Stable Sulfur Isotope Research Articles

Sulfur stable isotope ratios provide further insight into movements of the fin whale, an oceanic long-range migrant

Stable isotope ratios have proven a valuable tool to investigate marine mammal ecology, including diet, distribution, and migratory movements. While most studies have focused on δ15N and δ13C values, δ34S values have been little used because their pattern of variation and tissue dynamics remain unclear. We examined the sequential variation of δ15N, δ13C, and δ34S values along the baleen plates from fin whales occurring off West Iceland in summer. All baleen plates exhibited fluctuations along their growing axis. A significant synchronic correlation was found between δ15N and δ34S values, while the relation of these values to the δ13C value was highly variable and inconsistent. These results were similar to those obtained in previous studies of Greenland bowhead whales, although the pattern of the oscillations in fin whales showed an increase in values during winter, while those of bowhead whales showed a decrease. Although seasonal variations in food intake and the associated cycles of protein synthesis and catabolism may have played a role in such fluctuations and the observed differences between species, we suggest that the main driver for the δ34S fluctuations reflected in baleen plates is the variation of local baselines between winter and summer grounds. This suggests ample potential for using δ34S values to study migratory movements and destinations of marine megafauna, provided that the geographic variation in δ34S baselines is clarified.

Cooper-pair distribution function D_{cp}(omega ,T_c) for superconducting hbox {D}_3hbox {S} and hbox {H}_3hbox {S}

Cooper-pair distribution function, D_{cp}(omega ,T_c), is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the N_{cp} parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature T_c. Herein, we reported D_{cp}(omega ,T_c) function of the compressed D_3S and H_3S high-T_c conventional superconductors, including the effect of stable sulfur isotopes in H_3S. D_{cp}(omega ,T_c) suggests that the vibration energy range of 10–70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron–phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in H_3S by its stable isotopes can lead to important changes in T_c. The results also show proportionality between N_{cp} parameter and experimental or theoretical T_c values.

Feeding habits of Baffin Bay polar bears Ursus maritimus: insight from stable isotopes and total mercury in hair

Loss of sea ice brought on by climate change affects polar bear Ursus maritimus access to prey. Here we investigated variation in feeding habits of the Baffin Bay (BB) polar bear subpopulation in relation to sea ice, habitat use, season, and demography using hair carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) stable isotope values and total mercury (THg) concentrations as ecological tracers. We analyzed hair samples from BB polar bears (n = 131) of all age and sex classes live-captured in West Greenland during the spring in 2009-2013. BB polar bears occupied a narrow isotopic space, suggesting limited variation in carbon sources and trophic position within the subpopulation. THg concentrations (median ± SE: 5.1 ± 0.2, range: 0.3-12.5 µg g-1 dry weight, DW) were related to age class, and nearly half exceeded the suggested threshold for neurological effects in polar bears at 5.4 µg g-1 DW. Although distinct coastal and offshore space-use strategies have been reported for BB polar bears, our results suggest that both strategies lead to similar carbon sources and trophic positions. We found seasonal variation in δ13C and δ34S across both space-use strategies, with δ34S suggesting that all BB polar bears may prey on a higher proportion of benthic-feeding bearded seals Erignathus barbatus in late summer relative to spring. Despite wide fluctuations in inter-annual sea ice conditions and differences in space-use strategies among individuals, stable isotope values and THg concentrations suggested limited variation in feeding habits among BB polar bears. The variation of habitat tracers (δ13C and δ34S) was related to season, whereas trophic tracer (δ15N and THg) variation was driven by demographic group. The specialized BB polar bear diet suggests limited feeding plasticity under continued climate warming.

Sulfur Biogeochemical Cycle of Marine Sediments

Complex interactions between microbial communities and geochemical processes drive the major element cycles and control the function of marine sediments as a dynamic reservoir of organic matter. Sulfate reduction is globally the dominant pathway of anaerobic mineralisation and is the main source of sulfide. The effective re-oxidation of this sulfide at the direct or indirect expense of oxygen is a prerequisite for aerobic life on our planet. Although largely hidden beneath the oxic sediment surface, the sulfur cycle is therefore critical for Earth’s redox state. This Geochemical Perspectives begins with a brief primer on the sulfur cycle of marine sediments and a description of my own scientific journey through nearly fifty years of studies of sulfur geochemistry and microbiology. Among the main objectives of these studies were to quantify the main processes of the sulfur cycle and to identify the microbial communities behind them. Radiotracers in combination with chemical analyses have thereby been used extensively for laboratory experiments, supported by diverse molecular microbiological methods. The following sections discuss the main processes of sulfate reduction, sulfide oxidation and disproportionation of the inorganic sulfur intermediates, especially of elemental sulfur and thiosulfate. The experimental approaches used enable the analysis of how environmental factors such as substrate concentration or temperature affect process rates and how concurrent processes of sulfate reduction and sulfide oxidation drive a cryptic sulfur cycle. The chemical energy of sulfide is used by chemolithotrophic bacteria, including fascinating communities of big sulfur bacteria and cable bacteria, and supports their dark CO2 fixation, which produces new microbial biomass. During the burial and aging of marine sediments, the predominant mineralisation processes change through a cascade of redox reactions, and the rate of organic matter degradation drops continuously over many orders of magnitude. The main pathways of anaerobic mineralisation and the age control of the organic matter turnover are discussed. In the deep methanic zone, only a few percent of the entire degradation process remains, which provides a small boost of substrate for sulfate reduction through the process of anaerobic methane oxidation. The stable isotopes of sulfur provide an additional tool to understand these diagenetic processes, whereby the combination of microbial isotope fractionation and open system diagenesis generate a differential diffusion flux of the isotopes. In relation to the organic carbon cycle of the seabed and the contribution of methane, the paper discusses the global sulfur budget and the role of sulfate reduction for organic matter mineralisation in different depth regions of the ocean – from coast to deep sea. The published estimates of these parameters are evaluated and compared. Finally, the paper looks at future perspectives with respect to gaps in our current understanding and the need for further studies.

Understanding long-term groundwater flow at Pahute Mesa and vicinity, Nevada National Security Site, USA, from naturally occurring geochemical and isotopic tracers

Recently collected naturally occurring geochemical and isotopic groundwater tracers were combined with historic data from the Pahute Mesa area of the Nevada National Security Site (NNSS), Nevada, USA, to provide insights into long-term regional groundwater flow patterns, mixing and recharge. Pahute Mesa was the site of 85 nuclear detonations between 1965 and 1992, many of them deeply buried devices that introduced radionuclides directly into groundwater. The dataset examined included major ions and field measurements, stable isotopes of hydrogen (δ2H), oxygen (δ18O), carbon (δ13C) and sulfur (δ34S), and radioisotopes of carbon (14C) and chloride (36Cl). Analysis of the patterns of groundwater 14C data and the δ2H and δ18O signatures indicates that groundwater recharge is predominantly of Pleistocene age, except for a few localized areas near major ephemeral drainages. Steep gradients in sulfate (SO4) and chloride (Cl) define a region near the western edge of the NNSS where high-concentration groundwater flowing south from north of the NNSS merges with dilute groundwater flowing west from eastern Pahute Mesa in a mixing zone that coincides with a groundwater trough associated with major faults. The 36Cl/Cl and δ34S data suggest that the source of the high Cl and SO4 in the groundwater was a now-dry, pluvial-age playa lake north of the NNSS. Patterns of groundwater flow indicated by the combined data sets show that groundwater is flowing around the northwest margin of the now extinct Timber Mountain Caldera Complex toward regional discharge areas in Oasis Valley.

Seasonal Variation and Sources Identification of Dissolved Sulfate in a Typical Karst Subterranean Stream Basin Using Sulfur and Oxygen Isotopes

Karst water, which provides approximately 25% of the world's drinking water, is especially vulnerable to anthropogenic pollutants. To determine the variations between high and low flow periods and the sources of dissolved sulfate (SO42-) in small karst basins, SO42- concentrations, stable sulfur and oxygen isotopes (δ34S-SO4 and δ18O-SO4), and oxygen isotopes of water (δ18O-H2O) were investigated in surface and groundwaters, during the high and low flow seasons, within the Babu subterranean stream basin. Analysis showed that: ① the water samples that were directly impacted by acid mine drainage exhibited high SO42- concentrations (≥250 mg·L-1) and significant seasonal variation, while the seasonal variation of non-AMD-impacted water with low SO42- concentrations was not significant. ② During the high flow season, the mean δ34S-SO4 and δ18O-SO4 values of surface water were -10.5‰ and 4.7‰, respectively, and -11.5‰ and 1.3‰ during the low flow period; the mean values of δ34S-SO4 and δ18O-SO4 in groundwater samples were -2.9‰ and 7.1‰ during the high flow period, respectively, and -3.2‰ and 6.2‰ during the low flow period. Both surface and groundwater samples exhibited higher δ34S-SO4 and δ18O-SO4 values during the high flow period than during the low flow period. ③ The values of δ34S-SO4 in the surface and groundwater samples were relatively stable, indicating that the sources of SO42- at specific sampling sites were stable.④ The main sources of SO42- in surface and groundwaters were rain, sulfide, and gypsum, accounting for 13%, 40%, and 47%, respectively, of SO42- in samples taken from the basin outlet during the high flow season, and 18%, 39%, and 43%, respectively, in samples obtained during the low flow season.

Sulfur isotopes as a proxy for human diet and mobility from the preclassic through colonial periods in the Eastern Maya lowlands.

Maya archaeologists have long been interested in understanding ancient diets because they provide information about broad-scale economic and societal transformations. Though paleodietary studies have primarily relied on stable carbon (δ13C) and nitrogen (δ15N) isotopic analyses of human bone collagen to document the types of food people consumed, stable sulfur (δ34S) isotope analysis can potentially provide valuable data to identify terrestrial, freshwater, or marine/coastal food sources, as well as determine human mobility and migration patterns. Here we assess applications of δ34S for investigating Maya diet and migration through stable isotope analyses of human bone collagen (δ13C, δ15N, and δ34S) from 114 individuals from 12 sites in the Eastern Maya lowlands, temporally spanning from the Late Preclassic (300 BCE-300 CE) through Colonial periods (1520-1800 CE). Results document a diet dominated by maize and other terrestrial resources, consistent with expectations for this inland region. Because δ34S values reflect local geology, our analyses also identified recent migrants to the Eastern lowlands who had non-local δ34S signatures. When combined with other indicators of mobility (e.g., strontium isotopes), sulfur isotopic data provide a powerful tool to investigate movement across a person's lifespan. This study represents the largest examination of archaeological human δ34S isotope values for the Maya lowlands and provides a foundation for novel insights into both subsistence practices and migration.

Miniaturised Instrumentation for the Detection of Biosignatures in Ocean Worlds of the Solar System

This review of miniaturised instrumentation is motivated by the ongoing and forthcoming exploration of the confirmed, or candidate ocean worlds of the Solar System. It begins with a section on the evolution of instrumentation itself, ranging from the early efforts up to the current rich-heritage miniaturised mass spectrometers approved for missions to the Jovian system. The geochemistry of sulphur stable isotopes was introduced for life detection at the beginning of the present century. Miniaturised instruments allow the measurement of geochemical biosignatures with their underlying biogenic coding, which are more robust after death than cellular organic molecules. The role of known stable sulphur isotope fractionation by sulphate-reducing bacteria is discussed. Habitable ocean worlds are discussed, beginning with analogies from the first ocean world known in the Solar System that has always being available for scientific exploration, our own. Instrumentation can allow the search for biosignatures, not only on the icy Galilean moons, but also beyond. Observed sulphur fractionation on Earth suggests a testable “Sulphur Hypothesis”, namely throughout the Solar System chemoautotrophy, past or present, has left, or are leaving biosignatures codified in sulphur fractionations. A preliminary feasible test is provided with a discussion of a previously formulated “Sulphur Dilemma”: It was the Galileo mission that forced it upon us, when the Europan sulphur patches of non-ice surficial elements were discovered. Biogenic fractionations up to and beyond δ34S = −70‰ denote biogenic, rather than inorganic processes, which are measurable with the available high sensitivity miniaturised mass spectrometers. Finally, we comment on the long-term exploration of ocean worlds in the neighbourhood of the gas and ice giants.

The grandeur of death – Monuments, societies, and diets in middle Neolithic Paris Basin

This study investigates the relationship between monumental funerary structures, social organizations, and diets in Middle Neolithic France. Focusing on the Cerny culture based in the Paris Basin region, we analysed and compared bone collagen stable carbon, nitrogen, and sulfur isotope values of 113 individuals from three different types of Cerny cemeteries: the Passy type (Cerny STP), slab burials (Cerny Slab), and burials without major superstructure (Cerny Flat). Published stable isotopic data from one other Cerny Flat and two contemporaneous non-Cerny cemeteries (n = 140), together with new and published faunal isotopic data (n = 267) from across six different river valleys in the region are also included in the analysis. The results of this study have shown that (1) the Cerny diet was likely rich in animal protein; (2) comparing to all other cemetery types, Cerny STP sites were considerably homogenous isotopically and culturally, and (3) individuals buried in aberrant funerary arrangements tend to have outlying isotopic compositions, suggesting strong correlations between diets and burial practices. Interestingly, as oppose to the distinctly sex-related funerary arrangements, no obvious pattern can be observed in the isotopic compositions between males and females in Cerny cemeteries.

Multiple isotopic tracing for sulfate and base cation sources of precipitation in Hangzhou city, Southeast China: Insights for rainwater acidification mechanism

Acid deposition has been regarded as a serious factor in the deteriorative water environment and ecosystems. Despite the powerful acid emission control measures have been implemented by the Chinese government, many areas (especially Southeast China) are still suffering from acid deposition. The chemical and isotopic (δ34S and 87Sr/86Sr) compositions of rainwater in Hangzhou, a typical megacity in Southeast China with serious acid rain problem, for one year were studied with the aim to better constrain potential sources and explore the causes of rainwater acidification. Most rainwater samples were acidic, with a VWM pH value of 4.65. SO42− was the dominant anion and the main acid ion in rainwater. Sulfur isotope and the quantity equilibrium model revealed that sea salt, crustal, biogenic, and anthropogenic sulfur represented 2.3%, 0.1%, 16.7%, and 80.8% of the SO42− source in rainwater, respectively. The back trajectory and strontium isotopes indicated that the base cations (BCs) in rainwater originated mainly from anthropogenic sources. The relatively low neutralizing capacity caused by limited BCs input and emission control measures undermines some efforts to reduce rainwater acidity. This case study demonstrated that a valuable tool to probe the source of acid rain and unravel the mechanism of rainwater acidification can be provided by multiple lines of evidence, including rainwater chemical compositions, stable sulfur isotopes, and stable strontium isotopes.

Oil-source rock analysis and metallogenic significance of the palaeo-oil reservoir in the Qinglong antimony deposit, South China

The Qinglong antimony deposit is located in the Nanpanjiang (Youjiang) basin, South China. The role of organic matter in antimony mineralisation is often discussed due to hydrocarbon gases within inclusions of antimony deposits, which have been detected since the 1990s. However, as no macroscopic or mass organic material has been discovered, the origin of such hydrocarbon gases and their potential relation to mineralisation remain unclear. The discovery of the Qinglong palaeo-oil reservoir has provided a new opportunity for further study of the relationship between organic matter and antimony mineralisation. Five samples of bitumen from the palaeo-oil reservoir and seven samples of Devonian source rocks from the northern part of an antimony mine were analysed for organic elements, total organic carbon, chloroform bitumen ‘A’ and its group compositions, bitumen/vitrinite reflectance (Rb/Ro), biomarkers, carbon isotopes, and Rock-Eval pyrolysis. Kerogen microscopy and rare earth elements (REEs) analysis were also performed on the Devonian source rocks samples. Finally, seven samples of pyrite coexisting with bitumen in the palaeo-oil reservoir were analysed using stable sulphur isotope analysis.Results show that the Devonian source rocks are rich in organic matter, yet it is well known that few residual organic matters are capable of continuing hydrocarbon generation after strong thermal evolution. Both the palaeo-oil reservoir and source rocks are found to have the same source of parent material and belong to the same mixed type of kerogen, and have reached the over-mature stage. The ratio of pristane/phytane (Pr/Ph) and the gammacerane index (Ga/C30H) indicate that the source rocks were formed in a reductive brackish water sedimentary environment, with a parameter nearly the same as that of the palaeo-oil reservoir. The palaeo-oil reservoir samples are highly consistent with the source rocks in terms of the source and type of organic matter, as well as the sedimentary environment, thermal maturity, normal alkanes, key fingerprint parameters, and grey relevancy degree of REEs. In addition, the carbon isotopes (δ13C) of bitumen range from − 28.75‰ to − 30.23‰, with an average of − 29.45‰, while those of the source rocks vary from − 25.20‰ to − 28.56‰, with an average of − 27.06‰, which are consistent with each other in the range of carbon isotope fractionation generated by the thermal evolution of organic matter. Therefore, it is determined that the palaeo-oil reservoir was derived from the Devonian oil-source rocks.The sulphur isotopes (δ34S) of pyrite associated with bitumen in the palaeo-oil reservoir have a relatively narrow range (−1.9‰ to 3.1‰, average 0.97‰), which are very close to those of sulphides in the mineralisation period of the gold and antimony deposits. We believe that the sulphur needed for mineralisation was mainly derived from hydrocarbon fluids in the basin and speculate that the palaeo-oil and hydrocarbon gases formed by thermal cracking and then served as a reducing agent to convert SO42− in the oilfield brine into reduced sulphur (S2−/HS−) through the thermochemical sulphate reduction (TSR) reaction. It is found that although the Qinglong palaeo-oil reservoir did not contribute Sb to the deposit (existing Sb was instead found to be from the Dachang member and its overlying basalt), it did, however, provided a reductive metallogenic environment and contributed a relatively large amount of reduced sulphur (S2−/HS−) to participate the mineralisation.

Mineral dust and fossil fuel combustion dominate sources of aerosol sulfate in urban Peru identified by sulfur stable isotopes and water-soluble ions

High sulfur emissions in the Central Andes have in the past been attributed to active volcanoes and numerous copper smelting facilities in the region. This study evaluates the contribution of these sources on Arequipa, Peru through an evaluation of aerosol sulfate δ34S values and water-soluble ions (WSI). The anthropogenic and natural sources of particulate pollution were determined by aerosol filter sampling from four different locations (urban, suburban, industrial, and rural) providing a view of the spatial variability of aerosols within the city. Sulfate (avg. 2.97 μm/m3) is the most abundant ion species in the aerosols sampled contributing on average 20% of the molar mass. Ion composition profiles between sampling sites are very similar indicating common sources and high contributions of mobilized local surface salt to the aerosols in this desert region. The regional atmospheric chemistry model (RACM) 0-D run for the area confirms that emissions from fuel combustion sources alone cannot account for the high concentrations of sulfate observed. A combination of the RACM results, WSI data, and a Bayesian δ34S isotope mixing model determined that the majority of aerosol sulfates in the area are from mineral dust adding to fossil fuel combustion sources. Mineral dust entrainment in the region is likely elevated by the close proximity of open-pit mining and unpaved roads near the city. Marine organic aerosols and smelting located along the Pacific contribute little to Arequipa's aerosol sulfate concentration. While the influence of volcanic sulfate (9% on average) is low, overall natural sulfate (dust, volcanic, and DMS) accounts for 43% of the aerosol sulfate. Therefore, even though the local environment creates high sulfate background levels, a reduction of sulfate aerosol pollution would be possible if fossil fuel emissions were reduced.

Conservative transport of dissolved sulfate across the Rio Madre de Dios floodplain in Peru

AbstractMineral weathering plays a primary role in the geologic carbon cycle. Silicate weathering by carbonic acid consumes CO2 and stabilizes Earth's climate system. However, when sulfuric acid drives weathering, CO2 can be released to the atmosphere. Recent work has established that sulfuric acid weathering resulting from sulfide mineral oxidation is globally significant and particularly important in rapidly eroding environments. In contrast, if SO42− produced by sulfide oxidation is reduced during continental transit, then CO2 release may be negated. Yet, little is known about how much SO42− reduction takes place in terrestrial environments. We report oxygen and sulfur stable isotope ratios of SO42− in river waters and mass budget calculations, which together suggest that SO42− released from pyrite oxidation in the Peruvian Andes mountains is conservatively exported across ∼300 km of the Amazon floodplain. In this system, floodplain SO42− reduction does not counteract the large SO42− flux from Andean pyrite weathering or measurably affect the stable isotope composition of riverine SO42−. These findings support the hypothesis that uplift and erosion of sedimentary rocks drive release of CO2 from the rock reservoir to the atmosphere.

Connectivity of fish communities in a tropical floodplain river system and predicted impacts of potential new dams

Longitudinal and lateral connectivity is important for mobile aquatic species in rivers for reproductive migrations, recruitment, gene flow and access to food resources across habitat types. Water resource developments such as dams and levees may disrupt these connections, causing river fragmentation and loss of access to highly productive habitats such as floodplain wetlands. We used sulfur stable isotopes as a tracer to estimate patterns of fish movement in an unregulated river in tropical northern Australia, taking advantage of observed spatial variation in sulfur isotope values of their food resources across the catchment. We also modelled the flow and barrier related impacts of potential dam development scenarios on fish movement. Fish with isotope values significantly different from local prey values were determined to be migrants. In the ‘no dams’ scenario, movement varied among fish species (0–44% migrant fish within species where n > 5) and sites (0–40% migrant fish within sites where n > 5), and immigration was higher in more connected sites. Impacts of water resource development on fish movement varied between dam scenarios, with predictions that a dam on the main channel of the Mitchell River would have the highest impact of the three individual dam scenarios. This study provides critical information on how flow-mediated connectivity supports patterns of fish community movement in an unregulated river system. The generic quantitative approach of combining tracers of fish movement with connectivity modelling provides a powerful predictive tool. While we used sulfur stable isotopes to estimate fish movement, our approach can be used with other tracers of movement such as otoliths and acoustic telemetry, making it widely applicable to guide sustainable development in other river systems.

Mineralization, ore mineral chemistry and sulfur stable isotopes at the Chaldaq gold prospect (north Takab): evidence for gold formation mechanism

منطقه اکتشافی چالداغ با عیار متوسط 5/4 گرم در تن به‌عنوان یکی از اندیس­ های پرعیار کانسار زرشوران، در شمال تکاب واقع‌شده است. از لحاظ ساختاری این منطقه در غرب گسل رانده قینرجه و طاقدیس ایمان­خان (راستای NW) قرار دارد و واحد کربنات آهن­دار چالداغ به سن نئوپروتروزوئیک-کامبرین بالایی، سنگ میزبان اصلی کانه ­زایی است. طبق شواهد ریزکاوالکترونی، طلا به‌صورت محلول جامد با کاتیون Au+ و محتوای 10 تا 80 گرم در تن (ppm) در ترکیب کانه آرسنین­پیریت با فرمول (Fe2+As3+)S2Au2.S0 تمرکز دارد. شواهد ایزوتوپ پایدار گوگرد بر روی کانه ­های سولفیدی رالگار و پیریت گویای مقادیر δ34SCDT بین 5/3 تا ‰ 5/6 (متوسط ‰ 5 در تعداد 6 نمونه)، است. با توجه به مقادیر FeS mol% اسفالریت­، تغییرات LogfS2 در اندیس چالداغ بین 14- تا 16- به‌دست آمد که منطبق با شرایط سولفیداسیون متوسط است. طبق شواهد به‌نظر می­ رسد در اندیس طلای چالداغ، سیال گرمابی غنی از H2S هم‌ زمان با فرایند کربنات­ زدایی و آزاد‌شدن مقادیر بالای Fe2+ و As3+ در محیط، با این کاتیون­ ها واکنش داده و آرسنین­پیریت تشکیل‌ شده است. در پی این فرایند، ضمن کاهش محتوای H2S محیط، کمپلکس­ های بی­سولفیدی Au(HS)2– تحت شرایط خنثی تا اسیدی و ماهیت اکسیدی محیط ناپایدار شده و به دنبال آن ته‌نشینی طلا رخ‌داده است.

Evolution of a Deep Fluid in a Surficial Environment Using Stable Carbon and Sulfur Isotopes: Case of the Transitional Zone of the Edwards Aquifer in South Central Texas

The Edwards Aquifer in south central Texas (USA) features a distinct fault line defining the freshwater and saline water zones. We aim to elucidate the evolutionary behavior of carbon and sulfur emanating from deep environments and flowing in surficial environment so as to better understand the cycling of these metals in water environments. To characterize the evolution of carbon and sulfur species in surficial environment as the fluid emanates from a deep saline aquifer, we monitored the chemical and isotopic (δ13CDIC and δ34SSO4) parameters over a 700-m stretch on a stream-pond system situated on the saline-freshwater line of the Edwards Aquifer’s artesian zone. A three-tier evolution process associated with the interaction of a deep saline fluid with a fresh-ponded water was observed, namely: A deep fluid control zone characterized by decreasing pH values and relatively high total dissolved solids (TDS) concentrations along the stream path; a mixing zone of the deep fluid and fresh-ponded water where the TDS concentrations showed a sharp decline and a continual decrease in pH values; and a fresh-ponded water-controlled zone with a stable pH value and low TDS concentrations. The decreasing pH values were a result of CO2 outgassing due to the relatively high CO2 partial pressures (10–2.53 atm) relative to atmospheric (10–3.50 atm) in the aqueous system, and the high TDS concentrations were attributed to the deep saline fluid emanating at the well-head. The enrichment in the δ13CDIC and δ34SSO4 for the initial stream path reflects the kinetic isotopic fractionations associated with CO2 outgassing and with the microbial conversion. The zonation of the evolutionary process indicates that (i) solutes play a critical role in the evolution of carbon and sulfur in surficial environment, (ii) kinetic and chemical fractionation are the dominant processes controlling carbon evolution, and (iii) microbial metabolism primarily controls sulfate fractionation and evolution through the conversion of sulfate to thiosulfate.

A multi-isotopic (δ13C, δ15N, and δ34S) faunal baseline for Maya subsistence and migration studies

Subsistence practices and migration among the prehispanic Maya have been extensively studied using multiple isotopic techniques, although stable sulfur isotope (δ34S) analysis has been minimally applied in the Maya archaeology. This study compares expected variation in δ34S values in the Maya region with the values from 148 faunal specimens to create a sulfur isotope baseline for the Northern and Eastern lowlands. These data are combined with stable carbon (δ13C) and nitrogen isotope (δ15N) results to investigate the diets and identify nonlocal animals at Maya sites located in Belize, Guatemala, and Mexico. The δ13C and δ15N results are consistent with those of previous Maya archaeological faunal studies. The sulfur isotope data indicate that terrestrial, marine, and freshwater ecosystems exhibit different values, which were used to evaluate the hypothesized variation in δ34S values in this part of the Maya region. Marine taxa δ34S values were likely influenced by dissimilatory sulfate reduction (DSR) and freshwater sulfur inputs in coastal areas. The δ34S values of freshwater taxa similarly reflect the influence of DSR, but also the variable sulfur sources in freshwater ecosystems. The terrestrial fauna from coastal sites had δ34S values influenced by marine sulfate deposited by sea spray. The δ34S values of inland terrestrial animals overlap those from coastal sites due to the underlying limestone geology derived from marine evaporites. Eight terrestrial faunal δ34S values from six sites were statistical outliers, representing nonlocal animals that were exchanged from isotopically distinct regions. The results suggest δ34S values may differentiate between Maya consumption of terrestrial- and freshwater-based dietary protein and can identify nonlocal animals and, by extension, humans. This study presents the first extensive archaeological faunal sulfur isotope baseline for Mesoamerica and for a tropical continental setting in general. These results demonstrate a multi-isotopic framework that includes sulfur isotope analysis can provide important insights into Maya subsistence practices, migration, and animal exchange.

Sulfur isotope signatures of sulfides from the Khibina and Lovozero massifs (Kola Alkaline Province, Fennoscandian Shield)

The sulfur isotope geochemistry of the Khibina and Lovozero agpaitic massifs provides an opportunity to understand the role of plume-lithosphere interaction processes responsible for the Paleozoic alkaline igneous activity in the north-eastern part of the Fennoscandian Shield. The stable sulfur isotope δS analysis using triple collector isotope ratio mass spectrometer (IRMS) has been carried out on the pentlandite, chalcopyrite and pyrite from nepheline syenites. The δS values for pentlandite from Khibina rocks range from +0.69 to +2.06 ‰ relative to the Vienna Canyon Diablo Troillite standard (VCDT), and the pyrite has significantly higher δS values up to +4.92 ‰ VCDT. The pentlandite from the Lovozero samples has value +1.48 ‰ VCDT, δS values of chalcopyrite is +2.85 ‰ VCDT. The maximum positive δS values are obtained for Lovozero pyrite, which vary from +5.41 to +6.30 ‰ VCDT. Comparison of sulfur-geochemical features of Khibina and Lovozero nepheline syenite with δS data for the carbonatites from the Khibina, Sallanlatvi, Seblyavr, Vuoriyarvi, Salmagora and Kovdor massifs show later carbonatite formation relatively to associated alkaline rocks. Geochemical sulfur isotope δS investigations emphasizes that parental magmas of the Khibina and Lovozero alkaline massifs were derived from a metasomatized subcontinental lithospheric mantle (SCLM). We suggest that high-δS signature on the SCLM (δS of +1 to +6 ‰ VCDT) can be explained by subduction of the high-δS Archaean crust.

Stable isotope analysis of human bone from Ganj Dareh, Iran, ca. 10,100 calBP.

We report here on stable carbon, nitrogen, and sulfur isotope values from bone collagen of human (n = 20) and faunal (n = 11) remains from the Early Neolithic site of Ganj Dareh, Iran, dating to ca. 10,100 cal. BP. Our focus explores how isotope values of human bone vary by age and sex, and evaluates dietary practices at this site. It also provides a baseline for future studies of subsistence in the early Holocene Central Zagros Mountains, from the site with the first evidence for human ovicaprid management in the Near East. Human remains include individuals of all age groups for dietary reconstruction, as well two Ottoman intrusive burials for temporal and cultural comparison. All analyzed individuals exhibited δ13C and δ15N values consistent with a diet based heavily on C3 terrestrial sources. There is no statistically significant difference between the isotopic compositions of the two sexes, though males appear to show larger variations compared to females. Interesting patterns in the isotopic compositions of the subadults suggested weaning children may be fed with supplements with distinctive δ13C values. Significant difference in sulfur isotope values between humans and fauna could be the earliest evidence of transhumance and could identify one older adult male as a possible transhumant shepherd. Both Ottoman individuals had distinctively different δ13C, δ15N, and δ34S values compared to the Neolithic individuals. This is the first large scale analysis of human stable isotopes from the eastern end of the early Holocene Fertile Crescent. It provides a baseline for future intersite exploration of stable isotopes and insight into the lifeways, health, and processes of neolithisation associated with the origins of goat domestication at Ganj Dareh and the surrounding Central Zagros.

Stable Carbon and Sulfur Isotope Characteristics of Stream Water in a Typical Karst Small Catchment, Southwest China

Surface water samples from the Maolan National Natural Reserved Park (MNNRP) were analyzed from Sept. 2013 to June 2014, for major ion concentrations (K+, Na+, Ca2+, Mg2+, Cl−, SO42−, HCO3−), δ13C-DIC and δ34S-SO42− to quantify the sources of solutes and chemical weathering. The results show that HCO3− and SO42− are the main anions in Banzhai watershed, which account for 86.2 and 10.4% of the total anion equivalent, respectively. While Ca2+ and Mg2+ account for 76.9 and 20.5%, respectively. Considerable Mg2+ in stream water indicates that it may be affected by dolomite weathering. stream water samples present the δ13C-DIC values in the range of −16.9‰~−10.8‰ (mean value was −13.9‰), which were lower than that of the groundwater. The δ34S-SO42− values ranged from −15.2‰ to 1.7‰ (mean value was −4.4‰). There was a negative correlation between HCO3− content and δ13C value, implying the result of the interaction of temperature and precipitation intensity in different seasons. The significant positive correlation between SO42− content and δ13C-DIC indicates that H2SO4 may be involved in the weathering process of carbonate rocks in small watershed scale. The content of SO42− in a school sample site was much higher than that of other sample sites for the interference from human sources. The δ34S values show that the average δ34S-SO42− in most sites is close to the δ34S isotopic values of Guizhou coal and rain, indicating that they may be affected by local coal.