[DDTs and HCHs residues in soils around Guanting Reservoir and related environmental risk assessment]

Surface soil samples around Guanting Reservoir ranging from 2-10 km were measured for pesticide residues (HCHs and DDTs) concentrations in 2009. Occurrences and related environmental risk were analyzed; furthermore, GIS and geostatistical techniques were applied to analyze the spatial variation of organochlorine pesticides. The results show that concentrations of HCHs in soils range from n.d. to 14.97 ng x g(-1) with a mean value of 0.73 ng x g(-1), and DDTs range from n.d. to 64.91 ng x g(-1) with a mean value of 6.46 ng x g(-1). According to the isomers of HCHs and metabolites of DDTs, HCHs and DDTs residues in soils were primarily from historical use. The land use showed great effect on the degradation of HCHs and DDTs, with the residual level sequence of orchard >> crop land > barren land. Based on kriging interpolation, the spatial distribution of HCHs and DDTs around Guanting Reservoir was observed. Spatial variability indicated how HCHs and DDTs had been applied and distributed in the past. Compared with those in other national or international regions, the concentrations of HCHs and DDTs in soils around Guanting Reservoir were very low.