The concentration and distribution of different mercury species in the water columns of BaiHua reservoir

Abstract
Three study sites were selected at the upper, middle and down reach of the Baihua Reservoir and the water samples from different depth were collected in June 8 to 9, 2002. Dissolved gaseous mercury (DGM), reactive and total mercury concentrations in water profiles were measured by trap pre-concentration and CVAFS detection method. The results indicated, as a whole, the concentrations of all mercury species at the three sites gradually decreased along the water flow direction, and the highest concentration site presented in the upper stream (HuaQiao) ofthe reservoir. In water column (except bottom water), the highest average total and reactive mercury concentrations are 35.9 ngL ^-1and 5.7 ngL ^-1, respectively. Total mercury concentrations in bottom water reach 807-1963ngL ^-1. Sediments are potential mercury source to water column of the reservoir. Our preliminary study indicted that Baihua Reservoir is seriously contaminated in terms of mercury due to mercury discharge from Guizhou Organic Chemical Plant (GOCP). It is essential to carry out further study on mercury cycling in Baihua Reservoir to evaluate ecological effects from mercury contamination.