[Analysis and evaluation of heavy metals along the Chaohe River in Miyun County].

In order to explore the heavy metal concentrations in soils surrounding the Chaohe River, 15 soil samples were collected along the Chaohe River. Results show that average concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn are 7.94, 0.16, 127.71, 38.45, 0.22, 45.97, 21.98, 81.06 microg x g(-1), respectively. The mean concentrations of 15 samples for most heavy metals are higher than the background values of Beijing soil except Pb. Compared to the heavy metal concentrations in the soil of Shanghai Huangpu River water resource area, the mean concentrations of Cr, Cu and Ni are higher and concentrations of other heavy metals are at a moderate level. Geo-accumulation index method was used to evaluate the pollution status of different heavy metals. Results show that the pollution of Cr and Hg is moderate. The pollution of Cu and Ni is between no to moderate. There is no pollution of As, Cd, Pb and Zn in the study area. Ecological risk index method was also used to evaluate the ecological impact. Results show that the pollution level of Hg is strong and Cu is medium. Other heavy metals are at a slight pollution level. The samplings region as a whole is at a medium ecological pollution level. In a word, Hg, Cr, Ni, and Cu need to be controlled.