Heavy Metal and Pesticide Residues in Soils Around the Guanting Reservoir and Environmental Risk Assessment

Investigation and survey was carried out to determine heavy metals(Cu、Zn、Pb、Cr、Cd、Ni、As、Co) and pesticide residues(HCHs and DDTs) in soils around the Guanting Reservoir and their sources and environmental risks were analyzed as well.Results indicate that Cd is the major pollutant in this area,3.4 times as high as Grade Ⅰ criterion of the national standard for soil environment,with a mean of(0.68±0.17) mg·kg^-1.The area of soils with Cd concentration(higher) than Grade Ⅱ criterion of the national standard accounts for about 40% of the whole study area.DDT is the main load of pesticide pollution in the soils,accounting for 93% of the total residue.Fertilizers and pesticides used in farming and industrial waste from upstreams are the major sources of soil pollutants in the region.The integrated pollution is more serious in the Yanghe River and the Sanggan River watersheds than in other areas,with Cd being the most serious factor.The integrated pollution index of all soil samples is higher than 2;and more than 65% of them higher than 3,being up to the level of serious pollution.These suggest that more attention should be paid to the soil integrated pollution induced by multi-pollutants in planning,protection and management of the water resource of the Guanting Reservoir in future.