[Vertical distribution and source analysis of organochlorine pesticides in sewage irrigation area, Taiyuan city].

Nine profile soil samples were collected from Xiaodian sewage irrigation area in Taiyuan city, and the concentrations of organochlorine pesticides (OCPs) were determined by gas chromatography coupled with electron capture detector (GC-ECD) to analyze the vertical distribution. The results showed that the OCPs were mainly accumulated in the surface soil layer (0-30 cm) with the maximum concentration of 98.56 ng x g(-1), and HCHs, DDTs, endosulfans and methoxychlor were the predominant contaminants compared with other pesticides in the surface soil, which accounted for 85.1% in total OCPs. The concentrations of OCPs were clearly decreased with the increasing of the depth to the top layer in the most profile soils. Beta-HCH and DDE (sum of o,p'-DDE and p,p'-DDE) were the main contaminants in HCH pesticides and DDT pesticides, respectively. Composition analysis indicated that new DDT sources might be introduced into the groundwater irrigation and swamp area recently, and the main source of HCHs and DDTs was the residual of history use in other areas. Most profile soils were defined silt loam in study area. The correlations between the concentration of sigma OCPs and the total organic carbon (TOC) were positively significant in sewage irrigation area and groundwater irrigation area, but they were not significantly correlated in swamp area and background area.