Dissertations / Theses on the topic 'Organic pollutants in water'

Dans ce travail de thèse, les radicaux hydroxyles et sulfates, générés par les procédés électro-Fenton et électro-persulfate utilisant une anode en fer, respectivement, ont été utilisés pour la dégradation des édulcorants synthétiques et un colorant azoïque. Les études réalisées sont essentiellement concentrées sur : efficacité de dégradation, mécanismes d'oxydation, schémas de minéralisation et évolution de la toxicité lors de traitement des polluants cibles.1. Le procédé électro-Fenton a montré une grande efficacité dans la dégradation oxydative de l'Aspartame (ASP). La dégradation et la minéralisation sont essentiellement affectées par la concentration du catalyseur (Fe2+) et l'intensité du courant. La constante de vitesse absolue de la réaction d'hydroxylation de l'ASP a été déterminée comme (5,23±0,02) x 109 M-1 s-1. Les acides oxalique, oxamique et maléique ont été identifiés comme sous-produits aliphatiques. La toxicité de la solution (méthode Microtox) augment dans un premier temps et ensuite diminue progressivement lors du traitement.(2) L'édulcorant artificiel Saccarine (SAC) a été efficacement dégradée par procédé électro-Fenton avec anodes DSA, Pt et BDD. Cependant, l'utilisation de l'anode BDD a accéléré significativement la minéralisation de la SAC. Les conditions optimales pour la minéralisation efficace de la SAC étaient: [SAC]: 0,2 mM, [Fe2+] (catalyseur): 0,2 mM, [Na2SO4] (électrolyte): 0,05 M, I (courant): 200 mA et pH: 3. Les acides oxalique, formique et maléique ont été identifiés comme sous-produits aliphatiques. La mesure de la toxicité indique une augmentation en début d'électrolyse (formation des intermédiaires toxiques) et puis une diminution progressive le long du traitement.(3) L'édulcorant artificiel Sucralose (SUC) a été complètement minéralisée en 360 min de traitement par procédé électro-Fenton avec l'anode Pt ou BDD. Le taux de minéralisation est affecté par la concentration de Fe2+ et le courant appliqué. L'efficacité du courant de minéralisation diminue avec l'augmentation du courant de 100 à 500 mA avec les deux anodes. Les acides oxalique, pyruvique, formique et glycolique ont été détectés au cours du processus de minéralisation.(4) Les solutions du colorant azoïque Orange II ont été effectivement décolorées par les radicaux sulfates générés par l'activation électrochimique du peroxydisulfate (PDS) utilisant un catalyseur solide, FeOOH (procédé CE/α-FeOOH/PDS). Le pH initial a peu d'effet sur la décoloration. La méthodologie RSM (Response Surface Methodology) basée sur le modèle Box-Behnken a été appliquée pour analyser les variables expérimentales. Les résultats indiquent que le courant a un effet positif sur la vitesse de décoloration. L'interaction du dosage de l'α-FeOOH et la concentration de PDS ont des effets significatifs. Les résultats d'analyse de variance (ANOVA) ont confirmé que les modèles proposés étaient exactes et fiables pour l'analyse des variables du procédé CE/α-FeOOH/PDS. Le catalyseur solide α-FeOOH a montré une bonne stabilité structurelle et pourrait être réutilisé.(5) Les solutions d'Orange II ont été dégradés par les radicaux sulfates obtenus par le même procédé mais avec catalyseur Fe3O4 : EC/Fe3O4/PDS. La vitesse de décoloration est affecté principalement par : pH initial de la solution, densité du courant, concentration de PDS et dosage de Fe3O4. La solution a été totalement décolorée en 60 min dans les conditions suivantes: [Orange II]0: 25 mg/L, [PDS]: 10 mM, [Fe3O4]: 0,8 g/L, densité du courant (j): 8,4 mA/cm2 et pH initial: 6,0. Les expériences de recyclage ont montré que les particules de Fe3O4 étaient stables et pourraient être réutilisées. Les spectres XPS ont montré la formation de Fe(II) sur la surface des particules de Fe3O4 lors de traitement. Les principaux intermédiaires ont été séparés et identifiés par la technique GC-MS et un schéma plausible de dégradation d'Orange II a été proposé
In this paper, electro-Fenton and sulfate radical-based electro-Fenton-like processes were used to degrade artificial sweeteners and azo dye. The results obtained during the research concern the removal efficiency, the oxidation mechanism, degradation pathway and toxicity evolution of target pollutants.(1) Electro-Fenton process was a effective method for the degradation of ASP in water. The removal and mineralization rate was affected by the Fe2+ concentration and applied current. The absolute rate constant of hydroxylation reaction of ASP was (5.23 ± 0.02) × 109 M–1 S–1. Short-chain aliphatic acids such as oxalic, oxamic and maleic acid were identified as aliphatic intermediates in the electro-Fenton process. The bacteria luminescence inhibition showed the toxicity of ASP solution decreased after it reached a maximum during the first period of the oxidation reaction.(2) Artificial sweetener SAC could be degraded effectively by electro-Fenton process with a DSA, Pt or BDD anode. However, the using of BDD anode could accelerate the mineralization of SAC. The optimal conditions for SAC removal were SAC concentration 0.2 mM, Fe2+ concentration 0.2 mM, Na2SO4 concentration 50 mM, applied current 200 mA and initial pH 3.0. Oxalic, formic, and maleic acid were observed as aliphatic byproducts of SAC during electro-Fenton process. The bacteria luminescence inhibition showed the toxicity of SAC solution increased at the beginning of electrolysis, and then it declined until the end of the reaction.(3) Artificial sweetener Sucralose could be completely mineralized in a 360 min reaction by electro-Fenton process with a Pt or BDD anode. The mineralization rate was affected by the Fe2+ concentration and applied current. The mineralization current efficiency (MCE) decreased with rising applied current from 100 to 500 mA with both Pt and BDD anode. Oxalic, pyruvic, formic and glycolic acids were detected during the oxidation of sucralose.(4) Orange II was effectively decolorized by EC/α-FeOOH/PDS process. The initial pH of Orange II solution had little effect on the decolorization of Orange II. RSM based on Box-Behnken statistical experiment design was applied to analyze the experimental variables. The response surface methodology models were derived based on the results of the pseudo-first-order decolorization rate constant and the response surface plots were developed accordingly. The results indicated the applied current showed a positive effect on the decolorization rate constant of Orange II. The interaction of α-FeOOH dosage and PDS concentration was significant. The ANOVA results confirmed that the proposed models were accurate and reiable for the analysis of the varibles of EC/α-FeOOH/PDS process. The catalystα-FeOOH showed good structural stability and could be reused.(5) Aqueous solutions of Orange II have been degraded effectively in the EC/Fe3O4/PDS process. The decolorization rate was affected by the initial pH of Orange II solution, current density, PDS concentration and Fe3O4 dosage. Orange II can be totally decolorizated in a 60 min reaction when initial Orange II concentration was 25 mg/L, PDS concentration was 10 mM, Fe3O4 dosage was 0.8 g/L, current density was 8.4 mA/cm2 and initial pH was 6.0. Recycle experiments showed Fe3O4 particles were stable and can be reused. XPS spectrum indicated Fe(II) was generated on the surface of Fe3O4 particles after reaction. The main intermediates were separated and identified by GC-MS technique and a plausible degradation pathway of Orange II was proposed

In recent years, the increasing release of trace organic chemicals to the aquatic environment have been problematic to both the ecosystem and the human society. These trace organic chemicals, regarded as emerging contaminants, include different categories of chemicals, which are either deemed to be safe for human consumption or they are naturally occurring compounds. As a newly recognized class of emerging contaminant, artificial sweeteners are proven to be one of the most ubiquitous classes of emerging contaminants in environmental waters. Its transformation to different suite of TPs during water treatment processes generated more toxic influence than the parent compound is problematic. The realization of the widespread of emerging contaminants, together with their ambiguous fate and impact to the environment have led to the development of advanced oxidation processes that can effectively attenuate this wide range of contaminants. In this work, several catalytic advanced oxidation processes were studied. On one hand, it aimed to evaluate their effectiveness on the removal of the artificial sweetener - acesulfame; and on the other hand, to shed lights on the future development of catalytic advanced oxidation processes. In the first part of this thesis, the photo-Fenton treatment was evaluated on its potential to effectively remove acesulfame together with the produced transformation products, and the post-treatment toxicity screening. The photo-Fenton treatment was found to be effective in removing both the parent compound and the transformation products, without leading to an increase in toxicity, which is largely related to the effective removal of the transformation products. In attempt to reduce the reliance on UV irradiation, newly synthesized carbon and nitrogen co-doped TiO2-based photocatalyst was applied to capture the simulated sunlight for the degradation of acesulfame. The heterogenous photocatalytic treatment was found to involve several different oxidative reactive species for both degradation and transformation by using several scavengers to alter the degradation profile. Unexpected transformation product was also formed upon treatment in actual water matrix, suggesting the impact of water constituents to the transformation of emerging contaminants. Toxicity results indicated the inability to achieve detoxification, suggesting that a more effective degradation process was needed. To accelerate the degradation process, and enhance the performance at neutral pH, the use of redox mediators for Fenton/Fenton-like system was evaluated. Developed novel Fenton-like system involving copper(II) as transition metal ion, persulfate as oxidant and mercaptosuccinic acid as redox mediator led to effective removal of different contaminants. Elucidation of the proposed oxidation mechanism suggested the role of each components of the system, and the generation of different reactive species for degradation as indicated by the different acesulfame transformation profile obtained. The implementation of redox mediators to Fenton/Fenton-like system was beneficial and an effective approach. In short, this work presents several kinds of catalytic advanced oxidation process and shed lights on improving the degradation performance with directions for the future development of better and more effective water treatment processes.

This project aims to investigate whether it is possible to detect consentrations down to 0,3 µg/L of oseltamirir in waste water by Quartz Crystal Microbalance. The risks linked to this contaminant could be not only environmental, scientists have found that infuence recistence can propagate due to contaminats of this kind. Cases similar to the bird- and swine-flu could occure if the drug spreads through animals and mutate.   Four systems of different character was synthesised. As a result it was found that MAA functional monomer systems probably was interfering with charges within it’s own nanowires. Reference systems could not detect 0,01 mg/mL and HEMA polymer surfaces was the only reliable system, pH of 5,1. Lowest limit of detection (LOD) was found in Molecular Imprinted Polymer nanowires (MIP Nw) at 0,01 mg/mL and could be scaled down to 0,1 mg/L with increased loop size (injection at 10x that of 0,01 mg/mL at about 500 µL and a halved flow rate.)   An alternative could be nano structuring such as ”polystyrene balls” that possibly could be able to achieve surfaces with even more binding sites needed to detect the lowest limit at 0,3 µg/L.

Faecal contamination in water is detected using appropriate microbial models such as total coliforms, faecal coliforms and E. coli. Βeta-D-Galactosidase (β-GAL) and Beta-D-glucuronidase (β-GUD) are two marker enzymes that are used to test for the presence of total coliforms and E. coli in water samples, respectively. Various assay methods have been developed using chromogenic and fluorogenic substrates. In this study, the chromogenic substrates chlorophenol red β-D-galactopyranoside (CPRG) for β-GAL and p-nitrophenyl-β-D-galactopyranoside (PNPG) for β-GUD were used. Potential problems associated with this approach include interference from other organisms present in the environment (e.g. plants, algae and other bacteria), as well as the presence of certain chemicals, such as phenolic compounds in water. Phenolic compounds are present in the aquatic environment due to their extensive industrial applications. The USA Enviromental Protection Agency (EPA) lists 11 Priority Pollutant Phenols (PPP) due to their high level of toxicity. This study investigated the interfering effects of the eleven PPP found in water on the enzyme activities of both the β-GAL and β-GUD enzyme assays. The presence of these PPP in the β-GAL and β-GUD enzyme assays showed that over and underestimation of activity may occur due to inhibition or activation of these enzymes. Three types of inhibition to enzyme activities were identified from double reciprocal Lineweaver-Burk plots. The inhibition constants (Ki) were determined for all inhibitory phenolic compounds from appropriate secondary plots. Furthermore, this study presented a validated reverse phase high performance liquid chromatography (RP-HPLC) method, developed for the simultaneous detection, separation and determination of all eleven phenolic compounds found in the environment. This method demonstrated good linearity, reproducibility, accuracy and sensitivity. Environmental water samples were collected from rivers, streams, industrial sites and wastewater treatment plant effluent. These samples were extracted and concentrated using a solid phase extraction (SPE) procedure prior to analysis employing the newly developed HPLC method in this study. Seasonal variations on the presence of the PPP in the environment were observed at certain collection sites. The concentrations found were between 0.033 μg/ml for 2,4-dinitrophenol in a running stream to 0.890 mg/ml for pentachlorophenol from an tannery industrial site. These concentrations of phenolic compounds found in these environments were able to interfere with the β-GAL and β-GUD enzyme assays.

Graphitic carbon nitride (g-C3N4) heterojunction composites with the semiconducting metal oxides, CeO2, ZnO and TiO2 are prepared in situ by co-calcination of the precursor materials or by a solvothermal method. The structural, morphological and the optical properties of the prepared materials are studied using various microscopy and spectroscopy techniques. The synthesized composite materials, CeO2/g-C3N4, ZnO/g-C3N4 and TiO2/g-C3N4 are more efficient in the photocatalytic degradation of the water pollutants indigo carmine (IC) and atrazine than the pure metal oxide, g-C3N4, or their physical mixtures. The CeO2/g-C3N4 and ZnO/g-C3N4 composites also exhibit improved degradation efficiencies of atrazine as compared to the individual metal oxide or g-C3N4 materials. The improved photocatalytic activity of the composites are attributed to the effective electron-hole charge separation within composite heterojunction, resulting from the well matched energy levels of the metal oxide and g-C3N4. This strategy could be helpful for the synthesis of other metal oxide and g-C3N4 composites for photocatalytic applications.

This work explores the synthesis and photophysicochemical properties of zinc phthalocyanines when conjugated to cobalt ferrite magnetic nanoparticles. Phthalocyanines with amine and carboxylic acid functional groups were synthesised so as to covalently link them via amide bonds to cobalt ferrite magnetic nanoparticles with carboxylic acid and amine groups, respectively. Spectroscopic and microscopic studies confirmed the formation and purity of the phthalocyanine-cobalt ferrite magnetic nanoparticle conjugates which exhibited enhanced triplet and singlet quantum yields compared to the phthalocyanines alone. The studies showed that the presence of cobalt ferrite nanoparticles significantly lowered fluorescence quantum yields and lifetimes. The conjugates not only showed much higher singlet oxygen quantum yields compared to the phthalocyanines alone but were also attractive because of their magnetic regeneration and hence reusability properties, making them appealing for photocatalytic applications. The photocatalytic ability of some of the phthalocyanines and their conjugates were then tested based on their photooxidation and photoreduction abilities on Methyl Orange and hexavalent chromium, respectively. For catalyst support, some of the zinc phthalocyanines, cobalt ferrite magnetic nanoparticles and their respective conjugates were successfully incorporated into electrospun polystyrene and polyamide-6 fibers. Spectral characteristics of the functionalized electrospun fibers confirmed the incorporation of the photocatalysts and indicated that the phthalocyanines and their respective conjuagates remained intact with their integrity maintained within the polymeric fiber matrices. The photochemical properties of the complexes were equally maintained within the electrospun fibers hence they were applied in the photooxidation of azo dyes using Orange G and Methyl Orange as model organic compounds.

Water authorities are increasingly worried about the occurrence of organic micropollutants (e.g., algal toxins, endocrine disrupting compounds, pesticides, industrial chemicals, taste and odor compounds) in water supplies. Removal of organic micropollutants (OMPs) from water is cost-prohibitive, particularly for small and remote communities. Vacuum-UV/UV process, an incipient catalyst/chemical-free advanced oxidation process (AOP), is potentially a cost-effective solution for removal of harmful micropollutants from water. The main objective of this thesis was to investigate the feasibility of VUV/UV process for the removal of OMPs using a comprehensive computational fluid dynamics (CFD) analyzes. The developed model involved simultaneous resolution of the local transfer equations of momentum, mass, and radiative energy (for UV and VUV radiations), along with a complex kinetic scheme with more than 50 reactions. Given the importance of 185 nm and 254 nm emissions for the accurate modeling of the VUV/UV process, a new experimental method for measuring VUV and UV emissions of the mercury lamps was proposed. To assess the CFD model, VUV-induced degradation of model pollutants (atrazine, p-CBA) in ultrapure water samples was investigated under laminar flow conditions utilizing an axisymmetric laboratory-scale reactor. Afterwards, using an asymmetrical pilot-scale VUV/UV reactor, experimental validation of the CFD model was conducted for simulating the degradation of model pollutants (atrazine, 1,4-dioxane) in synthetic and natural contaminated waters under turbulent flow regime. Comparison of the modeling and experimental data indicated that the developed CFD model was able to predict successfully the degradation rate of target pollutants in the analyzed reactors. In addition, the proposed model showed to predict well the impact of the flow rates, and water matrix (NOM and alkalinity) on target pollutants degradation with less than 3 % average absolute relative deviation (AARD%). Relying on the insights gained by CFD analysis (e.g., knowing the critical role of pollutant mass transfer on the AOP performance of VUV systems), an improved VUV/UV process was developed through retrofitting baffles within the reactor. When compared the pollutant degradation and energy consumption of VUV/UV and H₂O₂/UV processes, superior performance of the improved VUV/UV process was observed.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2008.
Teja, Amyn S., Committee Chair ; Frederick, James, Committee Member ; Wine, Paul H., Committee Member ; Eckert, Charles A., Committee Member ; Nenes, Athanasios, Committee Member.

Thesis (M.S.)--West Virginia University, 2009.
Title from document title page. Document formatted into pages; contains ix, 117 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references.

Philosophiae Doctor - PhD
Organic and inorganic pollutants are two broad classes of pollutants in the environment with their main sources from waste waters that are indiscriminately dumped from chemical related industries. Among the organic pollutants are dyes that come as effluents from the textile industries. Toxic metals are the main inorganic pollutants with their sources from industries such as mining, electroplating, batteries etc. The presence of both classes of pollutants in the aquatic environment poses a serious threat to aquatic organisms and humans who depend on these waters for domestic purpose. Therefore, this research focused on the fabrication of materials and designing of methods for removal of both classes of pollutants from their aqueous solutions.

Urban runoff is generated by precipitation of rain and snowmelt on impervious surfaces.  The increasing demand of urbanization causes contaminants to accumulate on roads,  roofs and pathways. In turn, as runoff wash off these surfaces, contaminants such as heavy metals, particles and organic pollutants end up in the stormwater. Urban stormwater ponds improve water quality of runoff by facilitating contaminants in form of particles. To preserve the function of a stormwater pond accumulated sediment must periodically be removed.Therefore, upland disposal alternatives should be evaluated. This study examined stormwater sediment and outlet stormwater quality in seven and four ponds respectively in the vicinity of Halmstad. 7 heavy metals and 24 organic contaminants were analysed in both sediments and stormwater. Results showed metal and organic contaminant concentrations in stormwater pond discharge and sediment exceeding concentrations reported in guideline values. From the analysed heavy metals, Zn and Pb was considered the most critical contaminants. Heavier organic compounds were more frequently quantified than lighter ones, where 42 % of the analysed organic contaminants were quantified in at least one sample. Variability between inlets and outlets, between ponds and between sampling occasions was observed. The observed variability suggests that the contamination level is influenced by catchment area characteristics and activities. Significant correlation from Spearman’s rank correlation was found between the individual heavy metals (Cu, Cr, Ni, Pb and Zn), which suggest they originate from similar sources

The analysis of organic pollutants in water is traditionally done following EPA procedures which commonly use liquid-liquid extraction. One liter of water is extracted three times with 60 mL of an organic solvent. The extract is concentrated and analyzed by gas chromatography. This procedure is time consuming and can cause losses of semi-volatile components, in addition to requiring a relatively large amount of organic solvent (180 mL). By performing the extraction directly in a GC autosampler vial using one milliliter of contaminated water and one milliliter of organic solvent, then injecting a large volume (~150 mL) of the organic layer taken directly from the vial by an autosampler, the same analysis can be done simpler, quicker, and with much less organic solvent (1 mL).
Master of Science

[EN] Emerging organic pollutants include a wide array of different compounds. The main characteristic of these numerous substances is that they do not need to be persistent in the environment to cause negative effects, since their high transformation and removal rates can be offset by their continuous introduction into the environment. One of the main sources of these contaminants is untreated urban wastewaters and wastewater treatment effluents. Most current wastewater treatment plants are not designed to treat these types of substances, for that reason a high portion of these pollutants can escape and enter to the urban water cycle reaching, therefore, the drinking water supply. The problem is exacerbated by the fact that many of these compounds are non-regulated. For the same reason, although concentrations are generally low (ng/l- µg/l), there are worries about their potential and unknown risks of exposures. In this sense, it is known that emerging organic pollutants can have long-lasting effects on development and reproduction, sometimes even in subsequent generations, via epigenetic mechanisms or by mutagenic effects. For all the above reasons, bioindicators such as fishes can be used as an alternative, at least complementary, to monitor their presence. In this sense, in the present thesis was studied whether zebrafish could be established as a bioindicator to detect the presence of these substances in drinking waters through the study of the effects on development and, especially, on reproduction. To accomplish this objective, four studies were carried out. Firstly, it was compared whether keeping the chorion intact or, on the contrary, permeabilized with pronase with the aim to figure out if the chorion acts as a barrier to emerging pollutants. Results from this study suggest using embryos with the chorion intact from the outset when drinking water from different sources was to be tested. In the second study were defined and narrowed down the most sensitive biological parameters to detect the effects of emerging organic pollutants on the development and, especially, on the zebrafish reproduction. Results showed that the hatching, fertility and underdeveloped rates were the most sensitive parameters. In the third study was analyzed the possible cumulative effect along two generations and/or the possible reversibility of the effects from emerging organic pollutants in zebrafish specimens reared in drinking water. Results showed a non-reversible effect on fertility rate and an alteration of sex ratio towards females in one of the studied water, although in this last case the alteration was reversible. A transgenerational alteration in the germline via epigenetic mechanism from the previous generation is proposed as the most plausible explanation to this effect. Finally, it was developed the fourth study with the aim to discriminate the effects from organic pollutants through three different pathways: male, female or water where the fertilization took place. Results showed a decrease in the fertility rate and in the hatching rate, due to an effect of the water where fertilization took place.The most plausible explanation could be the presence of substances which affect the micropyle and chorion. In addition, it was observed a decrease in the fertility rate due to a female effect, but in this case by an alteration of the oocyte quality. Taking into account the results obtained, it could be stated that the zebrafish is a suitable bioindicator to detect the effects from organic pollutants at very low concentration, when are reared in drinking water throughout their life-cycle.
[ES] Los contaminantes orgánicos emergentes incluyen una amplia gama de compuestos diferentes. La principal característica de estas numerosas sustancias es que no necesitan ser persistentes en el medio para causar efectos negativos, ya que sus altas tasas de transformación y eliminación pueden ser compensadas por su continua introducción en el medio ambiente. Una de las principales fuentes de estos contaminantes son las aguas residuales urbanas no tratadas y los efluentes de tratamiento de aguas residuales. La mayoría de las plantas de aguas residuales actuales no están diseñadas para el tratamiento de este tipo de sustancias, por ello una alta porción de estos contaminantes pueden escapar y entrar al ciclo urbano del agua alcanzando, por lo tanto, el suministro de agua potable. El problema se agrava porque muchos de estos compuestos no están regulados. Por la misma razón, aunque las concentraciones son generalmente bajas (ng/l- µg/l), se desconocen los posibles riesgos a la exposición de estos compuestos. Por otro lado, se sabe que los contaminantes orgánicos emergentes pueden tener efectos a largo plazo sobre el desarrollo y la reproducción, a veces incluso en las generaciones posteriores, a través de mecanismos epigenéticos y/o por efectos mutagénicos. Por todas las razones citadas anteriormente, los bioindicadores como los peces pueden ser usados como una alternativa, al menos complementaria, para controlar su presencia. En este sentido, en la presente tesis se estudió si el pez cebra se podría establecer como bioindicador para detectar la presencia de estas sustancias en aguas potables a través del estudio de los efectos sobre el desarrollo y, en especial, sobre la reproducción. Para lograr este objetivo, se llevaron a cabo cuatro estudios. En primer lugar, se comparó mantener el corion intacto o, por el contrario, permeabilizarlo con pronasa para averiguar si el corion actúa como una barrera a los contaminantes emergentes. Los resultados de este estudio sugieren el uso de embriones con el corion intacto desde el principio, cuando va a ser usada agua potable procedente de diferentes orígenes. En el segundo estudio se definieron y acotaron los parámetros biológicos más sensibles para detectar los efectos de los contaminantes orgánicos emergentes sobre el desarrollo y sobre la reproducción del pez cebra. Los resultados mostraron que los parámetros más sensibles fueron la tasa de eclosión, la tasa de fecundidad y la tasa de especímenes subdesarrollados. En el tercer estudio fue analizado el posible efecto acumulativo a lo largo de dos generaciones y/o la posible reversibilidad de los efectos de los contaminantes orgánicos en especímenes de pez cebra criados en aguas potables. Los resultados mostraron un efecto irreversible en la tasa de fecundidad y una alteración de la proporción sexual hacia hembras en una de las aguas estudiadas, aunque en este último caso la alteración fue reversible. Una alteración transgeneracional en la línea germinal a través de mecanismos epigenéticos de la generación anterior se propone como la explicación más plausible para este efecto. Finalmente, se desarrolló el cuarto estudio con el objetivo de discriminar los efectos de los contaminantes orgánicos a través de tres vías diferentes: macho, hembra o agua donde la fertilización se llevó a cabo. Los resultados mostraron una disminución de la fertilidad y la tasa de eclosión, debido a un efecto del agua donde la fertilización tuvo lugar. La explicación más plausible podría ser la presencia de sustancias que afectan al micropilo y al corion. Además, se observó una disminución en la tasa de fertilidad debido a un efecto hembra, pero en este caso por una alteración de la calidad de los ovocitos. Teniendo en cuenta los resultados obtenidos, se puede afirmar que el pez cebra es un bioindicador adecuado para detectar los efectos de los contaminantes orgánicos en concentraciones muy bajas, cuando
[CAT] Els contaminants orgànics emergents inclouen una àmplia gamma de compostos diferents. La principal característica d'aquestes nombroses substàncies és que no necessiten ser persistents en el medi per causar efectes negatius, ja que les seves altes taxes de transformació i eliminació poden ser compensades per la seva contínua introducció en el medi ambient. Una de les principals fonts d'aquests contaminants són les aigües residuals urbanes no tractades i els efluents de tractament d'aigües residuals. La majoria de les plantes d'aigües residuals actuals no estan dissenyades per al tractament d'aquest tipus de substàncies, per això una alta porció d'aquests contaminants poden escapar i entrar al cicle urbà de l'aigua aconseguint, per tant, el subministrament d'aigua potable. El problema s'agreuja perquè molts d'aquests compostos no estan regulats. Per la mateixa raó, encara que les concentracions són generalment baixes (ng/l- µg/l), es desconeixen els possibles riscos a l'exposició d'aquests compostos. D'altra banda, se sap que els contaminants orgànics emergents poden tenir efectes a llarg termini sobre el desenvolupament i la reproducció, de vegades fins i tot en les generacions posteriors, a través de mecanismes epigenetics i/o per efectes mutagenètics. Per totes estes raons, els bioindicadors com els peixos poden ser usats com una alternativa, almenys complementària, per controlar la seva presència. En aquest sentit, en la present tesi es va estudiar si el peix zebra es podria establir com a bioindicador per detectar la presència d'aquestes substàncies en aigües potables a través de l'estudi dels efectes sobre el desenvolupament i, especialment, sobre la reproducció. Per aconseguir aquest objectiu, es van dur a terme quatre estudis. En primer lloc, es va comparar mantenir el cori intacte o, per contra, permeabilitzar-lo amb pronasa per esbrinar si el cori actua com una barrera als contaminants emergents. Els resultats d'aquest estudi suggereixen l'ús d'embrions amb el cori intacte des del principi, quan va a ser usada aigua potable procedent de diferents orígens. En el segon estudi es van definir i van fitar els paràmetres biològics més sensibles per detectar els efectes dels contaminants orgànics emergents sobre el desenvolupament i sobre la reproducció del peix zebra. Els resultats van mostrar que els paràmetres més sensibles van ser la taxa d'eclosió, la taxa de fecunditat i la taxa d'espècimens subdesenvolupats. En el tercer estudi es va analitzar el possible efecte acumulatiu al llarg de dues generacions i/o la possible reversibilitat dels efectes dels contaminants orgànics emergents en espècimens de peix zebra criats en aigües potables. Els resultats van mostrar un efecte irreversible en la taxa de fecunditat i una alteració de la proporció sexual cap a femelles en una de les aigües estudiades, encara que en aquest últim cas l'alteració va ser reversible. Una alteració transgeneracional en la línia germinal a través de mecanismes epigenètics de la generació anterior es proposa com l'explicació més plausible per a aquest efecte. Finalment, es va desenvolupar el quart estudi amb l'objectiu de discriminar els efectes dels contaminants orgànics a través de tres vies diferents: mascle, femella o aigua on la fertilització es va dur a terme. Els resultats van mostrar una disminució de la fertilitat i la taxa d'eclosió, a causa d'un efecte de l'aigua on la fertilització va tenir lloc. L'explicació més plausible podria ser la presència de substàncies que afecten al "micropilo" i al cori. A més, es va observar una disminució en la taxa de fertilitat a causa d'un efecte femella, però en aquest cas per una alteració de la qualitat dels ovòcits. Tenint en compte els resultats obtinguts, es pot afirmar que el peix zebra és un bioindicador adequat per detectar els efectes dels contaminants orgànics en concentracions molt baixes, quan es crien en l'aigua potable
Martínez Sales, MI. (2016). ZEBRAFISH AS BIOINDICATOR OF EPIGENETIC FACTORS PRESENT IN DRINKING WATER THAT MAY AFFECT DEVELOPMENT AND REPRODUCTIVE FUNCTION [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64081
TESIS