Isotope geochemistry, hydrochemistry, and mineralogy of a river affected by acid mine drainage in a mining area, South China†
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Abstract
The Hengshi River is a classic example of an acid mine drainage (AMD)-affected river located in the Dabaoshan mining area in southern China. This work utilized stable isotopes (δ34S and δ18O) and hydrochemical data of surface water samples as well as the mineralogical composition of sediment samples to evaluate the processes that affect the sulfate content in water of the Hengshi River. High concentrations of heavy metals (e.g. Fe: >347.78 mg L−1; Zn: >96.48 mg L−1) in the mud impoundment and relatively stable S isotope values (δ34S: −1.53‰ ∼ −0.88‰) in the upper stream suggested that most of the sulfates were derived from sulfide oxidation. Dilution and mineralization could decrease SO42− concentration, but had no significant influence on the isotope composition of SO42−. However, δ34S and δ18O increased with the decrease of SO42− concentration, accompanied by the elevation of pH and adequate organic matter being available, suggesting that bacterial (dissimilatory) sulfate reduction played an important role in the transformation of sulfate downstream. The methods used in this study can also be used in other natural systems. Furthermore, it is important to understand the causes of environmental pollution and to help environmental remediation.
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