The geochemical characteristics of mine-waste calcines and runoff from the Wanshan mercury mine, Guizhou, China

Mercury and other geochemical parameters were measured in mine-waste calcines, stream sediments and surface waters from the Wanshan Hg district in the Guizhou Province of China to evaluate adverse effects of Hg to the surrounding environment. Wanshan ore is dominantly cinnabar, and lacks other sulfide minerals and as a result, heavy metals other than Hg are rare in the calcines and mine-water runoff. Host rocks in the Wanshan area are dominantly carbonates, which upon weathering, produces alkaline-water runoff. Surface waters emanating from calcine piles have water pH varying from 10.6 to 11.8, contain high EC values, and variable major element geochemistries. Dissolved Hg concentration decreases from 300 to 1900 ng/l in mine water to 72 ng/l in stream water collected significantly downstream from the mine. High concentrations of Hg in mine-waste calcines and alkaline surface water are the major threats to the surrounding environment. Alkalinity is also naturally attenuated downstream from the Wanshan mine. However, erosion and transport of Hg in sediment and water and highly alkaline mine-water runoff, may adversely affect sediment, aquatic and biological columns downstream from the Wanshan mine area.