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Due to the local emissions and transportations of air pollution from the most polluted regions such as the North China Plain and Yangtze Delta metropolitan, Xuzhou is becoming one of the most polluted cities in East China. The sources and formation processes of nitrogen-containing aerosols are therefore very complex. Two continuous aerosol measurement campaigns were conducted in this industrial city during the wintertime and summertime of 2016, to investigate the chemical compositions and potential sources of total nitrogen (TN, including 89% inorganic nitrogen and 11% organic nitrogen) in PM2.5. Abrupt enhancements of nitrogen-containing aerosols (e.g., NO3− and NH4+) were found in the winter, and nitrate became as a dominant contributor in high pollution days (e.g., PM2.5 > 150 μg m−3). Nitrogen oxidation ratios (NOR) correlated significantly with aerosol liquid water content (ALWC), which was estimated by ISORPROPIA-II model. This suggested heterogeneous process might be an important pathway in nitrate formation during the high PM2.5 days. The nitrogen isotope composition (δ15N) in TN varied from −1.3 to +13.2‰ with a mean value of 6.9 ± 3.6‰ during the wintertime. An isotope-based source apportionment approach was then developed using a Bayesian isotope mixing model (SIAR) with chemical compositions as an important constrain, which improved accuracy and reduced the overall uncertainties in estimations of TN sources. From this optimized model, we identified six major sources including NH3 from combustion-related emissions (49%), NH3 derived from animal wastes (6%), NH3 from urban volatilization (3%), NOx derived from coal combustion (33%), NOx from biomass burning (5%) and NOx from vehicles (3%). Our results demonstrated that ambient NOx was dominated by coal combustion. Since NOx and NH3 are important precursors for ammonium nitrate aerosols, controlling of combustion related NOx and NH3 emissions might be an important way to reduce PM2.5 levels in this region.

The spread of millet agriculture to southeast (SE) China is critical to understanding the region's economic pattern and its potential impact on the proposed initial expansion of proto-Austronesians. In this study, we present new multidisciplinary evidence for the development of millet agriculture from three Neolithic sites in Fujian Province, China: Hulushan, Pingfengshan and Huangguashan. The carbonized seeds from Hulushan indicate the existence of millet agriculture around 3842-3649 cal. BP. Meanwhile, we tested stable carbon and nitrogen isotope ratios of faunal remains (n = 22) from Pingfengshan and Huangguashan shell midden sites in a coastal area of Fujian. The stable isotope results for pigs (δ15N values range from 4.9 to 11.2‰, and δ13C values range from −24.1 to −11.2‰) show significant variations, suggesting that these pigs were fed different foods, including C3 plants, C4 plants and marine resources. Specifically, two samples of pig collagen with strong millet signals were directly dated to about 4000-3600 cal. BP. These new findings provide substantial evidence for a new understanding of the development of millet agriculture in SE China.

24 pages; International audience; The Earth’s oxygenation represents one of the most important environmental drivers of life’s evolution, with the first rise, known as ‘the Great Oxidation Event’ (GOE), corresponding to unpreceded accumulation of atmospheric O2, changes in the flux of marine nutrients and possibly global glaciations. However, the detailed evolution of the GOE is still debated, as for instance the accumulation trends of oceanic versus atmospheric oxygen and the nature of biogeochemical responses to oxygenation. Here, we combine organic carbon and bulk nitrogen isotope compositions with major element concentrations and iron speciation data of sedimentary rocks recovered from two drill cores (T2 and T3) in the early Paleoproterozoic Turee Creek Group, Western Australia, to track the redox evolution of marine conditions during the GOE. T2 core samples of the Kungarra Formation, which consists of clastic sedimentary rocks overlaid by the glaciogenic Meteorite Bore Member, were deposited ∼2.31 Ga ago. T3 core intercepts, from bottom to top, quartzite of the Koolbye Formation, and shales and stromatolitic carbonates of the Kazput Formation, which were deposited around ∼2.25 Ga. Samples from T2 show minor variations of δ13Corg (avg. −34.5 ± 1.7‰, n = 30), with no significant difference between siliciclastic and glaciogenic sedimentary rocks. In contrast, T3 samples display an increase in δ13Corg from −32.0 to −24.8‰ (n = 54) from shales to carbonates. In both T2 and T3 cores, δ13Corg values are inversely correlated with Al2O3, suggesting a strong petrological control on δ13Corg values, inferred here as resulting from variable contributions of detrital organic matter. Bulk N contents are low, from 13.5 to 56.7 ppm and 15.7 to 53.4 ppm in T2 and T3 samples, respectively. The δ15N values show a bimodal distribution, with one mode at +2.6‰ in T2 and another at +8.8‰ in T3, independent from lithological variations. This δ15N values shift between T2 and T3 is interpreted as reflecting a change from dominating N2-fixers to NO3-assimilating organisms. This implies an increase of NO3− availability, and thus of O2 concentration, during the time interval separating the deposition of T2 and T3 sediments. Dissolved NO3− and O2 concentrations of the Turee Creek marine basin are estimated from two models using N isotope data. The dissolved NO3− concentration has an upper limit ranging from 1.91 to 3.04 µM, about one order of magnitude below the average value of modern oceans. The lower limit for dissolved oxygen concentration ranges from 1.8 to 4.4 µM, which is two orders of magnitude lower than modern oceans. Together with previous studies, the present data place quantitative constraints on the redox changes associated with the Great Oxidation Event and illustrate a stepwise increase of NO3− bioavailability between 2.31 to 2.25 Ga, in relation with increasing O2 level.

The Ediacaran to Cambrian periods are characterized by the diversification and extinction of metazoans, carbon-cycle perturbation, and ocean oxygenation. Ocean nutrient cycles play a major role in the primary production and productivity-driven shallow water anoxia that was responsible for mass extinction in some Phanerozoic intervals. However, the relationships between these cycles and primary production and biological events during the Ediacaran to Cambrian periods have not previously been well-explored. This study presents stratigraphic profiles of nitrogen and organic carbon isotopes for sections belonging to the shelf and deep basin regions of the Yangtze Platform, South China. The nitrogen isotope profiles for these two regions share a similar trend, showing 1) relatively stable δ15N values of 5–6‰ in the early–middle Ediacaran (635 Ma–ca. 560 Ma) and 2) a shift towards lower δ15N values (3–4‰) since the Shuram δ13Ccarb Excursion. The δ15N values in the shelf section experienced a two-stage decrease from the late Ediacaran to Cambrian Stage 2 of the Terreneuvian series (down to −1‰) and then an increase from −1‰ to +4‰ across the Cambrian Stage 2/3 boundary (i.e., the Terreneuvian/Cambrian Series 2 boundary at 521 Ma). These data, in combination with previously reported nutrient profiles (δ15N, P, and Mo), allow the following new conclusions to be drawn. 1) The early–middle Ediacaran ocean was characterized by N Mo colimitation of primary production on a geological timescale that is different from the P limitation on long-term primary production in the modern ocean. 2) A shift in the ultimate limiting nutrient from N and Mo to P likely occurred in late Ediacaran–early Cambrian marine systems. This shift may have been a prerequisite for the extinction of small shelly fossils in response to the development of photic zone anoxia for several million years in Cambrian Stage 2, which was followed by the third and most prominent phase of metazoan diversification.

The nitrogen stable isotope ratios of NH3 gas (δ15N-NH3(g)) and particulate NH4+ (δ15N-NH4+(p)) have been used to determine the sources and elucidate the environmental dynamics of NH3(g) and NH4+(p). Some studies have determined the sources from δ15N-NH4+(p) in the ambient environment by using the nitrogen isotope fractionation value (Δδ15N). Studies of Δδ15N are limited and estimated the Δδ15N by theoretical calculation or laboratory experiments in closed systems. Here, we produced actual submicron-sized particles and exposed them to NH3(g) in a dynamic chamber under various experimental conditions of temperature and NH3(g) turnover rate. Δδ15N was lower when temperature was higher. For low turnover rates (about 0.9 per day), the Δδ15N was 31.6 ± 2.0‰ (mean ± 1SD), almost equal to the Δδ15N from theoretical calculations and laboratory tests in closed systems. Also, the relationship between Δδ15N, the temperature, and the turnover rate can be described in the equation form. This relationship can help to explain the discrepancies between Δδ15N values in closed and open systems. Our results could help to clarify the sources and mechanisms of particle formation.

Algae blooms frequently occur in the coastal areas of China, and pose numbers of adverse effects to marine environment. Nitzschia closterium is one of the algal species associated with algae blooms and was selected as the target algae of this work. This study was the first attempt to investigate the effect of carbon source restriction on the growth of N. closterium during marine phytoplankton blooms. Experiments were implemented in the CO2-restricted (include three nutritional conditions) and CO2-unrestricted systems, respectively. The stable isotope ratios (δ13C and δ15N) and fatty acids (FAs) profiles were measured. Here we hypothesized that the deficient carbon source could lead to the changes of stable isotope ratios and FAs profiles in the N. closterium. The results showed that the δ13C of N. closterium enriched under the CO2 restriction during the culture time (the isotopic difference greater than 27.8‰), whereas depleted under CO2-unrestricted system. Furthermore, within the CO2 restriction, δ15N showed the enrichment trend with increasing culture time under the nitrogen deficiency conditions, where leveled off under the nitrogen non-deficiency conditions. A total of 12 FAs in N. closterium were detected. Within CO2 restriction, FA 20:5n-3c was the predominant congener in all the three conditions. In addition, FA 16:1n-7c was highest in nitrogen deficient, while FA 16:3 was highest in phosphorus deficient condition. Consequently, the deficient carbon sources leaded to inhibit the FA (14:0, 16:0, 16:1n-7c, 16:3, 18:0, 18:3n-3c) synthesis. Overall, the present study provided the new approach to investigate the forming mechanisms of marine phytoplankton blooms by using stable carbon and nitrogen isotope compositions as well as FAs profiles.

Since NH3 is a significant precursor to ammonium in PM2.5 and contributes significantly to atmospheric nitrogen deposition but largely remains unregulated in China, the insight into the source of NH3 emissions by the isotopic investigation is important in controlling NH3 emissions. In this study, atmospheric concentrations of NH3 and water-soluble ion composition in PM2.5 as well as nitrogen isotope ratios in NH4+ (δ15N-NH4+) in Xiamen, China, were measured. Results showed that average NH3 concentration for the five sites in Xiamen was 7.9 μg m−3 with distinct higher values in the warm season and lower values in the cold season, and PM2.5 concentration for the two sites (urban and suburban) was 59.2 μg m−3 with lowest values in summer. In the PM2.5, NH4+ concentrations were much lower than NH3 and showed a stronger positive correlation with NO3− than that with SO42− suggesting the formation of NH4NO3 and equilibrium between NH3 and NH4+. Although the concentrations of NH3 at the urban site were significantly higher than those at the suburban site, no significant spatial difference in NH4+ and δ15N-NH4+ was obtained. The distinct heavier δ15N-NH4+ values in summer than in other seasons correlated well with the equilibrium isotopic effects between NH3 and NH4+ which depend on temperature. The initial δ15N-NH3 values were in the range of waste treatment (− 25.42‰) and fossil fuel combustion (− 2.5‰) after accounting for the isotope fractionation. The stable isotope mixing model showed that fossil fuel–related NH3 emissions (fossil fuel combustion and NH3 slip) contributed more than 70% to aerosol NH4+. This finding suggested that the reduction of NH3 emissions from urban transportation and coal combustion should be a priority in the abatement of PM2.5 pollution in Xiamen.

Decomposition of organic substances is one of the main processes responsible for the signatures of stable carbon and nitrogen isotopes (δ13C and δ15N) in soils and peats. However, the applicability of δ13C and δ15N signatures at the natural abundance level as indicators of the degree of peat decomposition is still debatable. We evaluated δ13C and δ15N depth patterns of peat cores sampled at nine sites in two nearby Alpine peat bogs with varying degree of organic matter degradation. Based on water table depths and past drainage intensities, the peat cores were divided into three degradation classes. We found similar overall depths patterns of δ13C and δ15N across the nine depth profiles and distinct differences between aerobic and anaerobic peat layers. Considerable differences in stable C and N isotope signatures of same depths were detected between profiles of the three classes, whereas depth profiles of peat cores with similar degree in peatland degradation were nearly identical. In the aerobic peat layers, δ13C and δ15N increased with depths at all study sites from 2.6‰ to 4.9‰ for δ13C and 3.2‰ to 7.0‰ for δ15N compared to the initial signatures of the plant biomass. Standardised δ13C of aerobic layers differ distinctly between slightly degraded peats at the open peat bog area, intermediately degraded peats at the tree-covered edge areas and strongly degraded peats at the former peat-cutting site. δ13C signatures of aerobic layers of strongly degraded peats were markedly more negative compared to the slightly degraded peats because of the selective 12C losses by microbial respiration. δ15N were more positive at strongly degraded than at slightly degraded sites in both, aerobic and anaerobic peat layers. The uniform stable isotope ratios in the anaerobic layers deeper than the local maxima of the isotopic signatures support the assumption that minor 13C fractionation occurs under anaerobic conditions. δ13C slightly declining with depth in the waterlogged layers of strongly degraded peat reflects the preferential utilisation and loss of labile organic compounds enriched in 13C. δ15N of strongly degraded peats was higher compared to well-conserved peat. The close relationship between the measured δ15N to δ15N modelled based on C:N ratios and bulk densities supports the assumption that the δ15N signature is the result of isotopic fractionation by peat decomposition. We conclude that peat decomposition strongly affects the δ13C and δ15N depth profiles of peat bogs and most likely overrides other factors, such as differences between plant species, litter components, atmospheric δ13C shift during peat formation, temperature effects, or type of mycorrhizal symbiosis.

Following the Cambrian Explosion, a significant extinction event occurred during the Cambrian Stage 4, with the extinction rate second only to that experienced in the end-Permian. To figure out the variation of N supply and elucidate the combined effect of O2 and N availability on the extinction event, this study presents the first set of high-resolution N isotope data from two shallow-water Cambrian Stage 4 drilling sections on the eastern Yangtze Platform. The results indicate that the sections are characterized by highly negative δ15N signatures during the lowermost and uppermost Cambrian Stage 4, which are indicative of strong NH4+ assimilation in an anoxic shallow ocean. During the rest of the Cambrian Stage 4, both of the study sections show stable δ15N values close to 0. This phenomenon can be best explained by enhanced N2 fixation in an oxic shallow ocean characterized by strong N limitation, resembling the low-latitude oligotrophic regions in the modern ocean. The oligotrophic environment was likely caused by enhanced denitrification/anammox as well as elevated P input associated with eustatic changes, and may have been widespread in the global shallow ocean during the Cambrian Stage 4. Our results lend new support to the traditional view that anoxia contributed to the mass extinction event. More importantly, it is emphasized that the oligotrophic environment may have played an important role in the prolonged decline of metazoan diversity during this stage.

The authors acknowledge funding support from the NSF FESD and Earth-Life Transitions programs (T.L.), the NASA Astrobiology Institute under Cooperative Agreement No. NNA15BB03A issued through the Science Mission Directorate (T.L.), the key project of the Natural Science Foundation of China (C.-F.C.) (No. 41730424), and the program of China Scholarships Council (Y.C.) (No. 201504910582). Nitrogen and carbon isotope analyses were funded by startup funds from Virginia Tech to B.C.G. The Ediacaran-Cambrian transition is characterized by the evolution of complex eukaryotes and rapid diversification of metazoans. However, linkages between environmental triggers and evolutionary patterns remain unclear. Here, we present high-resolution records of carbon and nitrogen isotopic data (δ13C, δ15N) for a drill core extending from the early Ediacaran Doushantuo Formation to the early Cambrian Jiumenchong Formation, located on the slope of the Yangtze Block. Our data show that sedimentary bulk nitrogen isotope values (δ15Nbulk) decrease progressively from the early Ediacaran to the early Cambrian, broadly concurrent with nitrogen isotope data from other sections throughout the Yangtze Block. During the early Ediacaran, however, δ15Nbulk values from our study are higher (maximum 11.2‰) compared to those from more restricted coeval sections, suggesting a higher degree of denitrification in our slope section. The early Ediacaran δ15Nbulk data from the Yangtze Block may thus provide indirect evidence for an upwelling system that led to a shallower redoxcline in slope environments of the Upper Yangtze region. Widespread light δ15Nbulk values from the early Cambrian (minimum −7.5‰) paired with excess silicate-bound nitrogen throughout much of the Yangtze Block are most parsimoniously interpreted as non-quantitative assimilation of ammonium (NH4+) with relatively high concentrations of NH4+ accumulating in the deep basin. Overall, the spatial and temporal trends in nitrogen cycling across the Yangtze Block suggest that fixed nitrogen was more bioavailable in the Ediacaran-Cambrian Yangtze Basin compared to previously studied Mesoproterozoic sections, although nitrogen speciation in the photic zone may have varied with time. Environmental factors such as oxygen levels and nitrogen bioavailability may have shaped the evolutionary trajectory of life on the Yangtze Block and potentially elsewhere across the Ediacaran-Cambrian transition. Postprint

Trophic positions (TPs) are key parameters for determining trophic magnification factors (TMFs) of environmental pollutants. We used compound-specific nitrogen isotope analysis of amino acids (CSIA-AA), with which we expected to obtain precise TPs, to estimate the TMFs of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the pelagic and benthic food webs of Tokyo Bay. The objective of the present study was to evaluate the difference between TMFs derived from TPs estimated by CSIA-AA (TPGlu/Phe) and TMFs derived from TPs estimated by bulk stable isotope analysis (TPbulk). TPGlu/Phe tended to be lower than TPbulk for many pelagic and benthic fishes. In the pelagic food web, the slopes for the relationships between PCB concentrations and TPGlu/Phe exceeded those between PCB concentrations and TPbulk for many congeners in samples from December 2014, and TMFGlu/Phe values (0.89–6.9) were higher than TMFbulk values (0.92–3.8). However, there were no statistically significant differences between the slopes of the relationships between PCB and PBDE concentrations and TPbulk or TPGlu/Phe for any of the congeners (analysis of covariance, P ≥ 0.08). In the benthic food web, PCB concentrations correlated with TPGlu/Phe for 9 PCB congeners in the samples collected during December 2014, although the concentrations of none of the PCB congeners correlated with TPbulk. A decrease of TMFGlu/Phe and TMFbulk values from December 2014 to May 2015 suggested that variation of PCB and PBDE concentrations in the organisms had more effect than TPs on the TMFs.

This study investigates the concentrations and δ15N values of NH4+ in PM2.5 at three heights (8, 120, and 260 m) on a 325 m tower in urban Beijing. NH4+ concentrations were lower during the Parade ...

Developing high-resolution, well-dated, marine proxies of environmental, climatic, and oceanographic conditions is critical in order to advance our understanding of the ocean’s role in the global climate system. While some work has investigated bulk and compound specific stable nitrogen isotope (δ15N) values in bivalve shells as proxies for environmental variability, the small concentrations of nitrogen found in the organic matrix of the shell calcium carbonate (hereafter carbonate) makes developing high resolution records challenging. This study investigates the potential of using the bulk and amino acid δ15N values of bivalve periostracum, the protein layer on the outside of the shell, as a proxy archive of nitrogen cycling processes and water source variability. Bulk δ15N values were measured on the periostracum, carbonate, and adductor muscle of Arctica islandica shells collected in the Gulf of Maine. Increased variability of isotopic values across growth lines compared to along growth lines support mechanistic reasoning based on growth processes that periostracum is recording changes in δ15N values over the course of the clam’s lifetime (up to 500 years). In addition, the statistically significant relationship between periostracum δ15N values and contemporaneous carbonate δ15N values of the same shell (r = 0.82, p Compound specific δ15N analyses of the periostracum of A. islandica shells were used to determine that the calculated trophic position of the clams in this study (1.4 ± 0.4) did not change significantly between 1783 and 1997. Phenylalanine δ15N values over the last 70 years show similar trends to that of the bulk record, suggesting that changes in bulk δ15N values over that time period are related to changes in baseline δ15N values. Periostracum δ15N values from shells collected in the western Gulf of Maine have decreased by ∼1‰ since the mid-1920s. This trend (−0.008‰/year) is not statistically different from the trend of previously published δ15N values of deep-sea corals from the entrance to the Gulf of Maine over the same time period. This coral record has been shown to indicate a shift in water source in the region and therefore the similarity between the two records suggest that changes in periostracum δ15N values are reflecting broader North Atlantic hydrographic changes. Our study introduces a new, high-resolution, and absolutely dated paleoceanographic proxy of baseline δ15N values, presenting the opportunity for future reconstructions of aspects of nitrogen cycling and water source changes in the global oceans.

To assess how nitrogen (N) availability affected ectomycorrhizal functioning and to test a theoretical model of ectomycorrhizal 15N partitioning, we measured C/N and δ15N in soils and nine fungal taxa in two Swedish N addition experiments. Sporocarp C/N and soil C/N decreased with fertilization, implying that N uptake per unit fungal growth increased. The S horizon was more responsive than the F and H horizons to changes in N addition, with N turnover for these horizons of 24, 57, and 57 y, respectively. Fungal and soil δ15N patterns identified fungal N sources, with N acquisition primarily from the S, F, or H horizon for two, five, and two taxa, respectively. With increasing N availability, sporocarp 15N enrichment increased in five taxa, in agreement with our model of fungal-plant N partitioning. However, it decreased in Lactarius rufus and Russula aeruginea, perhaps indicating shifts towards greater inorganic N uptake in these two taxa. This may relate to the generally lower sensitivity of these taxa to N deposition compared to the Cortinarius and Suillus taxa that fit our model of 15N partitioning.

Methylmercury (MeHg) biomagnifies through aquatic food webs resulting in elevated concentrations in fish globally. Stable carbon and nitrogen isotopes are frequently used to determine dietary sources of MeHg and to model its biomagnification. However, given the strong links between MeHg and sulfur cycling, we investigated whether sulfur isotopes (δ34S) would improve our understanding of MeHg concentrations ([MeHg]) in Arctic lacustrine food webs. Delta34S values and total mercury (THg) or MeHg were measured in water, sediments, and biota from six lakes near Resolute Bay, NU, Canada. In two lakes impacted by historical eutrophication, aqueous sulfate δ34S was ∼8‰ more positive than sedimentary δ34S, suggestive of bacterial sulfate reduction in the sediment. In addition, aqueous δ34S showed a significant positive relationship with aqueous [MeHg] across lakes. Within taxa across lakes, [THg] in Arctic char muscle and [MeHg] in their main prey, chironomids, were positively related to their δ34S values across lakes, but inconsistent relationships were found across entire food webs among lakes. Across lakes, nitrogen isotopes were better predictors of biotic [THg] and [MeHg] than δ34S within this dataset. Our results suggest some linkages between Hg and S biogeochemistry in high Arctic lakes, which is an important consideration given anticipated climate-mediated changes in nutrient cycling.

International audience; Obesity increases protein metabolism with a potential effect on nitrogen isotope fractionation. The aim of this study was to test the influence of obesity on human milk extracted protein 15N natural isotope abundance (NIA) at one month post-partum and to compare human milk extracted protein 15N NIA and bulk infant hair 15N NIA. This cross-sectional observational study involved 16 obese mothers (body mass index (BMI) ≥ 30 kg m−2 before pregnancy) matched with 16 normal-weight mothers (18.5 kg m−2 ≤ BMI

Rationale Foodcrust, the charred deposit adhering to the surface of containers, is a possible source of information on the function of ancient vessels and the subsistence of prehistoric humans. While the carbon isotope ratios in those materials are useful in detecting the usage of C4 plants, the reliability of nitrogen isotopic signatures has not been fully investigated. Methods The validity of bulk nitrogen isotope ratios has previously been investigated in coastal or riverine environments, where multiple resources from terrestrial and aquatic ecosystems were available, but not in terrestrial settings which provide a simpler mixing of terrestrial animals and plants. Hence, we conducted an exhaustive study on charred deposits on potsherds at two inland archaeological sites belonging to prehistoric Jomon hunter-gathers in central Japan, focusing on δ15 N values and atomic N/C ratios determined using an isotope ratio mass spectrometer and an elemental analyzer, respectively. Results For both sites, the δ15 N values showed significant correlations with the N/C ratios among samples from the inner surface, suggesting that these have recorded animal contribution. Furthermore, previous studies of Neolithic pottery from North Europe and Far East Russia bearing strong marine signatures had shown reasonably higher δ15 N values and N/C ratios in comparison with our data from terrestrial settings. On the other hand, some charred materials probably originating from plant starch showed lower values with both parameters. Samples from the outer surface produced less meaningful isotopic and elemental ratios altered by a thermal effect and/or contamination from soot. Conclusions When the samples of foodcrusts were selected carefully from the inner surface, bulk nitrogen isotopes and N/C ratios reflect the composition of what was cooked or processed in containers. This will provide useful information for understanding the human adaptation from the Late Pleistocene to the Holocene in conjunction with residual lipid analyses.

Nitrate (NO3−) is a key component of secondary inorganic aerosols and PM2.5. However, the contributions of nitrogen oxides (NOx) emission sources to NO3− in PM2.5 remain poorly constrained. This study measured nitrogen (N) isotopes of NO3− (hereafter as δ15N-NO3-) in PM2.5 collected at Beijing in 2014. We observed that δ15N-NO3- values in PM2.5 (−2.3‰ − 19.7‰; 7.3 ± 5.4‰ annually) were significantly higher in winter (11.9 ± 4.4‰) than in summer (2.2 ± 2.5‰). The δ15N differences between source NOx and NO3− in PM2.5 (hereafter as Δ values) were estimated by a computation module as 7.8 ± 2.2‰ − 10.4 ± 1.6‰ (8.8 ± 2.4‰). Using the Δ values and δ15N values of NOx from major fossil (coal combustion, vehicle exhausts) and non-fossil sources (biomass burning, microbial N cycle), contributions of major NOx sources to NO3− in PM2.5 were further estimated by the SIAR model. We found that seasonal variations of δ15N-NO3- values in PM2.5 of Beijing were mainly caused by those of NOx contributions from coal combustion (38 ± 10% in winter, 20 ± 9% in summer). Annually, NOx from coal combustion, vehicle exhausts, biomass burning, and microbial N cycle contributed 28 ± 12%, 29 ± 17%, 27 ± 15%, and 16 ± 7% to NO3− in PM2.5, respectively, showing actually comparable contributions between non-fossil NOx (43 ± 16%) and fossil NOx (57 ± 21%). These results are useful for planning the reduction of NOx emissions in city environments and for elucidating relationships between regional NOx emissions and atmospheric NO3− pollution or deposition.

Objectives This study explored the correspondence between stable isotope ratios and indicators of non-specific (periostitis and/or osteomyelitis) and specific (venereal syphilis) disease in a sample of human skeletons from a Portuguese archaeological collection. Additionally, this study examined stable carbon (δ13C) and nitrogen (δ15N) isotope ratios between individuals at different disease stages. Materials and methods δ13C and δ15N data from previously analysed skeletons without signs of infectious disease or physiological stress (n = 32) were compared to new data from skeletons with active (n = 6), healed (n = 7) or a combination of both lesions (n = 10). Skeletons with lesions (n = 23) were also grouped as having only healed tibial periostitis (n = 7), generalised non-specific (n = 5) and generalised specific infections (n = 2). The skeletons with lesions that did not fit into these groups (n = 9) were not used in this analysis. Results The δ15N from skeletons with non-specific generalised infections in several bones differed significantly when compared to skeletons that had either only healed tibial periostitis or were without lesions. Skeletons with venereal syphilis had similar mean δ13C and δ15N to either skeletons without signs of disease or those with only healed tibial periostitis. Discussion These results suggest different diets may be linked into an individual's susceptibility to these pathogens. Diet influences resistance to infectious disease, while infections decrease nutrient availability, increase malabsorption and resting energy expenditure. Potentially therefore, combining isotopic evidence of diet with pathology may contribute to a new understanding of health and lifestyle in the past.

Variations of stable carbon (13С and 12С) and nitrogen (15N and 14N) isotopic composition are analyzed in forest plants subjected to the emissions of large copper smelting plant. The studies were carried out in pine forests at ten test plots near the Karabash copper smelting plant and in the Ilmen State Reserve at South Urals. The 13С/12С and 15N/14N isotopic ratios were analyzed in leaves of plants of different functional groups (with ecto-, ericoid, or arbuscular mycorrhiza; with nitrogen-fixing symbiosis, and non-mycorrhizal). The 13С/12С ratio did not change under technogenic pollution. The low isotopic 15N/14N ratio was established in ectomycorrhizal trees, while the high ratio was found in herbs with arbuscular mycorrhiza, nitrogenfixing symbiosis, and non-mycorrhizal groups. As compared to nonpolluted habitats, the 15N content in leaves near the copper smelting plant increases by 2.7‰ in the ectomycorrhizal trees and by 3.4‰ in undershrubs with ericoid mycorrhiza, and by 2.2‰ in herbs with arbuscular mycorrhiza. This indicates a significant change in conditions of mineral feeding of plants under heavy metal pollution of natural ecosystems.

Three different lithotypes (xylitic, gelified and matrix) of Pliocene lignite from the Velenje Basin, Slovenia, were investigated to establish the variations of biomarker compositions in solvent extracts and the stable isotope (carbon and nitrogen) compositions of bulk material. From the biomarker results, the xylitic lithotype almost exclusively originates from gymnosperms (conifers such as Taxodiaceae), as indicated by the very high contents of sesquiterpenoids and diterpenoids but very low abundances of n-alkanes and non-hopanoid triterpenoids. The relative proportion of gymnosperms to angiosperms in the paleomire is reflected by the ratio of diterpenoids to the sum of diterpenoids and non-hopanoid triterpenoids (Di-/(Di-+Tri-terpenoids)), which is close to 1 (av. 0.99) in the xylitic lithotype. The predominance of diterpenoids from conifers in the xylitic lithotype is associated with high C/N ratios and intermediate total sulfur (TS). The very low abundance of hop-17(21)-ene and the absence of further hopanoids in the xylitic lithotype indicate a restricted influence of bacterial degradation under relatively dry conditions in the paleomire. The matrix lithotype also originated preferentially from gymnosperms under dry depositional conditions, as indicated by the high Di-/(Di-+Tri-terpenoids) ratio (0.95), low amounts of hopanoids and low TS content. The gelified lithotype is characterized by a high content of n-alkanes and wide variation of the Di-/(Di-+Tri-terpenoids) ratio (0.13–0.88), indicating a fluctuating contribution of angiosperms to the plant community in the paleomire during formation of this lithotype. In addition, the high abundance of hop-17(21)-ene and TS in the gelified lithotype compared with the other two lithotypes suggests the effect of bacterial activity under relatively wet/humid conditions during formation of the gelified lithotype, which is also supported by the considerable content of mid-chain n-alkanes. The high correlation between the δ13C and δ15N values (R2 = 0.68) indicates that the stable carbon and nitrogen isotope composition in the Velenje lignites were probably influenced by the same factors (e.g. precursor plants and/or microbial activity). The stable carbon isotopic values (av. −25.44‰) and nitrogen isotopic values (av. 2.15‰) of the xylitic lithotype are higher than those of the gelified lithotype (av. δ13C = −27.48‰, δ15N = 1.37‰) and the matrix lithotype (av. δ13C = −27.09‰, δ15N = 1.10‰). The relatively high correlation between the diterpenoid content and both δ13C and δ15N values suggests that the stable carbon and nitrogen isotopic composition of the three lithotypes might reflect the composition of the original plant material in the paleomire. The dominance of conifers as precursor plants in the xylitic lithotype might be the main reason for the higher δ13C values and probably also the higher δ15N values. The relatively higher δ15N values in the xylitic lithotype than in the other types could be explained by the high amount of decay-resistant xylem and low mineral (e.g. clay) content in the xylitic lithotype. The slightly lower δ13C but higher δ15N values in the gelified lithotype than in the matrix lithotype can be explained by variation of parent plant materials and the influence of bacterial activity.

Analysis of stable carbon and nitrogen isotope values (δ13C and δ15N) of animal tissues can provide important information about diet, physiology, and movements. Interpretation of δ13C and δ15N values, however, is influenced by factors such as sample lipid content, tissue-specific isotope discrimination, and tissue turnover rates, which are typically species- and tissue-specific. In this study, we generated lipid normalization models for δ13C and investigated the effects of chemical lipid extractions on δ13C and δ15N in Pacific walrus (Odobenus rosmarus divergens) muscle, liver, and skin. We also evaluated tissue-specific isotope discrimination in walrus muscle, liver, skin, and bone collagen. Mean δ13Clipid-free of skin and bone collagen were similar, as were mean δ15N of muscle and liver. All other tissues differed significantly for both isotopes. Differences in δ13Clipid-free and δ15N among tissues agreed with published estimates of marine mammal tissue-specific isotope discrimination factors, with the exception of skin. The results of this work will allow researchers to gain a clearer understanding of walrus diet and the structure of Arctic food webs, while also making it possible to directly compare the results of contemporary walrus isotope research with those of historic and paleoecological studies.

Excess ammonia (NH3) emissions and deposition can have negative effects on air quality and terrestrial ecosystems. Identifying NH3 sources is a critical step for effectively reducing NH3 emissions, which are generally unregulated around the world. Stable nitrogen isotopes (δ15N) of ammonium (NH4+) in precipitation have been directly used to partition NH3 sources. However, nitrogen isotope fractionation during atmospheric processes from NH3 sources to sinks has been previously overlooked. Here we measured δ15N NH4+ in precipitation on a daily basis at a rural forested site in Northeast China over three years to examine its seasonal pattern and attempt to constrain the NH3 sources. We found that the NH4+ concentrations in precipitation ranged from 5 to 1265 μM, and NH4+ accounted for 65% of the inorganic nitrogen deposition (20.0 kg N ha−1 yr−1) over the study period. The δ15N values of NH4+ fluctuated from −24.6 to +16.2‰ (average −6.5‰) and showed a repeatable seasonal pattern with higher values in summer (average −2.3‰) than in winter (average −16.4‰), which could not be explained by only the seasonal changes in the NH3 sources. Our results suggest that in addition to the NH3 sources, isotope equilibrium fractionation contributed to the seasonal pattern of δ15N NH4+ in precipitation, and thus, nitrogen isotope fractionation should be considered when partitioning NH3 sources based on δ15N NH4+ in precipitation.

Fertilisation with animal manure has been shown to affect crop chemical and isotopic composition, indicating that if manuring effects are not taken into account, there is a risk of overestimating consumer trophic levels in palaeodietary studies. The effect of fertilisation with seaweed, a common fertiliser in the past in coastal areas, has been the subject of several hypotheses, but until now has not been studied in this particular context. In this study the impact of fertilising bere, an ancient type of Scottish barley (Hordeum vulgare L.), with 25 t/ha and 50 t/ha seaweed, in comparison to a modern commercial mineral fertiliser and to no fertilisation, was investigated in a field trial on the Orkney Islands, Scotland. Stable isotope ratios (δ13C and δ15N) and elemental concentrations (B, Mg, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Mo, Cd and Pb) of grain, husk and straw samples were determined. Significant differences were found between treatment groups, including increases in δ15N values of 0.6 ± 0.5‰ (average ± 1σ for five replicate plots) in grain, and 1.1 ± 0.4‰ in straw due to seaweed fertilisation. Elevated concentrations of Sr in grain and husk samples (factors of 1.2–1.4) indicate the geographic tracer 87Sr/86Sr may also be affected. Fertilisation with seaweed thus needs to be considered for archaeological interpretations of chemical and isotopic compositions of crop and skeletal material for accurate palaeodietary and provenance reconstructions, particularly in coastal areas. Further implications of these results for studies concerning the effects of sea spray, radiocarbon-dating, and for dietary reconstructions using trace elements are also identified.

Bell pepper is one of the most cultivated crops in the world. By means of δ13C and δ15N values (‰), red bell peppers from Germany, The Netherlands, and Spain could be distinguished from each other. German fruits cultivated under greenhouse conditions were extremely depleted in 13C with δ13C values for fatty acids of partly less than -50‰. The strong depletion in 13C was in accordance with the use of biomethane-derived CO2 as growth regulator in the greenhouses. Seasonal variations in the δ13C values (‰) of German samples were tentatively assigned to varying CO2 enrichment during the annual production cycle. δ13C values (‰) of Dutch samples also correlated with greenhouse production, whereas Spanish samples most likely originated from open field cultivation. Additionally, the use of color measurement as a tool for presorting the samples was investigated in order to slim the scattering ranges of δ13C and δ15N values (‰) for clearer differentiation.

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. The nitrogen isotope compositions of charred wheat and barley grains reflect manuring intensity and have been used to reconstruct past manuring practices at archaeological sites across Europe and western Asia. To assess whether this analytical method can be applied to a staple crop in the West African Sahel, the nitrogen isotope values of Pennisetum glaucum grains in this region were determined and the effect of charring ascertained. Pennisetum glaucum ears were collected from fields in northeast Senegal, where the fertilisation histories of the plots (manure and/or household waste) were known. The nitrogen isotope values of these millet grains provide an insight into the values to expect for P. glaucum grains grown with low to moderate addition of manure/household waste in a semi-arid climate. Charring of P. glaucum grains by heating at 215–260 °C for 4–24 h increases their nitrogen isotope values by a maximum of 0.34‰. In light of these modern data, the nitrogen isotope values of millet grains recovered from the archaeological settlement mound of Tongo Maaré Diabal, Mali, can be interpreted as evidence for modest levels of manure/household waste input throughout the occupation of the site from cal ad 500–1150. This study demonstrates the potential for nitrogen isotope values of P. glaucum grains to shed light on past farming practices in West Africa.

The report presents original data on the isotope and chemical composition of the nitric thermal, cold underground, and surface natural waters, along with the water-enclosing rocks, of the Ulsk occurrence of thermal mineral waters (coasts of the Sea of Okhotsk, Khabarovsk krai). The data on the concentrations of oxygen and nitrogen isotopes and rare-earth elements, as well as on the volume activity of radon, in the treated underground and surface waters are obtained for the first time. Based on the data of automated monitoring of the physical parameters, the hydrogeological characteristics of the thermal waters are determined and the balneal properties are evaluated. The results obtained show the atmospheric origin of the nitric thermal waters of the Ulsk spring; however, the indicative chemical elements occurring in the considered waters represent the effects of deep-seated high-temperature processes as well. It is found that the waters warmed to 31°C within fractured Paleocene granites do not show significant variations of temperature, and the chemical composition varies exclusively under the interaction with the water-enclosing rocks. The profiles of the distribution of rare-earth elements (REEs) in the thermal waters represent the REE distribution in the water-enclosing granitoids and point to the limitation of the thermal water circulation with the area of the occurrence of the Paleocene granites of the Bekchi–Ul Massif. The temperature of the deep-seated reservoir measured by geothermometers was 80°C or below, which may indicate a depth of water circulation of 1–2 km or less.

In this paper, three bio-reactors were designed to determine the effects of different zero-valent iron (ZVI) powder dosages on anammox. Initially, a high ZVI dosage inhibited the anammox process, while anammox adopted the habitat after long-term culture. The continuous experiment indicated that R2 (100 mg ZVI/L) had no notable effect on shortening the anammox start-up time, while R3 (1000 mg ZVI/L) reduced the start-up time from 96 to 87 days. The stable nitrogen isotope test suggested that the anammox activity of R3 was higher than that of R1 (without ZVI powder) during the stabilisation stage. The anammox growth rate increased by 20% in R3, which was verified by the real-time quantitative PCR results. In comparison to the control, the anammox quantity increased by approximately 44.5% and 54% at 100 and 1000 mg/L on day 120, respectively, which is likely due to lower dissolved oxygen and oxide-reduce potential created by the ZVI powder. The addition of ZVI may release iron ions, reduce the DO and ORP, and regulate the habitat pH conditions, which are beneficial for promoting anammox bacteria. Moreover, ZVI may directly partake in the anammox reaction pathway and improve the total nitrogen removal.

Stable carbon and nitrogen isotope compositions were determined for camelid bone collagen, hair, and wool (fibre) sampled from textiles from archaeological sites in the Santa Valley (north coast of...

Fermentation is seldom considered in paleodietary analyses of Arctic and Subarctic peoples despite its ubiquitous traditional use as a cooking technique in high latitudes. Further, chemists have yet to assess the potential isotopic effects of fermentation on animal tissues, though isotopic research has documented measurable isotopic effects associated with other cooking techniques such as stewing and boiling. To measure the effects of fermentation on stable carbon and nitrogen isotopes, muscle tissues from 11 central Alaskan Chinook salmon (Oncorhynchus tshawytscha) were fermented following ethnographic methods. The results of this experiment demonstrate statistically significant isotopic differences in both carbon (−1.5‰) and nitrogen (+1.3‰) values taken from fermented muscle tissues compared to raw muscle tissues. Additionally, this study found a significant physiological fractionation effect between bone collagen and raw muscle (+3.3‰) consistent with previous research on Pacific salmon. In contrast to previous research, however, these tissues' nitrogen values show no significant fractionation. These findings have implications for central Alaskan dietary reconstructions, residue analyses, and our understanding of past subsistence practices in the Arctic and Subarctic.

Chlorophylls are produced by all photosynthetic organisms and are ideal targets for compound-specific isotopic studies of phytoplankton. In laboratory cultures, the difference between the nitrogen (N) isotope ratio (δ15N value) of chlorophyll and the δ15N value of biomass, known as epor, varies taxonomically, yielding potential applications for studying productivity in modern and ancient environments. Here we take advantage of the annual cyanobacterial bloom in Lake Erie, USA, to demonstrate epor patterns in a natural community. The resulting time series shows that environmental observations are similar to laboratory cultures: predicted epor endmember values range from 4.6‰ to 7.4‰ for eukaryotic algae, and −18‰ to −21‰ for cyanobacteria. Because the range and sensitivity of epor is similar between laboratory and natural settings, the data support the use of epor as a reliable tracer of the relative contributions of cyanobacteria and eukaryotic algae to nutrient utilization and primary production in lacustrine environments.

The southern Iberian megalithic cemeteries of Panoria and El Barranquete offer an excellent opportunity to explore ancient dietary patterns. Due to the special nature of these funerary contexts as palimpsests, a multi-proxy approach including multi-isotopic determination and a high-resolution dating framework was carried out. As a result, 52 samples were isotopically measured, of which 48 were also radiocarbon dated. With this new isotopic series as a basis, three main conclusions can be drawn: (i) the diet was based on C3 plants and terrestrial animals with no evidence of marine protein consumption; (ii) there is a general tendency for carbon isotope values to increase during the Bronze Age, which is consistent with the intensification of crop farming taking place at the time; and (iii) nitrogen isotope variability is especially remarkable when comparing collective to individual tombs. People buried individually show the highest and the most variable nitrogen ratios in contrast with those buried in collective tombs that show similar nitrogen values over time. These differences support the hypothesis of a conservative megalithic population resisting cultural innovations during the Argaric Bronze Age.

Nitrification of the environment has resulted from tremendous increases in the use of fertilizers for crop plants. This has increased runoff to coastal marine areas with consequences for primary production, benthos and upper trophic-level consumers, including sea ducks such as eiders Somateria mollissima. This species primarily relies on filter-feeding bivalves, especially blue mussels Mytilus edulis. Stable isotopes of nitrogen (measured as δ15N) are incorporated in the feathers of eiders during molt at a constant rate reflecting the amount in food eaten. We examined if δ15N values in feathers can link eiders to the nitrogen loads in the marine waters surrounding Denmark, which is the main wintering grounds for the Baltic/Wadden Sea eider population. We also assessed how the abundance of eiders is related to nutrients and dead zones with oxygen deficit. During 2014–2018 we collected samples from 489 eiders, and of these 100 were analyzed for stable isotopes δ15N. Eider feather δ15N was positively related to nitrogen abundance in marine waters. Local aggregations of eiders in late summer (the molting period) and in winter increased with the amount of nitrogen in the marine environment. Large eiders took longer to molt, they molted later and the daily growth increments of feathers were larger. Finally, larger eiders and eiders in higher numbers occurred in areas with hypoxia. These findings show that anthropogenic inputs to the coastal marine environment positively influence the abundance and aggregations of eiders.

Current evidence for oxygenated environments in the Mesoarchean is limited to the shallowest marine and fluvio-lacustrine settings. It is not until the Neoarchean that signs of oxygenated surface waters above outer shelf and basinal depositional environments become evident. In order to further explore the Mesoarchean redox landscape for signs of basinward surface water oxygenation, we present nitrogen and carbon isotope ratios from the turbiditic Mosquito Creek Formation of the Nullagine Group (∼2.9 Ga). The δ15N and δ13Corg values are invariant around −1.8‰ and −32‰ respectively throughout a 70 m section of drill-core, suggesting an ecosystem dominated by nitrogen fixers (anaerobic nitrogen cycling) and CO2 fixation by the Calvin Cycle. When compared with other Archean isotopic data, these results (i) provide further evidence that the Mosquito Creek Formation was deposited in a marine basin, and (ii) contain δ15N values that highlight the prevalence of nitrogen fixation by Mo-nitrogenase and the dearth of aerobic nitrogen metabolisms in the Mesoarchean.

To constrain the redox conditions and related nitrogen cycles during the Middle Permian (Guadalupian) to latest Late Permian (Lopingian) deep mid-Panthalassa, we determined the abundances of major, trace, and rare earth elements along with the carbon and nitrogen isotope ratios in shales interbedded with deep-sea cherts that are well-exposed at the Gujo-Hachiman section in the Mino-Tanba belt, SW Japan. The positive Ce anomalies together with low Mo and U enrichment factors (MoEF

Skeletal remains from Tlajinga 33 (33:S3W1) have been the focus of research in the southern sector of Teotihuacan since excavations took place in the 1980s. Recent excavations in Tlajinga Compounds 17 and 18 (17:S3E1 and 18:S3E1, respectively), located along the southern Street of the Dead, recovered nine additional skeletons. This article is a description of the burials from Compounds 17 and 18 and a comparative analysis of health, diet, and chronology across all three compounds (Compounds 17, 18, and 33). Here, we test the hypothesis that individuals between residential compounds at Tlajinga lived similar lives and that health and biogeochemical markers of individuals will reflect these similarities. Although the sample size is small, the paleopathological analysis of individuals at Compounds 17 and 18 indicates morbidity patterns similar to Tlajinga 33, but also that these residents were perhaps less susceptible to stressors during periods of juvenile growth. Stable carbon and nitrogen isotopes suggest that, overall, diets were analogous across compounds, but Compounds 17 and 18 were able to supplement their diet with a greater variety of plant resources. There were no clear dietary differences between higher and lower status individuals, however. Finally, accelerated mass spectrometry radiocarbon (AMS14C) dates indicate that residential living may have occurred later at Compound 18 than at Compound 17 and Tlajinga 33.

Most biological nitrogen transformations have characteristic kinetic isotope effects used to track these processes in modern and past environments. The isotopic fractionation associated with nitrogen fixation, the only biological source of fixed nitrogen (N), provides a particularly important constraint for studies of nitrogen cycling. Nitrogen fixation using the ‘canonical’ Mo-nitrogenase produces biomass with a δ^(15)N value of ca. −1‰ (vs. atmospheric N_2). If the ‘alternative’ V- and Fe-only nitrogenases are used, biomass δ^(15)N can be between −6‰ and −7‰. These biomass values are assumed to be relatively invariant and to reflect the cellular level expressed isotope effect of nitrogen fixation. However, field and laboratory studies report wide ranges of diazotrophic biomass δ^(15)N (from −3.6‰ to +0.5‰ for Mo-based nitrogen fixation). This variation could be partly explained by the release of dissolved organic N (DON) that is isotopically distinct from biomass. The model nitrogen fixer Azotobacter vinelandii secretes siderophores, small molecules that aid in Fe uptake and can comprise >30% of fixed nitrogen. To test whether siderophores (and other released N) can decouple biomass δ^(15)N from the isotope effect of nitrogen fixation we measured the isotopic composition of biomass and released N in Fe-limited A. vinelandii cultures fixing nitrogen with Mo- and V-nitrogenases. We report that biomass δ^(15)N was elevated under Fe limitation with a maximum value of +1.2‰ for Mo-based nitrogen fixation. Regardless of the nitrogenase isozyme used, released nitrogen δ^(15)N was also 2–3‰ lower than biomass δ^(15)N. Siderophore nitrogen was found to have a slightly higher δ^(15)N than the rest of the DON pool but was still produced in large enough concentrations to account for increases in biomass δ15N. The low δ^(15)N of siderophores (relative to biomass) is consistent with what is known from compound specific isotope studies of the amino acids used in siderophore biosynthesis, and indicates that other amino-acid derived siderophores should also have a low δ^(15)N. The implications for studies of nitrogen fixation are discussed.

The Santonian–Campanian (S–C) transition notably coincides with the termination of the Cretaceous Normal Superchron, a positive carbon isotope anomaly, and the enhanced preservation of organic matter associated with an oceanic anoxic event at ca. 84 Ma. The driving factors for the OAEs should include global warming, widely believed to be from volcanic sources, the delivery of nutrients to surface oceans from the continents, anoxic sediments and atmosphere, and variations in the configuration of ocean basins. To further investigate this phenomenon and evaluate whether there was a teleconnection between the marine and continental realm, we have studied a lacustrine succession in northeastern China (the Songliao Basin, which is ~3× the size of Lake Superior) that preserves two thick horizons of oil shales and a positive carbon isotope anomaly recorded in ostracode carbonate near the S–C boundary. This freshwater basin is one of the many that formed as a consequence of Mesozoic extensional tectonics in eastern Asia. The stratigraphic trends illustrate broad excursions in the isotopic compositions of carbonate, total organic carbon (including black carbon), and total nitrogen. The carbon isotope data suggest that maximal fractionation (eTOC) at the S–C boundary is caused by enhanced burial of organic carbon and inputs from anoxygenic photoautotrophs and chemoautotrophs, or from the buildup of CO2 in a lake environment. On the other hand, the nitrogen isotope data suggest that the lake became limited in nitrogen immediately before the deposition of the younger oil shale, resulting in the addition of new nitrogen to the system, likely as the result of diazotrophy or ammonium assimilation. To some extent, all of the features we described from the Songliao Basin have been recognized in Jurassic and Cretaceous OAEs. Insofar as climatically-sensitive lakes are typically supersaturated with CO2 relative to the atmosphere, we speculate that nutrient-driven primary productivity in massive lake systems may have released enough greenhouse gas (CO2, CH4, and N2O) into the atmosphere and therefore played a role in enhancing global temperatures and driving widespread anoxia in the Mesozoic oceans.

The taste and aroma quality and the price of tea are largely impacted by the geographical origin and harvest season. Tieguanyin teas differing in sites of growth and harvest season were characterized by the analysis of stable isotopes of nitrogen, carbon, hydrogen and oxygen (δ15N, δ13C, δD and δ18O). The δ15N, δ13C, δD and δ18O values were determined by elemental analyzer-isotope ratio mass spectrometry (EA-IRMS). All δ15N, δ13C, δD and δ18O values exhibited significant differences (p < 0.05) in the samples of different regional origins, whereas the δD and δ18O values highly differed (p < 0.01) between spring and autumn Tieguanyin teas. With the aid of chemometrics, orthogonal projection to latent structures discriminate analysis (OPLS-DA) achieved 96.08% recognition rate for Tieguanyin teas from different regions, whereas stepwise linear discriminant analysis (SLDA) allowed 100% differentiation. Moreover, principal component analysis (PCA) and hierarchical cluster analysis (HCA) methods revealed excellent discrimination possibilities for the teas according to seasonal variations. Additionally, our study presented a good alternative to differentiate teas from different sites of growth and harvest seasons and also to address the quality control and food authenticity concerns.

Planktic foraminifera-bound organic nitrogen isotopes (FB-δ 15 N) archived in sediments provide an opportunity to reveal past changes in marine nitrogen cycling in the upper water column. However, detailed knowledge about living foraminifera FB-δ 15 N is still critically lacking. This study presents the FB-δ 15 N analysis of planktic foraminifera collected from plankton tows and sediment traps in the South China Sea and the Bay of Bengal. Tests of Globigerinoides sacculifer with- and without-sac like chamber from plankton tows showed almost identical FB-δ 15 N values, suggesting that high thermocline δ 15 N is not incorporated into the carbonate tests during gametogenic calcification. Sediment trap samples revealed that species dwelling in the upper euphotic zone, such as Globigerinoides sacculifer , contained slightly depleted FB-δ 15 N relative to the deeper-dwelling species, such as Orbulina universa and Globigerinella siphonifera . The three species also contained FB-δ 15 N similar to δ 15 N of the suspended particulate organic matter at corresponding dwelling depths. Our results confirm the increase in FB-δ 15 N from shallower-dwelling species to deeper-dwelling species and these FB-δ 15 N differences (Δ 15 N vertical ) between shallower- and deeper-dwelling species may shed light on the nitrogen dynamics of the euphotic zone in the South China Sea, which is under the influence of the East Asian winter monsoon.

Widely used isotope ratio mass spectrometers have limited capabilities to measure metabolites, drugs, or small polyatomic ions without the loss of structural isotopic information. A new approach has recently been introduced that uses electrospray ionization Orbitrap to measure multidimensional isotope signatures of intact polar compounds. Using nitrate as a model compound, this study aims to establish performance metrics for comparisons with conventional IRMS at the natural abundance level. We present a framework on how to convert isotopolog intensities to δ values that are commonly used in the isotope geochemistry community. The quantification of seven nitrate isotopologs provides multiple pathways for obtaining the primary N and O δ values including non-mass-dependent O isotope variations, as well as opportunities to explore nonrandom isotopic distributions (i.e., clumping effects) within molecular nitrate. Using automation and the adaptation of measurement principles that are specific to isotope ratio analysis, nitrate δ15NAIR, δ18OVSMOW, and δ17OVSMOW were measured with a long-term precision of 0.4‰ or better for isotopic reference materials and purified nitrate from environmental samples. In addition, we demonstrate promising results for unpurified environmental samples in liquid form. With these new developments, this study connects the two largely disparate mass spectrometry fields of bioanalytical MS and isotope ratio MS, thus providing a route to measure new isotopic signatures in diverse organic and inorganic solutes.

Loranthus europaeus is one of the major plant parasites threatening the fragile ecosystems of oak forests in western Iran. The mistletoe is a hemi-parasite plant which grows on forest species, especially oaks. Carbon isotope composition (δ13C) has been central to understand the behaviour of mistletoes in the field. This study investigated C and N isotope compositions in leaves of L. europaeus and of its host oaks (Quercus libani, Q. infectoria and Q. brantii) in western Iran. The goal was to assess the degree of heterotrophy, and to estimate the carbon partition between host and mistletoe and possible consequences of this phenomenon for the ecology of these hemi-parasites. Leaf samples from mistletoe and host oaks were collected in the Mirabad forests of Sardasht, Iran. Ten adult trees of each oak species, with the hemiparasite species, were sampled for determination of leaf dry weight and area, concentration in carbon and nitrogen, and contents of stable carbon and nitrogen isotopes. In all three species, we found that the levels of δ13C of the host, were higher than those of the mistletoes. Quercus infectoria, with the highest leaf mass per area and the highest carbon and nitrogen contents on a mass basis, was the oak species with the highest degree of mistletoe heterotrophy, which was negatively related with the host-mistletoe δ13C difference. Our results also showed that host and mistletoe leaf masses per area can be indicators of the heterotrophic degree of the mistletoe and an easy alternative to the determination of δ13C. In conclusion, it seems that the difference in δ13C between host and mistletoe is reduced when the host leaf mass per area, Cmass and Nmass increase. This condition relates to an increased heterotrophic degree of mistletoe.

Although groundwater nitrogen pollution has been widely studied, the control of hydrogeological conditions on behavior of nitrogen compounds has been poorly understood. In this study, multiple stable isotopes (N/C/H/O), spectral characteristics of DOM coupled with water chemistry were used to reveal the sources and fate of nitrate and ammonium in three subareas with different hydrogeological conditions in the Central Yangtze River Basin. We identified three contrasting patterns of nitrogen sources and fate in groundwater controlled by different aquifer features. In a reducing porous aquifer mainly composed of carbonate minerals overlain by a thick low-permeability layer, the NH4–N concentration is high (mean 4.12 mg/L) but with quite low NO3–N concentration (mean 0.28 mg/L). The high ammonium is mainly from intense degradation of organic matter (OM), while denitrification at a higher rate results in nitrate removal. Feammox may be favored owing to abundant humics acting as the electron shuttle. In a weakly reducing to oxidizing porous aquifer mainly composed of aluminosilicate minerals overlain by a varying thickness of low-permeability layer, high ammonium occurs in a weakly reducing condition and is affected by both anthropogenic input and OM degradation, while high nitrate occurs in a more oxidizing condition and could be mainly from soil nitrogen, manure or sewage. Feammox may be also favored due to more acidic environment formed by weathering of aluminosilicate minerals, fluctuating redox condition and low abundance of labile organic carbon, while denitrification occurs at a slower rate coupled with concurrent re-oxidation of nitrite to nitrate. In an oxidizing porous - fissured aquifer system overlain by a thin low-permeability layer, the concentrations of ammonium and nitrate are both low, possibly due to strong hydrodynamic and flushing condition, although slightly higher concentration of nitrate exhibit similar sources and fate with the weakly reducing to oxidizing porous aquifer mentioned above.

RATIONALE The precision of the standard measurements of reference materials (RMs) is critical to normalize the raw δ15 N values of samples to the international scale. Because the measurement configuration is required to moderate the properties of both RMs and samples for obtaining an ideal measurement precision, it is important to determine the appropriate measurement configurations of RMs to achieve accurate nitrogen isotope compositions of samples. Therefore, it is critical to systematically examine RMs for optimizing the configurations and further improve the measurement precision. METHODS Gas source isotope ratio mass spectrometry (IRMS) coupled with an online elemental analyzer (EA) equipped with a single-quartz reactor was performed to analyze the nitrogen isotope compositions. Some adjustments were made as follows: (a) as the in-house working standard, urea was used to investigate the influences of combustion through moderating the different oxygen injections (0-20 mL) and sample delay times (10-12 s) and optimize the combustion conditions to enhance oxidation ability; (b) CO2 from the sample gas stream was removed to prevent interferences between CO2 and N2 ; (c) international RMs, including USGS40 (l-glutamic), IAEA600 (caffeine), and soil standard (B2153) with a low organic content, were systematically analyzed under the optimized configurations, and the precisions of the δ15 N values were further examined. RESULTS Our results showed that sufficient oxygen should be injected to improve the sample combustion when analyzing δ15 N in natural samples such as soil or marine sediment with low organic content. In addition, the measurement precision of δ15 N was affected by the tailing of the CO2 peak from the gas chromatography column into the subsequent sample measurement if the EA is equipped with a single-quartz reactor column. Our adjustments can produce an optimized repeatability and accuracy of the δ15 N value, especially for RMs with low organic content, and the uncertainty of the measurements is improved to be better than 0.1‰ under optimized configurations. CONCLUSIONS The analytical conditions such as the oxygen flow rate and injection time or sample introduction time into the EA need to be adjusted depending on the combustion conditions of the RMs and samples to obtain a reliable accuracy of measurement. We recommend that when analyzing δ15 N of natural samples such as soil or marine sediment samples with low organic content, more oxygen should be injected to improve the combustion of the samples. In addition, CO2 should be removed from the sample gas stream before being introduced into the isotope ratio mass spectrometer when the EA is equipped with a single-quartz reactor.