Tracing natural and anthropogenic sources of dissolved sulfate in a karst region by using major ion chemistry and stable sulfur isotopes

This paper presents hydrogeochemical and S isotopic characteristics of karstic surface and ground water in the karstic aquifers of Zunyi city of Guizhou Province, SW China. The average delta(34)S value of SO(4) is +2.2% (n = 28) in ground waters and +7.0% (n = 15) in surface waters in the low flow season, while in the high flow season it is + 1.0% in ground waters and +2.8% in surface waters. Natural and anthropogenic sources of the dissolved SO(4)(2) can be discriminated by a combined approach using water chemistry and stable S isotope data. A pollutant source of SO(4) is estimated to have very high TDS contents and a narrow range of delta(34)S values (0% to +5.0%). The water with a distinctively high delta(34)S value of +30.5% originates from an evaporite (gypsum and anhydrite)-bearing aquifer, and the delta(34)S values lower than -10% suggest an origin by oxidation of sulfide minerals in coal seams with intermediate TDS contents. (C) 2011 Elsevier Ltd. All rights reserved.