Environmental geochemistry of water in the Wolongquan River valley, China

Abstract

Gold mining affects surface water and ground water to some extent in the Wolongquan River valley. Geochemical studies on the water environment show that pH, COD (sub cr) , K and TH of the water are higher and Eh and DO of the water are lower in the river near the gold mining district than in the river far from the gold mining district. The pH, COD (sub cr) and DO of the water in local rivers surpass the three-grade criterion of national surface water (GB3838-88), and the CN-content of ground water in local areas is 15 times greater than the criterion for drinking water in China (GB5749-85) and 80 times greater than the criterion for drinking water set by the World Health Organization in 1971. Cu, Pb, Zn, Cd, As and Hg of the water are higher in areas near the gold mining district than in areas far from the gold mining district. The type of ground water changes from Ca-HCO (sub 3) type water in the background area to Na-SO (sub 4) (super 2-) type water and Ca-SO (sub 4) (super 2-) type water in the gold mining district. The geochemistry of the water and the sediments indicates that the water pollution is mainly related to mining, and only partly due to natural weathering of rocks by water-rock reactions in the Wolongquan River valley, and that contaminants primarily derive from processing drainage, discarded tailings and discarded rocks, and partly from weathered rocks. The reasons for this pollution are insatiable tailing disposal sites, improper management of mining waste, and disordered mining.