mcyA, a montré la co-occurrence de ces deux cyanotoxines dès les premiers blooms cyanobactériens, il y a plus de 6700 ans ainsi que la récurrence d’anaC, associé à Dolichospermum macrosporum, au moins sur les 30 dernières années. Par ailleurs, d’importantes différences de pourcentage d’intégrité des akinètes ont été observées en fonction des espèces, variant en moyenne de 5 à 60% pour les deux espèces dominantes, D. macrosporum et D. flos-aquae respectivement. Cette variabilité serait le reflet des interactions écologiques survenues dans la colonne d’eau et traduirait des stratégies écologiques différentes. De même, la capacité et le temps de germination semblent être espèce dépendante, ce qui permettrait un étalement de la période de recrutement en fonction des conditions environnementales. Malgré une perte globale de viabilité avec le temps, des akinètes enfouis depuis 1800 ans dans les sédiments ont révélé leur capacité à germer, confirmant l'importance de ces cellules de résistance dans la pérennisation à long terme des proliférations nostocaléennes
Akinetes are resistant cells produced by cyanocteria of the Nostocales Order. Originating from the differentiation of vegetative cells, Akinetes are able to persist in surface sediment duringg winter and then germinate in spring to recolonize the water column. Monitoring on pelagic and benthic populations performed during two years in lake Aydat has shown that the akinetes present in surface sediments are representative of diversity and abundances of past nostocalean proliferations. Akinetes capacity to persist in sediment at large time scales has allowed to highlight cyanobacterial presence since several thousand years. Recurrences of akinetes in sediment from 6 700 years to present day presume that the trophic level stayed high through the history of this lake. In parallel, the toxic potential of akinetes, studied with the detection of anaC and mcyA genes, has shown the co-occurrence of anatoxin-a and microcystins the since first cyanobacterial blooms, 6 700 years ago and the recurrence of anaC associated to Dolichospermum macrosporum since at least the last 30 years. On the other hand, high differences of intact akinete percentages have been observed depending on the species, with mean values of 5 and 60 % for D. macrosporum and D. flos-aquae (the two dominant species) respectively. This varibiliy may be the reflect of ecologic interactions which occurred in the water column and may be due to different ecological strategies. Moreover, ability and time of germination seem to be dependent, which may allow to extend the window of recruitment depending on environmental conditions. Despite a high loss of viability over time, some akinetes buried since 1 800 years in sediments have shown their ability to germinate, confirming the importance of these resistant cells in the long scale perpetuation of nostocalean blooms

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Brisset, Elodie. "Sensibilité des milieux de montagne aux forçages climatiques et anthropiques depuis 14 000 ans dans les Alpes du Sud : Approche multidisciplinaire (sédimentologie, géochimie, palynologie) et multi-sites (lac Petit, lac de Vens et lac d’Allos)." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM3017.

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Dans le contexte d'augmentation de la pression démographique et des risques liés aux changements climatiques, la question de l'érosion est de plus en plus cruciale. La gestion actuelle des milieux des montagnes méditerranéennes, particulièrement affectés par ces phénomènes, repose sur une bonne connaissance de leurs sensibilités à l'érosion et de leurs trajectoires à long terme. Une approche rétrospective des trajectoires des environnements a été menée par l'étude de trois archives sédimentaires lacustres prélevées dans les Alpes du Sud (lacs Petit, Vens et Allos). L'étude multidisciplinaire (sédimentologie, géochimie, palynologie) a permis de caractériser les dynamiques érosives et végétales depuis 14000 ans. À Allos et Vens, le début de l'Holocène est marqué par la maturation des écosystèmes, l'altération chimique des sols et la progression altitudinale des forêts. Ces dynamiques environnementales conduisent à la stabilisation progressive des écosystèmes, suivie d'un optimum bio-pédologique, d'une ouverture des paysages et d'une déstabilisation des sols respectivement datées de 12000-8000 cal. BP, 8000-6000 cal. BP, 6000-1900 cal. BP et de 1900 cal.BP à aujourd'hui. Cette dernière période de déstabilisation des sols intervient plus tôt au Lac Petit, à 4200 cal. BP.Les dénominateurs communs au déclenchement de l'érosion sont à chaque fois une période de précipitations fréquentes sur un milieu fragilisé : l'impact des sociétés a provoqué un abaissement du seuil de sensibilité des milieux aux perturbations, particulièrement à l'agressivité des précipitations
Within the context of increasing demographic pressures and hazards related to climate change, the problems posed by landscape erosion have become particularly crucial. The current management of Mediterranean mountain environments, which are highly exposed to erosion hazards, needs to be supported by a thorough understanding of their susceptibility to these hazards and their long-term trajectories.A retrospective analysis of environmental trajectories has been conducted from the study of three lacustrine sedimentary archives in the Southern Alps (Lakes Petit, Vens and Allos). This multi-disciplinary study, based on sedimentology, geochemistry and palynology, has enabled characterization of the dynamics of erosion and changes in plant cover over the last 14,000 years.In Lakes Allos and Vens, the start of the Holocene is marked by the maturing of ecosystems, by chemical weathering of soils and by forest encroachment at higher altitudes. These environmental changes resulted in progressive ecosystem stabilization, followed by a bio-pedological optimum, and subsequently by more open landscapes, and then soil destabilization. These four successive phases have ben dated, respectively, at 12,000-8000 cal. BP, 8000-6000 cal. BP, 6000-1900 cal. BP, and 1900 cal. BP to Present. The last of these phases occurred earlier, at 4200 cal. BP, in Lake Petit.The triggering of soil erosion has systematically been hinged on periods of heavy precipitation affecting landscapes rendered vulnerable, by human societies, to the effects of such perturbations

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Borrel, Guillaume. "Diversité des archées et implication de la composante procaryote dans le cycle biogéochimique du méthane en milieu aquatique continental : études taxonomiques et fonctionnelles dans la colonne d'eau et les sédiments anoxiques du lac Pavin." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2011. http://tel.archives-ouvertes.fr/tel-00932300.

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Le méthane, un des principaux gaz à effet de serre, est majoritairement produit et consommé par l'activité métabolique de microorganismes affiliés aux domaines des Archaea et des Bacteria. Afin d'appréhender le cycle biogéochimique du méthane, il est essentiel d'identifier l'ensemble des acteurs impliqués dans ce dernier ainsi que les facteurs environnementaux modulant leurs activités. Les lacs d'eau douce constituent une source importante de méthane, car, dans ces écosystèmes, les conditions environnementales favorisent la méthanogenèse au détriment d'autres processus terminaux de la dégradation anaérobie de la matière organique. Au cours de cette thèse, les études sur les communautés impliquées dans le cycle biogéochimique du méthane ont été conduites dans la colonne d'eau et les sédiments anoxiques du Lac Pavin (Auvergne), unique lac méromictique de France. Cet écosystème a été choisi comme site d'étude en raison des fortes concentrations en méthane présentes dans sa couche d'eau profonde qui contrastent avec les faibles émissions de ce gaz vers l'atmosphère. Ces observations géochimiques suggèrent une intense activité de production et de consommation du méthane, offrant un cadre pertinent pour l'étude des communautés ciblées. Les approches moléculaires visant à caractériser la structure spatiale, la composition, les zones d'activité et les facteurs (ascendants et descendants) potentiellement impliqués dans la régulation des communautés de méthanogènes et de méthanotrophes ont été, au cours de ce travail, systématiquement associées à des approches culturales et microcalorimétriques afin d'acquérir des données sur la physiologie des microorganismes impliqués dans le cycle du méthane. Les résultats obtenus mettent en évidence que les communautés de méthanogènes sont distribuées sur l'ensemble de la colonne d'eau anoxique et dans la strate superficielle des sédiments profonds. Ce groupe métabolique, essentiellement représenté par des espèces affiliées aux Methanosaetaceae et aux Methanoregulaceae, est particulièrement actif dans la zone benthique qui constituerait la source principale de méthane dans cet écosystème. Une nouvelle espèce méthanogène, Methanobacterium lacus, a été isolée de ces sédiments et décrite, et vient enrichir le faible nombre d'espèces méthanogènes isolées à ce jour à partir des lacs d'eau douce. L'étude écophysiologique de cette souche suggère que la température pourrait en partie expliquer la faible représentativité des Methanobacteriales dans cet écosystème. Une partie du méthane semble être directement consommée dans la zone anoxique (pélagique et benthique). L'existence de ce processus d'oxydation anaérobie, soutenu par les approches microcalorimétriques, pourrait être, dans les sédiments profonds, sous la dépendance de lignées candidates archéennes dont la physiologie reste encore énigmatique. Le remplacement progressif des méthanogènes par 2 lignées candidates d'archaea (MBG-D et MCG) le long du profil sédimentaire suggère qu'elle se développe dans des niche contrastées. La régulation putative des communautés archéennes par les virus a été analysée. Cette étude est la première à rapporter la présence de particules virales de type "archaeovirus" dans un environnement non-extrême (en termes de température, pH et salinité) ainsi que des particules virales pouvant représentées de nouvelles familles de virus. Une activité virale intense est suggérée dans ces sédiments par le nombre important de cellules infectées, comparativement à d'autres sédiments, et par le changement concomitant de la structure de la communauté virale et procaryotique avec la profondeur. Bien qu'une partie du méthane soit probablement oxydée en anaérobiose, la consommation de ce métabolite est principalement dépendante de l'activité de méthanotrophes aérobies dominées par des espèces affiliées au genre Methylobacter, un des principaux genres de méthanotrophes rencontré en milieu d'eau douce. (...)

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Chassiot, Léo. "Forçages naturels et anthropiques sur la sédimentation holocène en domaine lacustre : application aux lacs d’Auvergne et aux réservoirs des bassins versants de la Loire et d’Adour Garonne." Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2056/document.

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Dans la perspective d’appréhender au mieux les conséquences des changements climatiques à l’échelle globale, l’étude des systèmes lacustres apparaît comme un moyen privilégié pour comprendre les interactions passées entre facteurs naturels (climat et tectonique) et anthropiques sur le long terme. Se concentrant sur une zone géographique peu étudiée, l’Auvergne et les bassins versants Loire et Adour-Garonne, ce travail précise les relations existantes entre dynamiques sédimentaires et forçages naturels (tectonique et climat) et anthropiques durant l’Holocène par une approche multi-sites incluant des lacs naturels et des réservoirs. A travers une analyse multi-paramètres du continuum bassin versant - lac, les résultats portant sur les lacs naturels d’Auvergne mettent en évidence : (1) une sédimentation évènementielle témoin de plusieurs aléas naturels (séismes, coulée de boue et éruptions limniques) et (2) une sédimentation de fond reliée aux fluctuations climatiques holocènes et aux activités anthropiques durant la fin de l’Holocène. La reconstitution de l’érosion des sols sur les 700 dernières années souligne une grande disparité entre les sites étudiés, principalement reliée de facteurs de station et de l’impact anthropique à l’échelle locale. L’étude limnogéologique des réservoirs illustre des natures et des processus sédimentaires assimilables aux milieux naturels, mais souligne une grande diversité de géométries de remplissages qui sont dépendantes des typologies d’ouvrages et de l’usage anthropique des réservoirs
In order to assess the consequences of global warming, lacustrine systems are well-indicated to infer past natural (climate and tectonic) and anthropogenic interactions over long time scales. Targeting a poorly documented area, the Auvergne region and the Loire and Adour-Garonne watersheds, this work clarifies relationships between sedimentary dynamics and natural and anthropogenic forcings during the Holocene with a regional multi-sites comparison including natural lakes and reservoirs. Through multi-proxies analyses performed within the lake - catchment continuum, results highlight: (1) sedimentary events related to various forms of natural hazards (earthquakes, debris flow and limnic eruptions) and (2) a background sedimentation related to Holocene climatic fluctuations and human activities during the Late Holocene. For the last 700 years, the reconstruction of soil erosion rates underlines a large disparity between studied sites, mainly connected to site effects and the intensity of human impact at local scale. The limnogeologic study of reservoirs shows similar sedimentary processes than in natural lakes, but highlights a wide range of sedimentary architectures related to the impoundment geometry and the reservoir management

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Luque, Marín José Antonio. "Lago de Sanabria: un sensor de las oscilaciones climáticas del Atlántico Norte durante los últimos 6.000 años, El." Doctoral thesis, Universitat de Barcelona, 2003. http://hdl.handle.net/10803/1971.

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El lago oligotrófico de Sanabria se encuentra situado en la vertiente Atlántica de la Península Ibérica, región geográfica cuyo régimen de precipitaciones está determinado por las fases negativas y positivas de la NAO (North Atlantic Oscillation).

Con el objeto de reconstruir la evolución paleoambiental durante el Holoceno, se ha efectuado un estudio paleolimnológico y sedimentológico del registro sedimentario del Lago de Sanabria en muy alta resolución. Para ello, han sido obtenidos varios testigos sedimentarios en el lago (4 testigos mediante la técnica del "piston coring", y 2 testigos mediante la técnica del "gravity coring").

Los testigos sedimentarios han sido correlacionados mediante datación radiométrica (C-14, Pb-210 y Cs-137), así como mediante los criterios aportados por los parámetros descriptivos. Los parámetros utilizados en la reconstrucción paleoambiental han sido:

- Contenido en agua
- LOI (Loss on ignition)
- TOC (Total Organic Carbon) y TN (Total Nitrogen)
- Granulometría
- Mineralogía
- Geoquímica
- Contenido en Diatomeas
- Contenido en Polen
- Lámina Delgada y SEM (Scanning Electron Microscope)

Considerados en conjunto, estos parámetros indican que el LOI constituye un buen parámetro descriptivo para obtener una reconstrucción paleoambiental en el Lago de Sanabria.

El carácter cristalino de su cuenca hidrográfica (rocas plutónicas y metamórficas) determina la ausencia de Carbono inorgánico en el sistema sedimentario, tal como confirma la significativa correlación entre los valores del TOC y del LOI.

Los valores de delta[elevat a 13]C (entre -26 o/oo y -28 o/oo) indican que la materia orgánica del sedimento es de origen alóctono (plantas terrestres). La cantidad de materia orgánica está determinada por el régimen de precipitaciones de la región, dado que esta materia orgánica entra en el sistema lacustre por escorrentía.

Conclusiones:

1)El registro sedimentario del Lago de Sanabria es altamente sensible a las variaciones medioambientales. El lago se comporta como un sensor de las variaciones acontecidas tanto a escala regional (clima de la región del Atlántico Norte) como a escala local (fenómenos catastróficos acontecidos en su cuenca hidrográfica).

2)El Loss on ignition (LOI) representa el contenido en materia orgánica en el sistema sedimentario del lago, constituyendo un indicador paleoambiental. El LOI reúne las siguientes características metodológicas: a) es económico; b) es rápido, y c) es fiable.

3)El análisis de la señal del LOI (mediante análisis de Fourier, análisis Wavelet, y densidad espectral) ha evidenciado la existencia de ciclos en el contenido de materia orgánica del sedimento. Los ciclos más destacables han sido: un ciclo de 1.500 años, un ciclo de 456 años, y un ciclo de 300-311 años.

4)El registro sedimentario es sensible a importantes cambios medioambientales: a) al ciclo climático de 1.500 años ampliamente detectado en la región del Atlántico Norte (eventos Dansgard/Oeschenger), b) a la tendencia de enfriamiento general característica de un ciclo de Bond, c) detecta con detalle el periodo climático Medieval Warm Period - Little Ice Age (MWP-LIA), d) a ciclos climáticos de mayor frecuencia (ciclos de 300-311 años y 456 años), e) al ciclo solar de Gleissberg, f) a los mínimos solares, g) a avenidas torrenciales acontecidas en su cuenca hidrográfica (flash floods).

5)La significativa correlación entre el contenido en materia orgánica del sedimento y el registro de C-14 atmosférico sugiere que las oscilaciones del contenido en materia orgánica están moduladas por la actividad solar.

6)La existencia del ciclo climático de 1.500 años, así como la de ciclos de más alta frecuencia (300-311 años y 456 años), podría suponer la futura implantación de condiciones climáticas frías hacia el 2.100-2.150 AD (300 años después de la Pequeña Edad de Hielo). Estas oscilaciones climáticas sugieren que el calentamiento actual de la Tierra no está siendo determinado únicamente por la acción del Hombre, sino que también está actuando una tendencia climática natural ya existente.

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Folcher, Nicolas. "Contrôles géodynamiques et climatiques du système fluvio-lacustre de Nouvelle-Calédonie, conséquences sur les gisements de nickel latériques." Thesis, Nouvelle Calédonie, 2016. http://www.theses.fr/2016NCAL0004/document.

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La Formation Fluvio-lacustre localisée dans le sud de la Grande Terre, se situe dans de petits bassins intramontagneux à la géométrie complexe. Cette formation d'une épaisseur maximale de 70 mètres a pour particularité de remanier les produits d'altération de péridotites et de gabbros (latérites ferrugineuses et argiles kaolinitiques). Contrairement à ce que suggère son nom, l'essentiel du remplissage des bassins est fluviatile, et débute le plus souvent par un conglomérat très grossier. Les seuls dépôts véritablement lacustres sont restreints aux lacs et dolines actuels. En raison de la forme lobée du contour de certains d'entre eux et de la présence de nombreuses dolines, ces bassins étaient interprétés comme des poljés résultant de la coalescence de dolines (Trescases, 1975). Cependant, la topographie ante fluvio-lacustre révélée par les sondages, montre d'anciennes vallées constituant un réseau hydrographique très semblable au réseau actuel, largement contrôlé par des fractures rectilignes. Dans la plupart des bassins (Pernod, Netcha, Plaine des Lacs, K04), les sédiments de la Formation Fluvio-lacustre reposent sur des formations d'altération en place, ce qui signifie qu'elles n'ont été que très peu érodées, contrairement à ce qui est observé plus au nord-ouest. En l'absence d'exutoires bien définis, ces bassins ont probablement connu une évolution partiellement endoréique. Dans le cas des bassins de la Rivière des Pirogues et de la Yaté, les dépôts sont limités au nord-est par le bloc surélevé d'Unia-Goro qui a joué un rôle de barrage permettant l'accumulation des sédiments. Les dépôts Fluvio-lacustres, limités par les accidents de Koum-Yaté-Goro et Koum-Col de Plum sont localisés à l'aplomb de l'anomalie gravimétrique du Grand Sud. Cette anomalie positive généralement interprétée comme un épaississement de la Nappe des Péridotites, pourrait tout aussi bien résulter d'un amincissement de la croûte continentale provoquant une remontée du manteau sous-jacent. La dépression topographique ainsi créée aurait favorisé l'accumulation et la préservation ultérieure des sédiments
The Fluvio-lacustrine Formation located in the southern part of the 'Grande-Terre' is confined to small intramontaneous basins which possess a complex geometry. This formation with a maximal thickness of 70m has a distinctive feature which is that it reworks weathering products formed upon peridotites and gabbros (iron-rich laterites, kaolinitic clays).Unlike its name suggests, most of the sedimentary infill occurs in fluvial conditions and often starts with a very coarse torrential conglomerate. The only known occurrences of lacustrine sediments are restricted to actual lakes and dolines. Due to the lobbed shape of some basins and the numerous dolines developed upon the infill, these basins were previously interpreted as 'poljes' resulting from the coalescence of dolines (Trescases, 1975). However, the ante fluvio-lacustrine sediments topography revealed by drillings highlight old valley established by a hydrographic network similar to the actual network, controlled by straight faults. ln most basins (Pernod, Netcha, Plaine des Lacs, K04), sediments from the Fluvio-lacustrine Formation lay directly on in situ weathering formation, which means they have not been much eroded, unlike the north-western part of the island. The lack of well-defined outlets imply a partially endoreic evolution of these basins. Concerning the Rivière des Pirogues basin and the Yaté basin, sediments are limited to the north east by the uplifted block of Unia-Goro which played the role of a dam allowing the accumulation of sediments. Sediments from the Fluvio-lacustrine Formation are constrained by Koum-Yaté-Goro and Koum-Col de Plum fault zone and located at the vertical of a positive gravimetric anomaly. The later, interpreted as a thickening of the Peridotite Nappe could aIso result from a crustal thinning which caused an ascent of the mantle below. Topographic depression created by this process could have favour the accumulation and later preservation of sediments

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Cisternas, Marco, Alberto Araneda, Oscar Retamal, and Roberto Urrutia. "Sedimentos como indicadores de eventos erosivos en una pequeña cuenca lacustre de Chile central." Pontificia Universidad Católica del Perú. Centro de Investigación en Geografía Aplicada, 2014. http://repositorio.pucp.edu.pe/index/handle/123456789/119666.

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En esta investigación se estudian, mediante geocronología radioisotópica (Pb210), las variaciones históricas en el proceso de erosión-sedimentación en Laguna Chica de San Pedro, VIII Región. Las estimaciones cronológicas indican que, durante los últimos 100 años, el aporte de sedimentos desde la cuenca de drenaje osciló drásticamente en un orden de magnitud. Se concluye que las variaciones son producto de los cambios históricos en el uso del suelo. Finalmente, se proponen tres períodos históricos que habrían provocado el aumento de la erosión de los suelos en la cuenca. In this study, the historical variations in the erosional-sedimentation process in the "Laguna Chica de San Pedro" (VIII Region), are studied using lead210 geochronology. The results indicate that over the last century, the sediment supply from the drainage basin fluctuated drastically in an order of magnitude. It is concluded that this variations are the result of the historical changes in the land use. Finally, three historic periods are proposed which would have caused an increase in the erosion in the basin soils.

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Pinheiro, Cyntia Helena Ravena. "Análise de diferentes fatores na disposição de metais pesados em sedimentos lacustres no Parque Ecológico do Tietê." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/44/44134/tde-24092015-163231/.

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Verificar a existência de metais pesados nos sedimentos lacustres do Parque Ecológico do Tietê - Centro de Lazer Engenheiro Goulart (PET), sua distribuição horizontal e a identificação das suas prováveis fontes constitui o objetivo desta dissertação, bem como avaliar os parâmetros físicos, físico-químicos e químicos que poderiam disponibilizá-los de maneira a comprometer a qualidade desse ambiente. As amostragens consistiram de dois períodos climáticos distintos, um na estação climática de menor pluviosidade (inverno) e outro na estação de maior pluviosidade (verão). Os sedimentos coletados em dezesseis estações foram subdivididos em duas subamostras denominadas de topo e base e essas submetidas a análises químicas dos teores totais dos metais cobre, cromo, níquel e zinco, bem como do ferro, alumínio, manganês e fósforo. Análises químicas totais foram efetuadas em água da interface e contribuíram para a melhor compreensão da provável dinâmica que resultou nas diferenças entre os teores dos metais nos sedimentos exibidos entre as duas coletas. Os parâmetros físico-químicos determinados no campo, tanto para os sedimentos do topo e da base, quanto da água da interface (Eh, pH, condutividade elétrica, temperatura e oxigênio dissolvido) foram fundamentais para consubstanciar a interpretação da transferência dos metais de um compartimento para outro nos dois períodos de coleta. Os particulados em suspensão, foram analisados em microscópio eletrônico de varredura (MEV), com Energy Dispersive Spectrum (EDS), acoplado. Análises granulométricas permitiram a determinação do porcentual das frações mais finas dos sedimentos, principalmente as frações argila e silte, bem como do teor de matéria orgânica, por exibirem alta capacidade de adsorção de metais. Essas amostras também foram submetidas à análise do conteúdo mineral por difratometria de raios-X (DRX). A caracterização dos sedimentos como ambientes altamente redutores e levemente ácidos também indicou que os sulfetos desses metais fazem parte do equilíbrio entre as formas químicas que constituem esses ambientes. Os resultados obtidos receberam tratamentos matemáticos e geoestatísticos para auxiliar na compreensão do comportamento dos metais e a similaridade entre eles. O fator de correlação de Pearson foi um dos instrumentos utilizados e permitiu verificar a correlação existente principalmente entre o ferro e os metais zinco e cromo; entre o cobre e o zinco; fósforo e os metais ferro e alumínio; entre o alumínio, o zinco e o ferro; entre o teor de umidade e zinco. Elevadas também foram as correlações entre os particulados mais finos (silite \'mais\' argila) e os metais zinco, cromo e cobre. O cálculo do fator de enriquecimento dos metais nos sedimentos incluiu a normalização de suas concentrações utilizando o teor de Al2O3, visando minimizar os efeitos das diferenças granulométricas e mineralógicas dos sedimentos. Esse fator permitiu verificar o enriquecimento dos sedimentos do topo com relação à base em ambas as coletas e de somente parte desses metais no topo da 2ª coleta em relação à 1ª. Algumas das estações de coleta mais próximas à entrada da água do rio Tietê apresentaram os sedimentos do topo mais enriquecidos que as demais. O emprego do programa geoestatístico SURFER permitiu uma clara visualização da distribuição das isolíneas de concentração. Através da intensidade das cores utilizadas nos mapas de isoteores pôde-se facilmente verificar as áreas com maiores concentrações associadas às tonalidades mais fortes, situadas à NW e a SE do lago. Esses mapas também auxiliaram na identificação de fontes de dispersão dos metais, provenientes tanto das entradas de esgoto quanto das águas do rio Tietê. A interação entre a biota e metais pesados foi verificada através da observação dos particulados em suspensão com o auxílio do MEV. Análises químicas qualitativas pontuais realizadas nesse material indicaram a presença desses metais nas estruturas internas de alguns exemplares do fitoplâncton.
The verification of the existence of heavy metals in the lacustrine sediments of the Parque Ecológico do Tietê - Centro de lazer Engenheiro Goulart (PET), their horizontal distribution and the identification of their probable sources constitute this dissertation objective, as well as to evaluate the physical, physicochemical and chemical parameters that could make them available in way to commit the environment quality. The sediments samples collected were divided in two sub-samples, top and bottom and submitted to chemical analysis with the objective of the detection of the metals cooper, chrome, nickel, zinc, iron, aluminum and manganese total concentration. The water interface total chemistries analyses contributed to the best understanding of the probable dynamics that resulted in different metals quantities in the sediments. The certain physical-chemical parameters in the work field, either for the top and bottom sediments as for the water interface (Eh, pH, electric conductivity, temperature and dissolved oxygen) were fundamental for the interpretation of those lacustrine dynamics. The particles in suspension were examined in electronic microscope (MEV) coupled with the Energy Dispersive Spectrum (EDS). Grain sizes analyses were realized for the percentile of the finest fractions (silt and clay) of the sediments determination, as well as the organic matter content. Both exhibit high capacity of adsorption of metals. Those samples were also submitted to the mineral content analysis by X-ray difratometry (DRX). The sediments characterization as highly reducers and slightly acids environments also indicated that the sulfides of those metals are part of the balance among the chemical forms that constitute these environments. The obtained results received mathematical and geostatistics treatments to aid in the understanding of the metals behavior and the similarity with which other. The Pearson correlation factor was one of the most important instruments used and it allowed verifying the great correlation that there is among the iron, copper, zinc, match and organic matter and at the same time between those metals and the sediments humidity content. The metals enrichment factor calculation in the sediments included their concentrations using the Al2O3 percent, seeking to minimize the effects of the grain and the mineralogical sediment differences. That factor allowed verifying the enrichment of the top sediments regarding the bottom, in both collections, and that only part of these metals in the top of the 2nd collection in relation to 1st. Some of the closer collection stations to the river Tietê water entrance presented the top sediments more enriched than others. The geoestatistic program SURFER allowed a clear visualization of the concentration isolines distribution. Through the colors intensity used in the isoteores maps we can easily verify the areas with larger concentrations associated to the strongest shades, located on NW and SE of the lake. Those maps also aided in the identification of probable sources of dispersion of the metals, like sewage emissions on lake and Tietê river water. The interaction between the biota and the heavy metals was verified through the observation of the particles in suspension with the aid of the electronic microscope. Punctual qualitative chemical analyses accomplished in that material indicated the presence of those metals in the internal structures of some copies of the phytoplankton.

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Andrade, Vanessa da Costa. "Estrutura e funcionamento da alça microbiana nos sedimentos da Baía do Araçá, São Sebastião - SP /." Rio Claro, 2015. http://hdl.handle.net/11449/134126.

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Orientador: Ana Júlia Fernandes Cardoso de Oliveira
Banca: Roberto Fioravanti Carelli Fontes
Banca: Edison Barbieri
Resumo: É sabido que grande parte da produção primária global ocorre nos oceanos, e que um problema fundamental é entender como os organismos usam este carbono e quais são os padrões das variações espaço-temporais do carbono e do fluxo de energia. Deste modo, o interesse no ciclo do carbono vem aumentando nos últimos anos devido ao aumento recente de problemas mundiais, tais como mudanças climáticas e antropização de zonas costeiras. A alça microbiana conduz energia e carbono por meio das bactérias, para os níveis tróficos superiores, além de promover a assimilação de elementos inorgânicos biologicamente importantes, como nitrogênio e fósforo, em matéria orgânica na coluna d'água, elementos estes que são de extrema importância biológica. O presente estudo teve por objetivo estudar a estrutura e o funcionamento da alça microbiana nos sedimentos da Baía do Araça, quantificar seus elementos, verificar as flutuações nas densidades e correlacionar com outros fatores analisados, tais como contaminantes metálicos, matéria orgânica e hidrocarbonetos. Foram coletadas amostras de sedimento em 37 pontos, divididos em duas regiões (entremarés e sublitoral), durante o período de um ano. As amostras foram analisadas quanto a granulometria, conteúdo de matéria orgânica, carbonos orgânicos totais, hidrocarbonetos, além da análise dos componentes microbiológicos. Foi observado que as maiores densidades de microrganismos foram observadas na região do sublitoral. Houve uma correlação negativa entre as densidades de bactérias heterotróficas e nano flagelados, podendo indicar bacterivoria. As variações de matéria orgânica ao longo do estudo afetaram diretamente as populações de bactérias heterotróficas
Abstract: It is known that great part of the global primary occurs in the oceans, and a problem is to understand how the organisms use this carbon, what are the patterns of the spatial-temporal variations of carbon and of the energy flow. Thus, the interest in the carbon cycle is increasig in recent years due to the increase of global problems, such as climate change and the increase of population in coastal areas. The microbial loop leads energy and carbon, by bacteria, to the other trophic levels, and it also promotes the assimilation of inorganic elements biologically relevants, such as nitrogen and phosphorus, in organic matter in the water column, which are extremely biologically importants. This study aims to analyze the structure and the functioning of the microbial loop, quantifying its elements, check the densities variations and correlate with other analyzed factors, such as metal contaminants, organic matter and hydrocarbons. Sediment samples were collected at 37 points, divided into two regions (intertidal and subcoastal), during the period of one year. The samples were processed for granulometric analyzis, organic matter, total organic carbons, hydrocarbons, and microbiological components. It was observed that the highest densities of microrganisms were at the subcoastal region. There was a negative correlation between the densities of heterotrophic bacteria and nanoflagellates, which may indicate bacterivory. Variations of organic matter throughout the study directly affected the heterotrophic bacteria populations
Mestre

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Perin, Roberta <1988&gt. "Determinazione di traccianti dell'attività antropica in sedimenti lacustri: messa a punto del metodo." Master's Degree Thesis, Università Ca' Foscari Venezia, 2015. http://hdl.handle.net/10579/6501.

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I biomarcatori lipidici come gli steroli fecali e i fitosteroli presentano stabilità chimica a lungo termine. Questo si può constatare in un ampio range di condizioni ambientali come i sedimenti lacustri, fluviali e il suolo. La determinazione di questi biomarcatori può essere sfruttata per identificare le sorgenti di materia fecale in campo ambientale o per ricostruzioni dell'attività umana in ambito paleoclimatico. In questa tesi è stato messo a punto un metodo GC-MS per la determinazione nei sedimenti dei cinque biomarcatori più rappresentativi: coprostanolo, epicoprostanolo, colesterolo, stigmastanolo e sitosterolo. Non essendo presente alcun materiale certificato per tali analiti, il metodo è stato validato fortificando diverse tipologie di matrici ed è stato applicato in un sedimento di estuario. Le prestazioni del metodo sono state valutate in termini di accuratezza, precisione, limite di rivelabilità e di recupero.

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Oliveira, Denis Augusto Gonçalves. "Caracterização bio-sedimentológica e proposta de setorização das lagunas de Camacho." Florianópolis, SC, 2004. http://repositorio.ufsc.br/xmlui/handle/123456789/86946.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas. Programa de Pós-Graduação em Geografia.
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As lagunas de Santa Marta e do Camacho & Garopaba do Sul encontram-se localizadas no litoral sul do Estado de Santa Catarina, entre os municípios de Laguna, Jaguaruna e Tubarão e apresentam potencial para o desenvolvimento de atividades ligadas à pesca artesanal, rizicultura, maricultura, extração de conchas, turismo e expansão imobiliária. O objetivo central deste trabalho é caracterizar o substrato destas lagunas com o objetivo de identificar setores com padrões sedimentológicos diferenciados. Para isso foram coletadas 5 amostras de sedimentos superficiais na laguna de Santa Marta e 11 em Camacho & Garopaba do Sul. Neste conjunto de 16 amostras foram realizadas analises granulométricas, quantificação da matéria orgânica total, do carbonato biodetrítico total, dos nitrogenados inorgânicos dissolvidos, dos fosfatos dissolvidos e da sílica dissolvida. Foi realizado também um estudo da distribuição de foraminíferos bentônicos e de tecamebas indicadores do balanço fluvio-marinho dentro da área. Estudos morfométricos, como área, volume, perímetro, comprimentos e larguras máximas, profundidade média e máxima e pista de vento foram quantificados para auxiliar nas interpretações sedimentológicas. A integração dos dados foi realizada através de técnicas estatísticas univariadas (correlações) e multivariadas (analise de agrupamento e componentes principais). Baseado nos parâmetros biogeoquimicos e morfométricos foi possível identificar na laguna de Santa Marta dois setores distintos sedimentologicamente # setor 1 e 2 # sendo que o ponto amostral denominado como C6 localizado no sul da laguna de Garopaba do Sul apresentou características semelhantes ao setor 2 e por isso foi agrupado a este. Na laguna de Camacho & Garopaba do Sul foram identificados mais dois setores distintos, os setores 3 e 4. Estes encontram-se dispostos ao longo de um gradiente longitudinal ao eixo lagunar principal, individualizando sedimentologicamente o segmento do Camacho do segmento de Garopaba do Sul. A distribuição destes setores parece estar relacionada com as condições fisiograficas locais e com os agentes hidrodinâmicos atuantes na área, sobretudo a ação eólica.

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Preiss, Nicolas. "Etude du 210Pb d'origine atmosphérique dans l'air, la neige, les sols et les sédiments : mesures, inventaires et interprétation à l'échelle globale." Phd thesis, Grenoble 1, 1997. http://tel.archives-ouvertes.fr/tel-00765239.

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L'étude présentée ici concerne la répartition du 210Pb atmosphérique à l'échelle globale dans l'environnement. Ce travail débute par une étude expérimentale concernant les mesures de flux de dépôt atmosphérique de 210Pb dans les pluies, les sols et la neige. Une base de données a ensuite été construite en regroupant les mesures effectuées ces quatre dernières décennies. Celle-ci se focalise sur les concentrations de 210Pb dans l'air de surface et sur les flux de dépôt d'origine atmosphérique mesurés aux interfaces atmosphère-surface terrestre (collecteurs artificiels, sols et neige) et eau-sédiment. Cette base de données est ensuite exploitée. Les données de 210Pb atmosphérique sont analysées qualitativement en termes de transport (circulation atmosphérique) et de mécanismes de dépôt, et utilisées quantitativement pour la validation d'un modèle de circulation générale (GCM). En dernière partie, les données de flux de dépôt de 210Pb à l'interface eau-sédiment sont comparées statistiquement aux données de flux de dépôt atmosphérique. Cette comparaison est appliquée à l'étude des transferts entre l'atmosphère et les sédiments et permet ainsi de distinguer quatre différents types de réservoirs aquatiques.

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Oliveira, Aline Fernandes de. "Influência da adição de nitrato de cálcio e de PhoslockTM no abatimento dos fluxos de nutrientes e metais na interface sedimento-coluna de água em um sistema lacustre eutrofizado." Universidade Federal de São Carlos, 2012. https://repositorio.ufscar.br/handle/ufscar/6528.

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Financiadora de Estudos e Projetos
This research project evaluated the changes in the fluxes of nutrients and metals at the sediment-water interface as a result of sediment treatment by the additions of PhoslockTM and calcium nitrate solution. The experiments were executed in situ using mesocosms that were assembled in the Ibirité Reservoir (MG). The calcium nitrate addition experiments showed nutrients flux abatement for Porthophosphate, ammoniacal-N and nitrate-N that were ≥ 90% whilst for the metals Fe and Mn the percentages reached 48 and 69%, respectively, as a result of sediment oxidation promoted by the intensification of denitrification rates. For the PhoslockTM addition the percentages of reduction in the fluxes across sediment-water interface was over 90% for P-orthophosphate and ammoniacal-N, 78% for nitrate-N and for the metals, Fe and Mn, 47 and 50%, respectively, as a result of the increased adsorption capacity of sediments due an excess of adsorbent material left on sediment surface.
Este projeto avaliou a capacidade de abatimento dos fluxos de metais e nutrientes na interface sedimento-coluna de água da represa de Ibirité (MG), comparando-se duas diferentes tecnologias de remediação de sistemas lacustres, a adição de PhoslockTM e de nitrato de cálcio. Os experimentos foram realizados in situ, com montagem de mesocosmos na citada represa. Os resultados referentes ao tratamento com injeção de nitrato de cálcio mostraram, em função da oxidação dos sedimentos promovida por esta tecnologia, um abatimento dos fluxos de nutrientes (P-ortofosfato, N-amoniacal, N-nitrato) iguais ou superiores a 90%, enquanto que para os metais Fe e Mn, as porcentagens de abatimento de fluxo alcançaram 48 e 69%, respectivamente. Para o tratamento dos sedimentos com a adição de PhoslockTM, devido ao aumento da capacidade de adsorção dos sedimentos promovida pelo excesso de material adsorvente depositado na superfície dos mesmos, as porcentagens de redução dos fluxos sedimento-água foram superiores a 90% para o P-ortofosfato e N-amoniacal, 78% para o N-nitrato, e para os metais (Fe e Mn), 47 e 50%, respectivamente.

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Moreira, Felipe Seibert. "Fluxos Gravitacionais Lacustres na Bacia Do Recôncavo – Um Estudo no Âmbito da Estratigrafia de Sequências de Bacias Rifte." Instituto de Geociências, 2015. http://repositorio.ufba.br/ri/handle/ri/21565.

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A Bacia do Recôncavo consiste em um rifte intracontinental com forma de meiográben, composto por uma fase pré-rifte, rifte e pós-rifte. Os conceitos de estratigrafia de sequencias aplicada à bacias do tipo rifte foi utilizado na análise da fase rifte, onde foram identificados três tratos tectônicos, sendo eles o “trato tectônico de início de rifte”, “desenvolvimento de rifte” e “final de rifte”. Os depósitos lacustres desta bacia encontram-se predominantemente no “trato tectônico de desenvolvimento de rifte” e são compostos por lamitos lacustres e fluxos gravitacionais, focos deste estudo. Através de descrição de afloramentos foram identificadas 13 fácies sedimentares, provenientes de processos de correntes de turbidez, fluxos laminares coesivos e não coesivos e decantação. Essas fácies foram organizadas em quatro Associações de Fácies, sendo elas: (I) Slides – corpos pouco deformados por deslizamento de frentes deltaicas e depósitos foreshore/shoreface; (II) Debritos Arenosos – corpos altamente deformados por escorregamentos e descargas deltaicas com concentrações de sedimento maior que 20% do volume; (III) Turbiditos – correntes de turbidez provenientes da diminuição da concentração dos debritos arenosos ou por turbiditos do tipo “quasy-steady” e; (IV) Background Lacustre – sedimentação lacustre por decantação ou por correntes de turbidez dos tipos “surge” e “surge-like”. Os padrões observados nos perfis de raios gama dos afloramentos foram correlacionados com os perfis de 31 poços, originando mapas estratigráficos de distribuição das Associações de Fácies através de três subfases do “trato tectônico de desenvolvimento de rifte” e da parte basal do “trato tectônico de final de rifte”. A identificação da “superfície de início de desenvolvimento de rifte” e a “superfície de máximo rifteamento”, que limitam o trato de desenvolvimento na base e no topo, respectivamente, indicou que a espessura deste trato aumenta no sentido SE e NE da área de estudo. O comportamento das estruturas, superfícies e espessuras identificadas nos poços foram corroborados através dos mapas provenientes das interpretações sísmicas, que se mostraram complementares nas interpretações devido a regiões sem dados de poços ou sem linhas sísmicas. A partir dos mapas estratigráficos foi identificada uma fase inicial com um lago restrito à região leste da área estudada e onde ocorreram as maiores taxas de subsidência durante o início do desenvolvimento do rifte. Em seguida ocorre a expansão do lago, com a maior distribuição e espessuras dos fluxos gravitacionais de sedimentos e padrão retrogradacional dos lamitos lacustres. Já na fase final ocorre a diminuição do volume dos fluxos gravitacionais devido ao distanciamento das áreas fontes e o máximo de expansão do sistema lacustre, o qual é preenchido posteriormente pelos depósitos do “trato de final de rifte”. O aporte sedimentar tem fonte a norte-noroeste, nordeste e secundariamente leste, tendo a atividade tectônica, o excesso de sedimentos das frentes deltaicas e descargas fluviais de tempestades como principal “gatilho” para os fluxos. Os depósitos turbidíticos ocorreram constantemente durante todos os estágios lacustres, evidenciando que esses não estão relacionados somente a depósitos distais, podendo ocorrer em regiões proximais onde a concentração de sedimento por volume é baixa o suficiente para gerar turbulência no fluxo, menor que 20%.
ABSTRACT - The Reconcavo Basin consists of a intracontinental rift shaped as a half-graben, consisting of a pre-rift, rift and post-rift stages. The concepts of sequences stratigrapy applied to rift basins was used in the analysis of the rift phase, where three tectonic tracts were identified, the "tectonic tract of rift initiation", "rift development" and " rift final". The lacustrine deposits of this basin are predominantly at the "tectonic tract of rift development" and consist of lacustrine mudstones and sediment gravitational flows, focuses of this study. Through outcrops Description 13 sedimentary facies were identified, from turbidity currents processes, cohesive and non-cohesive laminar flow and suspension fallout. These facies were organized into four facies associations, namely: (I) Slides - bodies low grade deformed by sliding of deltaic fronts deposits and foreshore / shoreface; (II) Sandy Debrites - highly deformed by slip bodies and deltaic sediment discharges with concentrations greater than 20% by volume; (III) turbidites - turbidity currents from decreased concentration of sandy debritess or turbidites of type "quasy-steady" and; (IV) Lacustrine Background - lacustrine sediment by suspension fallout or by "surge" and "surge-like" turbidity currents. The patterns observed in the gamma ray logs from the outcrops were correlated to 31 well logs, resulting in stratigraphic maps of distribution of facies associations through three sub-phases of the "tectonic tract of rift development" and the basal part of the "tectonic tract end of the rift". The identification of the "surface of rift initiation development" and "surface maximum rifting" that limit the development tectonic tract at the base and top, respectively, indicated that the thickness of this tract increases to SE and NE direction at the study area. The behavior of structures, surfaces and thicknesses identified in the wells were corroborated by the maps from seismic interpretations, which proved complementary interpretations due to regions without well data or without seismic lines. From the stratigraphic maps an initial phase was identified with a small lake in the eastern region of the study area occurred and where the highest rates of subsidence during the early development of the rift. Then the lake expansion occurs, with the larger distribution and thicknesses of gravitational flows retrogradational pattern of lake sediments and mudstone. In the final stage is decreasing volume flow due to the gravitational distance of the source areas and the maximum expansion of the lake system, which is filled by deposits of the "tectonic tract od rift final." The sand supply source has the north-northwest, northeast and east secondarily, with the tectonic activity, excess sediments of deltaic fronts and river discharges storms as the main "trigger" for the flows. The turbidites deposits occurred continuously during all stages lake, showing that these are not only related to distal deposits can occur in proximal regions where the volume of sediment concentration is low enough to generate turbulence in the flow, less than 20%.

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32

Gaillard, Jean-François. "Quelques processus geochimiques lies a la diagenese precoce." Paris 7, 1987. http://www.theses.fr/1987PA077205.

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On etudie la diagenese chimique dans les sediments lacustres et marins recents. L'analyse chimique des eaux interstitielles permet de dresser des bilans matieres et des bilans stoechiometriques rendant compte de l'ensemble des transformations diagenetiques, d'envisager la precipitation de mineraux authigenes, de quantifier les precipitations et dissolutions et d'estimer les flux de metaux trace a l'interface eau-sediment. On poursuit le travail par l'analyse des sediments et des interactions existant a la surface des particules. On presente un protocole experimental pour extraire selectivement les metaux traces des sediments et un modele de leur adsorption sur les surfaces des particules en suspension au-dessus du fond. On envisage enfin les phenomenes de diffusion et les mecanismes de transport ionique dans les eaux interstitielles

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Junior, Jaime Rissi Passarini. "Estudo interdisciplinar em sedimentos lacustres da região sul do estado de São Paulo. Reconstrução da vegetação e do clima no Quaternário tardio." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-16122009-102402/.

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O estudo de um testemunho coletado às margens de uma lagoa situada em meio a vegetação de Mata Atlântica no Parque Estadual Turístico do Alto Ribeira, sul do estado de São Paulo, permitiu a reconstituição da história da vegetação local ao longo dos últimos 2500 anos. Para isso, foram realizadas análises elementares, isotópicas e palinológicas. Também a partir de material retirado deste testemunho procedeu-se a comparação entre dois protocolos de tratamento químico para análises palinológicas do Quaternário. Os protocolos utilizados seguiram as metodologias propostas por Faegri e Iversen, 1989 (Protocolo 2) e por Colinvaux et al., 1999 (Protocolo 1). Foi desenvolvido um método de comparação que envolveu a quantidade de palinomorfos e a quantidade de matéria orgânica amorfa encontrados em 450 pontos escolhidos aleatoriamente em lâminas de ambos os protocolos e também foram levados em consideração o tempo, a praticidade de aplicação em rotina laboratorial, os custos e as quantidades e tipos de resíduos para cada protocolo. Cinco amostras de sedimento foram utilizadas para comparação e o Protocolo 1 apresentou em média 10% menos matéria orgânica amorfa e quase três vezes mais palinomorfos que o Protocolo 2. Os resultados das análises isotópicas e da palinologia mostraram que a vegetação da área em estudo teve uma fisionomia florestal pelo menos desde os últimos 2550 anos. Os valores de \'delta\'13C, em torno de - 29%o, indicaram a presença de plantas C3 em todo o período estudado e registraram um enriquecimento isotópico (-24,9%o) entre aproximadamente 1650 e 1480 anos AP. A análise palinológica apontou para a ocorrência de um clima mais frio que o atual entre 2550 anos AP e 2000 anos AP, com aumento na freqüência de Araucaria e diminuição de Arecaceae. Também foi detectada a ocorrência de um período de clima mais quente e mais úmido entre aproximadamente 1000 anos AP e 680 anos AP, com desaparecimento de Araucaria e aumento de Arecaceae, Weinmannia e de pteridófitas. A maior umidade deste período também é apontada pelos valores de C/N que indicam aumento de influência terrestre no sedimento e pelo aumento de Botryococcus. Em todas as camadas foram encontradas partículas carbonizadas, indicando períodos de ocorrência de paleoincêndios e de abertura florestal provavelmente associados à presença humana na região
One sediment core collected at the margins of a lake surrounded by Atlantic rainforest vegetation at Parque Estadual do Alto Ribeira (PETAR), southern São Paulo state (Brazil), was analyzed, in order to reconstruct the history of the local vegetation over the last 2500 years. Elemental (Total Organic Carbon TOC and Total Organic Nitrogen), isotopic (C and N), pollen analysis and radiocarbon dating were integrated on this work. Also was made a comparison of two protocols for Quaternary pollen chemical treatment. The tested protocols were proposed by Faegri and Iversen, 1989 (Protocol 2) and by Colinvaux et al., 1999 (Protocol 1). The comparison methods developed in this study checked the protocols performance on the quantity of palinomorphs and of organic matter found in 450 random areas of microscope slides of each protocol. The time consuming, laboratory routine, costs and residue production by the protocols were considered for comparison. Five samples were used for comparison and the Protocol 1 showed an average of 10% less organic matter and more palinomorphs than Protocol 2. According to the isotopic and pollen results, the study area vegetation maintained as a forest for the last 2500 years BP. \'delta\'13C values of -29%o indicated the presence of C3 plants during all the sediment study and a isotopic enrichment (- 24,9%o) was observed between 1650 and 1480 yrs BP. Pollen analysis suggested the occurrence of colder climatic conditions between 2550 and 2000 yrs BP and a warmer and humid period was suggested between 1000 and 680 yrs BP. Charcoal particles were found since 2550 yrs BP indicating paleofire probably associated to the human activities

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Lécrivain, Nathalie. "Étude de la contamination et de l'écotoxicité associée des sédiments de surface en zone littorale lacustre." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSET001/document.

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La zone littorale, de grande importance pour le fonctionnement écologique du lac, est souvent la première zone réceptrice de la contamination provenant du bassin versant. Cette pollution est majoritairement piégée dans les sédiments de surface. Pour autant, les conditions environnementales variables qui règnent en zone littorale sont susceptibles de favoriser la biodisponibilité des contaminants par le jeu des réactions physico-chimiques et biologiques. Cette thèse s’appuie sur l’étude de deux grands lacs péri-alpins, le Lac du Bourget et le Lac d’Annecy, pour mieux comprendre le comportement des polluants sédimentaires (ETM, HAP et PCB) en zone littorale lacustre. Nos travaux visent notamment (1) à caractériser la contamination littorale et l’influence des sources locales dans cette contamination, (2) à évaluer l’écotoxicité des sédiments littoraux et les changements de mobilité et de biodisponibilité des polluants sédimentaires sous l’influence de changements abiotiques de la zone littorale tels que ceux induits par le marnage lacustre. Nos résultats montrent que la contamination des sédiments et organismes autochtones présente une hétérogénéité spatiale significative sur le littoral des deux lacs, tant en intensité qu’en composition (i.e. profil de contamination). L’implication de sources locales (e.g. eaux pluviales drainées sur le bassin-versant) dans cette hétérogénéité spatiale a été mise en évidence. L’écotoxicité des sédiments de la zone littorale, évaluée via la réponse de biomarqueurs enzymatiques (AChE, GST), physiologiques (e.g. taux d’ingestion chez D. magna) et des traits de vie (e.g. taux de croissance, reproduction et survie) présente également une hétérogénéité spatiale significative. La biodisponibilité des ETM sédimentaires a été plus spécifiquement étudiée aux interfaces sédiment-eau-biote. Elle varie selon l’élément, le biote exposé (benthique ou pélagique) et sous l’effet du marnage. L’assèchement et remise en eau du sédiment littoral s’accompagnent d’une réduction de la fraction biodisponible des ETM. L’abaissement de la hauteur d’eau, en revanche, entraîne une accentuation de la remise en suspension de particules sédimentaires susceptibles d’exercer un risque écotoxicologique sur le biote littoral. Nos résultats soulignent la complexité de la contamination littorale et de son transfert dans les grands lacs péri-alpins et encouragent les approches écotoxicologiques dans l’évaluation de l’état écologique
The littoral zone of lakes is of great ecological importance and yet receives a large array of contaminants from the watershed. This pollution is mainly trapped by the surface sediment, but its bioavailability may be allowed by physico-chemical and biological reactions in this zone of high environmental fluctuations. This work aims at improving knowledge about the behavior of sediment-borne contaminants (trace metals, PAHs and PCBs) in the lake littoral zone by using two large perialpine lakes; Lake Bourget and Lake Annecy. More precisely, our goals were to (1) characterize the littoral contamination and the influence of local sources in this contamination, (2) assess the ecotoxicity of the sediment-borne contamination and the main changes in its mobility and bioavailability under abiotic changes in the littoral zone, such as those related to water-level fluctuations in lakes. The contamination of the sediments and native organisms exhibited a significant spatial heterogeneity along the lake littoral, in both intensity and profile’s composition. The involvement of local sources of contamination (e.g. stormwater runoff) as drivers of this spatial heterogeneity has been highlighted. The ecotoxicity of littoral sediments was assessed through the responses of enzymatic biomarkers (AChE and GST), physiological traits (e.g. ingestion rates in D. magna) and life-history traits (e.g. growth, reproduction and survival rates). Our results also underscored a significant spatial heterogeneity of the littoral sediment ecotoxicity. A greater focus on the bioavailability of trace metals at the sediment-water-biota interfaces showed that bioavailability depends on the metal, the exposed biota (benthic vs pelagic) and fluctuate under water-level fluctuations. Drought and re-immersion of surface sediments were followed with a reduction of the bioavailable fractions of the trace metals. However, decreases in the water-level led to increase suspended sediments in the water column, which may exert an ecotoxicological risk for the littoral biota. Our results underline how complex the littoral contamination and bioavailability are and promote ecotoxicological approaches in the assessment of the ecological status of large lakes

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Oliveira, Eduardo Roemers de. "Contexto deposicional da sequência Balbuena III (Maastrichtiano/ Daniano) da formação Yacoraite na sub-bacia metán-alemania, na região de Salta, Argentina /." Rio Claro, 2014. http://hdl.handle.net/11449/127651.

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Orientador: Luiz Sérgio Amarante Simões
Coorientador: Luiz Alberto Fernandes
Banca: José Alexandre de Jesus Perinotto
Banca: Luci Maria Arienti
Resumo: A Bacia de Salta localiza-se no noroeste argentino e sua origem está relacionada a um rifte intracontinental, formado durante o Cretáceo e início do Paleógeno. Subdivide-se em quatro sub-bacias (Lomas de Olmedo a leste; Sey a oeste; Tres Cruces a norte; e Metán-Alemania a sul) que foram preenchidas por sedimentos das supersequências Pirgua (fase sin-rifte) e Balbuena (fase sag). A seção sedimentar que compõe a fase sag é dividida em quatro sequências: Balbuena I, II, III e IV, da base para o topo. O presente estudo aborda a caracterização faciológica e estratigráfica com base em afloramentos da Sequência Balbuena III (Maastrichtiano/Daniano) da Fm. Yacoraite, na Sub-bacia Metán-Alemania, região do dique Cabra Corral, distrito de Coronel Moldes, Argentina. Os dados foram obtidos no levantamento de 14 seções estratigráficas verticais na escala 1:40, nas quais foram adquiridos perfis de raios gama espectral e realizada coleta de amostras para análises sedimentológicas. A análise faciológica revelou que a Sequência Balbuena III é composta por fácies carbonáticas, siliciclásticas e mistas, depositadas em ambiente lacustre. As fácies carbonáticas são constituídas por grainstones oolíticos e/ou bioclásticos, packstones oolíticos e/ou bioclásticos, rudstones e floastones bioclásticos, mudstones, laminitos e estromatólitos. As fácies siliciclásticas correspondem a arenitos muito finos ondulados, siltitos e lamitos. As litofácies de deposição mista (com componentes siliciclásticos e carbonáticos) são constituídas por arenitos híbridos e margas. As litofácies identificadas foram agrupadas em quatro associações de fácies, que a partir das observações de campo, resultaram em duas sucessões verticais ideais de fácies (sequências elementares). Tais sucessões foram hierarquizadas em sequências de média e alta frequências e puderam ser rastreadas por dezenas de quilômetros na bacia. A partir do...
Abstract: The Salta Basin is located in the northwest of Argentina and its origin is related to an intracontinental rift which was formed during the Cretaceous and early Paleogene. It is subdivided into four sub-basins (Lomas de Olmedo - east; Sey - west; Tres Cruces - north; and Metán-Alemania - south) that were filled by sediments from the Pirgua (synrift phase) and Balbuena (sag phase) supersequences. The sedimentary section that forms the sag phase is divided into four sequences: Balbuena I, II, III and IV, from bottom to top. This research covers the sedimentological and stratigraphical outcrops characterization of the Balbuena III Sequence (Maastrichtian/Danian) from Yacoraite Fm., in the Metán-Alemania sub-basin, Cabra Corral dam region, district of Coronel Moldes, Argentina. The data have been collected from the survey of 14 vertical stratigraphic sections measured in these outcrops at a 1:40 scale, where spectral gamma-ray logs have been acquired and samples for sedimentological analysis have been collected. Data analysis has shown that Balbuena III Sequence consists of carbonate, siliciclastic and mixed facies which have been deposited in a lacustrine environment. The carbonate facies are formed by oolitic/bioclastic grainstones, oolitic/bioclastic packstones, bioclastic rudstones and floatstones, carbonate mudstones, laminites and stromatolites.The siliciclastic facies correspond to very fine wavy sandstones, siltstones and mudstones.The lithofacies of mixed deposition (with carbonate and siliciclastic components) consist of hybrid sandstones and marls.The identified lithofacies have been grouped into four facies associations, which from field observations, could be grouped into two ideal vertical successions of facies (elementary sequences). The observed cycles have been ranked in sequences of medium and high frequencies and could be traced for tens of kilometers in the basin. From the understanding of the distribution of...
Mestre

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Remor, Marcelo Bevilacqua. "Histórico de contaminação por elementos-traços na planície aluvial do Alto Rio Paraná." Universidade Estadual do Oeste do Parana, 2013. http://tede.unioeste.br:8080/tede/handle/tede/678.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Objective: Investigate the temporal evolution of the supply of trace elements, identifying trends in the historical concentration of the drainage basin of the Upper Paraná River Floodplain. Material and Methods: The corers extracted of the Patos Pond and the Garças Pond were sliced into uniform intervals of 2.2 and 2.0 cm respectively. Later the geochronological analysis was performed by the method radiochemical of isotope 210Pb. The quantification of element Mercury was performed with the equipment LUMEX. While the others trace elements were quantified by flame atomic absorption spectrometry, opening following the Method USEPA 3050B. Results: The sedimentation rate of the Garças Pond is 7.7 mm year-1 (2.66 kg m-2 year-1) and of the Patos Pond is 6.0 mm year-1 (1.94 kg m-2 year-1). Conclusion: The sediments of the Patos Pond and the Garças Pond have concentrations of trace elements similar to the background. The main factor that regulates the supply of trace elements in the Upper Paraná River Floodplain is the flood pulses, which can be magnified by the El Niño phenomenon. The burning of cane sugar, increased agriculture, urbanization and release of effluents from steel mills contributed to the increase in the concentration of some trace elements. While the adsorption by macrophytes and process oligotrophication caused by damss upstream of the floodplain, resulted in the reduction of the concentration of other elements
Objetivo: Investigar a evolução temporal do fornecimento de elementos-traço, identificando tendências na concentração histórica da bacia de drenagem da Planície Aluvial do Alto Rio Paraná. Material e Método: Os corers extraídos da Lagoa dos Patos e na Lagoa das Garças foram fatiados em intervalos uniformes de 2,2 e 2,0 cm respectivamente. Posteriormente foi realizada a análise geocronológica pelo método radioquímico do isótopo 210Pb. A quantificação do elemento Mercúrio foi realizada com o equipamento LUMEX. Enquanto os demais elementos-traço foram quantificados por meio de absorção atômica de chama, com abertura seguindo o método USEPA 3050B. Resultados: A taxa de sedimentação da Lagoa das Garças é de 7,7 mm ano-1 (2,66 kg m-2 ano-1) e da Lagoa dos Patos é de 6,0 mm ano-1 (1,94 kg m-2 ano-1). Conclusão: Os sedimentos das Lagoas dos Patos e da Lagoa das Garças possuem concentrações de elementos-traço semelhantes aos valores de referência. O principal fator que regula o fornecimento de elementos-traço na planície aluvial do Alto Rio Paraná são os pulsos de inundação, que podem ser magnificados pelo fenômeno climático El Niño. A queima da cana-de-açúcar, aumento da agropecuária, urbanização e lançamento de efluentes de siderúrgicas contribuíram para o aumento da concentração de alguns elementos-traço. Enquanto a adsorção por macrofitas aquáticas e o processo de oligotrofização, causado pelas barragens a montante da planície aluvial, acarretaram na redução da concentração de outros elementos

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Junqueira, Valeria Christina Amstalden. "Clostridium botulinum em sedimentos lacustres e peixes de aquicultura, alternativas no seu isolamento e identificação e desenvolvimento em files de tilapia (Oreochtomis niloticus) refrigerados." [s.n.], 2002. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255120.

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Orientador: Mauro Faber de Freitas Leitão
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Nesta pesquisa procurou-se avaliar a validade e adequacidade de métodos alternativos aplicados no isolamento e identificação de Clostridium botulinum, a ocorrência do mesmo em sedimentos lacustres e em peixes de aqüicultura e a influência da temperatura, composição da atmosfera na embalagem e do lactato de sódio no desenvolvimento de esporos desta bactéria, inoculados experimentalmente em filés de tilápia. Os estudos efetuados permitiram otimizar o meio de Ágar Tripticase Glicose Extrato de Levedura para contagem em placas pela técnica de inoculação em profundidade, permitindo uma diferenciação na triagem inicial, podendo também ser utilizado adicionado dos antibióticos cicloserina, sulfametoxazole e trimethoprim, tornando-se seletivo para contagem preliminar de cepas proteolíticas da bactéria. Para avaliação da ocorrência de C. botulinum, foram analisadas um total de 200 amostras de vísceras de peixes e 100 amostras de sedimentos de tanques de criação através das técnicas de Número Mais Provável (NMP) e de contagem em placas por inoculação em profundidade, indicando ocorrência de 1% e 8%, respectivamente, constatando-se apenas a presença de cepas dos tipos C e E da bactéria. Em termos quantitativos, as populações de C. botulinum verificadas nas amostras positivas de vísceras e sedimentos foram muito reduzidas, na faixa de 0,01 a 0,05NMP/g. Os filés de tilápia inoculados experimentalmente com esporos de C. botulinum não se apresentaram tóxicos após armazenamento a 4°C durante 45 dias, em atmosfera modificada com ou sem tratamento com lactato. No entanto, pela elevação da temperatura para 12°C a toxicidade foi comprovada, independentemente do uso de outros obstáculos como o lactato de sódio ou a atmosfera modificada.
Abstract: In this research we aim to evaluate the validity and adequacy of alternative methods applied to the isolation and identification of Clostridium botulinum, its occurrence in lake sediments and farmed fish and the influence of temperature, atmospheric composition on the packaging and of sodium lactate in the development of its spores inoculated experimentally in tilapia fillets. The studies carried out led to the optimization of the Agar Tripticase Peptone Glucose Yeast Extract for pour-plate counting allowing for a preliminary differentiation as well as being able to be utilized when the antibiotics cicloserine, sulfametoxazole and trimethoprim are added, becoming selective for preliminary counting of proteolytic strains of the bacteria. To evaluate the occurrence of C. botulinum, a total of 200 fish gut samples and 100 samples of sediment from fish farm tanks were analyzed by the Most Probable Number (MPN) and by pour-plate techniques, indicating levels of 1% and 8%, respectively, and showing only the presence of the C and E C. botulinum types. In quantitative terms, the population of C. botulinum verified in the positive gut and sediment samples was very low, around 0.01 to 0.05 MPN/g. The tilapia fillets experimentally inoculated with C. botulinum spores did not become toxic after storage at 4°C for 45 days in modified atmosphere packaging with or without lactate treatment. However, when the temperature was increased to 12°C the toxicity was proven independently of the use of other barriers such as sodium lactate and modified atmosphere.
Doutorado
Doutor em Tecnologia de Alimentos

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Bak, Friedhelm. "Sulfatreduzierende Bakterien und ihre Aktivität im Litoralsediment der unteren Güll (Überlinger See) /." Konstanz : Hartung-Gorre, 1988. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=000688893&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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Massa, Charly. "Variabilité climatique holocène et impacts anthropiques historiques en zone subarctique : étude multiparamètre de la séquence sédimentaire du lac d'Igaliku (Groenland)." Thesis, Besançon, 2012. http://www.theses.fr/2012BESA1008/document.

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La colonisation médiévale scandinave au Groenland (986 – 1450 AD) et la reconquête agricole récente de la région sud-groenlandaise, favorisée par le réchauffement climatique en cours, constituent un modèle de référence particulièrement adapté à l’étude des relations entre une communauté humaine et son environnement. Dans cette perspective, une étude sédimentologique multiparamètre a été réalisée sur la séquence sédimentaire du lac d’Igaliku (N61°00’22”, W45°26’28”), situé au cœur de la principale implantation médiévale et du secteur agro-pastoral contemporain. Quatre mètres de sédiments, couvrant la totalité de l’évolution holocène du lac (~10000 ans), ont été étudiés à haute résolution temporelle. L’analyse comprend une caractérisation physico-chimique (densité, susceptibilité magnétique, diagraphie XRF, imagerie rayon-X, granulométrie laser, dosages carbone, azote et souffre, ICP-AES, isotopie δ13C et δ15N de la matière organique) et biologique (pollen, microfossiles non polliniques, diatomées) du sédiment. Vingt-huit datations radiocarbones, ainsi que la mesure l’activité du 210Pb et du 137Cs, permettent d’interpréter le signal sédimentaire dans un cadre chronologique très précis et de reconstruire l’évolution postglaciaire du lac et de son bassin versant, soumis aux contraintes glacio-isostatiques, aux forçages climatiques et aux impacts anthropiques. La première phase d’évolution du système lacustre est principalement sous contrôle isostatique avec une transition rapide d’un environnement marin pro-glaciaire vers un environnement lacustre après émersion du bassin, il y a 9500 ans. Par la suite, la séquence témoigne de l’évolution paléoclimatique de la région. Les paramètres limnologiques et terrestres suggèrent un réchauffement précoce, probablement interrompu par une période froide, sèche et venteuse entre 8600 et 8100 ans cal BP. Un second événement sec et venteux, de 5300 à 4800 ans cal BP, précède la transition néoglaciaire, qui se caractérise, à Igaliku, par une évolution vers un climat plus humide et peut-être plus froid à partir de 4800 cal BP, provoquant une mutation majeure des conditions écologiques terrestres et aquatiques. La diminution des flux de grains de pollen indique un refroidissement notable à partir de 3000 cal BP. Vers l’an 1000, suite à l’arrivée des colons scandinaves, le système lacustre passe sous un contrôle anthropique dominant. Le défrichement et l’introduction d’herbivores domestiques dans le bassin versant du lac produisent un doublement du taux d’érosion des sols (de 4 mm/siècle à 8 mm/siècle vers 1200 AD) et une modification de la qualité des influx organiques. Pour autant, les assemblages de diatomées indiquent que l’écologie du lac n’a été que faiblement affectée par l’agriculture médiévale. A partir de 1325 AD et jusqu’à la fin de la colonie scandinave, vers la moitié du XVe siècle, la végétation présente des signes de résilience et l’érosion des sols régresse. Cette déprise agro-pastorale, probablement en relation avec les prémices du Petit Âge Glaciaire, est en phase avec une importante mutation des pratiques de subsistance attestée par l’archéologie. Le retour du pastoralisme au début du XXe siècle marque une reprise des processus d’érosion, similaires, en intensité, à ceux engendrés par les colons scandinaves. En revanche, l’intensification et la modernisation des pratiques agricoles dans les années 1980 est responsable d’une érosion des sols spectaculaire (~21 mm/siècle) et d’une mutation de l’écosystème lacustre (eutrophisation) sans précédent depuis la formation du lac, il y a 9500 ans. Les effets combinés de l’agriculture et du réchauffement climatique en cours (amorcé dans les années 1920 à Igaliku) aura des conséquences environnementales difficiles à prévoir pour l’avenir de la région
The medieval Norse colonization of Greenland (986-1450 AD) and the subsequent reestablishment of agriculture in south Greenland, aided by recent climate warming, constitute a conceptual model that is particularly well adapted to understanding the relations between a community and its environment. In this perspective, a multi-parameter sedimentological study was undertaken on the sedimentary sequence of Lake Igaliku (N61°00’22”, W45°26’28”), situated in the heart of the medieval and current agricultural sector. The 4 m long sequence, covering the entire Holocene evolution of the lake (~10 000 years), was studied at high temporal resolution. The analyses included the physico-chemical characterization of the sediments (density, magnetic susceptibility, XRF, X-ray imaging, grain size, carbon, nitrogen, and sulphur content, ICP-AES, δ13C and δ15N isotopic ratios) as well as the biological components of the sediment (pollen, non-pollen palynomorphs, diatoms). 28 radiocarbon dates as well as 210Pb and 137Cs measurements created a precise temporal framework with which to reconstruct the postglacial evolution of the lake and its catchment in terms of isostatic constraints, climatic forcing and anthropogenic impacts. The first phase of basin evolution is primarily controlled by isostasy, with the rapid transition from glaciomarine conditions to a freshwater lake as the basin emerged from the fjord 9500 yr BP. Afterwards, the sedimentary sequence records the paleoclimatic evolution of the region. Paleolimnological and terrestrial proxies suggest an early warm phase likely interrupted by a cold, windy, dry period between 8600 yr BP and 8100 yr BP. A second dry, windy period between 5300 yr BP and 4800 yr BP predated the transition to neoglacial cooling, which is characterised at Igaliku by a switch to humid and perhaps cooler conditions after 4800 BP, and which caused a major shift in both aquatic and terrestrial ecology. Approximately 1000 AD, after the arrival of Norse settlers, the lacustrine system became anthropogenically dominated. Land clearing and domestic herbivores introduction in the lake catchment doubled the rate of soil erosion (from 4 mm century-1 to 8 mm century-1 by 1200 AD) and caused a major modification of the organic carbon influx. On the other hand, diatom assemblages demonstrate that the lake ecology was not strongly impacted by medieval agriculture at this site. After 1325 AD, until the end of the Norse tenure in the mid-15th century, terrestrial vegetation showed signs of rebound and soil erosion decreased. This agricultural diminishment, probably in relation to the beginning of the Little Ice Age, is consistent with an important change in subsistence patterns evidenced by archaeology in this region. The reestablishment of agriculture at the beginning of the 20th century marks the reinvigoration of erosional processes that are similar in intensity to that of the Norse settlement. On the other hand, the intensification and modernization of farming practices during the 1980s is responsible for marked soil erosion (21 mm century-1) and a shift in lake ecology (eutrophication) that is unprecedented in the 9500 yr history of the lake. The combined effects of agriculture and climate warming already underway (initiated in the 1920s at Igaliku) will have large environmental consequences for the future of this region

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CORREA, Sandra Lia de Almeida. "Evolução geoquímica das crostas lateríticas e dos sedimentos sobrepostos na estrutura de Seis Lagos (Amazonas)." Universidade Federal do Pará, 1996. http://repositorio.ufpa.br/jspui/handle/2011/7891.

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O estudo sobre a evolução mineralógica e geoquímica das crostas lateríticas e dos sedimentos sobrepostos na estrutura de Seis Lagos (Amazonas), foi baseado em amostras de crostas lateríticas superficiais e três furos de sondagem. Na caracterização química dos materiais estudados foram empregados métodos clássicos e espectroanalíticos. Na caracterização mineralógica foi utilizado difração de raios-X, microscopia ótica, espectroscopia no infravermelho e termogravimetria (ATD e ATG). Foram efetuadas análises por sistema dispersivo de energia (EDS), que foram aplicados nos estudos micromorfológicos das crostas e sedimentos da Bacia Esperança. Nas amostras de siderita foram determinados os isótopos de 13C e 18O e razões isotópicas 87Sr/86Sr. Na tentativa de datar as amostras totais e siderita da brecha carbonática, foi utilizado o método Rb/Sr. As características texturais, mineralógicas e geoquímicas observadas nas crostas superficiais e do perfil do furo 1, mostraram origem laterítica para esses materiais. A assinatura carbonatítica das crostas foi indicada pelos minerais como ilmenorutilo, Nb-rutilo, Nb-brookita, pirocloro e monazita, típicos de carbonatitos e rochas associadas e resistentes aos processos lateríticos e pelos teores elevados e anômalos de Nb, ETR, também de Ba, Mn, Th, Co, Zr, Sc, V, Mo e Be. O perfil do furo 3, que se apresentou estruturado em horizontes bem distintos, característicos de perfil laterítico, mostrou composição química-mineralógica indicativa de derivação laterítica a partir de rochas aluminosilicatadas pobres em ferro, como as encaixantes (granitos e gnaisses) de Seis Lagos. Os sedimentos da bacia Esperança mostraram que tiveram como área fonte os diferentes horizontes dos perfis lateríticos e grande contribuição orgânica vegetal e animal. Os materiais que constituiram a brecha carbonática, foram provenientes das crostas ferruginosas lateríticas dada a semelhança geoquímica entre esses materiais, a presença dos minerais resistatos da crosta ferruginosa e de minerais típicos de ambiente sedimentar-diagenético, essencialmente ferrosos como pirita e siderita. A argila carbonosa demonstrou ter como área fonte os horizontes argilosos lateríticos como aqueles do perfil do furo 3 e, que a deposição desta camada ocorreu em momento de menor subsidência da bacia Esperança, quando as crostas ferruginosas que estavam situadas em níveis mais elevados tinham sido erodidas e os horizontes argilosos estavam expostos. A camada de sapropelito indicou a instalação de um ambiente ácido redutor prolongado, dada pela sua elevada espessura, que sua constituição química-mineralógica foi contribuída também pelos lateritos, principalmente, dos horizontes argilosos, e que a formação de pirita foi a mesma daquela da brecha carbonática. A camada de argila creme-solo foi constituída também dos horizontes argilosos, como indicou sua composição química-mineralógica. Na brecha carbonática da seqüência litológica da bacia Esperança não foram encontrados minerais típicos de carbonatitos, a exceção dos resistatos (ilmenorutilo, Nb-rutilo, Nb-brokita, pirocloro e monazita) e siderita não comuns nessas rochas, mas minerais lateríticos como gibbsita e grupo da crandalita. As filiações geoquímicas encontradas entre crostas e brecha carbonática e argilas/sapropelito e horizontes argilosos lateríticos foram notáveis. O não alinhamento dos pontos analíticos no diagrama isocrônico (87Rb/86Sr vs. 87Sr/86Sr) obtidos tanto das amostras totais como de cristais de siderita da brecha carbonática não foram compatíveis com rochas homogêneas, como seriam esperados para carbonatitos, ao contrário do espesso pacote sedimentar. Os resultados mineralógicos, geoquímicos e isotópicos demonstraram que a brecha carbonática não corresponde à rocha carbonatítica, e que os sedimentos da bacia Esperança incluindo a brecha carbonática tiveram como área fonte principal os diferentes horizontes dos perfis lateríticos, onde a crosta ferruginosa foi a fonte de grande parte dos sedimentos da base da coluna (base da bacia, provavelmente) e os horizontes argilosos das camadas superiores. Isso permitiu que em toda a extensão da coluna, fosse transferida a assinatura geoquímica da fonte primária geradora dos lateritos que foram rochas carbonatiticas, e preservada nos lateritos.
The study of the mineralogical and geochemical evolution of the lateritic crusts and the overlying sediment in the structure of Seis Lagos (Amazonas State) has been based on the analyses of samples from the surface lateritic crusts and from three boreholes as well. In the chemical characterization of the examined material, it has been used both classic and spectroanalytic methods, while in the mineralogical characterization, x-ray diffraction, optical microscopy, infrared spectroscopy and thermogravimetry (DTA and DTG) have been employed. Energy dispersive system analyses (EDS) have been performed and applied to the micromorphologic study of the crusts and sediments from the Esperança Basin. In siderite samples, it has been determined 13C and 18O isotopic contents as well as the 87Sr/86Sr isotopic ratios. The Rb/Sr method has been used in an attempt to date whole samples and siderites from the carbonatic breccias. The textural, mineralogical and geochemical features observed, both in the surface crusts and in the profile of the borehole number 1, point to a lateritic origen for those materials. The carbonatitic signature of the crusts is indicated by typical minerals of carbonatites and associated rocks such as ilmenorutile, Nb-rutile, Nb-brookite, pyrochlore and monazite, which are resistant to lateritic processes; by high and anomalous contents of Nb, REE, as well as, Mn, Th, Co, Zr, Sc, V, Mo and Be. The profile of the borehole number 3 is arranged in well distinct horizons, what is characteristic of lateritic profiles, shows chemical and mineralogical compositions indicative of a lateritic derivation from aluminosilicatic iron-poor rocks, as those of the wall rocks (granites and gneisses) of Seis Lagos. The sediments of the Esperança Basin show evidence of being derived from the different horizons which make up the lateritic profiles, with a significant vegetable- and animal-derived organic contribution. The materials which constitute the carbonatic breccia are thought to be originated from lateritic ferruginous crust due to the existing geochemical similarities among them, to the presence of resistate minerais of the ferruginous crust and to the presence of essentially iron-bearing minerais, typical of sedimentary-diagenetic environment, such as pyrite and siderite. The carbonaceous clay proved to be derived from lateritic clayey horizons, as those of the profile of the borehole 3, and the deposition of this layer took place in a moment of lower subsidence rate in the Esperança Basin, when the ferruginous crust, positioned at higher levels, were being eroded and the cayey horizons were exposed. The sapropelite layer indicates, considering its large thickness, that a development of a long-lasting acid and reducing environment might have taken place; its chemical and mineralogical composition received contributions from latentes, mainly from the clayey horizons; and the pyrite formation has been the sanie of that of the carbonatic breccia. The beige-colored clay bed, as it is indicated by its chemical and mineralogical composition, was also formed by clayey-horizons material. In the carbonatic breccia of the Esperança Basin, typical caxbonatite minerals have not been found, except for the resistates (ilmenorutile, Nb-rutile, Nb-brookite, pyrochlore and monazite) and siderite, where the last one is not a common constituent of those rocks. Lateritic minerals, however, such as gibbsite and those of the crandallite group have been found. The geochemical filiation reported among crusts, carbonatic breccias, clay/sapropelite and clayey lateritic horizons is noteworthy. The nonalignment of the points plotted in isochronic diagram (87Rb/86Sr vs. "Sr/"Sr), obtained either from the whole sample or the individual siderite analyses of the carbonatic breccia are not compatible with homogenous rocks, as it would be expected for carbonatites, although they are with the thick sedimentary pile. The mineralogical, geochemical and isotopic data demonstrate that the carbonatic breccia composition does not correspond to that of the carbonatites and thus the sediments of the Esperança Basin, including the carbonatic breccia, might have had the various horizons of the lateritic profiles as their source, where the ferruginous crust might have largely been the source for the sediments of the base of column (probably the basal portion of the basin) as well as the clayey horizons of the upper beds might have been. This made possible that, along all the extension of the stratigraphic column, the geochemical signature of the carbonatitic source rock, from which the laterites were generated, was transferred to the sedimentary rocks as well as it was also preserved in the laterites.

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NASCIMENTO, Luiz Ricardo da Silva Lôbo do. "Palinoestratigrafia e paleoecologia da sequência lacustre do cretáceo inferior, em Serra Negra - PE, Bacia Sedimentar do Jatobá, NE do Brasil." Universidade Federal de Pernambuco, 2013. https://repositorio.ufpe.br/handle/123456789/10523.

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CAPES
O presente estudo baseou-se na análise palinológica de uma sondagem com 90,50 m, denominada 2 JSN-01-PE, na Serra Negra, Ibimirim, PE, realizada pelo Projeto Rede 07 - Caracterização Geológica e Geofísica de Campos Maduros – Fase 4, Convênio 01.07.0721.00 – FINEP/UFPE. Foram analisados 122 níveis estratigráficos, onde as amostras foram submetidas ao procedimento químico para a extração dos palinomorfos, segundo o protocolo palinológico para sedimentos mesozoicos. Após a leitura das lâminas observou-se que em 58 níveis não foi possível à recuperação de palinomorfos; e que 64 níveis são portadores de bom resíduo orgânico, permitindo o reconhecimento dos palinomorfos característicos do Cretáceo Inferior. Na análise quantitativa foram contados 200 palinomorfos para cada amostra. A associação palinofloristica descrita para a Formação Crato na Bacia do Jatobá, demonstra o predomínio de elementos de origem continental, com grãos de pólen de gimnospermas e angiospermas, esporos de pteridófitas e alga Botryococcus. Nota-se a abundância dos tipos de clima quente como Equisetosporistes, Cicatricosisporites, Crybelosporites e Classopollis, distribuídos entre 120 espécies. Observou-se a ocorrência de palinomorfos retrabalhados de idade Devoniana Superior, provavelmente dos sedimentos da Formação Inajá (Veryachium e Maranhites) que serviram de fonte de parte dos sedimentos Aptianos. A associação palinofloristica permitiu uma subdivisão da seção analisada em 4 palinozonas informais que pode, potencialmente ser aplicada a toda bacia. Através da análise palinológica atribuiu-se a Formação Crato idade aptiana, tendo correspondência com o Andar Alagoas (local). As evidências palinológicas sugerem uma deposição predominantemente continental lacustre. Devido as suas características, a associação palinoflorística pode ser inserida na província “WASA” (Oeste da África e América do Sul) por Herngreen & Chlonova (1981), atualmente denominada Província a “Pre-Albian Early Cretaceous Dicheiropollis etruscus/Afropollis” de Herngreen et al. (1996).

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Jesus, Tatiane Araujo de. "Avaliação do histórico de impactos antrópicos na bacia de drenagem do Lago das Garças (São Paulo-SP), durante o século XX, com base nos estoques de nutrientes, metais pesados e compostos orgânicos em sedimento lacustre." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-13122008-142525/.

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O presente estudo visou reconstruir o histórico de impactos antrópicos na bacia de drenagem do Lago das Garças durante o século XX por meio da deposição de contaminantes no compartimento sedimentar. O Lago das Garças está localizado em uma unidade de conservação, Parque Estadual das Fontes do Ipiranga (PEFI), inserida em área altamente povoada e urbanizada da cidade de São Paulo. Dois testemunhos de sedimento (LG05-03 e LG05-04, com 70 cm e 65 cm, respectivamente) foram amostrados mediante auxílio de mergulhadores no ponto mais profundo do reservatório, sendo, posteriormente, fatiados a cada 1 cm. Em LG05-03 foram quantificadas as distribuições verticais de carbono orgânico total (COT), nutrientes totais (NT e PT), hidrocarbonetos policíclicos aromáticos (HPA), hidrocarbonetos alifáticos (n-alcanos), bem como foi feita a classificação granulométrica. Em LG05-04 foi determinada a deposição de metais pesados (Co, Cr, Cu, Fe, Mn, Ni, Pb e Zn) e a geocronologia através do isótopo radioativo \'ANTPOT. 210 Pb\', usando o modelo CIC (Constant Initial Concentration). Os dados foram analisados por meio de análises estatísticas multivariadas (ACP: Análise de Componentes Principais). Com base nas tendências dos dados e na ACP, foi possível estabelecer três fases principais: Fase I: 64-43 cm (~1894-1975): caracterizada por baixas concentrações de nutrientes e contaminantes, sendo possível recuperar níveis préindustriais destes compostos, propostos como valores de referência regionais. Ainda, com base na razão C/N e em razões entre n-alcanos, notou-se, nesta fase o predomínio de aporte de matéria orgânica de origem alóctone; Fase II: 43-26 cm (~1975-1990): aumento abrupto das concentrações de metais pesados e HPA traçadores de veículos automotores, marcando o aumento da poluição atmosférica devido ao grande crescimento econômico do município e maior circulação de veículos na região. Ainda, foi observado aumento gradual das concentrações de NT e PT, atribuídos aos despejos de esgotos não tratados oriundos da Secretaria de Agricultura e Abastecimento e da Fundação Parque Zoológico; Fase III: 26-0 cm (~1990-2005): aumento mais acentuado das concentrações de nutrientes devido aos despejos de esgotos, acarretando em maior eutrofia do sistema, registrada pelo perfil do n-\'C IND.17\'. Pico das concentrações de HPA traçadores do uso de carvão mineral associado às atividades de uma siderúrgica vizinha (Siderúrgica J.L. Alipeti), bem como queda das concentrações destes traçadores coincidindo com mudanças no processo industrial da empresa. Ainda nesta fase notaram-se aumentos expressivos dos teores e fluxos dos HPA traçadores de veículos automotores, corroborando o cenário de aumento vertiginoso da frota de veículos na última década. Desse modo, este estudo contribuiu com o cenário nacional em termos de manejo de bacias hidrográficas urbanas, incluindo registros desde a época pré-revolução industrial no Brasil (~1894) até os dias atuais, demonstrando o potencial do uso de testemunhos lacustres no resgate de informações relativas à contaminação de ecossistemas aquáticos associadas às atividades antropogênicas.
Present study aimed to reconstruct the human impact history on the Garças Lake Drainage Basin during the 20th Century based on contaminants deposition on the lacustrine sediment. Garças Lake is located in a preservation area, the Parque Estadual das Fontes do Ipiranga (PEFI), located in a highly populated urban area within the city of São Paulo. Two sediment cores (LG05-03 and LG05-04, 70 cm and 65 cm long) were sampled by divers at the deepest site of the lake, which were sliced at 1 cm intervals. Information for LG05-03 included total organic carbon (TOC), total nutrients (TN and TP), polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (n-alkanes) and grain size vertical distributions. Deposition of heavy metals (Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and the geocronology by \'ANTPOT. 210 Pb\', using CIC model (Constant Initial Concentration), were determined in LG05-04. Data were analyzed by multivariate statistic analysis (PCA, principal components analysis). Based on data trends and PCA, it was possible to recognized three main phases: Phase I: 64-43 cm (~1894-1975) characterized by low nutrients and contaminants concentrations, allowing retrieving preindustrial levels of these compounds, which are proposed as regional reference values. Besides, C/N ratio and n-alkanes ratios demonstrated aloctonous organic matter predominance; Phase II: 43-26 cm (~1975-1990) characterized by the abrupt increase of heavy metals and vehicular PAHs concentration, indicating the atmospheric pollution increase, due to the great economic rise experienced by the city of São Paulo over that time and the higher vehicles circulation in the region. Yet, it was observed a gradual increase in nutrient concentration attributed to the untreated sewage inputs from the São Paulo State Department of Agriculture and Provisioning headquarters and the city Zoo; Phase III: 26-0 cm (~1990-2005) characterized by a marked increase in nutrient concentration related to the untreated sewage inputs, leading to the increase of eutrophication, as registered by the n-\'C IND.17\' distribution. A peak of coal PAHs concentration was also noticed, related to a neighbor steel mill (J.L. Aliperti), followed by a subsequent decrease of these compounds, coincident with industrial procedures changes. Besides, there was an expressive increase in vehicular PAHs concentrations, corroborating the scenery of a drastic raise of vehicles in the last decade. The present study contributed to the national scenario towards urban drainage basin management. It included records since preindustrial time (~1894) up to the present, highlighting the potential use of lacustrine sediment on the retrieval of historical environmental changes of aquatic ecosystems and associated anthropogenic impacts.

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Brucha, Gunther. "Avaliação da diversidade microbiana de consórcios anaeróbios enriquecidos a partir de amostras de sedimento lacustre na degradação anaeróbia do tricloroetileno - TCE, empregando-se a técnica de eletroforese em gel com gradiente desnaturante - DGGE." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-30012017-102026/.

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Sedimento do reservatório hipereutrófico de Salto Grande, localizado na cidade de Americana, São Paulo, foi cultivado em condições anaeróbias em meio mineral adicionado de compostos orgânicos (ácidos voláteis e álcoois) com a finalidade de favorecer a metanogênese do sistema. Com a produção de 70% de metano o sedimento foi utilizado para o teste de degradação anaeróbica do TCE. Os testes foram realizados sob atmosfera de N2/CO2 (70:30%) em frascos reatores a 25ºC e agitação constante de 150 rpm. Os frascos reatores foram preparados com meio mineral, acrescido de fontes orgânicas (5 mM de ácidos acético, fórmico e butírico, mas 2,5 mM de ácido lático e 5 mM de etanol e metanol) e inoculado com 5 g de sólidos totais voláteis por litro. Foram preparados frascos com 12 e 6 mg de tricloroetileno por litro. Dois tipos de controles foram preparados, um sem tricoroetileno e outro sem inóculo. Análise da diversidade microbiana utilizando a metodologia do DGGE - Eletroforese em Gel com Gradiente Desnaturante - foram feitas com amostras dos frascos reatores no final do experimento. O DNA da comunidade foi extraído de acordo com o protocolo descrito por TSAI & OLSON (1991) e fragmentos do DNAr 16S foram amplificados com \"primers\" do Domínio Archaea e Bacteria. Os resultados dos testes de degradação do TCE demonstraram a remoção biótica de 68% e 66% nos reatores contendo 6 e 12 mg TCE/L, respectivamente, depois de 56 dias de incubação. No final do experimento morfologias similares aos gêneros Methanosarcina e Methanosaeta estavam presentes. A análise da diversidade microbiana não revelou uma significativa na comunidade após a adição do TCE, demonstrando que a microbiota enriquecida proveniente do reservatório de Salto Grande foi resistente à concentração do TCE estudada podendo ser responsável pelo processo de degradação sob metanogênese.
Sediments from the supereutrophic reservoir of Salto Grande, City of Americana, São Paulo State, Brazil, were cultivated under anaerobic conditions in a mineral medium added of organic compounds (volatile fatty acids and alcohols) in order to produce methane. Under 70% of methane production, sediment samples were used for tests of TCE anaerobic degradation. The tests were carried out under N2/CO2 (70:30%) atmosphere in reactor flasks, at 25°C, and constant shaking at 150 rpm. The reactor flasks were prepared with mineral medium, added with organic sources [5 mM of acetic, formic and butyric acids, plus 2.5 mM of lactic acid and 5 mM of ethanol and methanol each], and inoculated with 5 g of STV/L of the sediments. Amounts of 6 and 12 mg/L of TCE concentrations were evaluated. Two types of control reactors were prepared, without TCE and without sediments. Diversity analyses using the DGGE - Denaturing Gradient Gel Eletrophoresis - technique were done with samples from the reactor flasks at the end of the experiment. The community DNA was extracted as described by TSAl & OLSON (1991) and fragments of the 16SDNAr were magnified using the PCR methodology, with Bacteria and Archaea domain primers. The results showed degradation of 40% of TCE at concentrations of 6 mg/L and 12 mg/L after 13 days of incubation time, and complete organic acids removal with 40% of methane in the atmosphere. A second addition of 9 mM of the former organic acids indicated and 4.5 mM of lactic acid resulted in 90% of TCE removal, with 50% of methane, after 56 days of incubation time. Morphologies similar to the genera Methanosarcina, Methanosaeta and Methanospirillum were verified. The microbial diversity analysis did not reveal significant differences among Bacteria and Archaea domains under TCE additions. It was possible to assume that the enriched microbiota from the Salto Grande reservoir was resistant to the concentrations of TCE studied and can be responsible for the degradation processes under methanogenesis.

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Lavrieux, Marlène. "Biomarqueurs moléculaires d'occupation des sols, du sol au sédiment : exemple du bassin-versant et du lac d'Aydat (Puy-de-Dôme)." Phd thesis, Université François Rabelais - Tours, 2011. http://tel.archives-ouvertes.fr/tel-00672307.

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Cette étude propose une analyse intégrée de biomarqueurs moléculaires de sols, depuis leur site de production jusqu'à leur archivage sédimentaire lacustre. Un inventaire des lipides neutres est d'abord réalisé sur des sols d'usages contrast és : prairies/pâtures et forêts. Globalement, cette approche permet de distinguer (1) des composés linéaires ubiquistes, et (2) des composés (poly-)cycliques, généralement spéci ques. Parmi ces derniers gurent les acétates de triterpényle et les méthoxyserrat ènes, respectivement biomarqueurs d'Astéracées et de Pinacées. La persistance de l'empreinte moléculaire d'un ancien usage des sols est aussi démontrée. Ensuite, l'analyse multi-proxy d'une carotte sédimentaire couvrant les 6700 dernières années révèle l'impact prépondérant des activités humaines sur le fonctionnement hydrologique du lac, depuis l'époque gallo-romaine. Les assemblages moléculaires précédemment dé- nis dans les sols sont globalement retrouvés, associés à un nouveau biomarqueur spéci que du chanvre, d'intérêt paléoenvironnemental. Une tentative de reconstitution des anciennes occupations des sols apparaît conforme aux données historiques et paléoenvironnementales antérieures.

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Regis, Julie. "Impact des hypoxies sur la mobilité des nutriments et ETMM présents dans les sédiments des lagunes méditerranéennes." Electronic Thesis or Diss., Nîmes, 2024. http://www.theses.fr/2024NIME0002.

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La concentration en oxygène dans la colonne d’eau est le principal facteur de contrôle de l’ensemble des réactions biogéochimiques dans les sédiments de surface et les transferts à l’interface eau-sédiment (IES) des nutriments, métaux et métalloïdes (ETMM). Trois lagunes de la façade méditerranéenne française (Berre, Thau et Prévost) font parties des zones côtières eutrophisées et impactées par des épisodes d’hypoxie dans le monde et ont de fortes accumulations de nutriments et d’ETMM dans les sédiments. Elles sont aussi caractérisées par des habitats benthiques différents incluant pour certaines la présence de macrophytes, dont le rôle de régulateur de flux de nutriments à l’IES a été démontré. Cette thèse vise à mieux comprendre l’impact des désoxygénations sur la mobilité des nutriments et ETMM contenus dans les sédiments des lagunes méditerranéennes, en présence de différents habitats benthiques représentant leur gradient d’eutrophisation. Les résultats montrent que la lagune de Berre est le site le plus impacté par des épisodes de désoxygénation de longue durée (1 semaine) et saisonniers, la lagune du Prévost présente de grandes variations nycthémérales passant de l’hypoxie à l’hyperoxie en moins de 12 h en saison estivale, et le site de la lagune de Thau semble le plus résilient vis à vis des problématiques de désoxygénation qui restent épisodiques. En conditions estivales, les profils de concentrations des sédiments et eaux porales indiquent des enrichissements en nutriments et en sulfures dans les substrats des habitats benthiques des lagunes aux statuts d’eutrophisation les plus avancés (Berre et Prévost) et également en présence de macroalgues (Prévost et Thau). Ces enrichissements sont issus d’une forte minéralisation de la matière organique et les conditions plus réductrices dans ces habitats fixent les ETMM (As, Sb, Cd, Pb, Zn, Ni, Cu, Co, Hgtot) à la phase solide du sédiment. La comparaison aux seuils environnementaux disponibles permet d’identifier les habitats de la lagune de Berre fortement a risque vis à vis du soutien de l’eutrophisation, de la remobilisation des ETMM à l’IES et du risque écotoxicologique. L’acquisition de gradients de concentration en oxygène dissous, au sein de la couche limite benthique (BBL) à haute résolution temporelle, a permis d’identifier la forte demande en oxygène des sédiments de la lagune de Berre et les désoxygénations nocturnes issues de la présence des macroalgues opportunistes sur la lagune du Prévost. L’acquisition ponctuelle, de gradients de concentration, illustre des exports de nutriments du sédiment vers la colonne d’eau plus intenses en conditions anoxiques et euxiniques ainsi que des exports de Mn, Fe, As, Co en conditions hypoxiques. A l’inverse, les gradients en conditions euxiniques indiquent des situations de piégeage d’ETMM (Mn, Fe, Cu, Mo) avec les phases sulfurées du sédiment. En parallèle, les expérimentations in situ et ex situ d’incubation en conditions de désoxygénation "forcées" pour les différents habitats benthiques présents dans ces trois sites, ont permis d’obtenir des flux à l’IES qui suivent également cette tendance. Une intensification des flux en nutriments suivant la désoxygénation a été mesurée dans les habitats sédiment nu impacté par la désoxygénation (Berre) et pour les habitats comportant des macroalgues pérennes (Thau) et opportunistes (Prévost). Pour ces mêmes habitats les exports d’ETMM (Mn, Fe, As, Co, V ,Mo) les plus intenses ont été mesurés en conditions hypoxiques et anoxiques et à l’inverse, des diminution et inversion des flux en conditions euxiniques. Cette approche comparative et expérimentale de terrain apporte le point de vue intégratif de la biogéochimie sur la qualité chimique des sédiments de ces milieux lagunaires en cours de re-oligotrophisation. Permettant de contextualiser leur grande variabilité temporelle et spatiale ainsi que leur vulnérabilité face aux changements climatiques
Studies carried out in recent years have shown that oxygen concentration in the water column is the main factor controlling all biogeochemical reactions in surface sediment, as well as controlling transfers of nutrients, trace elements (TE) at the sediment water interface (SWI). Three lagoons on France’s Mediterranean coast (Berre, Thau and Prévost) are among the world’s most eutrophied coastal zones impacted by hypoxia episodes, with high accumulations of nutrients, metals and metalloids in their sediment. They are also characterized by different benthic habitats, some of which include macrophytes, which have been shown to regulate nutrient flux at IES. This thesis project aims to better understand the impact of deoxygenation phenomena on the mobility of nutrients and TE present in Mediterranean lagoon sediment, in the presence of different benthic habitats representing their eutrophication gradient. The results show that the Berre lagoon is the site most impacted by long-lasting (1 week) and seasonal episodes of deoxygenation; the Prévost lagoon exhibits wide nycthemeral variations, going from hypoxia to hyperoxia in less than 12 h during the summer season; the Thau lagoon site seems the most resilient about deoxygenation. Under summer conditions, sediment and porewater concentrationprofiles show enrichments in nutrients and sulfides in the substrates of benthic habitats in lagoons with the most advanced eutrophication status (Berre and Prévost), and also in the presence of macroalgae (Prévost and Thau). These enrichments are the result of strong organic matter mineralization, and the more reducing conditions in these habitats binding the TE (As, Sb, Cd, Pb, Zn, Ni, Cu, Co, Hgtot) to the solid phase of the sediment. Comparison with available environmental thresholds enables us to identify habitats in the Berre lagoon that are highly at risk in terms of eutrophication support, remobilization of TE at SWI and ecotoxicological risk. The acquisition of dissolved oxygen concentration gradients within the benthic boundary layer (BBL) at high temporal resolution has enabled us to identify the high oxygen demand of sediment in the Berre lagoon and the nighttime deoxygenations resulting from the presence of opportunistic macroalgae in the Prévost lagoon. The punctual acquisition of concentration gradients illustrates nutrient exports from the sediment to the water column that are more intense under anoxic and euxinic conditions, and exports ofMn, Fe, As, Co under hypoxic conditions. However, concentration gradients under euxinic conditions indicate the trapping of TE (Mn, Fe, Cu,Mo) with the sulfide phases of the sediment. In addition, in situ and ex situ incubation experiments under "forced" deoxygenation conditions for the various benthic habitats present at these three sites yielded SWI fluxes that also followed this trend. Nutrient fluxes were shown to intensify following deoxygenation in eutrophied bare sediment habitats affected by deoxygenation (Berre) and specifically in habitats containing opportunistic (Prévost) and perennial (Thau) macroalgae. For these same habitats, the most intense exports of TE (Mn, Fe, As, Co, V , Mo) were measured under hypoxic and anoxic conditions, while fluxes decreased or reversed under euxinic conditions. This comparative and experimental field approach brings an integrative biogeochemical perspective on the chemical quality of sediment in lagoon environments undergoing re-oligotrophication. It provides a context for their great temporal variability, as well as their vulnerability to climate change

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Abdourhamane, Touré Amadou. "Erosion en milieu sableux cultivé au Niger : dynamique actuelle et passée en liaison avec la pression anthropique et les changements climatiques." Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00833028.

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Les écosystèmes sahéliens, et tout particulièrement ceux qui se développent sur des sols sableux, réagissent très vite et très intensément aux moindres changements climatiques. Dans cette zone semi-aride, l'érosion éolienne qui affecte essentiellement les surfaces cultivées met en péril l'exploitation durable des ressources en terre. Par ailleurs, l'explosion démographique de ces dernières décennies et les grandes crises climatiques à l'origine des sécheresses du vingtième siècle ont eu d'importantes répercussions sur le milieu. Pour gérer au mieux ce milieu fragile, il importe d'abord de bien comprendre son fonctionnement. Ce travail de thèse s'est donc inscrit dans le programme de recherche AMMA (Analyse Multidisciplinaire de la Mousson africaine) et se situe au coeur du programme CORUS2 (Coopération pour la Recherche Universitaire et Scientifique) concernant essentiellement l'étude de la dynamique éolienne des sols sableux cultivés de la région de Niamey. La stratégie suivie au cours de cette étude a été de s'appuyer sur un important dispositif de mesures expérimentales pour comprendre au mieux et quantifier le fonctionnement actuel du milieu essentiellement vis-à-vis de l'érosion éolienne. Ces mesures expérimentales ont permis d'interpréter les changements que nous avons pu mettre en évidence sur un ensemble de terroirs proches de Niamey qui constituent les bassins versants de deux lacs permanents récents : Bangou Bi et Bangou Kirey (13,51° N - 2,21° E). Les enregistrements sédimentaires recueillis dans ces lacs ont ensuite été analysés en regard de l'évolution de leur bassin versant. Au cours de cette étude nous avons mis en évidence le rôle majeur des résidus de culture dans les champs traditionnels et montré que même à des taux de recouvrement extrêmement bas, ils constituent une protection pour les sols. Cependant leur efficacité chute en deçà d'un seuil de 2% et l'érosion éolienne déplace alors des quantités considérables de terres (130 t/an en moyenne) et participe activement à l'encroûtement des sols. Il est probable qu'à la faveur combinée de la mise en culture de l'ensemble des versant avant 1975 et de la sécheresse de 1985, un tel processus d'érosion et d'encroûtement s'est mis en place expliquant ainsi la dégradation considérable du milieu que nous avons mise en évidence entre 1975 et 2009 à partir d'enquêtes auprès des population et par la cartographie diachronique des petits bassins versant étudiés. A partir de l'étude des sédiments collectés dans les lacs, nous avons pu proposer un modèle de mise en place de ces sédiments qui suggère une intensification de l'érosion à partir du milieu des années 80.

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Bouffard, Ariane. "Interaction entre le mercure élémentaire et les sédiments lacustres." Thèse, 2008. http://hdl.handle.net/1866/8127.

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48

Pereira, Cátia Alexandra Lúcio. "Modelos de inferência de alterações ambientais baseados em diatomáceas (Bacillariophyta) de sedimentos das lagoas dos Açores." Master's thesis, 2013. http://hdl.handle.net/10400.3/1951.

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Dissertação de Mestrado em Biodiversidade e Ecologia Insular.
As alterações ambientais locais e globais podem afectar a qualidade ecológica dos lagos. Na ausência de dados históricos, a detecção e quantificação destas alterações podem ser reveladas por técnicas paleolimnológicas. Os sedimentos lacustres têm sido utilizados cada vez mais nos últimos anos para inferir flutuações nas condições ambientais do passado, e vários estudos que abrangem diversas escalas, locais e temporais, têm mostrado a importância dos lagos como arquivos paleoclimáticos e ecológicos. Dos vários depósitos biológicos preservados nos sedimentos lacustres, as diatomáceas constituem indicadores paleoecológicos úteis, principalmente pela sua grande abundância, as suas frústulas de sílica encontram-se bem preservadas e pela elevada diversidade específica. De modo a desenvolver modelos de inferência para as variáveis ambientais a partir das diatomáceas dos sedimentos, 40 lagos, distribuídos pelas ilhas dos Açores, foram amostrados utilizando um corer gravimétrico e diversas variáveis ambientais foram medidas, entre as quais, variáveis hidromorfológicas, físico-químicas e variáveis de impacte. Identificaram-se 207 taxa de diatomáceas, distribuídos por 55 géneros. Realizaram-se análises multivariadas (PCA, ANOSIM, nMDS, SIMPER, DistLM) para analisar os conjuntos de diatomáceas dos sedimentos superficiais e para relacionar estes com as condições ecológicas e ambientais. Verificou-se que existem diferenças estatisticamente significativas na composição taxonómica para o grupo “Tipologia” (R = 0,449; p = 0,001), lagoas profundas e pouco profundas. As espécies que mais contribuem para a dissimilaridade entre as tipologias de lagoas são Aulacoseira ambigua, Asterionella formosa, A. granulata, características de lagoas profundas e Stauroforma exiguiformis, Tabellaria flocculosa morfo 1 e Brachysira brebissonii, características de lagoas pouco profundas. O dbRDA ilustra como as comunidades de diatomáceas se encontram separadas pela tipologia das lagoas, sendo as variáveis que mais contribuem para essa separação a condutividade e o pH e variáveis indicadoras do estado trófico, clorofila a e fósforo total. As variáveis que apresentaram maior correlação com as diatomáceas foram usadas para desenvolver funções de transferência baseadas no Weighted Averaging (WA) e Weighted Averaging Partial Least Squares (WA-PLS), modelos de calibração e regressão. De uma forma geral o método WA classical deshrinking foi aquele que apresentou melhor desempenho para as variáveis pH, condutividade, fósforo total, profundidade máxima, clorofila a, sílica e temperatura média do ar no mês de Julho. Os valores de predição por Jack-Knife obtidos para estas variáveis são bastante elevados (R2 Jack-Knife de 0,829; 0,797; 0,822; 0,848; 0,579; 0,529 e 0,485, respectivamente) e os erros de predição (RMSEP) e os enviesamentos são reduzidos. As funções de transferência revelam-se de uma importância extrema, pois permitem reconstruir quantitativamente as últimas condições ambientais, proporcionam ferramentas para a caracterização de tipologias de lagos, permitem definir as condições de referência ecológica e química e permitem avaliar o desvio a partir dos estados de referência. O reconhecimento do impacte que as alterações ambientais passadas exerceram sobre os ecossistemas pode contribuir significativamente para a previsão de alterações futuras resultantes de alterações ambientais locais e globais.
ABSTRACT: Local and global environmental changes can affect ecological quality of lakes. In the absence of historical data the detection and quantification of these changes can be reveled by paleolimnological approaches. Lake sediments have been used increasingly in recent years to infer past fluctuations in environmental conditions and several studies covering several local and temporal scales have shown the importance of lakes as paleoclimate and ecological archives. Of the range of biological remains preserved in lake sediments, diatoms are useful paleoecological indicators mostly because their wide distribution well preserved silicate frustules, high indicator values and high species diversity. In order to develop inference models for environmental variables from diatom assemblages in sediments, 40 lakes distributed throughout Azorean islands were sampled using a gravimetric corer and several environmental variables were measured. 207 taxa, spread over 55 genera were identified. Multivariate analyses (PCA, ANOSIM, nMDS, SIMPER, DistLM) were used in order to analyze the diatoms assemblages in the surface sediments and to relate them with the ecological and environmental conditions. Was verified that there are statistically significant differences in taxonomic composition for the “Typology” group (R = 0,449, p = 0,001), deep and shallow lakes. The species that most contributed to the dissimilarity between lakes typology were, Aulacoseira ambigua, Alterionella formosa, A. granulata, species mostly found in deep lakes and Stauroforma exiguiformis Tabellaria flocculosa morfo 1 and Brachysira brebissonii, species mostly found in shallow lakes. The dbRDA illustrates how diatom communities are separated by lakes typology. The variables conductivity and pH and the indicator variables of trophic state, chlorophyll a and total phosphorous were those that most contributed to this separation. The variables with the highest correlation with diatoms assemblages were used to develop transfer functions based in Weighted Averaging (WA) and Weighted Averaging Partial Least Square (WA-PLS), regression and calibration models. In general, the WA classical deshrinking method presented the best performance for pH, conductivity, total phosphorous, maximum depth, chlorophyll a, silica and average air temperature in July. The prediction values obtained by Jack-Knife for those variables are quite high (R2 Jack-Knife de 0,829; 0,797; 0,822; 0,848; 0,579; 0,529 e 0,485, respectively), and errors of prediction (RMSEP) and bias values are reduced. Transfer functions allow to reconstruct quantitatively past environmental conditions, provide tools for characterizing lake types, define the ecological and chemical reference conditions and allow to evaluate the deviation from the reference state. The recognition of the impact that past environmental changes exerted on the ecosystem can contribute significantly to the prediction of future changes resulting from local and global environmental changes.

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Dissertations / Theses on the topic 'Sediments lacustres'

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