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Colonisation of decaying leaves fallen from mangrove trees by bacteria and fungi is thought to play an important role at the base of food webs in most tropical estuaries. Compound-specific isotope analysis of amino acids (CSIA-AA) has enabled the previously difficult methodological task of measuring plant, bacterial and fungal energy flows to food webs. Here, we assessed the biosynthetic origins of amino acids at the base of a mangrove food web using the CSIA-AA approach. Trophic positions of the 2 most common mangrove fauna—fiddler crabs and sesarmid crabs—estimated from nitrogen isotopes in phenylalanine and glutamic acid approached 2, suggesting that these species are herbivores rather than microbivores. Consistent with this finding, carbon isotope fingerprints in AAs did not support the importance of essential AAs derived from fungi and bacteria but rather suggested the importance of those originating from plants, especially microalgae. These results suggest that (1) microbial mineralization of decaying leaves supports the production of more easily assimilated microalgae and (2) bacteria and fungi, as intermediates, also routinely incorporate plant-derived AAs into their biomass.

The forensic analysis of stable isotopes is a valuable tool to geo-source natural or semisynthetic drugs such as cocaine and heroin. The present study describes a novel methodology to isolate morphine from opium for isotopic analysis. Furthermore, this isotopic data from regional sources is corroborated with morphine data obtained from seized heroin (deacetylated to morphine) from the same regions. All five primary alkaloids of opium, namely, morphine, codeine, thebaine, noscapine, and papaverine, were quantified using high performance liquid chromatography with photodiode array (PDA) detector before the preparative experiment to gather a complete major alkaloidal profile. Morphine fractions of authentic opium submissions from Mexico, South America, Southwest Asia, and Southeast Asia were isolated and collected using preparative high performance liquid chromatography, and the collected morphine samples were subsequently analyzed by isotope ratio mass spectrometry. Carbon and nitrogen isotope data are presented. The data demonstrate that nitrogen ratios are capable of differentiating samples from Mexico and South America while carbon ratios are able to distinguish Southwest Asian samples from other source regions. Analogous results have routinely been observed (as part of Heroin Signature Program analysis) for morphine obtained from deacetylated authentic heroin samples from the same source regions. The results suggest that the poppy growing region has a greater influence on the carbon and nitrogen isotope values than the heroin manufacturing processes employed. When utilized in conjunction with existing signature methodologies, carbon and nitrogen isotope ratio data can enhance the ability to geo-source heroin.

The soil carbon (C) and nitrogen (N) dynamic was usually considered as a minor change based on a static process in the sealed soil under decades of impervious surface (IS). However, no systematic studies concerning the soil organic carbon (SOC) and nitrogen (SON) dynamic were conducted under IS in contrast with urban vegetation (i.e., forest, grass). Here we utilized fractional distillation of soils as well as stable isotopic analysis to examine soil C&N cycles after 20 and 30 years of vegetation planting and IS construction in Guangzhou and Shenzhen, Pearl River Delta, China. Soil samples including bare soil (CK) and four land use treatments were split into different chemical fractions. Then we analyzed the C&N content, C/N ratio, δ13C, δ15N, C&N recalcitrant indices (RIC, RIN), and the mean residence time (MRT). We found that the soil C&N increased first (i.e., 20 years) because of enhanced C&N stocks in both labile (LP) and recalcitrant pool (RP), and then stabilized or decreased (i.e., 30 years) with the IS ages in both cities. IS had a lower SOC decomposition rate and thus resulted in the five to ten times longer MRT (about 259–465 years) than that in vegetated soils (about 39–55 years). Moreover, the SOC&SON always showed a decoupling relation in labile pools (i.e., LC and LN) in forests in both cities. The study showed the IS remarkably altered the soil C&N dynamics, showing a great difference in SOC&SON fractions composition and turnover compared with vegetation.

The paper evaluates the species richness, material transfer, energy flow, and system function of the southwestern Yellow Sea Ecosystem (SYSE) indicating intensive human intervention affecting this large marine ecosystem. Twenty functional groups were chosen to represent the basic components of the SYSE for Ecopath modeling based on offshore surveys, annual bird observations, and the China Fisheries Statistical Yearbooks. Forty-nine species based on 15 functional groups of Ecopath model were assessed by stable isotopic analysis (SIA) to verify ecosystem features, energy flow, and trophic structure of the SYSE derived from Ecopath model. Results showed there was a clear correlation of the estimated trophic structure calculated from SIA and the Ecopath model with R2=0.7184. The SYSE Ecopath model was still at an immature and unstable stage according to outputs of the modeling parameters. This paper provides a verification method of detecting the ecosystem features and maturity, stability, and resilience of marine ecosystems by comparing outputs from Ecopath models with SIA.

Formation pathways and sources of atmosphere nitrate (NO3-) have attracted much attention as NO3- had detrimental effects on Earth's ecosystem and climate change. Here, we measured nitrogen (δ15N-NO3-) and oxygen (δ18O-NO3- and Δ17O-NO3-) isotope compositions in nitrate aerosols at the Qomolangma station (QOMS) over the Himalayan-Tibetan Plateau (HTP) to quantify the formation mechanisms and emission sources of nitrate at the background site. At QOMS, the enhanced NO3- concentrations were observed in the springtime. The average δ15N-NO3-, δ18O-NO3-, and Δ17O-NO3- values were 0.4 ± 4.9, 64.7 ± 11.5 and 27.6 ± 6.9‰, respectively. Seasonal variations of isotope ratios at QOMS can be explained by the different emissions and formation pathways to nitrate. The average fractions of NO2 + OH and N2O5 + H2O to nitrate production were estimated to be 43 and 52%, respectively, when the NO3 + hydrocarbon (HC)/dimethyl sulfide (DMS) (NO3 + HC/DMS) pathway was assumed to be 5%. Using stable isotope analysis in the R (SIAR) model, the relative contributions of biomass burning (BB), biogenic soil emission, traffic, and coal combustion to nitrate were estimated to be 28, 25, 24, and 23%, respectively, on yearly basis. By FLEXible PARTicle (FLEXPART) dispersion model, we highlighted that NOx from BB emission over South Asia that had undergone N2O5 + H2O processes enhanced the nitrate concentrations in the springtime over the HTP region.

Ferromanganese (Fe-Mn) crusts are potential archives of the Cu and Zn isotope compositions of seawater through time. In this study, the Cu and Zn isotopes of the top surface of 28 Fe-Mn crusts and 2 Fe-Mn nodules were analysed by MC-ICP-MS using combined sample-standard bracketing for mass bias correction. The Zn isotope compositions of the top surface of Fe-Mn crusts are in the range of 0.71‰ to 1.08‰, with a mean δB66Zn value of 0.94‰±0.21‰ (2SD, n=28). The δ65Cu values of the top surface of Fe-Mn crusts range from 0.33‰ to 0.73‰, with a mean value of 0.58‰±0.20‰ (2SD, n=28). The Cu isotope compositions of Fe-Mn crusts are isotopically lighter than that of dissolved Cu in deep seawater (0.58‰ vs. 0.9‰). In contrast, the δ66Zn values of Fe-Mn crusts appear to be isotopically heavy compared to deep seawater (0.94‰±0.21‰ vs. 0.51‰±0.14‰). The isotope fractionation between Fe-Mn crusts and seawater is attributed to equilibrium partitioning between the sorption to crusts and the organic-ligand-bound Cu and Zn in seawater. The Cu and Zn isotopes in the top surface of Fe-Mn crusts are not a direct reflection of the Cu and Zn isotopes, but a function of Cu and Zn isotopes in modern seawater. This study proposes that Fe-Mn crusts have the potential to be archives for paleoceanography through Cu and Zn isotope analysis.

One of the outstanding current problems in both geobiology and environmental microbiology is the quantitative analysis of in situ microbial metabolic activities. Techniques capable of such analysis would have wide application, from quantifying natural rates of biogeochemical cycling to identifying the metabolic activity of uncultured organisms. We describe here a method that represents one step towards that goal, namely the high-precision measurement of ^(13)C in specific populations of microbial cells that are purified by fluorescence-activated cell sorting (FACS). Sorted cells are concentrated on a Teflon membrane filter, and their ^(13)C content is measured by coupling an isotope ratio mass spectrometer (IRMS) with a home-built spooling wire microcombustion (SWiM) apparatus. The combined instrumentation provides measurements of δ^(13)C in whole cells with precision better than 0.2‰ for samples containing as little as 25 ng of carbon. When losses associated with sample handling are taken into account, isotopic analyses require sorting roughly 10^4 eukaryotic or 10^7 bacterial cells per sample. Coupled with ^(13)C-labelled substrate additions, this approach has the potential to directly quantify uptake of metabolites in specific populations of sorted cells. The high precision afforded by SWiM-IRMS also permits useful studies of natural abundance variations in ^(13)C. The approach is equally applicable to specific populations of cells sorted from multicellular organisms.

Methane (CH4) emission from tree stems (stem CH4 emission) is a previously overlooked emission pathway in forested wetlands. Despite growing evidence of its significance to both regional and global CH4 budgets, the drivers and mechanisms of stem CH4 emission in wetlands are not fully understood. To clarify the environmental drivers of stem CH4 emission, we conducted chamber-based flux measurements for mature Alnus japonica and Fraxinus mandshurica trees in a forested wetland in northern Japan over four snow-free seasons, as well as a short-term flooding experiment and an isotopic analysis of stem-emitted and soil porewater CH4. Stem CH4 fluxes varied seasonally and annually. The highest flux, exceeding 10,000 µg CH4 m−2 h−1, occurred in August 2016 following a record-breaking rainfall. Soil temperature and water-table depth had significant effects on stem CH4 flux. Artificial flooding remarkably increased stem CH4 flux more than tenfold within 4 days and elevated fluxes persisted for at least 1 day after the floodwater receded. Stem-emitted CH4 was depleted in 13C by an average of 2–3‰ relative to porewater CH4, implying isotopic fractionation of CH4 by diffusion and/or oxidation along its emission pathway. Belowground environmental conditions exhibited considerable control over stem CH4 emissions in forested wetlands; the biogeochemical and biological mechanisms of this influence should be further explored.

In order to understand origin and fate of particulate organic matter, the isotopic composition (δ13C and δ15N), total organic carbon content, total nitrogen content, and C/N ratios were measured for suspended particulate organic matter (POM) collected from the northern South China Sea (NSCS) during summer. Our study revealed that δ13C generally decreased from land to sea, and elevated δ13C occurred at the nearshore stations, suggesting that POC was mainly contributed from the eutrophic level and microbial activity. Moreover, the distribution of δ15N values were complicated, and heterotrophic modification was responsible for higher δ15N in the nearshore stations. These distribution patterns of δ13C and δ15N in the nearshore stations may be associated with the intensification of human activity in the coast. Based on the Stable Isotope Analysis in R model, 65% of POM was contributed by marine organic matter in the NSCS, 20% by terrestrial inputs, and 15% by freshwater algae.

Highlights: • Constraining sources of core and intact archaeal lipids with stable C isotopic ratios. • No evidence for sedimentary sources of IPL crenarchaeol. • Evidence of sedimentary production of IPL caldarchaeol and BDGT-0. • Higher organic matter content promotes higher activity of sedimentary archaea. • Archaeol is a sensitive indicator of sedimentary archaea. Archaea occupy an important niche in the global carbon cycle and their lipids are widely used as indicators of environmental conditions in both paleoenvironmental and modern biogeochemical studies. The principal sources of archaeal lipids in marine sediments are benthic archaea, fossil remnants of planktonic archaea, and allochthonous sources such as soils. However, the relative contributions of these sources to the sedimentary lipid pool have not been comprehensively constrained, complicating a mechanistic understanding of archaeal lipid proxies. In order to provide insights into the relative contributions of these sources and identify signals derived from sedimentary activity, we performed a systematic survey of stable carbon isotopic compositions (delta C-13) of both core and intact archaeal lipids via analyses of their phytanyl (Phy) and biphytanyl (BP) moieties in diverse marine sediments. The sample set consisted of 44 sediment horizons from the Mediterranean and adjacent basins and represented diverse sources of organic matter and depositional conditions. Complementary geochemical data enabled the comparison of lipid distributions and carbon isotopic signatures with prevailing redox conditions. The delta C-13 of tricyclic BP (BPcren) from the core and intact forms of crenarchaeol ranged from -19.1 to -28.6% and -18.1 to -27.4%, respectively. delta C-13 values of core and intact BPcren did not differ, suggesting that intact crenarchaeol is either a fossil relic from planktonic archaea or a product of lipid recycling by benthic archaea, as opposed to being synthesized de novo by sedimentary archaea. delta C-13 values of BP0 derived from core and intact forms of glycerol and butanetriol dibiphytanyl glycerol tetraethers (GDGTs and BGDTs, respectively), but predominantly from caldarchaeol (GDGT-0), ranged from -19.4 to -32.0% and -20.9 to -37.0%, respectively. In contrast to BPcren, intact-lipid derived BP0 was often C-13-depleted relative to its core counterpart, consistent with in situ production by sedimentary archaea. This relative depletion was most pronounced in sulfate reduction zones, likely due to heterotrophic activity. Core and intact archaeol exhibited the largest ranges in delta C-13 values, from -21.6 to -42.1% and -22.7 to -58.9%, respectively. This strong C-13-depletion relative to both total organic carbon and dissolved inorganic carbon is consistent with mixtures of functional sources of sedimentary chemolithoautotrophic, methanotrophic, methanogenic and heterotrophic archaea. Based on the substantial C-13-depletion of BPcren and BP0 in samples in the vicinity of the Rhone River delta relative to a distal marine reference site, we infer that the terrestrial soil contribution of archaeal lipids to these sediments is as high as 43%. Hence, terrestrial input of archaeal lipids, including their intact forms, can be substantial and suggests caution when using existing molecular proxies aimed at constraining riverine input. In summary, our comparative isotopic analysis of sedimentary core versus intact archaeal lipids improves the apportionment of their diverse sources and confidence in distinguishing in situ lipid production by sedimentary archaea.

During the past two decades, interest has developed in regard to the possibility that plant roots can take up organic N compounds directly, a concept which challenges the conventional wisdom that soil inorganic N forms ( NH 4 + and NO 3 - ) are the sole primary sources of N absorbed by plant roots. We reviewed the literature based on single or dual (15N, 13C) stable isotope labelling techniques to test the hypothesis of direct uptake. Both isotopically enriched and natural abundance approaches were reviewed. Of the methods examined, the dual enrichment technique, when combined with compound specific and position-specific stable isotope analysis, provided incontrovertible evidence for direct uptake of simple amino acids. We demonstrate that dual labelling lacks overall sensitivity due to the high C concentration in plant tissue relative to N, and the higher natural abundance of 13C cf. 15N, which limits the period of measurement due to isotope dilution, and hence an assessment of the long-term contribution of direct uptake to the N economy of plant communities.

International audience; Pesticides lead to surface water pollution and ecotoxicological effects on aquatic biota. Novel strategies are required to evaluate the contribution of degradation to the overall pesticide dissipation in surface waters. Here, we combined polar organic chemical integrative samplers (POCIS) with compound-specific isotope analysis (CSIA) to trace in situ pes-ticide degradation in artificial ponds and agricultural streams. The application of pesticide CSIA to surface waters is cur-rently restricted due to environmental concentrations in the low μg.L−1 range, requiring processing of large water volumes. A series of laboratory experiments showed that POCIS enables preconcentration and accurate recording of the carbon isotope signatures (δ13C) of common pesticides under simulated surface water conditions and for various sce-narios. Commercial and in-house POCIS did not significantly (Δδ13C < 1 %) change the δ13C of pesticides during uptake, extraction, and δ13C measurements of pesticides, independently of the pesticide concentrations (1–10 μg.L−1)orthe flow speeds(6or14cm.s−1). However, simulated rainfall events of pesticide runoff affected the δ13C of pesticidesinPOCIS. In-house POCIS coupled with CSIA of pesticides were also tested under different field conditions, including three flow-through and off-stream ponds and one stream receiving pesticides from agricultural catchments. The POCIS-CSIA method enabled to determine whether degradation of S-metolachlor and dimethomorph mainly occurred in agricultural soil or surface waters. Comparison of δ13C of S-metolachlor in POCIS deployed in a stream with δ13C of S-metolachlor in com-mercial formulations suggested runoff of fresh S-metolachlor in the midstream sampling site, which was not recorded in grab samples. Altogether, our study highlights that the POCIS-CSIA approach represents a unique opportunity to evaluate the contribution of degradation to the overall dissipation of pesticides in surface waters.

The stable isotope ratios of groundwater sulfate (34S/32S, 18O/16O) are often used as tracers to help determine the origin of groundwater or groundwater contaminants. In agricultural watersheds, little is known about how the increased use of sulfur as a soil amendment to optimize crop production is affecting the isotopic composition of groundwater sulfate, especially in shallow aquifers. We investigated the isotopic composition of synthetic agricultural fertilizers and groundwater sulfate in an area of intensive agricultural activity, in Ontario, Canada. Groundwater samples from an unconfined surficial sand aquifer (Lake Algonquin Sand Aquifer) were analyzed from multi‐level monitoring wells, riverbank seeps, and private domestic wells. Fertilizers used in the area were analyzed for sulfur/sulfate content and stable isotopic composition (δ18O and/or δ34S). Fertilizers were isotopically distinct from geological sources of groundwater sulfate in the watershed and groundwater sulfate exhibited a wide range of δ34S (−6.9 to +20.0‰) and δ18O (−5.0 to +13.7‰) values. Quantitative apportionment of sulfate sources based on stable isotope data alone was not possible, largely because two of the potential fertilizer sulfate sources had an isotopic composition on the mixing line between two natural geological sources of sulfate in the aquifer. This study demonstrates that, when sulfate isotope analysis is being used as a tracer or co‐tracer of the origin of groundwater or of contaminants in groundwater, sulfate derived from synthetic fertilizer needs to be considered as a potential source, especially when other parameters such as nitrate independently indicate fertilizer impacts to groundwater quality.

Stable carbon isotopic compositions of n-alkanes in surface sediments of the Bohai and North Yellow Seas were investigated to elucidate sources of sedimentary organic matter in these seas. The long-chain n-alkanes in surface sediments are predominantly long-chain C27, C29, and C31 types, with obvious odd carbon predominance. The δ13C values of long-chain n-C27, n-C29, and n-C31 alkanes are −30.8%±0.59‰, −31.9%±0.6‰, and −32.1%±1.09‰, respectively, within the range of n-alkanes of C3 terrestrial higher plants. This suggests that sedimentary n-alkanes are derived mainly from terrestrial higher plants. Compound-specific carbon isotopic analysis of long-chain n-alkanes indicates that C3 terrestrial higher plants predominate (64%–79%), with angiosperms being the main contributors. The n-alkane δ13C values indicate that mid-chain n-alkanes in sediments are derived mainly from aquatic emergent macrophytes, with significant petroleum pollution and bacterial degradation sources for short-chain n-alkanes.

We utilized lead (Pb) stable isotopes to identify the source of acute Pb poisoning in a Tundra Swan (Cygnus columbianus) and evaluated overall Pb exposure. Upon necropsy, we obtained samples of blood, liver, kidney, heart, thigh, breast, femur, and metallic objects (i.e., fishing sinker, spring and swivels) from the gizzard for Pb isotopic analysis. Pb isotope ratios of blood and soft tissues were essentially identical to the Pb ratios of the sinker, the likely source of acute poisoning. The spring and swivels had lower Pb content and ratios distinct from tissue, suggesting no significant contribution to poisoning. Femur Pb isotopic composition was the most distinct biological sample and indicative of a combination of sources. These results demonstrate isotopic analysis as a viable method for determining the source of acute Pb poisoning, and that Pb isotope ratios in bone most likely record a lifetime-averaged metric of Pb exposure.

Various samples of the Eastern oyster, Crassostrea virginica, were collected from five harvest bay areas in the Gulf of Mexico coastal waters of Florida (FL), Louisiana (LA) and Texas (TX). Cadmium and lead concentrations from the extracted whole-body soft tissues were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS), and bulk δ13C and δ15N isotope ratios and amino-acid-specific δ13C values were analyzed via isotope ratio mass-spectrometry (IRMS). The combined data was subjected to multivariate statistical analysis to assess whether oysters could be linked to their harvest area. Results indicate that discriminant analysis using the δ13C values of five amino acids-serine, glycine, valine, lysine and phenylalanine-could discriminate oysters from two adjacent harvesting in Florida with 90% success rate, using leave-one-out cross validation. The combination of trace elements and isotope ratios could also predict geographic provenance of oysters with a success rate superior to the isolated use of each technique. The combinatory approach proposed in this study is a proof-of-concept that compound specific stable isotope analysis is a potential tool for oyster fisheries managers, wildlife, and food safety enforcement officers, as well as to forensics and ecology research areas, although significantly more work would need to be completed to fully validate the approach and achieve more reliable statistical results.

Dissolved gaseous mercury (DGM) and reactive mercury (RHg) are important mercury (Hg) forms in natural water bodies. Knowledge of the concentration levels and isotope compositions of DGM and RHg in aquatic ecosystems is of crucial importance for understanding the fate of Hg and Hg cycle. In this study, we developed a method to preconcentrate the ultratrace levels of DGM and RHg in freshwater for stable isotope analysis. In this method, 10 L of amended water (or after addition of acidic SnCl2) was purged for 2 hours with Hg-free air gas at 4 L min−1, and the Hg(0) product was then collected onto a chlorine-impregnated activated carbon (CLC) trap. This process was repeated for a total of 80 L water for DGM collection or 40 L of water for RHg collection in order to obtain sufficient DGM and RHg amounts for isotope analysis. DGM and RHg collected on CLC traps were then thermally desorbed and further preconcentrated into 40% acid-trapping solutions for stable isotope analysis using cold vapor multicollector-inductively coupled plasma-mass spectrometry (CV-MC-ICPMS). The method was evaluated by laboratory tests using additions of certified Hg(0) and Hg(II) references with known concentrations and isotopic compositions as well as field measurements of duplicate samples. The laboratory tests showed that 98.1 ± 8.1% of DGM (1sd, ranging from 85.1 to 115.9%, n = 14) and 98.7 ± 8.7% of RHg (81.3 to 122%, n = 33) could be extracted from freshwater, and the isotopic compositions of the extracted Hg(0) and Hg(II) agreed well with the injected Hg(0) and Hg(II) references (paired sample T test: p values ≥ 0.20 for all Hg isotope signatures). Based on the results from the laboratory tests, we propose the expanded uncertainty (2sd) of δ202Hg, Δ199Hg, and Δ200Hg to be 0.28‰, 0.07‰, and 0.07‰, respectively, for DGM isotope analysis, and 0.25‰, 0.07‰, and 0.07‰, respectively, for RHg isotope analysis. The duplicate field tests showed negligible differences in DGM and RHg isotopic compositions between the paired samples. These results demonstrate that the extraction method can accurately measure DGM and RHg isotopic compositions in freshwater, providing a useful tool for investigating Hg at ultratrace levels in an aquatic environment.

Pesticides are commonly applied in agriculture to protect crops from pests, weeds, and harmful pathogens. However, chronic, low-level exposure to pesticides can be toxic to humans. Photochemical degradation of pesticides in water, soil, and other environmental media can alter their environmental fate and toxicity. Compound-specific isotope analysis (CSIA) is an advanced diagnostic tool to quantify the degradation of organic pollutants and provide insight into reaction mechanisms without the need to identify transformation products. CSIA allows for the direct quantification of organic degradation, including pesticides. This review summarizes the recent developments observed in photodegradation studies on different categories of pesticides using CSIA technology. Only seven pesticides have been studied using photodegradation, and these studies have mostly occurred in the last five years. Knowledge gaps in the current literature, as well as potential approaches for CSIA technology for pesticide monitoring, are discussed in this review. Furthermore, the CSIA analytical method is challenged by chemical element types, the accuracy of instrument analysis, reaction conditions, and the stability of degradation products. Finally, future research applications and the operability of this method are also discussed.

Nickel (Ni), copper (Cu), and zinc (Zn) are commonly used in human activities and pollute aquatic environments including rivers and oceans. Recently, Ni, Cu, and Zn isotope ratios have been measured to identify their sources and cycles in environments. We precisely determined the Ni, Cu, and Zn isotope ratios in rain, snow, and rime collected from Uji City and Mt. Kajigamori in Japan, and investigated the potential of isotopic ratios as tracers of anthropogenic materials. The isotope and elemental ratios suggested that road dust is the main source of Cu in most rain, snow, and rime samples and that some of the Cu may originate from fossil fuel combustion. Zinc in the rain, snow, and rime samples may be partially attributed to Zn in road dust. Zinc isotope ratios in the Uji rain samples are lower than those in the road dust, which would be emitted via high temperature processes. Nickel isotope ratios are correlated with V/Ni ratios in the rain, snow, and rime samples, suggesting that their main source is heavy oil combustion. Furthermore, we analyzed water samples from the Uji and Tawara Rivers and the Kakita River spring in Japan. Nickel and Cu isotope ratios in the river water samples were significantly heavier than those in rain, snow, and rime samples, while Zn isotope ratios were similar. This is attributed to isotopic fractionation of Cu and Ni between particulate-dissolved phases in river water or soil.

Mercury (Hg) isotopic geochemistry is a powerful tool for understanding the sources and geochemical processes of Hg in natural environments. Current Hg isotopic analysis mainly focuses on total Hg in natural samples, whereas the isotopic composition of methylmercury (MeHg), which is a neurotoxin to humans and wildlife, remains poorly understood. In this study, we developed an offline two-round purging-trapping method for MeHg separation from biological samples. This method enables high efficiency of MeHg separation and high precision analysis of MeHg in environmental samples. MeHg standard solution spiked with inorganic Hg (IHg) standard solution yielded MeHg recoveries of 94–112% (103 ± 4%, n = 9) and no obvious MeHg isotopic fractionation was observed. Analysis of various biological reference materials (CRMs) using this new method showed acceptable MeHg recoveries of 90–119% (101 ± 8%, n = 18). The measured MeHg isotopic composition for the CRMs using the new method agreed well with the values in the literature and with much lower uncertainties (0.02–0.15‰, 2SD) compared with GC or HPLC separation methods. This new method yields similar accuracy and uncertainty to the available toluene extraction method. Therefore, the new method provides another reliable and efficient method for MeHg isotopic analysis, which should be useful to the Hg isotope research community.

International audience; Tiemannite (HgSe) is considered the end-product of methylmercury (MeHg) demethylation in vertebrates. The biomineralization of HgSe nanoparticles (NPs) is understood to be an efficient MeHg detoxification mechanism; however, the process has not yet been fully elucidated. In order to contribute to the understanding of complex Hg metabolism and HgSe NPs formation, the Hg isotopic signatures of 40 samples of 11 giant petrels were measured. This seabird species is one of the largest avian scavengers in the Southern Ocean, highly exposed to MeHg through their diet, reaching Hg concentrations in the liver up to more than 900 µg g-1. This work constitutes the first species-specific isotopic measurement (δ 202 Hg, Δ 199 Hg) of HgSe NPs in seabirds and the largest characterization of this compound in biota. Similar δ 202 Hg values specifically associated to HgSe (δ 202 HgSe) and tissues (δ 202 bulk) dominated by inorganic Hg species were found, suggesting that no isotopic fractionation is induced during the biomineralization step from the precursor (demethylated) species. In contrast, the largest variations between δ 202 Hgbulk and δ 202 HgSe were observed in muscle and brain tissues. This could be attributed to the higher fraction of Hg present as MeHg in these tissues. Hg-biomolecules screening highlights the importance of the isotopic characterization of these (unknown) complexes.

Bioaccumulation of methylmercury (MeHg) in rice grains has been an emerging issue of human health, but the mechanism of bioaccumulation is still poorly understood. Mercury (Hg) isotope measurements are powerful tools for tracing the sources and biogeochemical cycles of Hg in the environment. In this study, MeHg compound-specific stable isotope analysis (CSIA) was developed in paddy soil and rice plants to trace the biogeochemical cycle of Hg in a paddy ecosystem during the whole rice-growing season. Isotopic fractionation was analyzed separately for MeHg and inorganic Hg (IHg). Results showed distinct isotopic signals between MeHg and IHg in rice plants, indicating different sources. δ202Hg values of MeHg showed no significant differences between roots, stalks, leaves, and grains at each growth stage. The similar Δ199Hg values of MeHg between rice tissues (0.14 ± 0.08‰, 2SD, n = 12), soil (0.13 ± 0.03‰, 2SD, n = 4), and irrigation water (0.17 ± 0.09‰, 2SD, n = 5) suggested that the soil-water system was the original source of MeHg in rice plants. Δ199Hg values of IHg in the paddy ecosystem indicated that water, soil, and atmosphere contributed to IHg in grains, leaves, stalks, and roots with varying degree. This study demonstrates that successful application of MeHg CSIA can improve our understanding of the sources and bioaccumulation mechanisms of MeHg and IHg in the paddy ecosystems.

Micropollutants are frequently detected in groundwater. Thus, the question arises whether they are eliminated by natural attenuation so that pesticide degradation would be observed with increasing residence time in groundwater. Conventional analytical approaches rely on parent compound/metabolite ratios. These are difficult to interpret if metabolites are sorbed or further transformed. Compound-specific stable isotope analysis (CSIA) presents an alternative for identifying degradation based on the analysis of natural isotope abundances in pesticides and their changes during degradation. However, CSIA by gas chromatography–isotope ratio mass spectrometry is challenged by the low concentrations (ng/L) of micropollutants in groundwater. Consequently, large amounts of water need to be sampled requiring enrichment and clean-up steps from interfering matrix effects that must not introduce artefacts in measured isotope values. The aim of this study was to evaluate the accuracy of isotope ratio measurements of the frequently detected micropollutants atrazine, desethylatrazine and 2,6-dichlorobenzamide after enrichment from large water volumes (up to 100 L) by solid-phase extraction with consecutive clean-up by HPLC. Associated artefacts of isotope discrimination were found to depend on numerous factors including organic matter content and extraction volume. This emphasizes the necessity to perform a careful method evaluation of sample preparation and sample pre-treatment prior reliable CSIA.

Mercury contamination in river systems due to historic and current Hg releases is a persistent concern for both wildlife and human health. In larger rivers, like the Ohio River, USA, it is difficult to directly link Hg discharges to bioaccumulation due to the existence of multiple industrial Hg sources as well as the varied dietary and migratory habits of biota. To better understand how industrial effluent influences the cycling and bioaccumulation of Hg within the Ohio River, Hg stable isotope analysis was applied to various nonbiological and biological media. High Hg concentrations in suspended particulate matter suggest this vector was the largest contributor of Hg to the water column, and distinct Hg source signatures were observed in effluent particulates from different industrial processes, such as chlor-alkali activity (δ202 Hg = -0.52‰) and coal power plant discharge (δ202 Hg = -1.39‰). Despite this distinction, average sediments (δ202 Hg = -1.00 ± 0.23‰) showed intermediate isotopic signatures that suggest the accumulation of a mixed Hg source driven by multiple industrial discharges. Biota in the system were shown to have a conserved range of δ202 Hg and estimation approaches related these signatures back to particulate matter within Hannibal Pool. Mussels were found to conserve Hg isotopes signatures independently of food web drivers and served as ideal water column indicators of bioaccumulated Hg sources. This study highlights the complexity of Hg cycling within an industrialized river and shows that an isotope tracer approach can provide insight to water column sources of Hg. Integr Environ Assess Manag 2021;17:233-242. Published 2020. This article is a US Government work and is in the public domain in the USA.

There is debate in the literature as to whether scales of fishes require acidification to remove inorganic carbonates prior to stable isotope analysis. Acid-treated and untreated scales from 208 Atlantic salmon from nine locations on both sides of the Atlantic were analysed for δ13C and δ15N. Linear mixed-effect models determined the effect of acid treatment to be statistically significant. However, the mean difference was small (δ13C 0.1 ± 0.2‰, δ15N -0.1 ± 0.2‰) and not of biological relevance. This study concludes that Atlantic salmon scales do not need to be acidified prior to stable isotope analysis.

A sequential chromatographic separation procedure for subsequent high-precision isotopic analysis of Mg and Ca via multi-collector ICP-mass spectrometry (MC-ICP-MS) from a single aliquot of sample was developed and used for a variety of animal/human biofluids and tissues. The procedure consists of a one-stage Mg isolation protocol (for most of the sample types) and a three-stage isolation protocol for Ca. AG50W-X8 strong cation exchange resin was used for the isolation of Mg and Ca, while Sr-resin was used to additionally purify the Ca fraction from Sr. Potential effects on the Mg isotope ratio measurement results caused by the possible presence of concomitant matrix elements (Cu, Fe, Zn, Ca) were systematically evaluated. δ26Mg values were biased for a Fe/Mg ratio > 0.13 and a Ca/Mg ratio > 1.5, resulting in a shift towards a lighter Mg isotopic composition. It was shown that the Mg isotope ratio data for Mg standards, the isotopic reference materials ERM-AE143 and IRMM 009 and the biological samples investigated are located on a mass-dependent fractionation line. Biological reference materials and commercially available serum samples were analyzed for both their Mg and Ca isotope ratios. For some of the biomaterials analyzed, the Ca isotope ratio data as obtained using MC-ICP-MS were further validated via their determination using double-spike thermal ionization mass spectrometry (DS-TIMS). The expanded uncertainty for δ26Mg was ≤ 0.12‰ and for δ44/42Ca ≤ 0.29‰. Biological fluids and tissues of mice were analyzed to characterize the body distribution of the stable isotopes of Mg and Ca. The isotopic variability among the body compartments was about 1.5‰ for Mg and 1.0‰ for Ca. Among the tissues explored, muscle tissue shows the lightest Mg and Ca isotopic compositions and liver the heaviest Mg and Ca isotopic compositions, respectively.

Sparse microbial populations persist from seafloor to basement in the slowly accumulating oxic sediment of the oligotrophic South Pacific Gyre (SPG). The physiological status of these communities, including their substrate metabolism, is previously unconstrained. Here we show that diverse aerobic members of communities in SPG sediments (4.3‒101.5 Ma) are capable of readily incorporating carbon and nitrogen substrates and dividing. Most of the 6986 individual cells analyzed with nanometer-scale secondary ion mass spectrometry (NanoSIMS) actively incorporated isotope-labeled substrates. Many cells responded rapidly to incubation conditions, increasing total numbers by 4 orders of magnitude and taking up labeled carbon and nitrogen within 68 days after incubation. The response was generally faster (on average, 3.09 times) for nitrogen incorporation than for carbon incorporation. In contrast, anaerobic microbes were only minimally revived from this oxic sediment. Our results suggest that microbial communities widely distributed in organic-poor abyssal sediment consist mainly of aerobes that retain their metabolic potential under extremely low-energy conditions for up to 101.5 Ma., The discovery of aerobic microbial communities in nutrient-poor sediments below the seafloor begs the question of the mechanisms for their persistence. Here the authors investigate subseafloor sediment in the South Pacific Gyre abyssal plain, showing that aerobic microbial life can be revived and retain metabolic potential even from 101.5 Ma-old sediment.

Benthic suspension feeders, such as bivalves, potentially have several different food sources, including plankton and resuspended detritus of benthic origin. We hypothesised that suspension feeders are likely to feed on detritus if it is present. This inference would be further strengthened if there was a correlation between δ13C of suspension feeder tissue and δ13C of particulate organic matter (POM). Since detritus is characterised by high particulate organic matter (POC):chl a ratios, we would also predict a positive correlation between POM δ13C and POC:chl a. We hypothesised that increasing depth and greater distance from shore would produce a greater nutritional reliance by experimentally transplanted blue mussels Mytilus edulis on plankton rather than macrophyte-derived detritus. After deployments of 3 mo duration in 2 different years at depths from 3 to 40 m, M. edulis sizes were positively correlated with POM concentrations. POC:chl a ratios and δ13C of POM and M. edulis gill tissue decreased with increasing depth (and greater distance from shore). δ13C of POM was correlated with δ13C of M. edulis. Our results suggest that detritus comprised a large proportion of POM at shallow depths (M. edulis ingested and assimilated carbon in proportion to its availability in POM, and that growth of M. edulis was higher where detritus was present and POM concentrations were higher.

Hexachlorocyclohexanes (HCHs) are persistent organic contaminants that threaten human health. Microbial reductive dehalogenation is one of the most important attenuation processes in contaminated e...

The loss of subsidies delivered by anadromous fish to inland stream ecosystems may have profound influences on stream food webs. However, studies have focused on food web responses in ecosystems where the fish assemblage is dominated by salmonids. We evaluated food web responses to carcass additions in three locations of an interior Columbia River Basin stream with varying native fish assemblages. Periphyton biomass responses were mixed with increases in treatment compared to control reaches of the middle and downstream pairs, but not in the upstream pair where scavenging by bears removed the majority of carcasses. Stable isotope analysis revealed marine-derived nutrient (MDN) enrichment of periphyton and invertebrate functional feeding groups in the middle and downstream pairs (up to 12% MDN derived), but not in the upstream pair. Non-salmonid fish exhibited limited MDN assimilation (~ 5 and 10% MDN derived), with isotopic enrichment patterns similar to lower trophic levels and little evidence of eggs and carcass material consumption, suggesting bottom-up transfer of MDN to non-salmonid fishes. In contrast, across the three study pairs, juvenile Chinook Salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss) assimilated MDN rapidly, obtaining up to 25% and 57% of their nitrogen from carcasses, respectively. Diet analysis and isotopic enrichment patterns indicated that juvenile salmonid assimilation occurred primarily through direct consumption of eggs and carcass tissue. Our findings suggest that salmonids in this region may experience more benefit from carcass additions containing eggs, while non-salmonids are likely to experience minimal MDN incorporation whether or not eggs are present.

Multi-elemental C-Br-Cl compound-specific isotope analysis was applied for characterizing abiotic and biotic degradation of the environmental pollutant 1-bromo-2-chloroethane (BCE). Isotope effects were determined in the model processes following hydrolytic dehalogenation and dihaloelimination pathways as well as in a microcosm experiment by the microbial culture from the contaminated site. Hydrolytic dehalogenation of BCE under alkaline conditions and by DhaA enzyme resulted in similar dual isotope slopes (ɅC/Br 21.9 ± 4.7 and 19.4 ± 1.8, respectively, and ɅC/Cl ~ ∞). BCE transformation by cyanocobalamin (B12) and by Sulfurospirillum multivorans followed dihaloelimination and was accompanied by identical, within the uncertainty range, dual isotope slopes (ɅC/Br 8.4 ± 1.7 and 7.9 ± 4.2, respectively, and ɅC/Cl 2.4 ± 0.3 and 1.5 ± 0.6, respectively). Changes over time in the isotope composition of BCE from the contaminated groundwater showed only a slight variation in δ13C values and were not sufficient for the elucidation of the BCE degradation pathway in situ. However, an anaerobic microcosm experiment with the enrichment cultures from the contaminated groundwater presented dual isotope slopes similar to the hydrolytic pathway, suggesting that the potential for BCE degradation in situ by the hydrolytic dehalogenation pathway exists in the contaminated site.

Waters coproduced with hydrocarbons from unconventional oil and gas reservoirs such as the hydraulically fractured Middle Devonian Marcellus Shale in the Appalachian Basin, USA, contain high levels of total dissolved solids (TDS), including Ba, which has been variously ascribed to drilling mud dissolution, interaction with pore fluids or shale exchangeable sites, or fluid migration through fractures. Here, we show that Marcellus Shale produced waters contain some of the heaviest Ba (high 138Ba/134Ba) measured to date (δ138Ba = +0.36‰ to +1.49‰ ± 0.06‰) and are distinct from overlying Upper Devonian/Lower Mississippian reservoirs (δ138Ba = -0.83‰ to -0.52‰). Marcellus Shale produced water values do not overlap with drilling mud barite (δ138Ba ≈ 0.0‰) and are significantly offset from Ba reservoirs within the producing portion of the Marcellus Shale, including exchangeable sites and carbonate cement. Precipitation, desorption, and diffusion processes are insufficient or in the wrong direction to produce the observed enrichments in heavy Ba. We hypothesize that the produced water is derived primarily from brines adjacent to and most likely below the Marcellus Shale, although such deep brines have not yet been obtained for Ba isotope analysis. Barium isotopes show promise for tracking formation waters and for understanding water-rock interaction under downhole conditions.

Compound-specific isotope analyses of geoporphyrins, which are derivatives of chloropigments possessed by phototrophs, provide essential records of the biogeochemical cycle of past aquatic environm...

Compound-specific isotope analysis (CSIA) is a powerful tool to evaluate transformation processes of halogenated compounds. Many halogenated hydrocarbons allow for multiple stable isotopic systems (C, H, Cl, Br) to be measured for a single compound. This has led to a large body of literature describing abiotic and biotic transformation pathways and reaction mechanisms for contaminants such as chlorinated alkenes and alkanes as well as brominated hydrocarbons. Here, the current literature is reviewed and a new compilation of Λ values for multi-isotopic systems for halogenated hydrocarbons is presented. Case studies of each compound class are discussed and thereby the current strengths of multi-element isotope analysis, continuing challenges, and gaps in our current knowledge are identified for practitioners of multi-element CSIA to address in the near future.

While development of the Utica/Point Pleasant Shale (UPP) is extensive in Ohio (U.S.) and increasing in Pennsylvania and West Virginia, few studies report the chemistry of produced waters from UPP wells. These data have important implications for developing best management practices for handling and waste disposal, or identifying the fluid in the event of accidental spill events. Here, we evaluated the elemental and isotope chemistry of UPP produced waters from 26 wells throughout Ohio, Pennsylvania, and West Virginia to determine any unique fluid chemistries that could be used for forensic studies. Compared to the Marcellus, UPP produced waters contain higher activities of total radium (226Ra + 228Ra) and higher 228Ra/226Ra ratios. As with the Marcellus Shale, elemental ratios (Sr/Ca) and isotope ratios (87Sr/86Sr) can distinguish UPP produced waters from many conventional oil and gas formations. Sr/Ca and 87Sr/86Sr ratios can fingerprint small fractions (∼0.1%) of UPP produced water in freshwater. However, because Marcellus and UPP produced waters display similar major elemental chemistry (i.e., Na, Ca, and Cl) and overlapping ratios of Sr/Ca and 87Sr/86Sr, 228Ra/226Ra ratios may be the best tracer to distinguish these waters.

International audience; Phyllosilicates may trap hydrogen (H2) in the crust, but they may also produce it through various processes, including oxidative dehydrogenation. The dehydrogenation temperature depends on the type and composition of the phyllosilicates considered, but it may be as low as 300 °C. Here, we document the release of H2 and CO during thermal treatment of chloritite (300 °C) and talc (500 °C) from the Trimouns deposits (Eastern Pyrenees, France). Thermal release of gases coupled to stable isotope analysis has been used to recover and characterize H2 and CO, the two detected gases. Hydrogen content may be as high as 7 ppm with δDH2 values ranging from −258‰ to – 224‰ for sub-pure chloritite and − 140‰ for pure talc. CO content ranges between 3 ppm and 35.3 ppm with very homogeneous δ13CCO values between −27.6‰ and − 25.7‰. This study supports the idea that H2 was produced during experiments by dehydrogenation. The origin of CO remains enigmatic, but its carbon isotope composition suggests a link to the few amounts of graphite documented in chloritite and talc from the deposit. This work also reports extensive hydrogen isotope fractionation between H2 produced by dehydrogenation and both talc and chloritite. Dehydrogenation of phyllosilicates is a potential source term of H2 in numerous magmatic-hydrothermal settings and must thus be accounted for in the budget of the H2 geochemical cycle

[EN] Water diversion and pollution are two pervasive stressors in river ecosystems that often co-occur. Individual effects of both stressors on basal resources available to stream communities have been described, with diversion reducing detritus standing stocks and pollution increasing biomass of primary producers. However, interactive effects of both stressors on the structure and trophic basis of food webs remain unknown. We hypothesized that the interaction between both stressors increases the contribution of the green pathway in stream food webs. Given the key role of the high-quality, but less abundant, primary producers, we also hypothesized an increase in food web complexity with larger trophic diversity in the presence of water diversion and pollution. To test these hypotheses, we selected four rivers in a range of pollution subject to similar water diversion schemes, and we compared food webs upstream and downstream of the diversion. We characterized food webs by means of stable isotope analysis. Both stressors directly changed the availability of basal resources, with water diversion affecting the brown food web by decreasing detritus stocks, and pollution enhancing the green food web by promoting biofilm production. The propagation of the effects at the base of the food web to higher trophic levels differed between stressors. Water diversion had little effect on the structure of food webs, but pollution increased food chain length and trophic diversity, and reduced trophic redundancy. The effects at higher trophic levels were exacerbated when combining both stressors, as the relative contribution of biofilm to the stock of basal resources increased even further. Overall, we conclude that moderate pollution increases food web complexity and that the interaction with water abstraction seems to amplify this effect. Our study shows the importance of assessing the interaction between stressors to create predictive tools for a proper management of ecosystems. Ministerio de Economia, Industria y Competitividad, Gobierno de Espana, Grant/Award Number: GL2016-77487-R; European Social Fund; Diputacion Foral de Bizkaia; Serra Hunter Fellow; Labex, Grant/Award Number: ANR-10-LABX-41; H2020 European Research Council; Eusko Jaurlaritza; Consejo Nacional de Investigaciones Cientificas y Tecnicas; FRAGCLIM Consolidator, Grant/Award Number: 726176

Multielement isotope fractionation studies to assess pollutant transformation are well-established for point-source pollution but are only emerging for diffuse pollution by micropollutants like pesticides. Specifically, chlorine isotope fractionation is hardly explored but promising, because many pesticides contain only few chlorine atoms so that "undiluted" position-specific Cl isotope effects can be expected in compound-average data. This study explored combined Cl, N, and C isotope fractionation to sensitively detect biotic and abiotic transformation of the widespread herbicides and groundwater contaminants acetochlor, metolachlor, and atrazine. For chloroacetanilides, abiotic hydrolysis pathways studied under acidic, neutral, and alkaline conditions as well as biodegradation in two soils resulted in pronounced Cl isotope fractionation (εCl from -5.0 ± 2.3 to -6.5 ± 0.7‰). The characteristic dual C-Cl isotope fractionation patterns (ΛC-Cl from 0.39 ± 0.15 to 0.67 ± 0.08) reveal that Cl isotope analysis provides a robust indicator of chloroacetanilide degradation. For atrazine, distinct ΛC-Cl values were observed for abiotic hydrolysis (7.4 ± 1.9) compared to previous reports for biotic hydrolysis and oxidative dealkylation (1.7 ± 0.9 and 0.6 ± 0.1, respectively). The 3D isotope approach allowed differentiating transformations that would not be distinguishable based on C and N isotope data alone. This first data set on Cl isotope fractionation in chloroacetanilides, together with new data in atrazine degradation, highlights the potential of using compound-specific chlorine isotope analysis for studying in situ pesticide degradation.

Isotope measurements were performed on dissolved nitrate (NO3−) and ammonium (NH4+) in the coastal waters of the northeastern Beibu Gulf, China, to investigate the seasonal nitrate sources and their biogeochemical processes, which are due to the rapid development of local industrialisation and urbanisation. The high N/P ratio observed in the coastal bay during both fall and spring suggests that P is a limiting nutrient, which in turn indicates that increasing P causes conditions favourable for algal blooms. Higher nutrient concentrations and δ15N-NO3− and δ15N-NH4+ values were found in the nearshore area in the fall, suggesting that nutrients originated mainly from land-based pollution. A Bayesian isotope mixing model was used to calculate the contribution of potential NO3− sources and the results showed that in the nearshore area, NO3− originated mainly from manure and sewage (58%). In the spring, however, in addition to the impact of urban sewage effluents, the exchange of sediment and water was another important factor causing higher nutrient concentrations and positive NO3− isotopes in the nearshore area. There were lower concentrations of nutrients and an increase in δ15N-NO3− and δ15N-NH4+ values in the offshore area in the fall, and the NO3− loss in the surface water was mainly caused by the process of assimilation. However, the exchange of sediment and water was the dominant factor causing higher nutrient concentrations (except for NO3−) and positive dual nitrate isotopes but lower NO3− concentration in the offshore area during the spring. Overall, isotope analysis of NO3− and NH4+ helps to illustrate the major sources of the former and their biological transformation in the northeastern Beibu Gulf.

Monomethylmercury (MMHg) exposure can induce adverse neurodevelopmental effects in humans and is a global environmental health concern. Human exposure to MMHg occurs predominately through the consumption of fishery foods and rice in Asia, but it is challenging to quantify these two exposure sources. Here, we innovatively utilized MMHg compound-specific stable isotope analyses (MMHg-CSIA) of the hair to quantify the human MMHg sources in coastal and inland areas, where fishery foods and rice are routinely consumed. Our data showed that the fishery foods and rice end members had distinct Δ199HgMMHg values in both coastal and inland areas. The Δ199HgMMHg values of the human hair were comparable to those of fishery foods but not those of rice. Positive shifts in the δ202HgMMHg values of the hair from diet were observed in the study areas. Additionally, significant differences in δ202Hg versus Δ199Hg were detected between MMHg and inorganic Hg (IHg) in the human hair but not in fishery foods and rice. A binary mixing model was developed to estimate the human MMHg exposures from fishery foods and rice using Δ199HgMMHg data. The model results suggested that human MMHg exposures were dominated (>80%) by fishery food consumption and were less affected by rice consumption in both the coastal and inland areas. This study demonstrated that the MMHg-CSIA method can provide unique information for tracking human MMHg exposure sources by excluding the deviations from dietary surveys, individual MMHg absorption/demethylation efficiencies, and the confounding effects of IHg.

Terrestrial carbon cycling is largely mediated by soil food webs. Identifying the carbon source for soil animals has been desired to distinguish their roles in carbon cycling, but it is challenging for small invertebrates at low trophic levels because of methodological limitations. Here, we combined radiocarbon ( 14 C) analysis with stable isotope analyses ( 13 C and 15 N) to understand feeding habits of soil microarthropods, especially focusing on springtail (Collembola). Most Collembola species exhibited lower Δ 14 C values than litter regardless of their δ 13 C and δ 15 N signatures, indicating their dependence on young carbon. In contrast with general patterns across all taxonomic groups, we found a significant negative correlation between δ 15 N and Δ 14 C values among the edaphic Collembola. This means that the species with higher δ 15 N values depend on C from more recent photosynthate, which suggests that soil-dwelling species generally feed on mycorrhizae to obtain root-derived C. Many predatory taxa exhibited higher Δ 14 C values than Collembola but lower than litter, indicating non-negligible effects of collembolan feeding habits on the soil food web. Our study demonstrated the usefulness of radiocarbon analysis, which can untangle the confounding factors that change collembolan δ 15 N values, clarify animal feeding habits and define the roles of organisms in soil food webs.

Dietary homogenization has progressed worldwide due to westernization and the globalization of food production systems. We investigated dietary heterogeneity in South Korea by examining the spatial distribution of carbon (C), nitrogen (N), and sulfur (S) isotope ratios using 264 human hair samples. Overall, variation in isotope values was small, indicating low dietary heterogeneity. We detected differences in δ13C, δ15N, and δ34S values between administrative provinces and metropolitan cities; inter-regional differences were typically < 1 ‰. Values of δ34S were significantly lower in hair samples from inland regions relative to those from coastal locations, and a similar pattern was observed in δ15N values. Understanding geographic variation in δ34S and δ15N values in human hair is useful for provenancing humans in South Korea.

Potential toxic element accumulation in soils and plants is one of the leading environmental problems in recent years. In many countries, mining enterprises are generally abandoned for reasons such as increasing costs, depleted reserves, and changes in ore quality. The negative effects on the environment during or as a result of these activities are known. The focus is on investigating the Hg concentration accumulated in the soil and plants around the abandoned mercury quarry located in the north-west Black Sea region (Tezcan Hg Mine). While the distribution of Hg and As is observed toward the downward slope in the mining area, it has been observed that it decreases as it moves away from the source area. The relationship of Hg concentration with granite intrusions in the areas of upward slope and topographic barriers is due to the alteration of the hydrothermal phase mineralizations and the accumulation of ore rocks. According to the Geoaccumulation Index in the lands around the abandoned mercury quarry in the Northwest Black Sea region, AsIgeo and HgIgeo accumulation are found as extremely; according to contamination factor, CFAs and CFHg values are found as very high; according to enrichment factor, EFAs and EFHg are found as extremely high; according to the Potential Ecological Risk Factor, As and Hg are found as very risky, and according to the Pollution Load Index, they are found as Pollution. As well as in soils, As and Hg concentrations were determined in Mentha longifolia (L.) L. subsp. typhoides (Briq.) Harley (dere nanesi) from the Lamiaceae (Turkish name: Ballibabagiller) family, Taraxacum buttleri Van Soest (karahindiba) from the Asteraceae (Turkish name: Papatyagiller) family, Plantago lanceolata L. (damarlica) from Plantaginaceae (Turkish name: Sinirotugiller) family, and Pyracantha coccinea M. Roem. (atesdikeni) from the Rosaceae (Turkish name: Gulgiller) family, which were collected from the same locations. According to 207Pb/206Pb—208Pb/206Pb, the origin of lead in the soils within the enterprise is of geogenic origin, and according to the results of 87Sr/86Sr—143Nd/144Nd, it is thought that the samples examined are caused by granitoid.

Isotopic effects of carbonyls were investigated using the simulation reactions of carbonyls with the cysteamine derivatization. Furthermore, variations of carbon isotopic for three dominant carbonyls including formaldehyde, acetaldehyde, and acetone in the roadside air of Nanning were measured using a developed method. It was found that there was a small difference in δ13C values (0.04 to 0.50‰) between the calculated and measured carbonyl derivatives, indicating that no effects on the carbon isotopic fractionation occurred in the simulation reactions of carbonyls with cysteamine. The subsequent ambient air measurements showed that $${\delta }^{13}$$ C values of formaldehyde, acetaldehyde, and acetone were − 36.02 to − 31.18‰, − 35.35 to − 32.01‰, and − 30.45 to − 29.09‰, respectively. Formaldehyde, acetaldehyde and acetone in the air were all enriched in the early afternoon by round 0.5–6‰ in 13C compared to other sampling durations, which caused likely due to the contribution from positive photo-oxidation production of hydrocarbons. Finally, it was revealed that all the measured $${\delta }^{13}$$ C values (− 36.02 to − 29.09‰) were in the range of the forecasted $${\delta }^{13}$$ C values (− 43.00 to − 26.00‰) in terms of 13C mass balance of carbonyls and their hydrocarbon precursors, indirectly confirming such positive productions in the air.

Upper Cretaceous sedimentary rocks are widely exposed around Trabzon, Giresun and Gümüşhane in the eastern Pontides. The sedimentary rocks are mainly composed of sandstones and marls, and the thicknesses of these rocks range from 170 m to 400 m. This paper focused on Late Cretaceous sandstones of Trabzon, Giresun and Gümüşhane regions to identify the concentrations, sources, deposition environment and conditions of certain heavy metal(loid)s (Zn, Pb, Cu, Ni, As, Co, Mo and V). Enrichment factor (EF), geo-accumulation index (Igeo), Pollution index (Pi), Pollution load index (Pln), Pb isotope and multivariate statistical analysis were performed to elucidate the pollution levels and sources. The mean concentrations of Zn, Pb, Cu, Ni, As, Co, Mo and V were 16.5, 10.8, 9.4, 13.2, 2.1, 4.4, 0.2 and 21 mg/kg, respectively in the Trabzon area, 35, 5.8,18.8, 102, 3.2, 18.6, 0.5 and 109 mg/kg, respectively in the Giresun area, and 36, 8.9, 14.7, 82, 3.9, 16.9, 0.3 and 106 mg/kg, respectively in the Gümüşhane area. In general, the evaluation indices exhibited that the sandstones were moderately polluted by As in the Trabzon area, and strongly polluted by Ni and As, moderately polluted by Co and V in the Giresun and Gümüşhane areas. The results of multivariate statistical analyses indicated that As and partly Pb might be originated from anthropogenic sources, whereas other metals were derived from geogenic origin. Lead isotopic analysis demonstrated two characterized signatures of the pollution sources in the sandstones, one related to geogenic origin and the other to coal, gasoline and pesticides. The sandstones were deposited in transition – marine environment under oxic – weak oxic conditions and paleoclimatic conditions ranged from arid to moist during Late Cretaceous period.

Bioaccessibility (the amount of a contaminant extracted by the gastrointestinal fluids during digestion) is often incorporated in the assessment of contaminated soils and foods. Current methods, including those published by the United States Environmental Protection Agency (US EPA) and United States Pharmacopoeia (USP), use a batch method of analysis which requires hours of extraction prior to instrumental analysis with inductively coupled plasma mass spectrometry (ICPMS). The continuous on-line leaching method (COLM) uses a more direct method of analysis as extracts are sent directly to the ICPMS instrument, which can reduce extraction time and give real-time elution kinetics. For this study, four reference soils (NIST 2710, NIST 2710a, NIST 2711a, and BGS 102) that are typically used with bioaccessibility methods were extracted using the COLM and US EPA and USP gastrointestinal fluids. With the transient time-resolved data from the COLM, differential elution indicating multiple Pb sources was observed in NIST 2710a, NIST 2711a, and BGS 102. Two methods for calculating the Pb isotope ratios to identify these sources included a point-by-point ratio average method and a more precise regression slope method. There was no statistically significant difference between the ratios obtained by these methods of calculation. Furthermore, NIST 2710a and NIST 2711a did not have any statistically significant difference between the Pb isotope ratios of two observed sources. BGS 102 had a significantly different secondary source of Pb, which was identified to be from Pb historically added to gasoline. Investigation into the regions these soil reference materials were sourced from supported this finding as BGS 102 comes from a more densely populated, industrialized area where soil contamination with Pb from gasoline is likely to be more prevalent. This type of bioaccessibility investigation is only possible with the COLM as it gives real time elution information. Incorporation of the COLM into future bioaccessibility studies (and inclusion of other elements for isotopic analysis, like Sr) will lead to more thorough and comprehensive bioaccessibility studies in the future.