[Temporal and spatial variation rule of methylmercury in water in the Second Songhua River]

The concentrations of methylmercury (MeHg) in water were investigated in both level period and flood period in the Second Songhua River. The results show that the MeHg concentrations in water of Hongshi, Shihaoxian and Ganshuigang sites are relatively higher than other sampling sites. The MeHg concentrations in the level period are higher than the flood season in most sampling sites beside Laozhou and Sifangtai sites. By comparing the MeHg concentrations in different years, the results reveal that the MeHg concentrations in 1981 decreased with the distances increasing from the sites to the pollution source. The MeHg concentrations in most sites greatly fell in 1983, when the pollution source had been ceased for one year. The concentrations approached the natural background level in most sites, however, they were over 0.35 ng x L(-1) from Zhaoyuan site to Sifangtai site. The MeHg concentrations in corresponding sites in 2006 were higher than that in 1983, but were lower than that in 1981. Moreover, the pollution level in water of the Second Songhua River was also discussed.