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1
Witt, Bradd. "Century-scale environmental reconstruction by using stable carbon isotopes: just one method from the big bag of tricks." Australian Journal of Botany 50, no. 4 (2002): 441. http://dx.doi.org/10.1071/bt02006.
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The field of 'historical ecology' is coming to maturity at a time when we, in Australia, are reflecting on our relationship with, and place in, the land. After an essentially ahistorical approach to land use we are now attempting to place land management into the context of environmental change since and immediately preceding Western European settlement. This volume reflects an emerging concern that, collectively, non-indigenous Australians have no 'environmental history'. One component of 'living in' rather than 'battling against' the land is developing a sense of our history. Without an oral narrative that is commonly shared, attempts to develop the story of environmental change have to be based on retrospective and reconstructive research. This volume captures part of this movement to develop an environmental narrative and context for our future relationship with the land. There are many methodological approaches to reconstructing a story of the past, from local knowledge and oral history to the 'high-tech' and hard sciences. This paper reviews methods that apply stable carbon isotope techniques to reconstruct environmental change. Although well suited to environmental history, carbon isotope techniques remain under-utilised in the Australian context. Here I review applications to highlight the strengths and limitations of carbon isotope techniques in the reconstruction of century-scale vegetation change. There have been two dominant applications of carbon isotope techniques to environmental reconstruction. These applications fall broadly into either stable carbon isotope analysis of organic matter in soils and sediments, or inferences of environmental states have been drawn from carbon isotope analysis of animal tissues and residues. The main strength of stable carbon isotope techniques is that they can be spatially precise while integrating a range of environmental information into one isotopic signal. This integrative strength is at the same time one of the major limitations of carbon isotope techniques because floristic (taxonomic) resolution is low.
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Magioncalda, Roberto, Christian Dupuis, Dominique Blamart, Muriel Fairon-Demaret, Michel Perreau, Maurice Renard, Janine Riveline, Marc Roche, and Edward Keppens. "L'excursion isotopique du carbone organique (delta 13 C org ) dans les paleoenvironnements continentaux de l'intervalle Paleocene/Eocene de Varangeville (Haute-Normandie)." Bulletin de la Société Géologique de France 172, no. 3 (May 1, 2001): 349–58. http://dx.doi.org/10.2113/172.3.349.
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Abstract The late Palaeocene carbon isotope excursion (C.I.E.) is often regarded as the best means of correlating marine and continental deposits. The few isotopic studies carried out in continental environments were based on pedogenic carbonate [Koch et al., 1992], or on organic matter. Sinha [1997] took up this subject starting from the outcrops on the coast of the English Channel at Varangeville, where marine sequences biostratigraphically constrain the isotopic excursion. His work documents a negative delta 13 C org excursion value approximately -27 per mil PDB. The present work points out that it is necessary to study more complete sections than those studied by Sinha. A section named Phare d'Ailly has been sampled in detail (figs. 1, 2, 3). In this section, for which detailed analysis of sedimentology, palaeontology and organic matter facies establish the continental nature of the palaeoenvironment, isotopic analysis of organic matter reveals a very negative delta 13 C org excursion value approximately -30 per mil PDB. The P/E interval synthesized in figure 2 shows three main groups, the stratigraphy of which is strongly constrained between the calcareous nannofossil Zones NP8 and NP11. The marine Thanetian facies belong to Zones NP8 and NP9. Above, the "Sparnacian" (Mont Bernon Group) is divided into 5 units referred to as SP. Unit SP2 is attributed to the Peckichara disermas Charozone, equivalent to Zone NP9. For unit SP4, an indirect correlation with Zone NP10 may be deduced. The upper part of the Varangeville Formation is known for its nannofossil association attributed to Zone NP11. We may conclude from these observations that the sparnacian sediments are synchronous with NP9-10 Zones and that they are effectively located in the time interval of the delta 13 C excursion. The SP1 and SP2 sediments were analysed for carbonate content, grain size distribution, clay mineralogy and total organic content (T.O.C.), using standard laboratory methods (fig. 3). An optical specification of the organic matter has been obtained from semiquantitative analysis of the organic matter facies. The survey of macro- and microfossils has supplied complementary supports for isotopic analysis (seed, wood and charcoal). The isotopic measurements were carried out on the bulk sediment and on complementary supports with a mass spectrometer in continuous flow delta + (Finnigan Mat). The measurement precision is better than 0.1 per mil and the reproducibility is about 0.15 per mil. Washing residues provide Gasteropoda, Bivalvia, Ostracoda, Characea, as well as fruits and seeds, microcodiums and otolith. All the palaeontological data illustrate a continental biota of a pure lacustrine environment, quiet and shallow, in a hot and humid climate. The organic matter facies analysis confirms the absence of any marine influence and documents a palaeoenvironment of lakes and ponds having an anoxic floor. Thus the carbon of the organic matter is considered to be continental and their isotopic variations linked to those of the atmospheric carbon.
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Hanke, U. M., L. Wacker, N. Haghipour, M. W. I. Schmidt, T. I. Eglinton, and C. P. McIntyre. "Comprehensive radiocarbon analysis of benzene polycarboxylic acids (BPCAs) derived from pyrogenic carbon in environmental samples." Radiocarbon 59, no. 4 (July 17, 2017): 1103–16. http://dx.doi.org/10.1017/rdc.2017.44.
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ABSTRACTCompound-specific radiocarbon analysis (CSRA) of benzene polycarboxylic acids (BPCAs) yields molecular-level, source-specific information necessary to constrain isotopic signatures of pyrogenic carbon. However, the purification of individual BPCAs requires a multistep procedure that typically results in only microgram quantities of the target analyte(s). Such small samples are highly susceptible to contamination by extraneous carbon, which needs to be minimized and carefully accounted for in order to yield accurate results. Here, we undertook comprehensive characterization and quantification of contamination associated with molecular radiocarbon (14C) BPCA analyses through systematic processing of multiple authentic standards with both fossil and modern 14C signatures at various concentrations. Using this approach, we precisely apportion the contribution of extraneous carbon with respect to the four implemented subprocedures. Assuming a constant source and quantity of extraneous carbon we correct and statistically evaluate uncertainties in resulting 14C data. Subsequently, we examine the results of triplicate analyses of reference materials representing four different environmental matrices (sediment, soil, aerosol, riverine natural organic matter) and apportion their BPCA sources in terms of carbon residues derived from biomass or fossil fuel combustion. This comprehensive approach to CSRA facilitates retrieval of robust 14C data, with application in environmental studies of the continuum of pyrogenic carbon.
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Fuller, Mark E., Linnea Heraty, Charles W. Condee, Simon Vainberg, Neil C. Sturchio, J. K. Böhlke, and Paul B. Hatzinger. "Relating Carbon and Nitrogen Isotope Effects to Reaction Mechanisms during Aerobic or Anaerobic Degradation of RDX (Hexahydro-1,3,5-Trinitro-1,3,5-Triazine) by Pure Bacterial Cultures." Applied and Environmental Microbiology 82, no. 11 (March 25, 2016): 3297–309. http://dx.doi.org/10.1128/aem.00073-16.
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ABSTRACTKinetic isotopic fractionation of carbon and nitrogen during RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) biodegradation was investigated with pure bacterial cultures under aerobic and anaerobic conditions. Relatively large bulk enrichments in15N were observed during biodegradation of RDX via anaerobic ring cleavage (ε15N = −12.7‰ ± 0.8‰) and anaerobic nitro reduction (ε15N = −9.9‰ ± 0.7‰), in comparison to smaller effects during biodegradation via aerobic denitration (ε15N = −2.4‰ ± 0.2‰).13C enrichment was negligible during aerobic RDX biodegradation (ε13C = −0.8‰ ± 0.5‰) but larger during anaerobic degradation (ε13C = −4.0‰ ± 0.8‰), with modest variability among genera. Dual-isotope ε13C/ε15N analyses indicated that the three biodegradation pathways could be distinguished isotopically from each other and from abiotic degradation mechanisms. Compared to the initial RDX bulk δ15N value of +9‰, δ15N values of the NO2−released from RDX ranged from −7‰ to +2‰ during aerobic biodegradation and from −42‰ to −24‰ during anaerobic biodegradation. Numerical reaction models indicated that N isotope effects of NO2−production were much larger than, but systematically related to, the bulk RDX N isotope effects with different bacteria. Apparent intrinsic ε15N-NO2−values were consistent with an initial denitration pathway in the aerobic experiments and more complex processes of NO2−formation associated with anaerobic ring cleavage. These results indicate the potential for isotopic analysis of residual RDX for the differentiation of degradation pathways and indicate that further efforts to examine the isotopic composition of potential RDX degradation products (e.g., NOx) in the environment are warranted.IMPORTANCEThis work provides the first systematic evaluation of the isotopic fractionation of carbon and nitrogen in the organic explosive RDX during degradation by different pathways. It also provides data on the isotopic effects observed in the nitrite produced during RDX biodegradation. Both of these results could lead to better understanding of the fate of RDX in the environment and help improve monitoring and remediation technologies.
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Ramnarine, R., C. Wagner-Riddle, K. E. Dunfield, and R. P. Voroney. "Contributions of carbonates to soil CO2 emissions." Canadian Journal of Soil Science 92, no. 4 (May 2012): 599–607. http://dx.doi.org/10.4141/cjss2011-025.
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Ramnarine, R., Wagner-Riddle, C., Dunfield, K. E. and Voroney, R. P. 2012. Contributions of carbonates to soil CO 2 emissions. Can. J. Soil Sci. 92: 599–607. Carbon dioxide (CO2) is released in soil as a by-product of microbial and root respiration, but soil carbonates may also be a source of CO2 emissions in calcareous soils. Global estimates of inorganic carbon range from 700 to 900 Pg as carbonates stored in soils, representing a significant potential source of CO2 to the atmosphere. While previous studies have focused on the total CO2 efflux from the soil, our goal was to identify the various sources and their contribution to total CO2 emissions, by measuring the isotopic signature of the CO2 emitted from the soil. Calcareous Luvisolic silt loam soil samples were obtained from conventional tillage (CT) and no-tillage (NT) plots in southern Ontario, Canada. Soil samples (root- and residue-free) were laboratory-incubated for 14 d and the isotopic signature of the CO2 (δ13CCO2) released was analyzed using isotope ratio mass spectrometry. Isotopic measurement was essential in quantifying the abiotic CO2 production from carbonates, due to the unique δ13C signature of carbonates and soil organic matter. A two-end member mixing model was used to estimate the proportion of CO2 evolved from soil carbonates and soil organic matter decomposition. Analysis of emitted CO2 collected after the 14-d incubation indicate that the proportion of CO2 originating from soil inorganic carbon was 62 to 74% for CT soil samples, and 64 to 80% for NT soil samples. Further work is recommended in the quantification of CO2 emissions from calcareous soils, and to determine the transferability of laboratory results to field studies.
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Barešić, Jadranka, Sanja Faivre, Andreja Sironić, Damir Borković, Ivanka Lovrenčić Mikelić, Russel N. Drysdale, and Ines Krajcar Bronić. "The Potential of Tufa as a Tool for Paleoenvironmental Research—A Study of Tufa from the Zrmanja River Canyon, Croatia." Geosciences 11, no. 9 (September 7, 2021): 376. http://dx.doi.org/10.3390/geosciences11090376.
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Tufa is a fresh-water surface calcium carbonate deposit precipitated at or near ambient temperature, and commonly contains the remains of macro- and microphytes. Many Holocene tufas are found along the Zrmanja River, Dalmatian karst, Croatia. In this work we present radiocarbon dating results of older tufa that was found for the first time at the Zrmanja River near the Village of Sanaderi. Tufa outcrops were observed at different levels, between the river bed and up to 26 m above its present level. Radiocarbon dating of the carbonate fraction revealed ages from modern, at the river bed, up to 40 kBP ~20 m above its present level. These ages fit well with the hypothesis that the Zrmanja River had a previous surface connection with the Krka River, and changed its flow direction toward the Novigrad Sea approximately 40 kBP (Marine Isotope Stage 3). Radiocarbon AMS dating of tufa organic residue yielded a maximum conventional age of 17 kBP for the highest outcrop position indicating probable penetration of younger organic material to hollow tufa structures, as confirmed by radiocarbon analyses of humin extracted from the samples. Stable carbon isotope composition (δ13C) of the carbonate fraction of (−10.4 ± 0.6)‰ and (−9.7 ± 0.8)‰ for the Holocene and the older samples, respectively, indicate the autochthonous origin of the carbonate. The δ13C values of (−30.5 ± 0.3)‰ and (−29.6 ± 0.6)‰ for organic residue, having ages <500 BP and >5000 BP, respectively, suggest a unique carbon source for photosynthesis, mainly atmospheric CO2, with an indication of the Suess effect in δ13C during last centuries. The oxygen isotopic composition (δ18O) agrees well with deposition of tufa samples in two stages, the Holocene (−8.02 ± 0.72‰) and “old” (mainly MIS 3 and the beginning of MIS 2) (−6.89 ± 0.34‰), suggesting a ~4 °C lower temperature in MIS 3 compared to the current one.
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Choy, Kyungcheol, Ben A. Potter, Holly J. McKinney, Joshua D. Reuther, Shiway W. Wang, and Matthew J. Wooller. "Chemical profiling of ancient hearths reveals recurrent salmon use in Ice Age Beringia." Proceedings of the National Academy of Sciences 113, no. 35 (August 30, 2016): 9757–62. http://dx.doi.org/10.1073/pnas.1606219113.
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Current approaches to reconstruct subsistence and dietary trends in ancient hunter-gatherer societies include stable isotope analyses, but these have focused on human remains, cooking pottery, and food residues, which are relatively rare in the archaeological record. In contrast, short-term hearths are more ubiquitous worldwide, and these features can provide valuable evidence for ancient subsistence practices, particularly when faunal remains are not preserved. To test the suitability of hearths for this purpose, we conducted multiple chemical analyses: stable carbon and nitrogen isotope analyses of total organic matter (expressed as δ13C and δ15N values) and compound-specific carbon isotope analyses of individual fatty acids (δ13C16:0 and δ13C18:0) from 17 well-preserved hearths present in three occupations dating between ∼13,200–11,500 calibrated years B.P. at the Upward Sun River (USR) site in central Alaska. We combined δ15N and δ13CFA data in a Bayesian mixing model (stable isotope analysis in R) with concentration dependency to each hearth. Our model values were tested against faunal indices, indicating a strong positive relationship between marine proportional contributions to each hearth and salmon abundance. Results of the models show substantial anadromous salmon use in multiple USR components, indicating recurrent use of the site for salmon processing during the terminal Pleistocene. Our results demonstrate that salmonid and freshwater resources were more important for late Pleistocene hunter-gatherers than previously thought and highlight the potential of chemical profiling of hearth organic residues for providing greater geographic and temporal insights into resource use by prepottery societies.
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Megens, Luc, Johannes Van Der Plicht, and Jan W. De Leeuw. "Molecular, Radioactive and Stable Carbon Isotope Characterization of Estuarine Particulate Organic Matter." Radiocarbon 40, no. 2 (1997): 985–90. http://dx.doi.org/10.1017/s0033822200018956.
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Organic matter in sediments and suspended matter is a complex mixture of constituents with different histories, sources and stabilities. To study these components in a suspended matter sample from the Ems-Dollard Estuary, we used combined molecular analysis with pyrolysis/gas chromatography/mass spectrometry and stable and radioactive carbon isotope analyses of the bulk and separated chemical fractions. Carbohydrates and proteins, ca. 50% of the total organic carbon (TOC), are much younger than the bulk sample and have a somewhat higher δ13C value. Lipids and the final residue are considerably older and have lower δ13C values. The final residue, ca. 17% of the total carbon, consists mainly of aliphatic macromolecules that could be derived from algae or terrestrial plants. The δ13C value points to a marine origin.
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Kayler, Z. E., M. Kaiser, A. Gessler, R. H. Ellerbrock, and M. Sommer. "Application of δ<sup>13</sup>C and δ<sup>15</sup>N isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms." Biogeosciences 8, no. 10 (October 17, 2011): 2895–906. http://dx.doi.org/10.5194/bg-8-2895-2011.
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Abstract. Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. Analysis of δ13C and δ15N isotopic signatures of stabilized OM fractions along with soil mineral characteristics may yield important information about OM-mineral associations and their processing history. We anlayzed the δ13C and δ15N isotopic signatures from two organic matter (OM) fractions along with soil mineral proxies to identify the likely binding mechanisms involved. We analyzed OM fractions hypothesized to contain carbon stabilized through organo-mineral complexes: (1) OM separated chemically with sodium pyrophosphate (OM(PY)) and (2) OM occluded in micro-structures found in the chemical extraction residue (OM(ER)). Because the OM fractions were separated from five different soils with paired forest and arable land use histories, we could address the impact of land use change on carbon binding and processing mechanisms. We used partial least squares regression to analyze patterns in the isotopic signature of OM with established mineral and chemical proxies indicative for certain binding mechanisms. We found different mechanisms predominate in each land use type. For arable soils, the formation of OM(PY)-Ca-mineral associations was identified as an important OM binding mechanism. Therefore, we hypothesize an increased stabilization of microbial processed OM(PY) through Ca2+ interactions. In general, we found the forest soils to contain on average 10% more stabilized carbon relative to total carbon stocks, than the agricultural counter part. In forest soils, we found a positive relationship between isotopic signatures of OM(PY) and the ratio of soil organic carbon content to soil surface area (SOC/SSA). This indicates that the OM(PY) fractions of forest soils represent layers of slower exchange not directly attached to mineral surfaces. From the isotopic composition of the OM(ER) fraction, we conclude that the OM in this fraction from both land use types have undergone a different pathway to stabilization that does not involve microbial processing, which may include OM which is highly protected within soil micro-structures.
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Šoberl, Lucija, Andreja Žibrat Gašparič, Mihael Budja, and Richard P. Evershed. "Early herding practices revealed through organic residue analysis of pottery from the early Neolithic rock shelter of Mala Triglavca, Slovenia." Documenta Praehistorica 35 (December 31, 2008): 253–60. http://dx.doi.org/10.4312/dp.35.19.
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A collection of pottery from the early Neolithic site of Mala Triglavca was analysed with the aim of obtaining insights into vessel use and early animal domestication and husbandry practices in the Adriatic region. Total lipid extracts were submitted to gas chromatography (GC), GC-mass spectrometry (GC-MS) and GC-combustion-isotope ratio MS (GC-C-IRMS) in order to obtain molecular and stable carbon isotope signatures as the basis for determining the nature and origins of the residues. The extracts were dominated by degraded animal fats. The majority (70%) of the total lipid extracts displayed intact triacylglycerol distributions attributable to ruminant adipose and dairy fats, which were subsequently confirmed through C16:0 and C18:0 fatty acid δ13C values.
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Šoberl, Lucija, Milena Horvat, Andreja Žibrat Gašparič, Marko Sraka, Richard Evershed, and Mihael Budja. "Neolithic and Eneolithic activities inferred from organic residue analysis of pottery from Mala Triglavca, Moverna vas and Ajdovska jama, Slovenia." Documenta Praehistorica 41 (December 30, 2014): 149–79. http://dx.doi.org/10.4312/dp.41.9.
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The research discussed in this paper focused on the analysis and identification of organic residues either preserved as visible or absorbed organic remains on Neolithic and Eneolithic pottery from various archaeological and geographical contexts. These are connected with various food preparation strategies and past human activities, i.e. cave burials in Ajdovska jama (food as a grave good/offering), the rock shelter at Mala Triglavca (meat and dairy animal husbandry practices) and Moverna vas, which had a long occupation sequence (complex farming and animal management). The preservation of biomarkers mirrored past human activities and different pottery uses at various types of sites. The carbon stable isotope ratios of primary fatty acids in lipid pottery extracts confirmed the presence of adipose and dairy fats as well as biomarkers of plant fats, beeswax and birch bark tar.
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Horiuchi, Akiko, Yoshiki Miyata, Nobuhiko Kamijo, Lucy Cramp, and Richard P. Evershed. "A Dietary Study of the Kamegaoka Culture Population during the Final Jomon Period, Japan, Using Stable Isotope and Lipid Analyses of Ceramic Residues." Radiocarbon 57, no. 4 (2015): 721–36. http://dx.doi.org/10.2458/azu_rc.57.18455.
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The Jomon culture is an ancient Japanese society that existed during approximately 14,000 to 400 BC and which is characterized by Jomon (cord pattern) pottery. To investigate the paleodiet of the people of northeastern Tohoku in Japan during the Final Jomon period (about 1000–400 BC), we studied three sites in Aomori Prefecture, the center of the Kamegaoka culture. The Fubinashi site is on the coast and was supported by a rich fishing culture. Imazu was a coastal salt-making site. Sugisawa is a mountainous inland site on the banks of a river. We determined the 14C ages of the interior and exterior surfaces of carbonized material on potsherds and compared the data with pottery typology and age to study the marine reservoir effect. We also analyzed the bulk carbon and nitrogen stable isotopes and C:N ratios to determine the presence of aquatic foodstuffs. The organic residues from pottery typology corresponding to the described analyses provided a general perspective of differences in the ancient diets at each site. When we recovered sufficient lipids, we analyzed compound-specific stable isotopes of fatty acids to obtain a multilateral view of those diets. Our findings indicate that the diets of inhabitants of both Fubinashi and Imazu consisted primarily of marine products and some terrestrial foodstuffs, whereas people from Sugisawa processed mainly C3 plants and some terrestrial animals and aquatic commodities.
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Sánchez P., Maureen, Sally P. Horn, and Chad Steven Lane. "Stable carbon and nitrogen isotope ratios of surface food residues in pre-Columbian ceramics from the southern Pacific of Costa Rica as evidence of prehistoric human diets." UNED Research Journal 11, no. 2 (February 26, 2019): 89–97. http://dx.doi.org/10.22458/urj.v11i2.2121.
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Introduction: to understand and interpret the consumption of plants and animals by humans in the past requires the investigation of different lines of evidence. Identifiable macroscopic remains of plants and animals, for example seeds and bones, are frequently found at archaeological sites and provide key data on food resources. Their analysis is complemented by the study of pollen grains or phytoliths of cultivated plants within archaeological horizons or in sediment cores recovered from lakes and wetlands near archaeological sites. Another important source of information on human diets in the past consists of food residues preserved in or on artefacts excavated from archaeological sites. Objective: to examine food residues in archaeological pottery from coastal and interior sites in the southern Pacific region of Costa Rica. Methods: we focus on isotopic analysis of carbonized food residues preserved on the inner surfaces of ceramic pots, plates, and other ceramic pieces from archaeological excavations in the intermediate zone (elevations 500-1500m) and coastal zone of the southern Pacific region of Costa Rica. Isotopic analysis of surface food residues on pottery relies on the fact that stable isotopes of carbon (12C and 13C) and nitrogen (14N and 15N) in foods differ based on the photosynthetic pathway of plants and on trophic level. Results: in our analysis of material from twelve sites we found evidence of diets with high amounts of C4 plants (likely maize), legumes, herbivores, and mixtures, but we did not find robust evidence of food residues with isotopic signatures characteristic of reef animals and mollusks, even though some sites are shell mounds. Conclusion: our research represents one of the first studies of surface food residues from Costa Rican pottery, and indicates the potential for studies of this type to strengthen understanding of indigenous subsistence patterns through time and across Costa Rican archaeological regions.
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Miljević, Nada, and Dušan Golobočanin. "Potential Use of Environmental Isotopes in Pollutant Migration Studies." Archives of Industrial Hygiene and Toxicology 58, no. 2 (June 1, 2007): 251–62. http://dx.doi.org/10.2478/v10004-007-0015-5.
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Potential Use of Environmental Isotopes in Pollutant Migration StudiesThis article presents the use of natural abundance stable isotope (hydrogen, carbon, nitrogen, oxygen, chlorine) analysis data as a tool for providing important information about the origin of contaminants, the contribution of different sources to a multi-source plume, characterisation of their complex transport (rate and mechanisms) and for evaluating the success of contaminated site remediation. Isotopic signatures of contaminants are useful tracers of their sources, while isotopic fractionation can be used to quantitatively assess the progress of an environmental process such as biodegradation. This new isotopic approach is reliable and can offer more information than traditional techniques in pollutant migration studies, particularly after waste disposal. During biological degradation of any organic compound, molecules containing lighter isotopes are degraded, and the portion of heavier isotopes in the substrate is increased, identifying specific microbial roles in biogeochemical cycling. Since isotopic fractionation is proportional to degradation, depending on the type of contamination, a microbial degradation of 50% to 99% of the initial concentration can be quantified using isotope ratio measurements.
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Vimont, Isaac J., Jocelyn C. Turnbull, Vasilii V. Petrenko, Philip F. Place, Colm Sweeney, Natasha Miles, Scott Richardson, Bruce H. Vaughn, and James W. C. White. "An improved estimate for the <i>δ</i><sup>13</sup>C and <i>δ</i><sup>18</sup>O signatures of carbon monoxide produced from atmospheric oxidation of volatile organic compounds." Atmospheric Chemistry and Physics 19, no. 13 (July 5, 2019): 8547–62. http://dx.doi.org/10.5194/acp-19-8547-2019.
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Abstract. Atmospheric carbon monoxide (CO) is a key player in global atmospheric chemistry and a regulated pollutant in urban areas. Oxidation of volatile organic compounds (VOCs) is an important component of the global CO budget and has also been hypothesized to contribute substantially to the summertime urban CO budget. In principle, stable isotopic analysis of CO could constrain the magnitude of this source. However, the isotopic signature of VOC-produced CO has not been well quantified, especially for the oxygen isotopes. We performed measurements of CO stable isotopes on air samples from two sites around Indianapolis, US, over three summers to investigate the isotopic signature of VOC-produced CO. One of the sites is located upwind of the city, allowing us to quantitatively remove the background air signal and isolate the urban CO enhancements. as well as the isotopic signature of these enhancements. In addition, we use measurements of Δ14CO2 in combination with the CO:CO2 emission ratio from fossil fuels to constrain the fossil-fuel-derived CO and thereby isolate the VOC-derived component of the CO enhancement. Combining these measurements and analyses, we are able to determine the carbon and oxygen isotopic signatures of CO derived from VOC oxidation as -32.8‰±0.5‰ and 3.6 ‰±1.2 ‰, respectively. Additionally, we analyzed CO stable isotopes for 1 year at Beech Island, South Carolina, US, a site thought to have large VOC-derived contributions to the summertime CO budget. The Beech Island results are consistent with isotopic signatures of VOC-derived CO determined from the Indianapolis data. This study represents the first direct determination of the isotopic signatures of VOC-derived CO and will allow for improved use of isotopes in constraining the global and regional CO budgets.
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Gu, Binhe, Donald M. Schell, and Vera Alexander. "Stable Carbon and Nitrogen Isotopic Analysis of the Plankton Food Web in a Subarctic Lake." Canadian Journal of Fisheries and Aquatic Sciences 51, no. 6 (June 1, 1994): 1338–44. http://dx.doi.org/10.1139/f94-133.
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Carbon and nitrogen stable isotopes (δ13C and δ15N) were used to track energy flow and nutrient cycling pathways in the plankton food web of a subarctic Alaskan lake. Results indicated that planktonic primary production was the major energy source fueling the zooplankton community. In spring, δ15N of Daphnia was strongly influenced by atmospheric nitrogen derived from a N2-fixing blue-green algal bloom. In winter, δ13C evidence suggested that phytoplankton comprised a small fraction (~15%) of particulate organic matter (POM) in the water column, largely due to low primary productivity. The disparity between δ13C of POM and Daphnia in winter may result from preferential assimilation of isotopically light algal carbon from POM. Nitrogen isotope values showed that Heterocope, a presumed carnivore, probably relied heavily on POM as a nutrient source. In common with some arctic lakes, the δ15N data showed less than three trophic levels in this plankton food web. The energy transfer pathways and trophic levels revealed a simple plankton trophic structure in this subarctic lacustrine system.
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Litvin, Steven Y., and Michael P. Weinstein. "Multivariate analysis of stable-isotope ratios to infer movements and utilization of estuarine organic matter by juvenile weakfish (Cynoscion regalis)." Canadian Journal of Fisheries and Aquatic Sciences 61, no. 10 (October 1, 2004): 1851–61. http://dx.doi.org/10.1139/f04-121.
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Canonical discriminant analysis of the natural carbon, nitrogen, and sulfur stable isotopes in tissues of young weakfish (Cynoscion regalis) captured in Delaware Bay was used to infer movements of juveniles and to estimate the utilization of estuarine organic matter in this marine transient species. Two gradients emerged in the data. The first was associated with contributions from tidal salt marsh macrophytes, Spartina alterniflora in the polyhaline lower Bay and Phragmites australis in the brackish upper Bay. The second was associated with the expected change in phytoplankton carbon-isotope values along the salinity gradient in addition to the availability of macrophyte-derived organic matter within the Bay. The separation of the gradients reflected differences in the relative contribution of phytoplankton to weakfish secondary production in open waters versus marsh habitats. As they grew, discrepancies between the anticipated isotopic signatures of juvenile weakfish collected in a specific habitat and their actual signatures were interpreted as down-bay movements based on known life-history patterns. The size-specific differences in the isotopic signatures of weakfish suggested that stable-isotope data can be used to gauge the relative magnitude of marsh-derived organic matter exported from Delaware Bay via movements of juveniles out of the estuary.
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Currie, L. A., J. E. Dibb, G. A. Klouda, B. A. Benner, J. M. Conny, S. R. Biegalski, D. B. Klinedinst, D. R. Cahoon, and N. C. Hsu. "The Pursuit of Isotopic and Molecular Fire Tracers in the Polar Atmosphere and Cryosphere." Radiocarbon 40, no. 1 (1997): 381–90. http://dx.doi.org/10.1017/s0033822200018269.
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We present an overview of recent multidisciplinary, multi-institutional efforts to identify and date major sources of combustion aerosol in the current and paleoatmospheres. The work was stimulated, in part, by an atmospheric particle “sample of opportunity” collected at Summit, Greenland in August 1994, that bore the 14C imprint of biomass burning. During the summer field seasons of 1995 and 1996, we collected air filter, surface snow and snowpit samples to investigate chemical and isotopic evidence of combustion particles that had been transported from distant fires. Among the chemical tracers employed for source identification are organic acids, potassium and ammonium ions, and elemental and organic components of carbonaceous particles. Ion chromatography, performed by members of the Climate Change Research Center (University of New Hampshire), has been especially valuable in indicating periods at Summit that were likely to have been affected by the long range transport of biomass burning aerosol. Univariate and multivariate patterns of the ion concentrations in the snow and ice pinpointed surface and snowpit samples for the direct analysis of particulate (soot) carbon and carbon isotopes. The research at NIST is focusing on graphitic and polycyclic aromatic carbon, which serve as almost certain indicators of fire, and measurements of carbon isotopes, especially 14C, to distinguish fossil and biomass combustion sources.Complementing the chemical and isotopic record, are direct “visual” (satellite imagery) records and less direct backtrajectory records, to indicate geographic source regions and transport paths. In this paper we illustrate the unique way in which the synthesis of the chemical, isotopic, satellite and trajectory data enhances our ability to develop the recent history of the formation and transport of soot deposited in the polar snow and ice.
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Jessberger, Elmar K., and Jochen Kissel. "Chemical Properties of Cometary Dust and A Note on Carbon Isotopes." International Astronomical Union Colloquium 116, no. 2 (1991): 1075–92. http://dx.doi.org/10.1017/s0252921100012823.
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AbstractOn board the space probes Giotto and VEGAs and 2, which were sent through the coma of comet Halley, were the mass spectrometers PIA and PUMAs 1 and 2 for the in situ analysis of cometary dust. This paper summarizes the results obtained up to now, about four years after the flybys. It is sought to make the reader aware of the significance, but also of the limitations, of these unprecedented data gathered within a few hundred seconds with an innovative instrument about 1.5 x 108 km away from Earth. The first part of this paper shows how the bulk properties of the dust are derived—the main constituents CHON and silicates, the core-mantle structure, the molecular composition of the organic component, the average composition of the dust and of the whole comet, and the gas/dust ratio. The second part reviews what can safely be said about the properties of the individual grains—their similarity to a certain class of interplanetary dust particles and their distinction from others, and their density and masses. The final part of this paper shows that some cometary grains contain isotopically ultra-light carbon (12C/13C up to 5000), a finding that is significantly substantiated by reports of similar carbon isotopic composition in meteoritic graphite.
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Rustiah, Wa Ode, Alfian Noor, Maming, and Muhammad Lukman. "ANALYSIS OF THE SEASONAL IMPACT ON ISOTOPIC BASELINES OF DISSOLVED INORGANIC CARBON (DIC) IN COASTAL WATERS SPERMONDE, SOUTH SULAWESI." Jurnal Ilmu dan Teknologi Kelautan Tropis 11, no. 1 (April 1, 2019): 141–49. http://dx.doi.org/10.29244/jitkt.v11i1.24778.
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Stable carbon isotopes have been commonly used as indicators for assessing environmental changes in aquatic ecosystems. They can be used to study the dynamics of organic matter as for understanding the overall functioning of the ecosystem, the connectivity of estuaries with terrestrial and marine coastal habitats. The objective of this study is determining the seasonal natural effects over isotopic (13C/12C) baselines in monitoring CO2 storage in dissolved inorganic materials in Spermonde waters on the west coast of South Sulawesi to some outermost island. The results show that the stable carbon isotopic of DIC (d13C-DIC) in the wet season varied between -5.36 ‰ and -7.74 ‰. These value are higher than on dry season (-4.34 ‰ to -6.82 ‰). Likewise, DIC concentration in the rainy season ranged between 9.5 mg C/L and 11.7 mg C/L, while in the dry season it varied from 8.5 mg C/L to 9.3 mg C/L. The d13C-DIC and DIC concentrations decreased towards offshore, up to some of the outer islands. Increasing in the d13C-DIC in Spermonde waters indicate that the DIC is most likely enriched by atmospheric CO2(g), which is outnumbered those of aquatic photosynthesis. This study shows that different levels and composition of d13C-DIC stretch along different rivers are attributable to the varying landscapes and quality of organic matters.
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Watson, Elizabeth Burke, Alejandro Hinojosa-Corona, Johannes R. Krause, Juan Carlos Herguera, Julianna McDonnell, Karen Raquel Villegas Villegas Manríquez, Michelle E. Gannon, and Andrew B. Gray. "Lagoon Biogeochemical Processing is Reflected in Spatial Patterns of Sediment Stable Isotopic Ratios." Journal of Marine Science and Engineering 8, no. 11 (November 3, 2020): 874. http://dx.doi.org/10.3390/jmse8110874.
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The spatial analysis of biota, particulate organic matter, and sediments for stable isotopes of carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) have proved useful for identifying patterns in productivity, nutrient pollution, and relationships between biological and physiochemical variables at the local and global scales. Yet such approaches are rarely applied to studies of lagoon or estuarine metabolism. Focusing on Bahía San Quintín, a heterotrophic seagrass-dominated lagoon on the Pacific coast of Baja California, México, we report on spatial patterns in surficial sediment CNS stable isotopic ratios as tracers of lagoon biogeochemical function. Stable nitrogen isotopes highlighted potential spatial variability in the balance between denitrification and nitrogen-fixation within the lagoon and identified an association between elevated δ15N levels and oyster culture, suggesting that oyster presence may be enhancing N2 production. Spatial patterns in δ34S covaried with sediment particle size, underlining the importance of sediment texture in determining the depth of sub-oxic-anoxic redox zones. Sediment carbon stable isotope ratios highlighted the lack of incorporation of seagrass carbon into seagrass meadow sediments, thus emphasizing the importance of phytoplankton or microphytobenthos for carbon accumulation in seagrass meadows. This report highlights the value of sediment isotopic values in corroborating spatial patterns in estuarine metabolism or macronutrient processing identified from chamber or flux-based studies. Stable isotope mapping can provide a useful addition to assessment of estuarine metabolism, or act as a stand-alone tool for generating hypotheses, identifying the influence of spatial gradients, and/or suggesting prime locations for investigation of microbial abundance or function.
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Golubkov, Mikhail S., Vera N. Nikulina, Alexei V. Tiunov, and Sergey M. Golubkov. "Stable C and N Isotope Composition of Suspended Particulate Organic Matter in the Neva Estuary: The Role of Abiotic Factors, Productivity, and Phytoplankton Taxonomic Composition." Journal of Marine Science and Engineering 8, no. 12 (November 24, 2020): 959. http://dx.doi.org/10.3390/jmse8120959.
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Knowledge of carbon and nitrogen isotopic ratios in organic matter and their changes is important when studying nutrient cycles in aquatic ecosystems. Relationships between δ13C and δ15N values of suspended particulate organic matter (POM), water temperature, salinity, pH, redox potential, chlorophyll a concentration, primary production, and biomasses of different taxonomic groups of phytoplankton in the Neva Estuary were statistically analyzed. We tested the hypothesis that the studied physicochemical and biogeochemical characteristics, as well as the species composition of phytoplankton and its productivity, can be significant predictors of changes in the isotopic ratios of suspended particulate organic matter in estuaries. In the Neva Estuary, δ13CPOM (−16.8–−27.6‰) and δ15NPOM (2.3–7.3‰) changed synchronously. Statistical analysis showed that for both isotopes, the photosynthetic activity and taxonomic composition of phytoplankton are important. For 13CPOM, the second most important factor was water salinity, which was apparently associated with the transition of algae from CO2 to HCO3 consumption during photosynthesis in estuarine waters. For 15NPOM changes, the most important abiotic factor was pH. The study showed that the dependences of POM isotopic ratios on environmental variables obtained for continental and oceanic waters are also valid in transitional zones such as the Neva Estuary.
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Niu, Yong, Hui Yu, Yuan Niu, Xia Jiang, Xiaochun Guo, Yong Pang, and Xiangyang Xu. "Isotopic fractionation of particulate organic matter and its biogeochemical implication in the littoral zone of Lake Taihu, China." Water Science and Technology 76, no. 10 (August 1, 2017): 2690–97. http://dx.doi.org/10.2166/wst.2017.439.
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Abstract Signatures of stable isotope ratios have previously been used to trace the source and transport of particulate organic matter (POM) in freshwater and marine ecosystems. In this study, water columns were collected at 22 sites in the littoral zone of Lake Taihu in 2014 to investigate the distribution and concentration of nutrients and the stable isotope signatures of POM, and their potential interrelation. Generally, mean concentration of nitrogen forms (NH4+-N) showed substantial variation, probably because they had received large amounts of wastewater from various local industrial enterprises. Source analysis by stable carbon and nitrogen isotopic ratios showed that the main POM sources were phytoplankton. Contrasting correlations were obtained between δ15N and N concentrations in effluent river mouths when compared with influent river mouths. In effluent river mouths, there was a significant positive correlation between δ15N and nitrogen concentration (total nitrogen and ammonia-nitrogen), in contrast with the negative correlation in influent river mouths. According to these results, more factors should be taken into consideration when stable carbon and nitrogen isotopes of POM are used to assess the feeding relationship between consumers and prey, as well as the energy flow pathways that support the lake pelagic food webs.
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Krasnova, Elizaveta A., Anna Yu Yurchenko, Anton G. Kalmykov, and Maria M. Fomina. "Isotopic-geochemical peculiarities of distribution of gas hydrocarbons in the Bazhenov formation section (South part of the Western Siberia)." Georesursy 21, no. 2 (May 2019): 153–58. http://dx.doi.org/10.18599/grs.2019.2.153-158.
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In this work we describe the distribution of stable carbon isotopes in hydrocarbon gases from four wells located in the southern and central parts of the Western Siberia. The main goal was to understand the influence of the lithological composition and geological settings on isotopic composition of gases and their formation. Two genetically different groups of hydrocarbon gases were identified based on the author’s research, as well as analysis of archival and literature materials on the isotope composition of hydrocarbons. We estimated the close relationship between the main factors of the migration, degree of metamorphism of organic matter and the isotope composition of hydrocarbon gases produced by the Bazhenov formation.
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Nadeu, E., A. A. Berhe, J. de Vente, and C. Boix-Fayos. "Erosion, deposition and replacement of soil organic carbon in Mediterranean catchments: a geomorphological, isotopic and land use change approach." Biogeosciences 9, no. 3 (March 27, 2012): 1099–111. http://dx.doi.org/10.5194/bg-9-1099-2012.
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Abstract. Determination of whether soil erosion can constitute a net terrestrial carbon dioxide (CO2) sink continues to suffer from lack of sufficient focused studies and field data. Two of the major gaps in our understanding of the erosion induced terrestrial carbon sink issue include rate of eroded soil organic carbon replacement by production of new photosynthate and stability of eroded organic carbon (OC) post deposition. Here we examined the effect of erosion processes and land use change on the stock, type, and stability of OC in two medium-sized subcatchments (18 and 50 ha in size) in SE Spain. We analysed soil samples from drainage areas and depositional settings for stock and isotopic composition of OC (14C and 13C), and particle size distribution. In addition, we conducted land use change analysis for the period 1956–2008 and a geomorphological survey of the current erosion processes taking place in the slope-streambed connections. Our findings demonstrate that land use change influenced the dominating erosion processes and, thus, the source of eroding sediments. Carbon isotopes used as tracers revealed that in one of the subcatchments the deposited sediments were derived from deep soil (average Δ14C of −271.5 ‰) through non-selective erosion processes and channel incision. In the other subcatchment, topsoil material was predominantly eroded and the average Δ14C in sediments was −64.2 ‰. Replacement of eroded soil OC was taking place in the analysed soil profiles in the slopes suggesting that erosion processes do not necessarily provoke a decrease in soil OC stock over time.
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Nadeu, E., A. A. Berhe, J. de Vente, and C. Boix-Fayos. "Erosion, deposition and replacement of soil organic carbon in Mediterranean catchments: a geomorphological, isotopic and land use change approach." Biogeosciences Discussions 8, no. 4 (August 18, 2011): 8351–82. http://dx.doi.org/10.5194/bgd-8-8351-2011.
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Abstract. The assessment of the net effect of soil erosion on the global carbon budget is still incomplete because of lack of enough focused studies and field data. Two of the major gaps on our understanding of the erosion induced terrestrial carbon sink issue include rate of eroded soil organic carbon (OC) replacement by production of new photosynthate and stability of eroded OC post deposition. Here we examine the effect of erosion processes and land use change on the stock, type and stability of OC in two medium-sized subcatchments (18 and 50 ha in size) in SE Spain. We analysed soil samples from drainage areas and depositional settings for stock and isotopic composition of OC (14C and 13C) and particle size distribution. In addition, we conducted land use change analysis for the period 1956–2008 and a geomorphological survey of the current erosion processes taking place in the slope-streambed connections. Our findings demonstrate how land use change influenced the dominating erosion processes and, thus, the source of eroding sediments. Carbon isotopes used as tracers revealed that in one of the subcatchments the deposited sediments derived from deep soil (average Δ14C of −271.5 ‰) through non-selective erosion processes. In the other subcatchment, topsoil material was predominantly eroded and the average Δ14C in sediments was −64.2 ‰. Replacement of eroded soil OC was positive (4 and 11 times-fold losses by erosion) for the analyzed soil profiles in the slopes suggesting that erosion processes do not necessarily provoke a decrease in soil OC stock.
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Schmittner, A., N. Gruber, A. C. Mix, R. M. Key, A. Tagliabue, and T. K. Westberry. "Biology and air–sea gas exchange controls on the distribution of carbon isotope ratios (<i>δ</i><sup>13</sup>C) in the ocean." Biogeosciences Discussions 10, no. 5 (May 21, 2013): 8415–66. http://dx.doi.org/10.5194/bgd-10-8415-2013.
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Abstract. Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate the processes that control the distribution of δ13C in the contemporary and preindustrial ocean. Biological fractionation dominates the distribution of δ13CDIC of dissolved inorganic carbon (DIC) due to the sinking of isotopically light δ13C organic matter from the surface into the interior ocean. This process leads to low δ13CDIC values at dephs and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air–sea gas exchange provides an important secondary influence due to two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature dependent fractionation tends to increase (decrease) δ13CDIC values of colder (warmer) water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, air-sea gas exchange is slow, so biological effect dominate spatial δ13CDIC gradients both in the interior and at the surface, in constrast to conclusions from some previous studies. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed (δ13Cpre) and remineralized (δ13Crem) contributions as well as the effects of biology (Δδ13Cbio) and air–sea gas exchange (δ13C*). The model reproduces major features of the observed large-scale distribution of δ13CDIC, δ13Cpre, δ13Crem, δ13C*, and Δδ13Cbio. Residual misfits are documented and analyzed. Simulated surface and subsurface δ13CDIC are influenced by details of the ecosystem model formulation. For example, inclusion of a simple parameterization of iron limitation of phytoplankton growth rates and temperature-dependent zooplankton grazing rates improves the agreement with δ13CDIC observations and satellite estimates of phytoplankton growth rates and biomass, suggesting that δ13C can also be a useful test of ecosystem models.
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Cawley, Kaelin M., Yan Ding, James Fourqurean, and Rudolf Jaffé. "Characterising the sources and fate of dissolved organic matter in Shark Bay, Australia: a preliminary study using optical properties and stable carbon isotopes." Marine and Freshwater Research 63, no. 11 (2012): 1098. http://dx.doi.org/10.1071/mf12028.
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Low latitude, seagrass-dominated coastal bays, such as Shark Bay, Australia, are potential sources of chromophoric dissolved organic matter (CDOM) to coastal regions. Dissolved organic matter (DOM) is known to influence aquatic nutrient dynamics, microbial community structure, and depth of light penetration in estuarine systems. Shark Bay is a sub-tropical ecosystem with limited freshwater inputs and restricted tidal flushing. As such, much of the DOM is expected to be seagrass-derived. However, combining excitation/emission fluorescence spectroscopy and parallel factor analysis (EEM-PARFAC) with 13C stable isotope analysis of DOM, we found evidence for DOM inputs from terrestrial (riverine and possibly groundwater), autochthonous plankton, macroalgae, and seagrass sources. Isotopic analysis of 13C in DOM supports the idea that seagrass inputs contribute substantially to the DOM pool in Shark Bay, whereas, EEM-PARAFAC data suggests that much of this input is derived from decomposing seagrass detritus and to a lesser extent due to exudation during primary production. We also report increases in DOM concentrations and changes in DOM characteristics with increasing salinity in surface water samples, indicating that evaporation is an important control on DOM concentration and photo-degradation may play a critical role in transforming DOM within the system.
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Elshayeb, Monalisa, Michael D. MacKinnon, D. George Dixon, and Michael Power. "The Use of Carbon and Nitrogen Stable Isotope Analysis to Characterize Food Web Changes in Aquatic Systems for Reclamation of Oil Sands Process-Affected Materials." Water Quality Research Journal 44, no. 4 (November 1, 2009): 313–22. http://dx.doi.org/10.2166/wqrj.2009.032.
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Abstract One strategy for reclamation of oil sands leases in northern Alberta is the construction of lakes and wetlands by capping oil sands process-affected material (OSPM) with water. To assess this approach, experimental sites containing a range of OSPM have been constructed to monitor the evolution of the resulting aquatic habitats. Stable isotopes of carbon and nitrogen were used to assess the effects of OSPM on aquatic food webs. Carbon and nitrogen isotopic signatures of sediment, dissolved inorganic and organic carbon, particulate organic matter, periphyton, plants, plankton, aquatic invertebrates, and fish were used to assess differences related to the naphthenic acid (NA) concentration in OSPM and reference sites. NAs are a principal contaminant of concern in OSPM. Sites were grouped into low (0 to 4 mg/L), medium (4 to 15 mg/L), and high (>15 mg/L) NA concentrations. There were no significant differences in food web area or length among the three NA groupings. In most cases, carbon isotope analyses of samples from low, medium, and high NA concentration sites were not significantly different, suggesting that OSPM is not a significant contributor to food web carbon sources. Significant differences were found in nitrogen isotope signatures between low, medium, and high NA sites. Ammonia from OSPM is suggested as the main contributor to δ15N enrichment.
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Grocholska, Paulina, and Remigiusz Bąchor. "Trends in the Hydrogen−Deuterium Exchange at the Carbon Centers. Preparation of Internal Standards for Quantitative Analysis by LC-MS." Molecules 26, no. 10 (May 18, 2021): 2989. http://dx.doi.org/10.3390/molecules26102989.
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The application of internal standards in quantitative and qualitative bioanalysis is a commonly used procedure. They are usually isotopically labeled analogs of the analyte, used in quantitative LC-MS analysis. Usually, 2H, 13C, 15N and 18O isotopes are used. The synthesis of deuterated isotopologues is relatively inexpensive, however, due to the isotopic effect of deuterium and the lack of isotopologue co-elution, usually they are not considered as good internal standards for LC-MS quantification. On the other hand, the preparation of 13C, 15N and 18O containing standards of drugs and their metabolites requires a complicated multistep de novo synthesis, starting from the isotopically labeled substrates, which are usually expensive. Therefore, there is a strong need for the development of low-cost methods for isotope-labeled standard preparations for quantitative analysis by LC-MS. The presented review concentrates on the preparation of deuterium-labeled standards by hydrogen−deuterium exchange reactions at the carbon centers. Recent advances in the development of the methods of isotopologues preparation and their application in quantitative analysis by LC-MS are evaluated.
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Schmittner, A., N. Gruber, A. C. Mix, R. M. Key, A. Tagliabue, and T. K. Westberry. "Biology and air–sea gas exchange controls on the distribution of carbon isotope ratios (δ<sup>13</sup>C) in the ocean." Biogeosciences 10, no. 9 (September 4, 2013): 5793–816. http://dx.doi.org/10.5194/bg-10-5793-2013.
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Abstract. Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate processes that control the distribution of δ13C of dissolved inorganic carbon (DIC) in the contemporary and preindustrial ocean. Biological fractionation and the sinking of isotopically light δ13C organic matter from the surface into the interior ocean leads to low δ13CDIC values at depths and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air–sea gas exchange has two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature-dependent fractionation tends to increase (decrease) δ13CDIC values of colder (warmer) water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, since air–sea gas exchange is slow in the modern ocean, the biological effect dominates spatial δ13CDIC gradients both in the interior and at the surface, in contrast to conclusions from some previous studies. Calcium carbonate cycling, pH dependency of fractionation during air–sea gas exchange, and kinetic fractionation have minor effects on δ13CDIC. Accumulation of isotopically light carbon from anthropogenic fossil fuel burning has decreased the spatial variability of surface and deep δ13CDIC since the industrial revolution in our model simulations. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed and remineralized contributions as well as the effects of biology and air–sea gas exchange. The model reproduces major features of the observed large-scale distribution of δ13CDIC as well as the individual contributions and effects. Residual misfits are documented and analyzed. Simulated surface and subsurface δ13CDIC are influenced by details of the ecosystem model formulation. For example, inclusion of a simple parameterization of iron limitation of phytoplankton growth rates and temperature-dependent zooplankton grazing rates improves the agreement with δ13CDIC observations and satellite estimates of phytoplankton growth rates and biomass, suggesting that δ13C can also be a useful test of ecosystem models.
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de Lecea, Ander M., Rachel Cooper, and Albertus J. Smit. "Identifying the drivers of the pelagic ecosystem of an oligotrophic bight (KwaZulu–Natal, South Africa) using stable isotopes (δ13C, δ15N) and C : N ratio analysis." Marine and Freshwater Research 67, no. 11 (2016): 1750. http://dx.doi.org/10.1071/mf15256.
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The international literature highlights the importance of understanding the role and fate of terrestrial organic matter (OM) in the marine system, yet little is known about this on the oligotrophic east coast of South Africa. Within the Bight, three important processes make OM biologically available: (1) a topographically induced upwelling cell (north), (2) a Cyclonic Eddy (south), and (3) riverine input. We hypothesise that: (i) these OM sources differ substantially in their isotope ratios, and (ii) zooplankton at the inshore region has an isotope signature linked to localised fluvial fluxes. Particulate OM samples were collected at five locations along the Bight and in three main estuaries during austral summer and winter seasons in 2010 and subjected to isotopic and mixing model analysis. Riverine input played an important role in this ecosystem inshore during the wet season. Only marine OM played a role as a biological driver offshore and at all sites during the dry season. Although there were indications that the upwelling cell did occur, it was not confirmed as active in either season. The current study provides valuable insights into the Bight's biological functioning and principle insights into the fate of terrestrial organic carbon on the east coast of southern Africa.
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Bieleń, Wojciech, and Marek Janiga. "Spektrometria masowa i analiza izotopowa biomarkerów frakcji nasyconej." Nafta-Gaz 77, no. 8 (August 2021): 512–28. http://dx.doi.org/10.18668/ng.2021.08.02.
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GC-IRMS analysis extends and confirms (or not) the interpretation based on the results of GC-MS analyses. For example, it is very useful in determining the sedimentation environment of organic matter. GC-MS analysis of biomarkers and the results are reliable, but only GC-IRMS studies can confirm it. In this study, the origin of BNH (28,30-bisnorhopane from chemoautotrophic bacteria) and origin of higher carotenoids and their derivatives from Chlorobiaceae or Chromotiaceae bacteria were confirmed through isotopic analyzes. Biomarkers were analyzed using the GC-IRMS and EA-IRMS apparatus. The obtained chromatograms from the IRMS analyses were compared with the archival GC-MS analyses for the same samples in order to identify individual chemical compounds. In addition to the existing methodology of sample preparation for analyses, a non-standard method was also used, consisting in the separation of n-alkanes from branched hydrocarbons. The repeatability of the method was determined on the GC-IRMS and the values of δ13C for selected biomarkers from the saturated fraction were determined. It was found that samples with low biomarker content are not suitable for analysis. On the other hand, too high concentration of the analyte causes an increase of the chromatogram baseline and worse separation of the peaks, which is also a problem. For the crude oils the δ13C values were initially determined for the biomarkers of the saturated fraction from the hopanes group: bisnorhopane (BNH), oleanane, C29 norhopane, C30 hopane, moretane and the C31-C35 homohopane series. Relatively small differences in δ13C values were found between BNH/hopanes and BNH/crude oils, which suggests the same source of origin for all biomarkers (including BNH). Determining biomarkers in the aromatic fraction using the GC-IRMS method was not successful. In the future, a special methodology for preparing samples for carbon isotopic analyses of aromatic fraction will be required.
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Jeffreys, R. M., E. H. Fisher, A. J. Gooday, K. E. Larkin, G. A. Wolff, and D. S. M. Billett. "The trophic and metabolic pathways of foraminifera in the Arabian Sea: evidence from cellular stable isotopes." Biogeosciences Discussions 11, no. 12 (December 20, 2014): 18145–88. http://dx.doi.org/10.5194/bgd-11-18145-2014.
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Abstract. The Arabian Sea is a region of elevated productivity with the highest globally recorded fluxes of particulate organic matter (POM) to the deep ocean, providing an abundant food source for fauna at the seafloor. However, benthic communities are also strongly influenced by an intense oxygen minimum zone (OMZ), which impinges on the continental slope at bathyal depths. We compared the trophic ecology of foraminifera on the Oman and Pakistan margins of the Arabian Sea (140–3185 m water depth). Organic carbon concentrations of surficial sediments were higher on the Oman margin (3.32 ± 1.4%) compared to the Pakistan margin (2.45 ± 1.1%) and sedimentary organic matter (SOM) quality estimated from the Hydrogen Index was also higher on the Oman margin (300–400 mg HC (mg TOC)−1) compared to the Pakistan margin (<250 mg HC (mg TOC)−1). δ13C and δ15N values of sediments were similar on both margins (−20 and 8‰, respectively). Stable isotope analysis (SIA) showed that foraminiferal cells had a wide range of δ13C values (−25.5 to −11.5‰), implying that they utilise multiple food sources; indeed δ13C values varied between depths, foraminiferal types and between the two margins. Foraminifera had broad ranges in δ15N values (−7.8 to 27.3‰). The enriched values suggest that some species may store nitrate to utilise in respiration; this was most notable on the Pakistan margin. Depleted foraminiferal δ15N values were identified on both margins, particularly the Oman margin, and may reflect feeding on chemosynthetic bacteria. We suggest that differences in productivity regimes between the two margins may be responsible for the differences observed in foraminiferal isotopic composition. In addition, at the time of sampling, whole jellyfish carcasses (Crambionella orsini) and a carpet of jelly detritus were observed across the Oman margin transect. Associated chemosynthetic bacteria may have provided an organic-rich food source for foraminifera at these sites. Our data suggest that foraminifera in OMZ settings can utilise a variety of food sources and metabolic pathways to meet their energetic demands.
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Jeffreys, R. M., E. H. Fisher, A. J. Gooday, K. E. Larkin, D. S. M. Billett, and G. A. Wolff. "The trophic and metabolic pathways of foraminifera in the Arabian Sea: evidence from cellular stable isotopes." Biogeosciences 12, no. 6 (March 18, 2015): 1781–97. http://dx.doi.org/10.5194/bg-12-1781-2015.
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Abstract. The Arabian Sea is a region of elevated productivity with the highest globally recorded fluxes of particulate organic matter (POM) to the deep ocean, providing an abundant food source for fauna at the seafloor. However, benthic communities are also strongly influenced by an intense oxygen minimum zone (OMZ), which impinges on the continental slope from 100 to 1000 m water depth. We compared the trophic ecology of foraminifera on the Oman and Pakistan margins of the Arabian Sea (140–3185 m water depth). These two margins are contrasting both in terms of the abundance of sedimentary organic matter and the intensity of the OMZ. Organic carbon concentrations of surficial sediments were higher on the Oman margin (3.32 ± 1.4%) compared to the Pakistan margin (2.45 ± 1.1%) and sedimentary organic matter (SOM) quality estimated from the Hydrogen Index was also higher on the Oman margin (300–400 mg HC mg TOC−1) compared to the Pakistan margin (< 250 mg HC mg TOC−1). The δ13C and δ15N values of sediments were similar on both margins (−20 and 8‰, respectively). Stable isotope analysis (SIA) showed that foraminiferal cells had a wide range of δ13C values (−25.5 to −11.5‰), implying that they utilise multiple food sources; indeed δ13C values varied between depths, foraminiferal types and between the two margins. Foraminifera had broad ranges in δ15N values (−7.8 to 27.3‰). The enriched values suggest that some species may store nitrate to utilise in respiration; this was most notable on the Pakistan margin. Depleted foraminiferal δ15N values, particularly at the Oman margin, may reflect feeding on chemosynthetic bacteria. We suggest that differences in productivity regimes may be responsible for the differences observed in foraminiferal isotopic composition. In addition, at the time of sampling, whole jellyfish carcasses (Crambionella orsini) and a carpet of jelly detritus were observed across the Oman margin transect. Associated chemosynthetic bacteria may have provided an organic-rich food source for foraminifera at these sites. Our data suggest that foraminifera in OMZ settings can utilise a variety of food sources and metabolic pathways to meet their energetic demands.
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Iverach, Charlotte P., Sabrina Beckmann, Dioni I. Cendón, Mike Manefield, and Bryce F. J. Kelly. "Biogeochemical constraints on the origin of methane in an alluvial aquifer: evidence for the upward migration of methane from underlying coal measures." Biogeosciences 14, no. 1 (January 17, 2017): 215–28. http://dx.doi.org/10.5194/bg-14-215-2017.
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Abstract. Geochemical and microbiological indicators of methane (CH4) production, oxidation and migration processes in groundwater are important to understand when attributing sources of gas. The processes controlling the natural occurrence of CH4 in groundwater must be understood, especially when considering the potential impacts of the global expansion of coal seam gas (CSG) production on groundwater quality and quantity. We use geochemical and microbiological data, along with measurements of CH4 isotopic composition (δ13C-CH4), to determine the processes acting upon CH4 in a freshwater alluvial aquifer that directly overlies coal measures targeted for CSG production in Australia. Measurements of CH4 indicate that there is biogenic CH4 in the aquifer; however, microbial data indicate that there are no methanogenic archaea in the groundwater. In addition, geochemical data, particularly the isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC), as well as the concentration of SO42−, indicate limited potential for methanogenesis in situ. Microbial community analysis also shows that aerobic oxidation of CH4 occurs in the alluvial aquifer. The combination of microbiological and geochemical indicators suggests that the most likely source of CH4, where it was present in the freshwater aquifer, is the upward migration of CH4 from the underlying coal measures.
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Macko, Stephen A., Michael H. Engel, Vladimir Andrusevich, Gert Lubec, Tamsin C. O'Connell, and Robert E. M. Hedges. "Documenting the diet in ancient human populations through stable isotope analysis of hair." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 354, no. 1379 (January 29, 1999): 65–76. http://dx.doi.org/10.1098/rstb.1999.0360.
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Fundamental to the understanding of human history is the ability to make interpretations based on artifacts and other remains which are used to gather information about an ancient population. Sequestered in the organic matrices of these remains can be information, for example, concerning incidence of disease, genetic defects and diet. Stable isotopic compositions, especially those made on isolates of collagen from bones, have been used to help suggest principal dietary components. A significant problem in the use of collagen is its long–term stability, and the possibility of isotopic alteration during early diagenesis, or through contaminating condensation reactions. In this study, we suggest that a commonly overlooked material, human hair, may represent an ideal material to be used in addressing human diets of ancient civilizations. Through the analysis of the amino–acid composition of modern hair, as well as samples that were subjected to radiation (thus simulating ageing of the hair) and hair from humans that is up to 5200 years old, we have observed little in the way of chemical change. The principal amino acids observed in all of these samples are essentially identical in relative abundances and content. Dominating the compositions are serine, glutamic acid, threonine, glycine and leucine, respectively accounting for approximately 15%, 17%, 10%, 8% and 8% of the total hydrolysable amino acids. Even minor components (for example, alanine, valine, isoleucine) show similar constancy between the samples of different ages. This constancy clearly indicates minimal alteration of the amino–acid composition of the hair. Further, it would indicate that hair is well preserved and is amenable to isotopic analysis as a tool for distinguishing sources of nutrition. Based on this observation, we have isotopically characterized modern individuals for whom the diet has been documented. Both stable nitrogen and carbon isotope compositions were assessed, and together provide an indication of trophic status, and principal type (C 3 or C 4 ) of vegetation consumed. True vegans have nitrogen isotope compositions of about 7‰ whereas humans consuming larger amounts of meat, eggs, or milk are more enriched in the heavy nitrogen isotope. We have also analysed large cross sections of modern humans from North America and Europe to provide an indication of the variability seen in a population (the supermarket diet). There is a wide diversity in both carbon and nitrogen isotope values based at least partially on the levels of seafood, corn–fed beef and grains in the diets. Following analysis of the ancient hair, we have observed similar trends in certain ancient populations. For example, the Coptics of Egypt (1000 BP) and Chinchorro of Chile (5000–800 BP) have diets of similar diversity to those observed in the modern group but were isotopically influenced by local nutritional sources. In other ancient hair (Egyptian Late Middle Kingdom mummies, ca . 4000 BP), we have observed a much more uniform isotopic signature, indicating a more constant diet. We have also recognized a primary vegetarian component in the diet of the Neolithic Ice Man of the Oetztaler Alps (5200 BP). In certain cases, it appears that sulphur isotopes may help to further constrain dietary interpretations, owing to the good preservation and sulphur content of hair. It appears that analysis of the often–overlooked hair in archaeological sites may represent a significant new approach for understanding ancient human communities.
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Cabanillas-Terán, Nancy, Héctor A. Hernández-Arana, Miguel-Ángel Ruiz-Zárate, Alejandro Vega-Zepeda, and Alberto Sanchez-Gonzalez. "Sargassum blooms in the Caribbean alter the trophic structure of the sea urchin Diadema antillarum." PeerJ 7 (August 30, 2019): e7589. http://dx.doi.org/10.7717/peerj.7589.
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The arrival of large masses of drifting Sargassum since 2011 has caused changes in the natural dynamics of Caribbean coastal ecosystems. In the summer of 2015, unprecedented and massive mats of S. fluitans and S. natans have been observed throughout the Mexican Caribbean including exceptional accumulations ashore. This study uses stable isotopes to assess the impact of Sargassum blooms on the trophic dynamics of the Diadema antillarum sea urchin, a keystone herbivore on many Caribbean reefs. Bayesian models were used to estimate the variations in the relative proportions of carbon and nitrogen of assimilated algal resources. At three lagoon reef sites, the niche breadth of D. antillarum was analysed and compared under massive influx of drifting Sargassum spp. vs. no influx of Sargassum blooms. The effects of the leachates generated by the decomposition of Sargassum led to hypoxic conditions on these reefs and reduced the taxonomic diversity of macroalgal food sources available to D. antillarum. Our trophic data support the hypothesis that processes of assimilation of carbon and nitrogen were modified under Sargassum effect. Isotopic signatures of macroalgae associated with the reef sites exhibited significantly lower values of δ15N altering the natural herbivory of D. antillarum. The Stable Isotopes Analysis in R (SIAR) indicated that, under the influence of Sargassum blooms, certain algal resources (Dictyota, Halimeda and Udotea) were more assimilated due to a reduction in available algal resources. Despite being an abundant available resource, pelagic Sargassum was a negligible contributor to sea urchin diet. The Stable Isotope Bayesian Ellipses in R (SIBER) analysis displayed differences between sites, and suggests a reduction in trophic niche breadth, particularly in a protected reef lagoon. Our findings reveal that Sargassum blooms caused changes in trophic characteristics of D. antillarum with a negative impact by hypoxic conditions. These dynamics, coupled with the increase in organic matter in an oligotrophic system could lead to reduce coral reef ecosystem function.
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McInerney, Francesca A., Caroline A. E. Strömberg, and James W. C. White. "The Neogene transition from C3 to C4 grasslands in North America: stable carbon isotope ratios of fossil phytoliths." Paleobiology 37, no. 1 (2011): 23–49. http://dx.doi.org/10.1666/09068.1.
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C4 grasses form the foundation of warm-climate grasslands and savannas and provide important food crops such as corn, but their Neogene rise to dominance is still not fully understood. Carbon isotope ratios of tooth enamel, soil carbonate, carbonate cements, and plant lipids indicate a late Miocene-Pliocene (8–2 Ma) transition from C3 vegetation to dominantly C4 grasses at many sites around the world. However, these isotopic proxies cannot identify whether the C4 grasses replaced woody vegetation (trees and shrubs) or C3 grasses. Here we propose a method for reconstructing the carbon isotope ratio of Neogene grasses using the carbon isotope ratio of organic matter trapped in plant silica bodies (phytoliths). Although a wide range of plants produce phytoliths, we hypothesize that in grass-dominated ecosystems the majority of phytoliths will be derived from grasses, and will yield a grass carbon isotope signature. Phytolith extracts can be contaminated by non-phytolith silica (e.g., volcanic ash). To test the feasibility of the method given these potential problems, we examined sample purity (phytolith versus non-phytolith silica), abundance of grass versus non-grass phytoliths, and carbon isotope ratios of phytolith extracts from late Miocene-Pliocene paleosols of the central Great Plains. Isotope results from the purest samples are compared with phytolith assemblage analysis of these same extracts. The dual record spans the interval of focus (ca. 12–2 Ma), allowing us, for the first time, to investigate how isotopic shifts correlate with floral change.We found that many samples contained high abundances of non-biogenic silica; therefore, only a small subset of “pure” samples (>50% of phytoliths by volume) with good preservation were considered to provide reliable carbon isotope ratios. All phytolith assemblages contained high proportions (on average 85%) of grass phytoliths, supporting our hypothesis for grass-dominated communities. Therefore, the carbon isotope ratio of pure, well-preserved samples that are dominated by grass biosilica is considered a reliable measure of the proportion of C3 and C4 grasses in the Neogene.The carbon isotope ratios of the pure fossil phytolith samples indicate a transition from predominantly C3 grasses to mixed C3-C4 grasses by 5.5 Ma and then a shift to more than 80% C4 grasses by 3–2 Ma. With the exception of the Pliocene sample, these isotopic data are broadly concordant with phytolith assemblages that show a general increase in C4 grasses in the late Miocene. However, phytolith assemblage analysis indicates lower relative abundance of C4 grasses in overall vegetation than do the carbon isotopes from the same phytolith assemblages. The discrepancy may relate to either (1) incomplete identification of (C4) PACMAD phytoliths, (2) higher production of non-diagnostic phytoliths in C4 grasses compared to C3 grasses, or (3) biases in the isotope record toward grasses rather than overall vegetation. The impact of potential incomplete characterization of (C4) PACMAD phytoliths on assemblage estimates of proportion of C4, though important, cannot reconcile discrepancies between the methods. We explore hypothesis (2) by analyzing a previously published data set of silica content in grasses and a small data set of modern grass leaf assemblage composition using analysis of variance, independent contrasts, and sign tests. These tests suggest that C4 grasses do not have more silica than C3 grasses; there is also no difference with regard to production of non-diagnostic phytoliths. Thus, it is most likely that the discrepancy between phytolith assemblages and isotope ratios is a consequence of hypothesis (3), that the isotope signature is influenced by the contribution of non-diagnostic grass phytoliths, whereas the assemblage composition is not. Assemblage-based estimates of % C4 within grasses, rather than overall vegetation, are in considerably better agreement with the isotope-based estimates. These results support the idea that, in grass-dominated assemblages, the phytolith carbon isotope method predominantly records shifts in dominant photosynthetic pathways among grasses, whereas phytolith assemblage analysis detects changes in overall vegetation. Carbon isotope ratios of fossil phytoliths in conjunction with phytolith assemblage analysis suggest that the late Neogene expansion of C4 grasses was largely at the expense of C3 grasses rather than C3 shrubs/trees. Stable isotopic analysis of phytoliths can therefore provide unique information about grass community changes during the Neogene, as well as help test how grass phytolith morphology relates to photosynthetic pathway.
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Berdnikov, I. M., O. I. Goriunova, A. G. Novikov, N. E. Berdnikova, I. V. Ulanov, N. B. Sokolova, M. E. Abrashina, et al. "Chronology of the Neolithic Ceramics of Baikal-Yenisei Siberia: Basic Ideas and New Data." Bulletin of the Irkutsk State University. Geoarchaeology, Ethnology, and Anthropology Series 33 (2020): 23–53. http://dx.doi.org/10.26516/2227-2380.2020.33.23.
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There are two main research areas in the Neolithic studies of the Baikal-Yenisei Siberia. One of them relates to research of mortuary traditions, another with a research of hunter-gatherer’s campsites. Ceramics is of the greatest importance for the cultural identification of campsites complexes. As a result of the Canadian-Russian project, for the Neolithic burials a clear chronological model based on AMS radiocarbon dates corrected for the freshwater reservoir effect (FRE) was created. There are several hypotheses for ceramic complexes that were proposed, but all of them predominantly were based on the radiocarbon dates obtained by the liquid scintillation counting method. This data cannot be admitted as reliable because of the limitation of this method, the big root-mean-square deviation, and the lack of data on stable carbon and nitrogen isotopes. Over the past few years, we have received in the Keck-CCAMS Group and Oxford Radiocarbon Accelerator Unit laboratories 35 new AMS-radiocarbon dates for the complexes with Neolithic ceramics. Samples taken for analyses were obtained from the 14 multilayered sites of the Angara region, Tunka valley, and Lake Baikal coast. They are represented by fragments of teeth, bones, and horns of the mammals (predominantly Cervidae and large ungulates) that accompanied pottery in cultural horizons. In five cases the carbonized organic residues (foodcrusts) from the inner surface of ceramic vessels were used as samples. In one more case, it was a strong humified soil cleaned from impurities. The technical assessment of the reliability of all dates was provided. The definitions obtained for faunal remains look the most correct. Dates obtained for foodcrust are likely significantly older, because of possible FRE influence. The geoarchaeological assessment of new dates and their correlation with the most reliable dates of previous years is provided. Based on the AMC-dating, the following chronometric frames for the Neolithic pottery of the Baikal-Yenisei Siberia are offered: Early Neolithic Net-impressed and the Khaita ceramics in the Angara region – 8539–6914 cal BP, on the Lake Baikal coast – 8160–6960 cal BP, in the Tunka valley – 7843–7681 cal BP; Ust-Belaya ceramics in the Northern Angara region – 7421–7014 cal BP (perhaps the real age is younger), in the Southern Angara region – 6730–6306 cal BP; Posolskaya ceramics on the Lake Baikal coast – 6750–6300 cal BP, in the Southern Angara region – 6730–6306 cal BP; Serovo and Dotted-comb ceramics on the Lake Baikal coast – 5841–4620 cal BP.
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Verburg, Piet, Susan S. Kilham, Catherine M. Pringle, Karen R. Lips, and Dana L. Drake. "A stable isotope study of a neotropical stream food web prior to the extirpation of its large amphibian community." Journal of Tropical Ecology 23, no. 6 (October 29, 2007): 643–51. http://dx.doi.org/10.1017/s0266467407004518.
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Rapid and massive amphibian population declines have been reported throughout upland areas of the Neotropics. The abundance and species richness of Neotropical amphibian communities suggest that losses of this magnitude are likely to have strong effects at the ecosystem level. To improve understanding of the implications of their loss we used stable isotope analysis to examine trophic relationships in an ecosystem in which amphibians are dominant in a second-order forest stream at 750 m asl in Parque Nacional Omar Torrijos Herrera, Panama. We analysed δ13C, δ15N and C:N ratios of major biotic components (basal resources, invertebrates, amphibians, fish and reptiles) in the stream and of the adjacent riparian food web. Tadpoles (mean δ15N = 4.49‰) and adult amphibians (mean δ15N = 5.45‰) were intermediate links in the aquatic and terrestrial food web respectively. High δ15N signatures identified fish as top predators in the aquatic food web and snakes and the toad Bufo as top predators in the terrestrial food web. Isotopic signatures clearly distinguished between trophic groups of tadpoles: microbial feeders (Centrolenidae, δ15N range = 0.91–3.05‰), herbivores (Rana and Hyla, δ15N range = 4.74–5.15‰) and neuston feeders (Colostethus, δ15N range = 5.31–6.40‰). Dependence on autotrophic production was indicated by enriched signatures of carbon isotopes in pool dwellers versus those that reside in faster-flowing sections of the stream. High nitrogen concentrations in detrital matter (average 0.8%, C:N = 10.3) suggested that grazing tadpoles enhanced nitrogen fluxes and improved the quality of organic matter available to detritivores.
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Bestland, E., S. Milgate, D. Chittleborough, J. VanLeeuwen, M. Pichler, and L. Soloninka. "The significance and lag-time of deep through flow: an example from a small, ephemeral catchment with contrasting soil types in the Adelaide Hills, South Australia." Hydrology and Earth System Sciences 13, no. 7 (July 16, 2009): 1201–14. http://dx.doi.org/10.5194/hess-13-1201-2009.
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Abstract. The importance of deep soil-regolith through flow in a small (3.4 km2) ephemeral catchment in the Adelaide Hills of South Australia was investigated by detailed hydrochemical analysis of soil water and stream flow during autumn and early winter rains. In this Mediterranean climate with strong summer moisture deficits, several significant rainfalls are required to generate soil through flow and stream flow [in ephemeral streams]. During autumn 2007, a large (127 mm) drought-breaking rain occurred in April followed by significant May rains; most of this April and May precipitation occurred prior to the initiation of stream flow in late May. These early events, especially the 127 mm April event, had low stable water isotope values compared with later rains during June and July and average winter precipitation. Thus, this large early autumn rain event with low isotopic values (δ18O, δD) provided an excellent natural tracer. During later June and July rainfall events, daily stream and soil water samples were collected and analysed. Results from major and trace elements, water isotopes (δ18O, δD), and dissolved organic carbon analysis clearly demonstrate that a large component of this early April and May rain was stored and later pushed out of deep soil and regolith zones. This pre-event water was identified in the stream as well as identified in deep soil horizons due to its different isotopic signature which contrasted sharply with the June–July event water. Based on this data, the soil-regolith hydrologic system for this catchment has been re-thought. The catchment area consists of about 60% sandy and 40% clayey soils. Regolith flow in the sandy soil system and not the clayey soil system is now thought to dominate the deep subsurface flow in this catchment. The clayey texture contrast soils had rapid response to rain events and saturation excess overland flow. The sandy soils had delayed soil through flow and infiltration excess overland flow. A pulse of macropore through flow was observed in the sandy soils three days after the rainfall event largely ended. The macropore water was a mixture of pre-event and event water, demonstrating the lag-time and mixing of the water masses in the sandy soil system. By contrast, the clayey soil horizons were not dominated by pre-event water, demonstrating the quicker response and shallow through flow of the clayey soil system. Thus, the sandy terrain has a greater vadose zone storage and greater lag time of through flow than the clayey terrain.
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Bestland, E., S. Milgate, D. Chittleborough, J. VanLeeuwen, M. Pichler, and L. Soloninka. "The significance and lag-time of deep throughflow: an example from a small, ephemeral catchment with contrasting soil types in the Adelaide Hills, South Australia." Hydrology and Earth System Sciences Discussions 6, no. 2 (March 24, 2009): 2599–632. http://dx.doi.org/10.5194/hessd-6-2599-2009.
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Abstract. The importance of deep throughflow in a small (3.4 km2) ephemeral catchment in the Adelaide Hills of South Australia was investigated by detailed hydrochemical analysis of soil water and stream flow during autumn and early winter rains. In this Mediterranean climate with strong summer moisture deficits, several significant rainfalls are required to generate soil throughflow and stream flow (in ephemeral streams). During Autumn 2007, a large (127 mm) drought-breaking rain occurred in April followed by significant May rains; most of this precipitation occurred prior to the initiation of stream flow in late May. These early events, especially the 127 mm event, had low (depleted) stable water isotope values compared with both later rains and average winter precipitation. Thus, this large depleted early rain event provided an excellent natural tracer. During the June and July rainfall events, daily stream and soil water samples were collected and analysed. Results from major and trace elements, water isotopes (δ18O, δD), and dissolved organic carbon analysis clearly demonstrate that a large component of this early April and May rain was stored and later pushed out of deep soil or regolith zones. This pre-event water was identified in the stream as well as identified in deeper soil horizons due to its different isotopic signature which contrasted sharply with the June–July event water. Based on this data, the regolith and throughflow system for this catchment has been re-thought. The catchment area consists of about half sandy and half clayey soils. Regolith flow is now thought to be dominated by the sandy soil system not the clayey soil system. The clayey duplex soils had rapid response to rain events and saturation excess overland flow. The sandy soils had delayed soil throughflow and infiltration excess overland flow. A pulse of macropore throughflow was observed in the sandy soils three days after the rainfall event largely ended. The macropore water was a mixture of pre-event and event water, demonstrating the lag-time and mixing of the water masses in the sandy soil system. By contrast, the clayey soil horizons were dominated by pre-event water to a much lesser degree, demonstrating the quicker response and shallow flow through of the clayey soil system. Thus, the sandy terrain has a greater vadose zone storage and greater lag time of through-flow than the clayey terrain.
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Denimal, Sophie, Florent Barbecot, Laurent Dever, Nicolas Tribovillard, and Francis Meilliez. "Tracage chimique et isotopique des eaux souterraines en relation avec les eaux de lixiviation de terrils, bassin minier du Nord-Pas-de-Calais (France)." Bulletin de la Société Géologique de France 172, no. 1 (January 1, 2001): 111–20. http://dx.doi.org/10.2113/172.1.111.
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Abstract Introduction. - In the Nord-Pas-de-Calais region (northern France), the mining activity linked to the coal extraction resulted in the existence of many mine spoils. Most of the time, the choice of the mine spoil location has been made without knowing the potential contamination of the aquifers contained in the underlying formations by substances which can be solubilized and released in relation with the weathering of these mine spoils. The aim of this study is to determine the possible role of the mine spoils in the sulfate mineralization of the chalk aquifer. Previous works [Bernard, 1979; Droz, 1985] allow to consider several possible sources of sulfate in the coal basin: the dissolution of evaporitic minerals present in the Carboniferous limestones Formation which can locally contaminate per ascensum the chalk aquifer; the dissolution of gypsum contained in the Tertiary formations (Argiles de Louvil, Sables d'Ostricourt); sulfates of anthropic origin linked to the waste water discharge and/or to the agricultural practices; finally, the weathering of mine spoils which leads to the oxydation of the pyrite contained in the Carboniferous shales, and can release sulfate ions that may be transferred to the aquifer. Two sites have been selected 30 km to the south of Lille: site 1 lies directly on the Senonian-Turonian chalk while site 2 lies on the sandy-clayey Tertiary formations overlying the chalk formations (fig. 1-3). Geology and hydrogeology. - The waters have been sampled within the chalk aquifer (fig. 2). This water table forms the main resource in drinking water, currently exploited. The chalk aquifer is a free water table except where the Tertiary formations make this water table confined, as is the case for site 2. The recharge of the chalk aquifer is made by the percolation of the impluvium through the microporosity of the chalk with an infiltration velocity of 0.5 to 0.7 m per year [Vachier et al., 1979]. The chalk aquifer flow is schematically SW-NE to the Orchies basin (fig. 1). This flow is caused by the piezometric depression in the Orchies basin linked to industrial pumpage. Since the decrease of these pumpages, we can observe a rise of the chalk aquifer piezometric level evaluated to 10 m in the studied area. Material and methods. - Rock samples have been collected on the surface of the two sites and below it at site 1. Mineralogical analyses have been carried out on the bulk fraction as on the clayey fraction, the elementary analysis of total carbon and total sulphur has also been performed. Two water sampling surveys have been carried out on 19 sites. Sampling has been made from piezometers which reach the chalk aquifer and that are placed close to the mine spoils but also in a radius of 5 to 10 km around. Chemical and isotopic analyses have been made on the waters sampled at hydraulic upstream and dowstream of the mine spoils. In situ measurements have been carried out during the sampling. Piezometric levels have been taken at all the sampling sites. Results and discussion. - The carbon and sulphur contents have shown a superficial leaching of these elements on the mine spoils (fig. 9). The use of isotopic geochemistry and in particular the sulphur isotopes as tracers of the sulfate origin has permitted to identify two contribution sources at the two sites: a "mine spoil" source with a delta 34 S weakly negative (delta 34 S = -2,8 per mil, -3,9 per mil) which corresponds to the oxidation of sulfides contained by the Carboniferous shales and another source (delta 34 S = -20 per mil) corresponding to the gypsum of the "Sables d'Ostricourt" which is present only at site 2 (fig. 7, 10 & 11). This study has revealed the different behaviour of the two sites: for site 1, with a free water-table zone, the mine spoil leaching carries sulfate ions directly to the table whereas in the second site, with a confined aquifer zone, a part of the sulfate ions are reduced once exported to the table (the redox potential presents negative values; fig. 6). This bacterial reduction is made possible by the organic carbon leaching concomitant to the sulphur leaching on the mine spoils. This carbon contribution has been confirmed by the 14 C activity analysis: 14 C activity is characteristic of the chalk aquifer waters at the upstream of the mine spoil and noticeably lower downstream, this decrease can be linked to the "dead carbon" supply from the mine spoils (fig. 8). This organic carbon is involved in bacterially-mediated sulfate reduction (2CH 2 O + SO 4 (super 2-) --> 2HSO 3 (super -) + H (super +) + HS (super -) ). Conclusion. - Both studied mine spoils release sulfate ions to the Chalk aquifer, in response to the weathering and leaching of their surficial part. Using an isotope study-grounded approach, the influence of the mine spoils upon the sulfate enrichment of the water table can be distinguished from that of Cenozoic formations sometimes present between the chalk aquifer and the mine spoil basis. No other sulfate source seems to be involved in the studied area. Together with sulfate ions, the mine spoils export dissolved organic carbon. Both chemical species sustain bacterial activity (sulfate reducers) that develops where the water table is made confined by overlying, almost impervious, Cenozoic deposits. In that case, reducing conditions in the aquifer decrease the amount of sulfate ions present. Thus the simultaneous supply of sulfate and carbon by the mine spoils leads to a self-purification process where the aquifer is confined.
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Kejžar, Jan, Marta Jagodic Hudobivnik, Marijan Nečemer, Nives Ogrinc, Jasmina Masten Rutar, and Nataša Poklar Ulrih. "Characterization of Algae Dietary Supplements Using Antioxidative Potential, Elemental Composition, and Stable Isotopes Approach." Frontiers in Nutrition 7 (February 5, 2021). http://dx.doi.org/10.3389/fnut.2020.618503.
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Dietary supplements based on algae, known for their nutritional value and bioactive properties, are popular products among consumers today. While commercial algal products are regarded safe by numerous studies, information about the production and origin of such products is scarce. In addition, dietary supplements are not as strictly regulated as food and medicinal drugs. We characterized different algal products (kelps: Laminariales, Spirulina spp., Chlorella spp., and Aphanizomenon flos-aquae), obtained on Slovenian market, based on their elemental composition (X-ray fluorescence, inductively coupled plasma–mass spectrometry), antioxidative potential [DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, total phenolic content], and stable isotope values [carbon (C), nitrogen (N), and sulfur (S); elemental analyzer isotope ratio mass spectrometry (EA-IRMS) method]. Antioxidative potential is consistent among products of the same type, with A. flos-aquae samples having 4.4 times higher antioxidative potential compared to Chlorella spp. and 2.7 times higher compared to Spirulina spp. Levels of toxic trace elements (arsenic, cadmium, mercury, and lead) are below the maximum allowed values and as such do not pose risk to consumers' health. Samples of Spirulina spp. have relatively high δ15N (7.4 ‰ ± 4.4‰) values, which indicate use of organic nitrogen sources in certain samples. Likewise, different elemental composition and isotopic ratios of stable elements (C, N, and S) for the samples with Spirulina spp. or Chlorella spp. are the consequence of using different nutrient sources and algae-growing techniques. Statistical analysis (principal component analysis) has confirmed that all tested A. flos-aquae samples originate from the same source, supposedly Klamath Lake (Oregon, USA). Hawaiian Spirulina pacifica can also be differentiated from all the other samples because of its characteristically high metal content (iron, manganese, zinc, cobalt, nickel, vanadium). Chlorella spp. and Spirulina spp. require further analyses with larger number of samples, as differentiation is not possible based on results of this study.