Deterioration of water quality in a reservoir receiving pyrite-bearing rock drainage and its geochemical modeling

摘要

The investigation of water chemistry of a reservoirand the geochemical modeling were carried out to elucidate thedeterioration of the water quality. The chemical properties showedthat the sulfate ion concentration was high at the samplinglocations in the reservoir where the pH value was less than 5, andthat there was sufficient dissolved oxygen to keep the redoxcondition in the reservoir oxic. Reddish-brown iron precipitateswere also observed on the surface of the excavated rocks used forthe landfill constructed in the center of the reservoir, because therocks contained an appreciable amount of pyrite. Accordingly, thecause of the reservoir acidification was expected to be theoxidation of pyrite contained in the excavated rocks. Thegeochemical code. PHRREQE, was applied to evaluate thebehavior of aluminum detected in the reservoir. The calculatedresults showed that the aluminum concentration was restricted bythe solubility products of aluminum hydroxides. This suggests thatthe acidified reservoir water leached aluminum from thesurrounding soils, rocks and suspended solids.