The Use of Stable Sulfur, Oxygen and Hydrogen Isotope Ratios as Geochemical Tracers of Sulfates in the Podwiśniówka Acid Drainage Area (South-Central Poland)

Abstract

The paper presents the results of determinations of stable S and O isotopes of dissolved sulfates and O and H stable isotopes of waters from three ponds, that is, Marczakowe Doły acid pond, Marczakowe Doły fish pond and Podwiśniówka acid pit pond, located in the Holy Cross Mountains (south-central Poland). The δ 34 S V-CDT and δ 18 O V-SMOW of SO 42- in waters of three ponds (n = 14) varied from -16.2 to -9.5 ‰ (mean of -13.6 ‰) and from -8.1 to -3.2 ‰ (mean of -4.8 ‰), respectively. The mean δ 34 S-SO 42- values were closer to those of pyrite (mean of -25.4 ‰) and efflorescent sulfate salts (mean of -25.6 ‰), recorded previously in the Podwiśniówka quarry, than to sulfates derived from other anthropogenic or soil and bedrock sources. The SO 42- ions formed by bacterially induced pyrite oxidation combined with bacterial (dissimilatory) dissolved sulfate reduction, and presumably with subordinate mineralization of carbon-bonded sulfur compounds, especially in both Marczakowe Doły ponds. In addition, the comparison of δ 18 O-SO 42- and δ 18 O-H 2 O values indicated that 75-100 % of sulfate oxygen was derived from water. Due to the largest size, the Podwiśniówka acid pit pond revealed distinct seasonal variations in both δ 18 O-H 2 O (-9.2 to -1.6) and δD-H 2 O (-29.7 to -71.3) values. The strong correlation coefficient (r 2 = 0.99) was noted between δ 18 O-H 2 O and δD-H 2 O values, which points to atmospheric precipitation as the only source of water. The sediments of both acid ponds display different mineral inventory: the Marczakowe Doły acid pond sediment consists of schwertmannite and goethite, whereas Podwiśniówka acid pit pond sediment is composed of quartz, illite, chlorite and kaolinite with some admixture of jarosite reflecting a more acidic environment. Geochemical modeling of two acid ponds indicated that the saturation indices of schwertmannite and nanosized ε-Fe 2 O 3 (Fe 3+ oxide polymorph) were closest to thermodynamic equilibrium state with water, varying from -1.44 to 3.05 and from -3.42 to 6.04, respectively. This evidence matches well with the obtained mineralogical results. © 2013 The Author(s).