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• Stable isotopes of sulfate in wastewater, fertilizers and manure in the Upper Silesia are generally more homogeneous compared to the literature data. • Isotopic composition of sulfate from landfill leachates is enriched with heavy isotopes of S and O. • Isotopic studies of local sources of contamination reduce the uncertainty in the interpretation of sulfate sources in groundwater. Isotopic signatures of anthropogenic sulfate sources within the Upper Silesian urban area (southern Poland) were investigated to increase the reliability of the origin assessment of groundwater contaminants. To analyze δ34S and δ18O in sulfate, 64 samples were collected, representing several sulfate sources: synthetic and organic fertilizers, raw and treated wastewater, mine water, leachate from landfills, mine heaps, and industrial waste dumps. Additionally, 10 surface water samples were taken from contaminated rivers regarded as potential groundwater pollution sources. Results of δ34S and δ18O in sulfate derived from anthropogenic sources were compared with literature data, which indicated significant discrepancies for some contamination sources. The results were applied to assess SO 4 2- origin in groundwater samples from the Gliwice aquifer. Apart from the δ34S and δ18O data, the study included measurements of major ions, inorganic nitrogen forms, trichloroethene and tetrachloroethene in groundwater. Isotopic analyses of river water samples confirmed the impact of urbanized and industrialized areas on surface water pollution and possible influence on groundwater contamination. The values of δ34S and δ18O similar to wastewater were reported for most groundwater samples from the Gliwice carbonate aquifer. Groundwater contamination was also manifested by higher values of electrical conductivity and concentrations of chloride, sodium, trichloroethene and tetrachloroethene. The comparison of recent isotopic data on SO 4 2- sources with literature values clearly shows that it is very important to investigate local potential contamination sources to increase their reliability in determining the source of groundwater or river water pollution. [ABSTRACT FROM AUTHOR]

• Stable isotopes of sulfate in wastewater, fertilizers and manure in the Upper Silesia are generally more homogeneous compared to the literature data. • Isotopic composition of sulfate from landfill leachates is enriched with heavy isotopes of S and O. • Isotopic studies of local sources of contamination reduce the uncertainty in the interpretation of sulfate sources in groundwater. Isotopic signatures of anthropogenic sulfate sources within the Upper Silesian urban area (southern Poland) were investigated to increase the reliability of the origin assessment of groundwater contaminants. To analyze δ34S and δ18O in sulfate, 64 samples were collected, representing several sulfate sources: synthetic and organic fertilizers, raw and treated wastewater, mine water, leachate from landfills, mine heaps, and industrial waste dumps. Additionally, 10 surface water samples were taken from contaminated rivers regarded as potential groundwater pollution sources. Results of δ34S and δ18O in sulfate derived from anthropogenic sources were compared with literature data, which indicated significant discrepancies for some contamination sources. The results were applied to assess SO 4 2- origin in groundwater samples from the Gliwice aquifer. Apart from the δ34S and δ18O data, the study included measurements of major ions, inorganic nitrogen forms, trichloroethene and tetrachloroethene in groundwater. Isotopic analyses of river water samples confirmed the impact of urbanized and industrialized areas on surface water pollution and possible influence on groundwater contamination. The values of δ34S and δ18O similar to wastewater were reported for most groundwater samples from the Gliwice carbonate aquifer. Groundwater contamination was also manifested by higher values of electrical conductivity and concentrations of chloride, sodium, trichloroethene and tetrachloroethene. The comparison of recent isotopic data on SO 4 2- sources with literature values clearly shows that it is very important to investigate local potential contamination sources to increase their reliability in determining the source of groundwater or river water pollution. [ABSTRACT FROM AUTHOR]

Summary: Groundwater within the unconfined or semi-confined parts of Triassic carbonate aquifers in Upper Silesia (Poland) contains high concentrations of sulphate (up to 290mg/L), sometimes in excess of drinking water limits (>250mg/L). To assess the influence of different possible sulphate sources, isotopic analyses of S and O were performed on groundwater sulphate and potential sulphate sources and combined with literature data. Three dominant sources of sulphate were delineated, based on the geological and literature study and supported by the mixing relations between inverse concentration of sulphate and its isotopic compositions. These sources are: (i) sulphate from rainfall; (ii) weathering of sulphide minerals in ore deposits in the aquifer-forming carbonate rocks; (iii) dissolution of sulphate evaporites in the Triassic sequence. Fortunately these three sources have distinctive S and O isotope compositions and thus their contributions to the total dissolved sulphate could be estimated. The application of linear mixing models for three sources in the dual isotope system allowed the impact of the three different sulphate sources on particular parts of the aquifers to be calculated. The average isotopic composition of sulphate in abstracted groundwater indicates that the most important source of sulphate is sulphide weathering, contributing about 50% of total sulphate. The second most significant source of sulphate input is rainfall and it is characterised by a mean contribution of 30%. Application of Monte Carlo analysis that incorporates the full variability in distributions of isotopic compositions for the three sources and all mixing fractions between them gave the most probable ranges of the dissolved in groundwater sulphate. This analysis indicated that the proportion of sulphate derived by sulphide oxidation is comparable with the estimations based on linear models. This study has shown that the water quality of these important groundwater resources is under threat from both natural sources, i.e. metal sulphide oxidation and gypsum dissolution. Analysis of the mathematical models analysis shows that the first process is the predominant source of sulphate in groundwater. However, the highest concentrations of dissolved sulphate are positively correlated with the increasing proportion of sulphate derived from gypsum dissolution. Moreover, one should keep in mind that natural processes might be anthropogenically accelerated due to variable water demands and groundwater abstraction. Eventually, the statistically second-order source of sulphate – rainfall might contain surface-derived contaminants, and its contribution to the total load of sulphate might indirectly indicate the vulnerability of aquifers for the pollution. [Copyright &y& Elsevier]