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Lake Sevan is a meso-eutrophic water body, which was severely impacted by anthropogenic level decrease, pollution and eutrophication during the last century. Starting in the 1970s, these processes resulted in the formation of an oxygen-depleted hypolimnion during summer–autumn stratification of the lake. In this work, we demonstrate for the first time that eutrophication of the lake leads not only to the full depletion of oxygen and nitrate in the hypolimnion but as well to the presence of sulfate-reducing microorganisms and toxic hydrogen sulfide. Concentrations of hydrogen sulfide in the hypolimnion of Major and Minor Sevan in October were as high as 9 and 39 μM, respectively. In October 2019, 66 % of lake's bottom was covered by sulfidic waters, while the fraction of sulfidic water volume reached 19 %. Values of δ34S for hypolimnetic sulfide are lower by only 7–12 ‰ compared to epilimnetic sulfate, while δ33S values of sulfide are similar to the δ33S values of sulfate. These isotopic fingerprints are not consistent with microbial sulfate reduction as the sole source of hydrogen sulfide in the hypolimnion. We attribute the formation of a sulfidic deep-water layer to a combination of microbial sulfate reduction in the water column and diffusion of hydrogen sulfide from the sediments. [ABSTRACT FROM AUTHOR]

Highly mineralized springs in the Scuol-Tarasp area of the Lower Engadin and in the Albula Valley near Alvaneu, Switzerland, display distinct differences with respect to the source and fate of their dissolved sulphur species. High sulphate concentrations and positive sulphur (δ34S) and oxygen (δ18O) isotopic compositions argue for the subsurface dissolution of Mesozoic evaporitic sulphate. In contrast, low sulphate concentrations and less positive or even negative δ34S and δ18O values indicate a substantial contribution of sulphate sulphur from the oxidation of sulphides in the crystalline basement rocks or the Jurassic sedimentary cover rocks. Furthermore, multiple sulphur (δ34S, Δ33S) isotopes support the identification of microbial sulphate reduction and sulphide oxidation in the subsurface, the latter is also evident through the presence of thick aggregates of sulphide-oxidizingThiothrixbacteria. [ABSTRACT FROM AUTHOR]

Pretreatment methods for measuring stable sulphur (δ34S) and oxygen (δ18O) isotope ratios of dissolved sulphate from watersheds have evolved throughout the last few decades. The current study evaluated if there are differences in the measured stable S and O isotope values of dissolved sulphate from forested watersheds when pretreated using three different methods: Method 1 (M1): adsorb sulphate on anion exchange resins and send directly to isotope facility; Method 2 (M2): adsorb sulphate on anion exchange resins, extract sulphate from anion exchange resins, and send the produced BaSO4 to the isotope facility; and Method 3 (M3): directly precipitate BaSO4 without anion exchange resins with the precipitates being sent to the isotope facility. We found an excellent agreement of the δ34Ssulphate values among all the three methods. However, some differences were observed in the δ18Osulphate values (M1 versus M2:−1.5 ‰; M1 versus M3:−1.2 ‰) associated with possible O contamination before isotope measurement. Several approaches are recommended to improve the pretreatment procedures for δ18Osulphate analysis. [ABSTRACT FROM AUTHOR]

The isotope ratios of various sulphur components (total sulphur content in the sediment, sulphate and H2S in the pore-water) were measured in a number of cores from recent marine sediments taken from the Kieler Bucht (Kiel Bay) region in the western Baltic Sea. Additionally, the quantitative contents of total sulphur, sulphate, sulphide, chloride, organic carbon, iron and water in the sediment and in the pore-water solutions, respectively, were determined. These investigations provided the following results: 1. The sulphur contained in the sediment (∼ 0.3–2% of the dry sample) was for the most part introduced only after sedimentation. This confirms the deliberations of Kaplan et al. [The Distribution and Isotopic Abundance of Sulfur in Recent Marine Sediments off Southern California, Geochim. Cosmochim. Acta 27, 297 (1963)]. The organic substance contributes to the sulphur content of the sediment only to an insignificant degree (in our samples with ∼5–10% of the total sulphur). 2. The sulphate in the pore-waters has been identified as a source for sulphur in the sediment. During normal sedimentation, the exchange of sulphate by diffusion significant for changes in the sulphur content goes down to a sediment depth of 4–6 cm. In this process, the sulphate consumed by reduction and formation of sulphide or pyrite is mostly replaced. The uppermost sediment layer thus represents a partially open system for the total sulphur. The diagenesis of the sulphur is allochemical. At depths below 4–6 cm, we are dealing with a closed system. The further diagenesis of sulphur here is isochemical. 3. The isotope values of the sediment sulphur are influenced primarily by sulphur which comes into the sediment by diffusion and which is bound by subsequent bacteriological reduction as either sulphide or pyrite. As a consequence of the prevailing reduction of 32S and reverse-diffusion of sulphate into the open sea water, a 32S enrichment takes place in the uppermost layer of the sediment. The δ34S values in the sediment range in general between−15 and−35‰, while seawater sulphate is+20‰. No relationship could be established between sedimentological or chemical changes and isotope ratios. In the cores, successive sandy and clayish layers showed no change in the δ34S values. However, the sedimentation rate seems to influence δ34S values. In one core with relatively low sedimentation rates, the δ34S values varied between−29 and−33‰, while cores with higher sedimentation rates showed values between−17 and−24‰. 4. As sediment depth increases, the pore-water sulphate shows, as expected, decreasing concentrations (in a depth of 30–40 cm, we found between 20 and 70% of the seawater values), and increasing δ34S values (in one case reaching more than+60‰). The concentration of sulphide in the pore-water increases, however, with sediment depth (to various extents, reaching 80 mg S per litre in one case). The δ34S values of the pore-water sulphide in all cores show increases paralleling the sulphate sulphur, with a nearly constant δ difference of 50–60‰ in all cores. This seems to confirm the genetic relationship between the two components. [ABSTRACT FROM AUTHOR]

Batch experiments with the lead sulphide ore mineral galena were carried out in order to get information about the oxidation mechanisms and to contribute to the understanding of field data, especially those obtained from the mining-affected sites. Results indicate that oxygen and sulphur isotopes of dissolved sulphate may be useful tools for the investigation of galena oxidation mechanisms. However, some methodological modifications are necessary to obtain sufficient sulphate yields, which are a prerequisite for the reduction of the analytical uncertainty. Surface and hydrochemical investigations indicated that galena was dissolved non-oxidatively during the experiment at initial pH 2, whereas the oxidative dissolution of galena dominated in experiments at initial pH 6 and 8. No isotope results could be obtained from the experiment at initial pH 2 due to the low sulphate production. The oxidative dissolution of galena resulted in somewhat higher sulphate yields. Thus, the oxygen isotope composition of sulphate produced from galena oxidation could be determined for the first time. Oxygen in sulphate derived largely from water molecules; but minor amounts of molecular oxygen could be also observed. Both molecular oxygen and ferric iron may act as oxidants of galena. A variety of intermediate reactions allow for a variable oxygen isotope composition of sulphate. Sulphur isotopes of sulphate showed an enrichment of 32S in sulphate (relative to galena), which increases with increasing pH. Sulphur isotope enrichment processes may be associated with the formation of anglesite. [ABSTRACT FROM AUTHOR]

The curative waters of HCO3-SO4-Mg-Na+H2S chemical type and 0.6-0.8 g/dm3 total dissolved solids are exploited in Horyniec Spa located at the northern boundary of the Carpathian Foredeep, near the Polish-Ukrainian border. Although these waters occur at relatively shallow depths (their aquifer is encountered about 30 m below the ground surface), they are quite well protected from surface pollutants by a cover of clayey sands. This paper revises and discusses the origin of specific chemical components of these waters based on the following analyses of stable isotopes: (a) δ34S in [image omitted] , H2S, and CaSO4·2H2O, (b) δ18O in [image omitted] , H2O, and CaSO4·2H2O, and (c) δ2H in H2O and CaSO4·2H2O. The most important process which takes place in the aquifer is the dissolution of gypsum present in the Miocene formation and subsequent bacterial reduction of sulphate ion to hydrogen sulphide in the presence of an organic matter. This process shifts both δ34S and δ18O of sulfate ions towards higher concentration of heavy isotopes by several per mil in comparison to that in the original Miocene gypsum. The hydrogen sulphide generated this way (up to a concentration of 45 mg/dm3) is highly depleted in a heavy isotope by about 41 ‰ with respect to a sulphate ion. [ABSTRACT FROM AUTHOR]

Oxidation experiments with different pyrite grain sizes (63-100, 100-140, 140-180 μm) were carried out to investigate the oxygen and sulphur isotope composition of sulphate produced under aerobic acid conditions, which may help to understand oxidation mechanisms and to interpret data from natural sites. Long-term experiments with grain size 63-100 μm showed that constant δ 18OSO4 values were not achieved before 100 days. The final oxygen isotope difference between water and sulphate indicates that a small proportion of molecular oxygen is incorporated into sulphate even in the later course of the oxidation due to sulphite oxidation by molecular oxygen. However, most of the sulphate oxygen derives from water. Similar δ 18OSO4 values from experiments with grain sizes 63-100, 100-140, and 140-180 μ m indicate similar oxidation mechanisms for all three grain sizes. These results differed from previous results of identical experiments with grain size<63 μ m, where higher δ 18OSO4 values were obtained. We propose that the greater proportion of molecular oxygen in sulphate from oxidised fine-grained pyrite is caused by an intensified adsorption of molecular oxygen on sulphur sites of ultrafine pyrite particles. Hence, the formation of sulphate from the (initial) reaction on sulphur sites of pyrite and from sulphite oxidation should be more dominant if ultrafine material is present. The δ 34SSO4 values (2.0-2.7) obtained from experiments with the coarser grain sizes agreed with the δ 34S value of pyrite (2.4), whereas sulphur isotopes of sulphate obtained from previous experiments with fine-grained pyrite showed an initial 32S enrichment compared with pyrite. Due to the lack of δ 34SSO4 values from the beginning of the experiments with coarser grain sizes, it remains speculative that sulphur isotopes indicate at least initial differences in oxidation mechanisms between fine and coarser pyrite grain sizes. [ABSTRACT FROM AUTHOR]

This paper describes the results of isotopic analyses of (i) hydrogen and oxygen in water (δ D[image omitted] and δ18O[image omitted] ) and (ii) sulphur and oxygen in sulphates (δ34Ssulphate and δ18Osulphate) from atmospheric precipitation collected within a one-year period between 25 May 2004 and 25 May 2005 in Wrocław (SW Poland). The resulting equation of Local Meteoric Water Line for Wrocław is δ D=6.373×δ18O-0.047, (r2=0.97, n=32). The δ34Ssulphate varies from 1.1 to 4.2‰ (with an average of 2.5‰), δ18Osulphate varies from 9.0 to 16.7‰ (with an average of 13.8‰) and δ18O[image omitted] varies from-0.8 to-16.3‰ (with an average of-8.2‰). The above results indicate two main sources of sulphates in Wrocław precipitation: (i) low-temperature secondary sulphates forming in situ in Wrocław from the atmospheric SO2 as well as precipitation water (heterogeneous and homogeneous pathways oxidation) and (ii) high-temperature primary sulphates forming in rapid high-temperature hydratation of SO[image omitted] in an immediate proximity of industrial chimneys. We hypothesise that the secondary low-temperature type of sulphates is probably formed from the local sulphur and oxygen reservoirs, whereas the primary high-temperature type is allochthonous and it is probably transported from industrial areas located outside of Wrocław. [ABSTRACT FROM AUTHOR]

Recovery of gold from arsenopyrite-hosted ore in the Giant Mine camp, Yellowknife, NWT, Canada, has left a legacy of arsenic contamination that poses challenges for mine closure planning. Seepage from underground chambers storing some 237,000 tonnes of arsenic trioxide dust, has As concentrations exceeding 4000 ppm. Other potential sources and sinks of As also exist. Sources and movement of water and arsenic are traced using the isotopes of water and sulphate. Mine waters (16 ppm As; As V /As III ≈ 150) are a mixture of two principal water sources - locally recharged, low As groundwaters (0.5 ppm As) and Great Slave Lake (GSL; 0.004 ppm As) water, formerly used in ore processing and discharged to the northwest tailings impoundment (NWTP). Mass balance with δ 18 O shows that recirculation of NWTP water to the underground through faults and unsealed drillholes contributes about 60% of the mine water. ;[emsp]>Sulphate serves to trace direct infiltration to the As 2 O 3 chambers. Sulphate in local, low As groundwaters (0.3-0.6 ppm As; δ 34 S SO 4 ∼ 4 ‰ and δ 18 O SO 4 ∼ - 10 ‰) originates from low-temperature aqueous oxidation of sulphide-rich waste rock. The high As waters gain a component of 18 O-enriched sulphate derived from roaster gases (δ 18 O SO 4 = + 3.5 ‰), consistent with their arsenic source from the As 2 O 3 chambers. High arsenic in NWTP water (∼ 8 ppm As; δ 18 O SO 4 = - 2 ‰) derived from mine water, is attenuated to close to 1 ppm during infiltration back to the underground, probably by oxidation and sorption by ferrihydrite. [ABSTRACT FROM AUTHOR]

Surface water and deep and shallow groundwater samples were taken from selected parts of the Grand-Duchy of Luxembourg to determine the isotopic composition of nitrate and sulfate, in order to identify sources and/or processes affecting these solutes. Deep groundwater had sulfate concentrations between 20 and 40 mg/L, δ 34 S sulfate values between -3.0 and -20.0‰, and δ 18 O sulfate values between +1.5 and +5.0‰; nitrate was characterized by concentrations varying between <0.5 and 10 mg/L, δ 15 N nitrate values of ∼-0.5‰, and δ 18 O nitrate values ∼+3.0‰. In the shallow groundwater, sulfate concentrations ranged from 25 to 30 mg/L, δ 34 S sulfate values from -20.0 to +4.5‰, and δ 18 O sulfate values from ∼+0.5 to +4.5‰; nitrate concentrations varied between ∼10 and 75 mg/L, δ 15 N nitrate values between +2.5 and +10.0‰, and δ 18 O nitrate values between +1.0 and +3.0‰. In surface water, sulfate concentrations ranged from 10 to 210 mg/L, δ 34 S sulfate values varied between -9.3 and +10.9‰, and δ 18 O sulfate values between +3.0 and +10.7‰ were observed. Nitrate concentrations ranged from 10 to 40 mg/L, δ 15 N nitrate values from +6.5 to +12.0‰, and δ 18 O nitrate values from -0.4 to +4.0‰. Based on these data, three sulfate sources were identified controlling the riverine sulfate load. These are soil sulfate, dissolution of evaporites, and oxidation of reduced S minerals in the bedrock. Both groundwater types were predominantly influenced by sulfate from the two latter lithogenic S sources. The deep groundwater and a couple shallow groundwater samples had nitrate derived mainly from soil nitrification. All other sampling sites were influenced by nitrate originating from sewage and/or manure. A decrease in nitrate concentration observed along one of the rivers was attributed to denitrification. It appears that sulfate within Luxembourg's aquatic ecosystem is mainly of lithogenic origin, whereas nitrate is often derived from anthropogenic activities. [ABSTRACT FROM AUTHOR]

Springs on Roztocze and Lublin Upland have been studied. Isotopic data are compared with data of chemical analyses. The results of studies allow us to distinguish five types of groundwaters. The differentiation is based upon different lithology; opokas, gaizes, sandy-silty-clay deposits, sands with shell sandstones, marly opokas, marly limestones and soft limestones of chalk type. A correlation can be observed between δ 34 S and the concentration of Ca or Mg ions also a correlation between \hbox{HCO}^{-}_{3} ion concentration and δ 18 O in sulphates. Probably these correlations are the result of some simultaneous processes, which occur in groundwater. The seasonal variations of the isotopic composition and sulphate concentration were observed in four springs feeding the upper Wieprz. The variations were simultaneous and often similar in these springs. Probably, these variations are caused by the admixture of sulphates coming from shallow water layers (or leached from soil); however the variations of the groundwater level may also change chemical and isotopic composition in groundwater. [ABSTRACT FROM AUTHOR]

A modified technique for the conversion of sulphates and sulphides to SO 2 with the mixture of V 2 O 5 -SiO 2 for sulphur isotopic analyses is described. This technique is more suitable for routine analysis of large number of samples. Modification of the reaction vessel and using manifold inlet system allows to analyse up to 24 samples every day. The modified technique assures the complete yield of SO 2 , consistent oxygen isotope composition of the SO 2 gas and reproducibility of δ 34 S measurements being within 0.10‰. It is observed, however, oxygen in SO 2 produced from sulphides differs in δ 18 O with respect to that produced from sulphates. [ABSTRACT FROM AUTHOR]

We investigated physical, chemical and isotope (S, O) parameters of sulfate from acid mine drainage from the polymetallic sulfide ore deposit Freiberg (Germany), which was mined for more than eight hundred years. Two main groups of water were distinguished: 1.Flowing mine water with sulfate concentrations of less than 9000 mg/l and pH values higher than 3.2, 2.Pore water in weathered low grade ores and pools with sulfate concentrations higher than 9000 mg/l and pH values below 3.2. The sulfur and oxygen isotope composition of sulfate from flowing mine waters reflects mixing of sulfate from two sulfur sources: a) atmospheric sulfur from precipitation and b) sulfate formed as a result of sulfide oxidation processes. Sulfur isotope values of mine water sulfate were used to estimate the contribution of sulfate derived through oxidation of sulfides. The sulfur isotope composition of pore water sulfate and precipitated sulfate (jarosite) from weathered low grade ore samples is identical to the sulfur isotope composition of primary sulfides. The oxygen isotope composition of pore water sulfate from low grade ore samples indicates that the oxidation process proceeds relatively slowly in O 2 -depleted waters, probably without significant microbial catalysis. [ABSTRACT FROM AUTHOR]

Elevated sulfate concentrations and their heterogeneous distribution in the drinking water catchment area Torgau-Mockritz (Germany) were investigated by means of multiple isotope signatures such as δ 34 S, δ 18 O-H 2 O, δD, tritium, and 85 Kr. δ 34 S values of the groundwater sulfate vary between -19…+37‰ CDT. No simple correlation exists between sulfate concentrations and δ 34 S. Superimposition of different sulfur sources and mobilization processes combined with a complicated groundwater movement create a complex distribution pattern. The oxidation of reduced sedimentary sulfur has to be regarded as a main source of dissolved sulfate at least regionally. Tritium and 14 C data revealed that old groundwater can be excluded as source for high sulfate contents. Correlated temporal variations in the concentrations of tritium and sulfate are observed in deeper sampling positions. Highly variable δ 18 O and δD, as detected in parts of the catchment area, indicate local influences of surface water infiltration into the aquifer. The spatial distribution of isotope signatures enables the identification of zones with descending younger water or hindered groundwater movement and hence provides useful hints for flow modeling. [ABSTRACT FROM AUTHOR]