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The stable carbon (δ13C) and nitrogen (δ15N) isotope composition of human bone collagen is increasingly used to investigate past mobility and subsistence strategies. This study presents a compilation of 1298 carbon and nitrogen isotope analyses of archaeological human bone collagen from the British Isles spanning much of the Holocene, along with a compilation of 4148 analyses of modern and ancient isotope analyses from the major marine and terrestrial dietary resources from the same region. We convert ancient human stable isotope data to modern diet equivalent (MDE) values for humans, and convert the isotope composition of ancient dietary items to modern tissue equivalent (MTE) isotope values. These conversions enable a direct comparison of ancient and modern datasets. Results for food groups (plants, grain, herbivores, omnivores, shellfish, freshwater fish and marine fish) show a remarkably broad range of δ13CMTE values from ∼-36 to −7‰ and δ15NMTE values from ∼-2 to +21‰ and we provide estimates for each food type that can be used in dietary reconstruction in the absence of site-specific data. We further show that there is no significant change in terrestrial stable isotope baseline values over the Holocene, with observed variability in baseline values due to local eco-physiological, edaphic and microclimatic factors. The range of values expressed in the human sample set from the beginning of the Iron Age is relatively tightly clustered with 50% of all human modern diet equivalent results falling within a ∼2‰ range in δ13CMDE values (−25.5 to −27.5‰) and a ∼3.5‰ range in δ15NMDE values from (+4‰ to +8‰). From the Iron Age to post-medieval times there is a consistent progressive shift to higher δ13CMDE and δ15NMDE values at the population level. This shift likely reflects a combination of successive innovations associated with food production, preservation and transport that enabled a broader cross-section of the population of the British Isles to incorporate a higher proportion of animal, and particularly marine protein, into their diets.

Owing to the local characteristics of stable nitrogen isotopes in nitrogen oxides (δ15N-NOx) emitted from biomass burning, the lack of data on δ15N-NOx values associated with biomass burning in China limits the use of this parameter in identifying and quantifying the sources of atmospheric nitrate (NO3-) and NOx. The results showed that the δ15N-NOx values of open burning and rural cooking stoves in China ranged from -3.7‰ to 3.1‰ and -11.9‰ to 1.5‰, respectively. The δ15N values of nine biomass fuel sources (δ15N-biomass) ranged from 0.1‰ to 4.1‰. Significant linear relationships between the δ15N-biomass values and δ15N-NOx values of open burning (δ15N-NOx = 1.1δ15N-biomass - 2.7; r2 = 0.63; p

Ammonium (NH4+) is a well-known alkaline species for haze formation and possesses potential impacts on human health and biological diversity. To date, regional source apportionments of NH4+ have been poorly understood in Northern China Plain (NCP). In this study, daily PM2.5 samples were synchronously collected in eight cities over the NCP region. In addition to water-soluble ions, the nitrogen isotopic composition of NH4+ (δ15N–NH4+) was also analyzed. The average concentrations of NH4+, a targeted species, varied from 0.9 μg/m³ to 42.5 μg/m³. Note that the significant enhancements of NH4+ coincided with increasing PM2.5 masses, suggesting that NH4+ was one of the contributing species for haze formation. The δ15N–NH4+averaged 12.4 ± 6.9‰ and the average δ15N–NH3 were further calculated to be −9.0 ± 6.7‰ over the NCP region. Both δ15N–NH4+ and δ15N–NH3 showed negative correlations with PM2.5 mass and there were no obvious differences among those 8 cities. Combining air-mass backward trajectories and quantifying contributions of potential sources, we pointed out that non-agricultural sources (fossil fuel related and NH3 slip) were dominant sources (totally contributed 42%–85%) not only on extreme haze phase but also on haze accumulation/dissipation phase in all 8 cities of NCP region in winter, the heating season in North China. However, the contribution of fossil fuel related source reduced to only 20%–35% while livestock breeding source rose to about 15%–32% and NH3 slip source kept contributing about 30% on the extreme haze phase. Thus, we considered that volatilization-related agricultural sources (especially livestock breeding) could discharge considerable NH3 to form SIA-led haze event in urban cities of the NCP region, even though non-agricultural sources were the foremost sources.

Free amino acids (FAAs) are particularly interesting because they play an important role in the atmosphere, but their origins are not well understood. This study measured the concentrations of FAAs and water-soluble ions as well as δ15N values of Glycine (Gly) in total suspended particle (TSP) samples collected at Nanchang in 2017. The correlation of total FAAs concentrations with meteorological conditions and atmospheric oxidants showed that secondary formation processes could be an important contribution sources for FAAs in the atmosphere. Moreover, the concentrations of FAAs in aerosols may be affected by the wind directions and the regions where air mass passed. The correlations of FAAs with water-soluble ions and PMF analysis indicated that the concentration of FAAs in Nanchang aerosols was influenced by agricultural activities and dust sources, mixture of natural origins and biomass burning and mixture of secondary formation process and biomass burning. Interestingly, we also found that coal combustion and vehicle emission are not the sources for atmospheric FAAs. Based on δ15N values of free Gly, a Bayesian model was performed to obtain the individual fractional contributions of free Gly from major sources (natural and biomass burning sources) to aerosol Gly. Subsequently, applying fractional contributions of free Gly from biomass burning obtained by Bayesian model to the analysis result of PMF, the overestimated of the contribution of secondary formation processes and natural sources to atmospheric FAAs concentration caused by biomass burning source could be excluded. Our findings suggest that combining δ15N values of free Gly and PMF analysis could provide further information on the sources of atmospheric FAAs.

Stable nitrogen isotopes (δ15N) are used as indicators of trophic position (TP) of consumers. Deriving TP from δ15N of individual amino acids (AAs) is becoming popular in ecological studies, because of lower uncertainty than TP based on bulk δ15N (TPbulk). This method would also facilitate biomagnification studies provided that isotope fractionation is unaffected by toxic exposure. We compared TPAA and TPbulk estimates for a sediment-dwelling bivalve from two coastal sites, a pristine and a contaminated. Chemical analysis of PCB levels in mussels, sediments, and pore water confirmed the expected difference between sites. Both methods, but in particular the TPAA underestimated the actual TP of bivalves. Using error propagation, the total uncertainty related to the analytical precision and assumptions in the TP calculations was found to be similar between the two methods. Interestingly, the significantly higher intercept for the regression between TPAA and TPbulk in the contaminated site compared to the pri...

RATIONALE Squid is an important seafood resource for Asian and European countries. With the continuous development of processed squid products, an effective traceability system has become increasingly prominent. Here, we attempt to trace the fishery products of the main target species, jumbo squid (Dosidicus gigas), by using biochemical tracers. METHODS Carbon and nitrogen isotope ratios (δ13 C and δ15 N values) and fatty acid profiles were identified in squid from three harvest locations in the eastern Pacific Ocean by isotope ratio mass spectrometry and gas chromatography/mass spectrometry, respectively. Comparative analysis was used to evaluate the geographic variations in tracers and to identify the suitable discriminatory variables among origins. RESULTS Significant spatial variations were found in isotopic values and fatty acid profiles in squid muscle tissues, possibly because of different food availability and/or oceanographic conditions that each group experiences at a given location. The stepwise discriminant analysis indicated that δ15 N, C16:1n7, C17:1n7, C18:2n6, C20:1 and C20:4n6 were effective variables at differentiating origin. CONCLUSIONS Combined use of stable isotope ratios and fatty acid analyses could trace geographic origins of jumbo squid. This study provides an alternative approach for improving authenticity evaluation of commercial squid products.

Establishing links between migration patterns and trophic dynamics is paramount to ecological studies investigating the functional role habitats provide to resident and transient species. Natural tags in fishes, such as otolith chemistry and tissue stable isotopes, can help reconstruct previous environmental and dietary histories, although these approaches are rarely combined. A novel multiproxy natural tag approach was developed to estimate immigration patterns of juvenile Atlantic croaker Micropogonias undulatus, across contrasting salinity gradients in three subtropical estuaries of the western Gulf of Mexico. Juvenile young-of-year Atlantic croaker were collected along a latitudinal gradient that included positive, neutral, and negative estuaries, based on physicochemical (temperature, salinity, dissolved element) and isotopic (δ15N and δ13C) parameters. Otolith elemental chronologies of Sr/Ca and Ba/Ca were used to classify migratory types within each estuary, while tissue-specific isotope ratios revealed time since recent (liver~weeks) and longer term (muscle~months) diet shifts. Nitrogen isotopes in both liver and muscle tissues were highly correlated, suggesting tissue equilibrium and estuarine residence of at least 3 months, with geographic δ15N gradients reflecting the magnitude of anthropogenic nutrient enrichment within each estuary. Differences in isotopic equilibrium of muscle-liver δ13C values and variation in marginal edge otolith Sr/Ca and Ba/Ca suggested recent shifts in carbon source and habitat utilization, reflecting individualized movement across seascapes and connectivity of habitat mosaics. The multiproxy approach presented here identified diverse migration patterns and linked feeding and movement on regional (inter-estuary), local (intra-estuary), and individual scales to improve our understanding of habitat function across estuarine gradients.

Recent excavations at the sites of Strandvagen and Kanaljorden in Motala, Eastern Central Sweden, have unearthed complex and varied funerary remains from the Mesolithic. The two sites are situated ...

We report here stable nitrogen isotope values of amino acids and stable carbon and nitrogen isotope values of collagen in human (n = 18) and faunal remains from Tell el-Kerkh, which was a large settlement in the northern Levant during the Neolithic period. A unique outdoor communal cemetery involving > 240 individual burials was found in the Pottery Neolithic levels at Tell el-Kerkh. To test the hypothesis that the burial locations of individuals within the cemetery were determined by household units sharing food resources, we separated individuals from one layer into seven groups within the cemetery, and compared the isotope values of collagen, glutamic acid, and phenylalanine. The results of analysis of individual skeletons in the cemetery suggest that the early farmers had different isotope values based on their burial locations, perhaps indicating distinct household burial spaces.

Rationale Pesticide self-poisoning is a major method of suicide in many agricultural communities worldwide. In addition, there are a number of known crime cases related to people being harmed by insecticides. Methomyl, a prohibited insecticide in the Republic of Korea, has high toxicity and is frequently used for self-poisoning. In this study, we investigated the source of origin of methamyl in a fatal poisoning case using stable isotope ratio analysis. Methods Two bottles of Soju from a crime scene were seized and nine different brands of methomyl products were collected from the neighborhood for analysis. In addition, the gastric contents and energy drink from the person who had committed suicide were analyzed. Isotope analysis using GC/Isolink/IRMS was conducted to determine the source of the methomyl by comparing their carbon and nitrogen isotope ratios. Linear discriminant analysis was utilized to verify the results. Results Isotope ratio analysis showed that the isotope ratio ranges of methomyl found in the Soju, the gastric contents of the suicide victim, and the energy drink bottle were similar to those of a seized methomyl product, Samgong methomyl 2011 (SG11). Thus, it was assumed that SG11 was used in this fatal poisoning case. Conclusions This study demonstrates the potential of stable isotope ratio analysis for the determination of insecticide origin in fatal poisoning cases.

The Early Mississippian K-O (Kinderhookian-Osagean) carbon isotope (δ13C) excursion or TICE (mid-Tournaisian carbon isotope excursion) is one of the most prominent positive δ13C excursions of the Phanerozoic. Recent studies raise uncertainties about the representative shape (single vs. double spikes) and magnitude of this δ13C excursion (3‰ to ≥ 6‰ in South China; ≥ 5.5‰ in Europe; and ≥ 7‰ in North America) and the 3‰ unidirectional increase in nitrogen isotopes across the δ13C excursion, which is unanticipated considering the amount of organic carbon burial required to form the δ13C excursion and the resultant oxygen increase and global cooling. To test if stratigraphic completeness and spatial isotope variations caused such uncertainties, we have conducted paired carbonate carbon (δ13Ccarb), organic carbon (δ13Corg) and nitrogen (δ15N) isotope analyses across the K-O interval in two well-exposed sections of the southern Great Basin, western United States. The two sections represent proximal shallow-water and distal deep-water depositional settings of a west-dipping carbonate ramp. In the distal ramp section where no exposure surface is present, both δ13Ccarb and δ13Corg show double spikes with peak δ13Ccarb values up to 7‰ and a negative shift down to 4‰ between the peaks. In the proximal shallower-water section where two karstic disconformities are observed, δ13Corg shows similar double spikes but δ13Ccarb displays only a single peak with the highest value of 5.5‰. The missing δ13Ccarb spike is likely caused by diagenetic alteration below a karstic disconformity that lowered δ13Ccarb but not δ13Corg values, resulting in smaller magnitude of the δ13Ccarb excursion. These features suggest that the 7‰ magnitude and double spikes are more representative of the K-O δ13C excursion in the southern Great Basin. The smaller magnitude of the K-O δ13Ccarb excursion in some sections of the Great Basin and the TICE in other sections globally may have overprinted with local environmental/diagenetic signal or resulted from stratigraphic hiatus/truncation, which needs to be clarified in future research. The δ15N across the K-O δ13C excursion in the distal ramp section is decoupled from δ13C, with the majority of δ15N values around 4 ± 1‰ that do not show any obvious temporal trend. In contrast, δ15N values in the shallow-water section is coupled with the K-O δ13C excursion, with a 3‰ positive shift from 4‰ to 7‰ at the rising limb of the δ13C excursion and a negative shift from 7‰ to 1–2‰ at the falling limb of the δ13C excursion. The δ15N trend from the distal ramp section is, in some extent, comparable with that documented from a section in South China, while the coupled δ13C–δ15N pattern in the proximal section seems better explain the potential redox change across a prominent δ13C excursion. Considering the sensitivity of δ15N to redox conditions of depositional environments, a more comprehensive δ15N study in a broader paleogeographic context is required to better understand the interactions between carbon and nitrogen cycles across the K-O interval—a critical transition from the mid-Paleozoic greenhouse clime to Late Paleozoic Ice Age (LPIA).

This study explores the use of compound-specific nitrogen isotopes of amino acids (δ 15 N AA ) of coupled dissolved and particulate organic nitrogen (DON, PON) samples as a new approach to examine relative sources, transformation processes, and the potential coupling of these two major forms of N cycle in the ocean water column. We measured δ 15 N AA distributions in high-molecular-weight dissolved organic nitrogen (HMW DON) and suspended PON in the North Pacific Subtropical Gyre (NPSG) from surface to mesopelagic depths. A new analytical approach achieved far greater δ 15 N AA measurement precision for DON than earlier work, allowing us to resolve previously obscured differences in δ 15 N AA signatures, both with depth and between ON pools. We propose that δ 15 N values of total hydrolysable amino acids (THAA) represents a proxy for proteinaceous ON δ 15 N values in DON and PON. Together with bulk δ 15 N values, this allows δ 15 N values and changes in bulk, proteinaceous, and “other-N” to be directly evaluated. These novel measurements suggest three main conclusions. First, the δ 15 N AA signatures of both surface and mesopelagic HMW DON suggest mainly heterotrophic bacterial sources, with mesopelagic HMW DON bearing signatures of far more degraded material compared to surface material. These results contrast with a previous proposal that HMW DON δ 15 N AA patterns are essentially “pre-formed” by cyanobacteria in the surface ocean, undergo little change with depth. Second, different δ 15 N AA values and patterns of HMW DON vs. suspended PON in the surface NPSG suggest that sources and cycling of these two N reservoirs are surpisingly decoupled. Based on molecular δ 15 N signatures, we propose a new hypothesis that production of surface HMW DON is ultimately derived from subsurface nitrate, while PON in the mixed layer is strongly linked to N 2 fixation and N recycling. In contrast, the comparative δ 15 N AA signatures of HMW DON vs. suspended PON in the mesopelagic also suggest a possible PON source for some HMW DON in the mid-water column. Together, these results suggest that conversion of relatively labile ON to less labile DON by heterotrophic bacteria (a “microbial nitrogen pump”) may be the key pathway for production and alteration of DON in both the surface and the mesopelagic oligotrophic ocean. Finally, in contrast to THAA, δ 15 N values of the other-N were substantially less affected by heterotrophic alteration, which may be consistent with a larger than expected contribution of amino sugars, or other less labile nitrogenous organic molecules.

Great attention has been paid to the origin of anomalously low nitrogen isotope values during the Late Cretaceous. Nitrogen isotope values are often as low as − 3 ‰ and are typically less than + 2 ‰ , even in relatively organic matter-lean sediments. Here we evaluate nitrogen isotope variability during a relatively quiescent phase of the Late Cretaceous Greenhouse, between Oceanic Anoxic Events 2 and 3, using the black shales of Demerara Rise (DR). Selection of this site allows us to isolate some of the factors that control nitrogen cycle dynamics and contribute to low nitrogen isotope values. New N-isotope measurements from ODP Site 1259 reveal δ 15 N values that range from + 0.2 ‰ to −3.5‰ and oscillate by 1.5‰ to 3‰ over 1.6 million years (Ma). Temporal calibration of our data using a new astronomical time scale reveals a strong ∼100 thousand year (ka) eccentricity cyclicity in δ 15 N. We attribute this cyclicity to oscillations in the position of the intertropical convergence zone (ITCZ) over DR that modulate upwelling intensity, chemocline depth and the degree of 15N-depletion. We also recognize a statistically significant correlation ( p = 0.0022 ) between the TEX86 indices and δ 15 N, with the lowest δ 15 N corresponding to the highest TEX86 indices. This relationship suggests that the activity and ecology of ammonia oxidizing Thaumarchaeota and the δ 15 N of dissolved inorganic nitrogen utilized by primary producers are linked. We therefore interpret the observed variability in the δ 15 N data and TEX86 indices as primarily reflecting fluctuation of upwelling intensity and chemocline depth, and the significant inverse relationship between these data sets suggests that caution should be exercised when interpreting the TEX86 in terms of temperature in similar paleoenvironmental settings.

Stable isotope ratios (13C/12C and 15N/14N) of South African lambs from different regions were measured by isotope ratio mass spectrometry (IRMS). Homogenised and defatted meat of the Longissimus lumborum muscle was assessed. The Ruens and Hantam Karoo regions had the lowest (P≤0.05) δ13C values related to the presence of C3 plants (lucerne and Karoo bushes, respectively). The Northern Karoo, Namibia and Bushmanland had the highest δ13C values likely due to a high proportion of dietary C4 grass species. The δ15N values were highest for Central Karoo, Semi-extensive, Namibia and Hantam Karoo, while Ruens and Feedlot had the lowest nitrogen isotope values (P≤0.05). Classification of origin (Karoo vs. Non-Karoo) using discriminant analysis allowed 95% and 90% correct classification of the samples for the estimation model and validation models, respectively. The results confirm that IRMS provides sufficient discriminative power to classify lamb meat of varying origin.

The beginning of the Romano-British period in the 1st century AD was marked by changes in agriculture, economy and material culture at varying rates. Rural areas such as Oxfordshire may have been slower to incorporate Roman agriculture practices, possibly as a result of limited demand from urban centres or local conditions. In order to gauge the scope of agricultural continuity in rural areas, this study uses stable carbon and nitrogen isotope analysis of bone and tooth dentine collagen from forty cattle and sheep from five sites from the Chalk Downs of the Ridgeway and the adjacent Vale of the White Horse to determine where these animals grazed. While no significant differences in δ13C are present, the data show a clear distinction in δ15N values, suggesting that herds from the Downs and the Vale were largely kept separately, while a small number of outliers also suggest that some individual animals were moved between different pastures earlier in their lives. This mirrors very similar findings from the Early-Middle Iron Age in the same study area (Schulting et al., 2019), suggesting long-term continuity in at least some aspects of animal husbandry. The results of this study suggest that local environment and the identities of rural communities may have had a major impact in determining which agricultural practices were adopted or rejected.

The Ordovician-Silurian (O/S) transition was a critical geological interval, during which significant biological events and dramatic environmental changes occurred. Extensive research has proven that changes in the ocean environment are one of the main causes of events that affect the biosphere. However, the redox structure and related geochemical evolution of the ocean during the O/S transition remain under debate. N isotopes are thought to have significant potential for further elucidating the oceanic redox structure and related geochemical evolution during the O/S transition, and are an effective supplement to the former environmental proxies of bottom sediments. This study presents high-resolution N isotope data from a well-sequenced drill core across the O/S transition from the Lower Yangtze Platform, South China, showing an interesting isotopic variation with high δ15N values (+1‰ to +4‰) during the Late Katian to Hirnantian ages of the Ordovician and much lower values (−1‰ to +1‰) during the Rhuddanian Age of the earliest Silurian. This δ15N variation is mostly controlled by ocean redox conditions and the corresponding changes in the nitrate reservoir. Combined with previously reported δ15N data, a redox-stratified ocean with a relatively deep redox transition zone was reconstructed according to the distribution of δ15N profiles across different palaeogeographic locations. The lower δ15N values and more reducing conditions in deep water sections demonstrate that glacio–eustatic fall, rather than increased upwelling, was likely the main driver of the global redox change during the Late Ordovician. Furthermore, a global δ15N decrease during the Late Katian may be associated with the debated Boda warm event, and the up to six positive δ15N excursions observed during the Hirnantian might suggest the cyclicity of the glaciation process.

Our aim is to measure the interstellar 14N/15N ratio across the Galaxy, to establish a standard data set on interstellar ammonia isotope ratios, and to provide new constraints on the Galactic chemical evolution. The (J, K) = (1, 1), (2, 2), and (3, 3) lines of 14NH3 and 15NH3 were observed with the Shanghai Tianma 65 m radio telescope (TMRT) and the Effelsberg 100 m telescope toward a large sample of 210 sources. One hundred fourty-one of these sources were detected by the TMRT in 14NH3. Eight of them were also detected in 15NH3. For 10 of the 36 sources with strong NH3 emission, the Effelsberg 100 m telescope successfully detected their 15NH3(1, 1) lines, including 3 sources (G081.7522, W51D, and Orion-KL) with detections by the TMRT telescope. Thus, a total of 15 sources are detected in both the 14NH3 and 15NH3 lines. Line and physical parameters for these 15 sources are derived, including optical depths, rotation and kinetic temperatures, and total column densities. 14N/15N isotope ratios were determined from the 14NH3/15NH3 abundance ratios. The isotope ratios obtained from both telescopes agree for a given source within the uncertainties, and no dependence on heliocentric distance and kinetic temperature is seen. 14N/15N ratios tend to increase with galactocentric distance, confirming a radial nitrogen isotope gradient. This is consistent with results from recent Galactic chemical model calculations, including the impact of superasymptotic giant branch stars and novae.

For nitrogen (N) migration and transformation from unsaturated soil to groundwater, the N stable isotope (δ15N) was modified due to the isotope fractionation effect. To quantitatively evaluate the N cycle in groundwater systems, the determination of isotope fractionation is decisive. In this research, for the first time, incubation experiments were conducted to quantitatively investigate the N isotope enrichment factor (ϵp/s) associated with ammonification in unsaturated soil. Under weak isotopic fractionation, the Rayleigh function cannot be directly applied during ammonification. Thus, we proposed a different method calculating the ϵp/s values during ammonification, which were −0.03‰ for 15 °C and −2.34‰ for 30 °C. Moreover, for the first time, experimental equipment is presented to explore the isotopic fractionation effects under the co-occurrence of nitrification and volatilization. The results indicated that the isotope effect of volatilization during nitrification can be ignored in this study, and the ϵp/s values during nitrification were −10.59 and −6.81‰ at 15 and 30 °C, respectively. This work provides a novel arrangement determining the crucial parameters for identifying nitrate pollution sources in groundwater systems.

The δ13C, δ15N and C/N ratio of the particulate organic matter (POM) in western Guangdong waters were determined to evaluate the impacts of the coastal currents on the POM in spring and summer. The predominance of photosynthetic organic matter in the nearshore was triggered by nutrients brought by the coastal currents in spring and summer, while the proportion of terrestrial organic matter in the offshore was very high in spring but low in summer. In spring, the weaker and narrower coastal currents carried insufficient nutrients (phosphate deficiency) to the offshore and prohibited phytoplankton production. This scenario contributes to the dominance of terrestrial organic matter transported by the cyclonic circulation beyond the coastal currents in the offshore in spring. The Bayesian mixing model reveals that the proportion of terrestrial organic matter (with 75.8% of C3 plants) in the offshore was higher in spring than in summer (with 33.7% of C3 plants).

The surface distribution of lipid biomarkers, elemental and isotopic compositions ( δ 13 C and δ 15 N, C/N) were investigated from coastal sediments of Brunei Bay, in order to understand the sources and biogeochemical processes of the organic matter. Fatty acid biomarkers from terrestrial higher plants (e.g., long-chain fatty acids > 20), phytoplankton (e.g., 20:5n-3 and 22:6n-3) and microbial activity (e.g., iso-, anteiso fatty acids, 10Me-16:0) were identified. The ratios of carbon and nitrogen isotopes ( δ 13 C, δ 15 N) and C/N had values ranging from –30.62 to –27.43‰, 1.70 to 3.57‰, and 4.07 to 15.62 respectively, suggesting the prevailed inputs of terrestrially-derived organic matter sources with typical characterization of mangrove estuaries. Principal component analysis separated lipids of autochthonous aquatic production as the major source, followed by allochthonous terrestrial derived input. The presence of bacterial derived lipids and short chain lipids with low and C/N ratios suggest the preferential utilization and decomposition of organic matter by microbial activity. An enrichment of the δ 15 N ratios could be due to marine cage culture activities and surface runoff from cultivated areas via fluvial transport.

The present study aimed to determine the total organic carbon (TOC), total nitrogen (TN), the carbon‑nitrogen ratio (TOC/TN), carbon isotope (δ13C), and nitrogen isotope (δ15N) in five sediment cores collected from upstream to downstream of the Rio Serinhaem estuary, State of Bahia, Northeast Brazil, in order to investigate the origin of the deposited organic matter (OM).Significant positive correlation was found between TOC and NT (rs = 0.75); TOC/TN and TOC (rs = 0.64); δ15N and TOC (rs = 0.72); and δ15N and TOC/TN (rs = 0.63). The values of δ13C and δ15N found are characteristic of terrestrial sources. The TOC/TN ratio confirmed the data found for δ13C and δ15N, which recorded the origin of organic matter from terrestrial C3 type plants. Upstream of the estuary, the highest means of TOC/TN were found (T1 = 36.9 and T2 = 24.4), as reflected by the increase in TOC content or reduction in TN. The OM along the estuary is predominantly from plants with a C3 photosynthetic pattern, indicating that the Serinhaem River estuary is considered a relatively well-preserved environment.

Carbonate hardparts of marine organisms are frequently explored archives of their ambient seawater composition. Among the various materials used, the hardparts of molluscs are particularly relevant because their accretionary growth allows for the compilation of time-resolved proxy data sets. Here, we explore to which extent the calcium isotope values of aragonitic cephalopod hardparts represent proxies for seawater composition or record a trophic level signal. In a first step, we collect Ca isotope data from a diverse set of modern cephalopods, including Nautilus, Sepia and Spirula. These taxa differ in their external/internal hardparts, life spans, trophic levels, habitat depth, hinterland geology, and resulting runoff. In a second step, we have put these concepts to the test and explore the calcium isotope signatures of Lower Cretaceous (lower Albian) well-preserved cephalopods (nautiloids, ammonoids and belemnites) and bivalve shells from Madagascar. In the sense of a methodological comparison, two measurement approaches (double spike (δ44/40Ca, TIMS) and bracketing standard (δ44/42Ca, MC-ICP-MS) techniques are applied. Calcium from organic matter and intra-shell variations on bulk δ44/40Ca isotope values are explored. Four protocols (H2O2, NaOH, HClO4, incineration up to 250 °C including subsequent rinsing with deionised water and Ca removal) are applied to destroy organic matter in the shell material and to dissolve any non‑carbonate bound Ca, i.e., its metastable secondary Ca reservoir. These are equally successful, and the Ca isotope values of the purified carbonate phase plot on the equilibrium mass fractionation line. Samples not treated to destroy or remove their organic matter do not fall on the equilibrium mass fractionation line. Limitations of sample pre-treatment are reflected by a slight shift towards lower values in the case of incineration experiments at 650 °C. This feature is best explained in the context of a mineralogical phase transformation of aragonite to calcite. Calcium isotope values show no significant variability when sampling hardparts with different microstructures (callus, nacre, prismatic layer) and mineralised during different ontogenetic phases (outer shell, septa). Perhaps most relevant, mean δ44/40Ca (‰ SRM-915a) isotope values for Nautilus (0.72‰ ±0.19 2SD), Sepia (0.79‰ ±0.18 2SD), and Spirula (0.50‰ ±0.18 2SD) lack evidence for a significant control by trophic levels. Nitrogen isotope data and known diets for all three cephalopods serve as a litmus test for these data, which do not correlate with this dietary proxy information. These results are considered encouraging and suggest that Ca isotope values of cephalopod shells are proxies for their ambient seawater Ca isotope signatures. According to our data, however, it remains unclear to which extend cephalopod hardparts record the Ca isotopic composition of past seawater. Specifically, the data from three different modern species point to a mean Δ44/40Ca(ceph-seawater) fractionation of −1.21‰ (± 0.15 2SD). Based on our work, we present a best practice guide for cephalopod Ca isotope analysis and interpretation.

We sampled mussels (Mytilus edulis) along the coast of the Korean peninsula, and determined their trophic position (TP) using the nitrogen isotope ratio of amino acids (TPglu/phe). The TPglu/phe of mussels (2.0 to 2.5) is higher than TP of herbivores, suggesting that TP normalization is required to remove the trophic enrichment effect on basal nitrogen isotope ratio. We found similar trends in spatial variation between nitrogen isotopic baseline based on nitrogen isotope ratio of bulk tissue (δ15Nbase-bulk) and that of phenylalanine (δ15Nbase-phe) in mussels, reflecting different nitrogen sources among sampling sites. The present study suggests that δ15Nbase-bulk and δ15Nbase-phe are powerful tools to trace nitrogen isotopic baselines from primary consumers as well as higher TP organisms.

This study extends the analysis of previously well studied biodegraded crude oil case history sample sets. The analytical window is extended into the high molecular weight, aromatic hydrocarbon and non-hydrocarbon fraction of crude oils, using a 12 T ultra-high resolution mass spectrometer (FTICR-MS). Biodegradation is pervasive across compound groups and extent of degradation appears dependent on compound abundance and hence availability. Oil constituents with molecular weights up to m/z 600 (carbon number 44) are affected by in-reservoir biodegradation. Apart from special, specific compound groups possibly related to the active reservoir biomass, all hydrocarbon and single heteroatom-containing compound classes are depleted by biodegradation. Production of various highly alkylated species indicate that transformation of crude oil components often involves derivatization and preservation rather than just complete destruction of high molecular weight compounds. Whereas one case study shows good correlation between depletion of S1 species and a strong increase in SO2 species, a nitrogen enriched oil suite shows an analogous trend in the transformation of N1 species to the corresponding NO2 species. Increase in O2 species are seen in both sample sets indicating partial oxidation is a major overall process in in-situ reservoir biodegradation. These variations are important geochemically but also impact transport, interfacial and corrosion properties of oils. Nitrogen isotope systematics indicate that nitrogen-containing compounds might act as nitrogen nutrient sources or mainly as carbon sources for the microorganisms causing in-situ reservoir biodegradation depending level of biodegradation. Distributions of some heterocyclic species add a very biodegradation resistant parameter set, to the petroleum geochemists arsenal.

Made available in DSpace on 2018-11-26T17:44:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-12-01 National Forest of Carajas Instituto Tecnologico Vale (Paleoclimate Project) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Lake Tres Irmas (LTI), the largest upland lake in the Brazilian Amazonia, located in Serra dos Carajas, was characterized using multi-elemental and isotope geochemistry (delta 13(C) and delta N-15) to understand the significance of organic and inorganic sources, weathering and sedimentary processes on the distribution of elements in lake bottom (surficial) sediments. Carbon and nitrogen isotopes from sedimentary organic matter suggest C3 terrestrial plants (forests > canga vegetation), macrophytes and freshwater DOC as the main sources. Sediments are depleted in most of the major oxides (except Fe2O3 and P2O5) when compared to upper continental crust (UCC) and their spatial distribution is highly influenced by catchment lithology. Principal Component Analysis revealed that most of the trace elements (Ba, Sr, Rb, Sc, Th, U, Zr, Hf, Nb, Y, V, Cr, Ga, Co, Ni) and REEs are closely correlated with Al and Ti (PC1; Group-1), so their redistribution is less influenced by post-depositional process. This is due to their relative immobility and being hosted by Al-bearing minerals during laterization. High Chemical Index of Alteration (CIA), Mafic Index of Alteration (MIA) and Index of Laterization (IOL) values indicate intense chemical weathering at source areas, but the weathering transformation was better quantified by IOL. A-CN-K plot along with elemental ratios (Al/K, Ti/K, Ti/zr, La/Al, Cr/Th, Co/Th, La/Sm, La/Gd, Zr/ Y, and Eu/Eu*) as well as chondrite-normalized REE patterns show that the detritic sediments are mainly sourced from ferruginous laterites and soils in the catchment, which may have characteristics similar to mafic rocks. (C) 2017 Elsevier Ltd. All rights reserved. Inst Tecnol Vale, Rua Boaventura da Silva 955, BR-66055090 Belem, Para, Brazil Univ Fed Para, Inst Geociencias, Programa Posgrad Geol & Geoquim, Av Augusta Correa 1, BR-66075110 Belem, Para, Brazil Geocon Environm Consulting, London, ON N6G 3H9, Canada Ctr Energia Nucl Agr, Lab C-14,Av Centenario 303, BR-13400970 Piracicaba, SP, Brazil Dept Ferrosos Norte, Gerencia Meio Ambiente Minas Carajas, Estr Raymundo Mascarenhas S-N Mina N4, BR-68516000 Parauapebas, Para, Brazil Univ Estadual Paulista, Inst Biociencias, Ctr Isotopos Estaveis, Dist Rubiao Jr S-N, BR-18618970 Botucatu, SP, Brazil Univ Estadual Paulista, Inst Biociencias, Ctr Isotopos Estaveis, Dist Rubiao Jr S-N, BR-18618970 Botucatu, SP, Brazil National Forest of Carajas: SISBIO 35594-2 CNPq: 442088/2014-0 CNPq: 302839/2016-0 CNPq: 306450/2013-5

Freshwater resources are under stress around the world due to rapid urbanization and excessive water consumption. Cyanobacterial blooms have occurred frequently in surface waters, which produced toxic secondary metabolites causing a potential harm to aquatic ecosystems and humans. In this study, the relationship between different types of nitrogen source and the algal growth of Anabaena flos-aquae, which was isolated from Dianchi Lake in southern China, was investigated. Experiments were accomplished by using four types of isotope tracers including 15N-ammonium chloride, 15N-sodium nitrate, 15N-urea, 15N-l-alanine in culture medium to characterize the biosynthesis of 15N-anatoxin-a (ATX-A), which is a major algal toxin from A. flos-aquae, through liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that all these four types of nitrogen can be incorporated into algal cells. The ATX-A production with urea as the nitrogen source was much higher than that with the other three types of nitrogen. The 15N labeling experiments further demonstrated that the uptake of organic nitrogen nutrients was significantly greater than that of inorganic nitrogen. These results provide new evidence and deeper insight to explore the biosynthesis of ATX-A in the specific strain of A. flos-aquae.

Seasonal reductions in food availability may cause animals to catabolize endogenous tissue and the resulting loss of lean mass can hinder their ability to forage and reproduce. While several studies have considered nitrogen isotopes (δ15N) as an indicator of catabolism, relationships between protein intake, body condition, and tissue δ15N have not been assessed simultaneously in controlled conditions. We conducted a feeding experiment on laboratory mice (Mus musculus) to test the effects of low (5%) versus high (30–40%) dietary protein content on lean mass, fat mass, and tissue δ15N. This approach enables the distinction between use of exogenous and endogenous nitrogen, illuminating a framework of protein metabolism and tissue synthesis. As expected, lean mass and body fat were lower in mice fed low-protein diets. Nitrogen isotope discrimination (Δ15N) between blood plasma-diet and liver-diet did not differ between diet treatments. In contrast, Δ15N for hair decreased while Δ15N for muscle and RBC increased in the low-protein treatment. These patterns suggest that animals in negative nitrogen balance catabolize labile endogenous protein (e.g., muscle) to maintain vital tissues (e.g., liver) required to survive. Consequently, muscle and RBC δ15N values appear to be the most useful in assessing the nutritional state of animals. Our combination of direct measurements of body condition with δ15N analysis suggest how nitrogen isotopes can be better used as tracers of catabolic and anabolic activity by demonstrating connections between tissue-specific metabolic processes and Δ15N, thus refining the application of δ15N as a tool for assessing nitrogen balance in wild animals.

Wild boar and roe deer samples from an excavation in Dispilio, Greece, were subjected to collagen extraction protocols to reconstruct the paleoecological regime. Radiocarbon (14C) analysis suggested the Middle/Late Neolithic period and the database was updated with collagen samples. The14C model concluded to a possible local deforestation effect in the settlement subbasin confirmed by sediment δ13C and δ15N values. Carbon isotope values in collagen samples concluded in C3 plant type. Both carbon and nitrogen isotopes indicated the differences in dietary habits and/or metabolic system between the two Late Neolithic I species. Roe deer samples were classified as purely herbivorous. δ15N values of wild boar collagen samples from Dispilio reflected a diet mainly characterized by terrestrial protein. Compared to literature data, wild boar samples from the Dispilio excavation concluded that the animals might have lived close to the settlement where their diet could be supplemented by a consistent animal protein fraction. Finally, it is concluded that rainfall is an important factor that affects plant, and consequently animal, δ15N values. Therefore, the rainfall regime should always be considered in paleodietary studies.

Background: Plant and soil nitrogen stable isotope (δ15N) can integrate several fundamental biogeochemical processes in ecosystem nitrogen dynamics, and reflect characteristics of ecosystem nitroge...

The spatial distribution of carbon and nitrogen isotopes and of nitrogen concentrations is studied in detail in three gem quality cubic diamonds of variety II according to Orlov’s classification. Combined with the data on composition of fluid inclusions our results point to the crystallization of the diamonds from a presumably oxidized carbonate fluid. It is shown that in the growth direction δ13C of the diamond becomes systematically lighter by 2–3‰ (from –13.7 to –15.6‰ for one profile and from –11.7 to –14.1‰ for a second profile). Simultaneously, we observe substantial decrease in the nitrogen concentration (from 400–1000 to 10–30 at ppm) and a previously unrecognized enrichment of nitrogen in light isotope, exceeding 30‰. The systematic and substantial changes of the chemical and isotopic composition can be explained using the Burton-Prim-Slichter model, which relates partition coefficients of an impurity with the crystal growth rate. It is shown that changes in effective partition coefficients due to a gradual decrease in crystal growth rate describes fairly well the observed scale of the chemical and isotopic variations if the diamond-fluid partition coefficient for nitrogen is significantly smaller than unity. This model shows that nitrogen isotopic composition in diamond may result from isotopic fractionation during growth and not reflect isotopic composition of the mantle fluid. Furthermore, it is shown that the infra-red absorption at 1332 сm-1 is an integral part of the Y-defect spectrum. In the studied natural diamonds the 1290 сm-1 IR absorption band does not correlate with boron concentration.

This work was financially supported by a NASA Exobiology grant to RB (# NNX16AI37G), an NSF graduate student research fellowship to JZ, and a NASA postdoctoral fellowship to EES. The last decade has seen a steady rise in the number of publications on nitrogen isotopes in sedimentary rocks, which have become an established tool for investigating the evolution of life and environmental conditions. Nitrogen is contained in sedimentary rocks in two different phases: bound to kerogen or substituted in potassic minerals (mostly K-bearing phyllosilicates and feldspars). Isotopic measurements and interpretations typically focus either on kerogen extracts alone or on bulk rocks that include both phases. The community is split about which sample type more accurately captures the original composition of the biomass. To address this question, we combined nitrogen isotopes and carbon-to-nitrogen ratios with carbon-to-hydrogen ratios which act as an independent proxy for metamorphic alteration. Our results reveal that metamorphism drives kerogen-bound nitrogen isotopically lighter while silicate-bound nitrogen becomes heavier. For rocks up to greenschist facies, the isotopic effect of this internal partitioning (up to 3-4‰) is larger than the isotopic effect of metamorphic nitrogen loss from the system (up to 1-2‰). The opposite may be true for higher metamorphic grades. We conclude that for low-grade sedimentary rocks with more than 60% of their total nitrogen residing in the silicate phase the primary isotopic composition of the biomass is best approximated by the bulk rock measurement, whereas for high-grade rocks the kerogen extract may be the more accurate proxy. The isotopic difference between nitrogen phases can thus serve as a rough indicator of the degree of metamorphic alteration. Postprint

Compound-specific stable isotope analysis (CSIA) has been used to quantify and identify biodegradation of organic pesticides in the environment. In this work, the kinetic isotope fractionation of carbon and nitrogen was investigated during rapid atrazine degradation by two bacterial isolates, CX-T (Ensifer sp.) and K (Sinorihizobium sp.), under aerobic conditions. Significant isotope fractionation (ecarbon = -2.40 ± 0.07‰, enitrogen = 1.30 ± 0.13‰, strain CX-T; ecarbon = -1.40 ± 0.07‰, enitrogen = 2.5 ± 0.5‰, strain K) was observed for both isolates. The same pattern of normal carbon and inverse nitrogen isotope effects were obtained, confirming the same reaction mechanisms of atrazine. The calculated, apparent kinetic isotope effects of strain CX-T (AKIEcarbon = 1.020; AKIEnitrogen = 0.994) and strain K (AKIEcarbon = 1.011; AKIEnitrogen = 0.988) were observed, implying that carbon-chlorine bonds weakened and additional bonds appeared on the triazine ring nitrogen at the transition state. However, isotope enrichment factors and dual isotope slopes (Δ = δ15N/δ13C) of both isolates (Δ = -0.55 ± 0.05, strain CX-T; Δ = -1.07 ± 0.14, strain K) were, nevertheless, inconsistent even for the same compound and same transformation pathway.

Reliable indicators on whether natural and cultured fish exhibit differences in habitat preferences are lacking. In this study, δ13C and δ15N were used to distinguish the habitat preferences of cultured versus natural ayu and their prey (periphyton) in a typical riffle-pool river reach. It found that the δ13C of natural ayu (−13.747‰) was consistent with that of periphyton in riffles (−14.611‰), while the δ13C of cultured ayu (−19.088‰) was consistent with that of periphyton (−19.711‰) in pools. The results indicated that cultured ayu appear to favor pools whereas natural ayu favor riffles, and δ13C and δ15N represent potential reliable indicators of habitat preferences of cultured ayu.

To elucidate the sources and transformations of nitrogen in the South China Sea (SCS), the nitrogen isotopic composition of nitrate ( $${\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}$$ ) was measured in seawater samples from the water column of this marginal sea and the adjacent western North Pacific Ocean (WNP). Comparison of the isotopic signatures from these two locations suggests that the main source of nitrogen into the SCS was nitrate that entered from the WNP through the Luzon Strait. Values of $${\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}$$ were generally lower in the SCS than in the WNP, and the $${\updelta }^{ 1 5} {\text{N}}_{{{\text{NO}}_{ 3} }}$$ maximum observed in the SCS intermediate water was lower than the corresponding WNP maximum. This pattern is attributed to mixing within the SCS in combination with the outflow of SCS intermediate water to the WNP. A mass balance model indicates that atmospherically derived N (a combined input of new nitrogen from marine N2 fixation and atmospheric deposition) supplied approximately 6% of the particulate nitrogen exported from the euphotic zone to the deep SCS. This supply of isotopically light nitrogen cannot, however, explain the low and downward-decreasing δ15N that has been previously observed in sinking particles of the deep SCS. We propose that an alternative explanation might be a downward-increasing ratio of isotopically light NH4 +-N to organic N due to the degradation of organic N within the sinking particles (i.e., relative enrichment of the NH4 +) and also particle incorporation of excreted ammonium from zooplankton.

We show how we used stable nitrogen and oxygen isotopes in ammonium and nitrate to identify and quantify nitrogen transformation and nitrogen sources at the LKAB mining site in northern Sweden. Stable nitrogen isotope analysis worked as an excellent tool for tracing nitrogen cycling in rapidly moving process waters. The isotope analysis was performed on the mining process waters at seven different key points along the water flow and we identified nitrification, ammonia volatilisation, and ammonium adsorption as nitrogen transformation processes. The source of nitrogen is historically explained as undetonated ammonium-nitrate based explosives. We used nitrate nitrogen and oxygen isotopes to quantify four nitrogen sources in the accumulated water in the mine as well as three sources in an above ground process water reservoir. The nitrate isotope data showed that most of the nitrate (70–80%) in the accumulated water underground originated from a sampling point located close to the surface and only a minor fraction (5–20%) originated directly from undetonated explosives (direct dissolution of NH 4 NO 3 and nitrification of NH 4 ). Nitrate from natural groundwater formed roughly 12% of mine water nitrate. In the above ground process water reservoir isotope data indicated another source of nitrogen coming from undetonated explosives.

The concentration and isotope composition of molybdenum (Mo) in sediments and sedimentary rocks are widely used proxies for anoxic conditions in the water column of paleo-marine systems. While the mechanisms leading to Mo fixation in modern restricted basins with anoxic and sulfidic (euxinic) conditions are reasonably well constrained, few studies have focused on Mo cycling in the context of open-marine anoxia. Here we present Mo data for water column particulate matter, modern surface sediments and a paleo-record covering the last 140,000 years from the Peruvian continental margin. Mo concentrations in late Holocene and Eemian (penultimate interglacial) shelf sediments off Peru range from ∼70 to 100 µg g−1, an extent of Mo enrichment that is thought to be indicative of (and limited to) euxinic systems. To investigate if this putative anomaly could be related to the occasional occurrence of sulfidic conditions in the water column overlying the Peruvian shelf, we compared trace metal (Mo, vanadium, uranium) enrichments in particulate matter from oxic, nitrate-reducing (nitrogenous) and sulfidic water masses. Coincident enrichments of iron (Fe) (oxyhydr)oxides and Mo in the nitrogenous water column as well as co-variation of dissolved Fe and Mo in the sediment pore water suggest that Mo is delivered to the sediment surface by Fe (oxyhydr)oxides. Most of these precipitate in the anoxic-nitrogenous water column due to oxidation of sediment-derived dissolved Fe with nitrate as a terminal electron acceptor. Upon reductive dissolution in the surface sediment, a fraction of the Fe and Mo is re-precipitated through interaction with pore water sulfide. The Fe- and nitrate-dependent mechanism of Mo accumulation proposed here is supported by the sedimentary Mo isotope composition, which is consistent with Mo adsorption onto Fe (oxyhydr)oxides. Trace metal co-variation patterns as well as Mo and nitrogen isotope systematics suggest that the same mechanism of Mo delivery caused the ‘anomalously’ high interglacial Mo accumulation rates in the paleo-record. Our findings suggest that Fe- and nitrate-dependent Mo shuttling under nitrogenous conditions needs to be considered a possible reason for sedimentary Mo enrichments during past periods of widespread anoxia in the open ocean.

This paper describes a novel approach to reassess the water status in vineyards based on compound-specific isotope analysis (CSIA) of wine volatile organic compounds (δ13CVOC/VPDB) and bulk carbon and nitrogen isotopes, and the C/N molar ratios of the wine solid residues (δ13CSR/VPDB, δ15NSR/Air-N2). These analyses link gas chromatography/combustion and elemental analysis to isotope ratio mass spectrometry (GC/C/IRMS, EA/IRMS). Field-grown cultivars of Pinot Noir grapevines were exposed during six growing seasons (2009-2014) to controlled soil water availability, while maintaining identical the other environmental variables and agricultural techniques. Wines were produced from the grapes by the same oenological protocol. This permitted for the assessment of the effects in the biochemistry of wines solely induced by the changes in the plant-soil water status. This mimicked the more recurrent and prolonged periods of soil water deficiency due to climate changes. Water stress in grapevine was assessed by the measurement of the predawn leaf water potential (Ψpd) and the stable carbon isotope composition of the berry sugars during harvest (must sugars). For quantitation purposes and the normalization of the measured stable carbon isotope ratios of the VOCs, the wine samples were spiked with three standard compounds with known concentration and δ13CVPDB values. VOCs were extracted by liquid-liquid extraction and analyzed by gas chromatography/flame ionization detection (GC/FID), gas chromatography/mass spectrometry (GC/MS), and GC/C/IRMS. δ13C values were obtained for eighteen VOCs. The solid residues were obtained by freeze-drying wine aliquots and were analyzed for their C and N content and isotope composition by EA/IRMS. All the isotopic ratios (δ13CSR, δ15NSR, δ13CVOC) are highly correlated with the Ψpd values, indicating that the proposed gas chromatography and isotope ratio mass spectrometry approach is a useful tool to assess the changes in the water status of grapevine cultivars in different terroirs. The combined analytical approach was used for the first time to complement the assessment of soil water availability effects on the grapevine. The δ13C values of the volatile compounds helped confirm (or establish) their main source(s) and biosynthetic pathway(s). Importantly, we also show for the first time that the combination of C/N and δ15N values of freeze-dried wines have an unexplored potential for the study of nitrogen dynamics in soil/grape/wine systems.

The nitrogen isotopic composition of amino acids (δ15NAA) is a promising tool for estimating the trophic position and nitrogen sources of organisms in grazing food webs. The utility of δ15NAA analysis of microbial processes in the biogeochemistry remains uncertain, because information about the δ15NAA values of chemotrophic microbes are still limited. In this study, we report the δ15NAA values in five cultured heterotrophic or chemolithoautotrophic microbes (one fungus, one bacterium, and three archaea) with controlled nitrogen sources in synthetic media. When the microbes were grown on ammonium, the apparent nitrogen isotopic fractionation of amino acids relative to glutamic acid in the microbes (e.g., −3.0 ± 1.0‰ for phenylalanine) was similar to those in algae. When the microbes were grown on a free amino acid mixture, the δ15N offsets of amino acids in the microbial cells relative to the amino acids in the culture media (e.g., +8.2 ± 0.8‰ for glutamic acid and +0.1 ± 0.2‰ for phenylalanine) were close to the standard isotopic fractionation between animals and their diets. These results suggest that the δ15NAA pattern can be used to distinguish two end-member metabolic modes in microbes (i.e., de novo synthesis of amino acids from inorganic nitrogen vs. assimilation of amino acids from environments). We also discussed the effects of metabolic pathways on the δ15NAA values and their fractionation with respect to the diversity of amino acid metabolism in microbes. These findings will form an important baseline for interpreting the δ15NAA values of organisms and detritus in natural environments.

Carbon and nitrogen isotopes in sediments collected from the Manwan and Dachaoshan Reservoirs, which were created by cascade dams along the Lancang–Mekong River, were measured to preliminarily analyse their organic matter sources. Sediment samples were collected from the Manwan and Dachaoshan Reservoirs twice during both the rainy and dry seasons by using a gravitational bottom sampler. One set of samples was collected from the river centres of each reservoir, and the other set was collected from the river edges, 5 m from each bank. Sediments were divided by wet sieving into three classes of water-stable aggregates based on sizes, including macroaggregates, microaggregates, and silt and clay. At the same time, terrestrial plants (Phragmites) and surface soil samples (0–5 cm) were collected from the river bank. The total organic carbon (TOC), total nitrogen (TN), stable carbon isotope (δ13C), and stable nitrogen isotope (δ15N) were measured for sediments, soils, and plants to preliminarily analyse the sources of organic matter in the sediments. Because of the presence of dams, a greater amount of the fine fraction was deposited in the reservoirs, which adsorbed and preserved more organic matter. Although terrestrial sources of organic matter dominate in riverine systems, aquatic sources have been shown to act as new organic matter sources in the Manwan Reservoir. Input from C3 plants was the major new organic matter source in the Dachaoshan Reservoir, which also had strong inputs from aquatic sources. In the dry season, C3 plant input was significantly reduced and less fine fraction was found in the sediments. The high nitrogen isotope values of the sediments collected during the dry season indicated that strong organic matter decomposition decreased the storage of organic matter. The cascade dams permanently changed the aquatic environment and modified regional carbon flows resulting in the diversification of organic matter sources. The major source of sedimentary organic matter was terrestrial, including from plants, soils, and particle organic matter, with the new organic matter absorbed by macroaggregates primarily stemming from aquatic organisms and C3 plants. Samples collected during the dry season exhibited strong decomposition, which further weakened the preservation of organic carbon in sediments.

Carbon and nitrogen stable-isotope ratios were compared of fin and muscle tissue from 15 fish species collected from seven headwater rivers in eastern and western Thailand. In addition, two-source stable-isotope mixing models were used to derive estimates of each fish's reliance on allochthonous and autochthonous energy based on fin and muscle tissues. Across the dataset, fish fin was enriched in 13 C relative to muscle by c. 1·5‰. Variation in δ15 N between tissues was below statistically significant levels. Estimates of autochthonous resource use calculated from fin tissue were on average 15% greater than those calculated from muscle. Linear mixed-effects models indicated that inter-tissue variation in estimates of resource use was predominantly related to inter-tissue variation in δ13 C. Fish fin is a credible and desirable alternative to tissues such as muscle or liver which require destructive sampling of fishes. Care must be taken, however, when estimating resource use or interpreting previous estimates of resource use derived from different tissues.

The nitrogen isotope ratios (δ15N) of atmospheric N species are commonly suggested as indicators of N emission sources. Therefore, numerous research studies have developed analytical methodologies and characterized primary (gases) and secondary emission products (mostly precipitation and aerosols) from various emitters. These previous studies have generally collected either reduced or oxidized N forms, and sampled them separately prior to determining their δ15N values. Distinctive isotopic signals have been reported for emissions from various sources, and seasonality of the δ15N values has been frequently attributed to shifts in relative contributions from sources with different isotopic signals. However, theoretical concepts suggest that temperature effects on isotopic fractionation may also affect the δ15N values of atmospheric reaction products. Here we use a sector-based multi-stage filter system to simultaneously collect seven reduced and oxidized N species downwind from five different source types in Alberta, Canada. We report δ15N values obtained with a state-of-the-art gold-furnace pre-concentrator online with an isotope ratio mass spectrometer (IRMS) to provide representative results even for oxidized-N forms. We find that equilibrium isotope effects and their temperature dependence play significant roles in determining the δ15N values of the secondary emission products. In the end, seasonal δ15N changes here are mainly caused by temperature effects on fractionation, and the δ15N values of only two N species from one source type can be retained as potential fingerprints of emissions.

The Pearl River plays an important role in transporting terrestrial organic carbon (OC) to the South China Sea (SCS). However, the sources and compositional distribution of OC in the system are poorly understood. This study focused on delineating the sources and determining the fate of surface sedimentary OC from the Feilaixia Hydropower Station to the coastal SCS. Elemental, stable carbon/nitrogen isotope (δ13C and δ15N), and lignin-phenol analyses have been conducted. The total OC (TOC) from the upstream sites were generally derived from vascular plants (higher C/N and and depleted δ13C) and soils. Additional input was attributed to riverine primary production (lower C/N and enriched δ13C), which was enhanced near the dam-created reservoir. The C/N and δ13C values were not significantly different among sites in the midstream. The estuary/coastal sites witnessed hydrodynamically sorted riverine OC, which was diluted by marine primary production (lower C/N and more enriched δ13C). The lignin concentration was the highest in the upstream sites, remained relatively unchanged in the midstream sites, and decreased significantly along the estuary/coastal sites, which was corroborated by variation in TOC. A comprehensive five-end-member Monte Carlo simulation suggested that previous studies had underestimated the C4 plant input by 14 ± 11% and overestimated the riverbank soil input by 21 ± 17%. Thus, our study provided valuable information for more accurate source and mass balance studies of terrestrial OC transported to the SCS, which helped to further understand the carbon cycling in the large river-ocean continuum.

Compound-specific nitrogen stable isotope analysis provides an approach for estimating animal trophic position that may overcome key issues associated with stable isotope analysis of bulk tissue. Yet compound-specific trophic discrimination factors have not been estimated for a broad range of habitats, taxa, and diets. We conducted a controlled-feeding experiment to characterize the variation in compound-specific (TDFAA) and bulk (TDFBulk) trophic discrimination factors of four freshwater fish species fed on three distinct diets. We also compared TDFAA of fish muscle and scale to evaluate the viability of scales for making food web inferences. Mean ± 1 SD TDFBulk was 2.2‰ ± 0.9‰, and there were significant effects of species and diet trophic position on TDFBulk. Mean ± 1 SD TDFAA was 6.9‰ ± 0.8‰. Although there was no effect of species on TDFAA, there were significant differences in TDFAA across the three diets. TDFAA from fish scales were not significantly different from those of muscle. Our study illustrates the advantages of estimating trophic position using compound-specific stable isotopes and the need for continued investigation of factors resulting in variation in TDF values.

We report here on an isotopic study of carbon, nitrogen and oxygen isotopes in Equus tooth enamel and dentine from multiple layers from the site of Combe Grenal, France, which date to between approximately 150,000 and 50,000 years BP. We found that there were significant variations in all three elemental isotope ratios through time, although the variations were not synchronous. This study shows the utility of using herbivore tooth dentine carbon and nitrogen isotope values as indicators of environmental changes, in addition to their use as dietary indicators.

Aktopraklik is a settlement site composed of three areas (A–C) in the Marmara region of northwest Anatolia, with phases of occupation that date to the Late Neolithic and Early Chalcolithic periods, mid-seventh to mid-sixth millennium bc (ca. 6400–5600 cal. bc). Here, we present 54 human and fauna bone collagen stable isotope results from the site, alongside five modern fish bone collagen isotope results, to examine the nature of human diet. The stable isotope analysis shows that human diet comprised the consumption of select C3 terrestrial resources, with a preference for domestic animal proteins over plant proteins. The evidence to date suggests that animal husbandry was at the forefront of Late Neolithic and Early Chalcolithic subsistence practices. No isotopic difference in humans is observed between biological sex or between areas B and C at the settlement.

Strontium, carbon, and nitrogen isotopes of human bone and tooth remains have been used to reconstruct residential mobility and diet of early medieval populations at Las Gobas from the sixth to eleventh centuries. Most non-local individuals correspond to the tenth to eleventh centuries and were mostly women and infants. This residential mobility coincided with the formation of Lano village and the abandonment of artificial cave settlement. Carbon and nitrogen isotope ratios of bone collagen indicate an omnivorous homogenous diet based on terrestrial plant resources, with few animal-derived proteins from livestock. Millet consumption was restricted to an earlier period of time (seventh to ninth centuries); and in later periods (tenth to eleventh centuries), mainly C3 plants such as wheat and barley were consumed. In general, there were no dietary differences between individuals according to sex or age. Sex-related dietary differences have only been observed in the tenth to eleventh centuries, when females consumed a more vegetarian diet and less animal protein. The higher δ 15N values in infants reflect the weaning effect, while the differences in δ 15N values between young adult men and young adult women can be explained as a physiological factor related to pregnancy or different origins. In a comparison with contemporaneous medieval populations in the northern Iberian Peninsula, both δ 13C and δ 15N values suggest similar foodstuff resources and diet among Christian and Muslim populations.