Distribution Characteristics and Risk Assessment of Organochlorine residues in Surface Soil of Pearl River Delta Economic Zone

The contents of 17 Organochlorine pesticides (OCPs) of 605 samples collected from the surface of agriculture land from Pearl River Delta Economic Zone were determined by gas chromatography with electron capture detector (GC-ECD). The residual characteristics, sources and ecological risk of OCPs were also analyzed. The results showed that the detection rate of OCPs was 97.85%. The mean value of residue level was 20.67 microg x kg(-1), with the highest value of 649.33 microg x kg(-1). The main contaminants included DDTs, HCHs, endosulfan sulfate and methoxychlor. Compared with the soils of other cities, the levels of HCHs and DDTs in the studied area were arranged from low to middle levels. The OCPs were obviously regionally distributed. High content areas were mainly distributed in the central area with dense population, intense industrial and agricultural activities. The residue levels in different types of lands were significantly different: the arable land > garden land > woodland. Especially, the residue level was the highest in the vegetable land. Source analysis indicated that the HCHs might come from the use of lindane. DDTs in soil mainly came from early residues, but the dicofol might be the important source in partial area. Comparing the contents of HCHs and DDTs with our National Standard (GB 15618-2008), the qualified rates of the first and second standard of HCHs were 97.5% and 100%, respectively, and the DDTs were 95.5% and 97.7%, respectively. According to the risk assessment, DDTs may still have some potential ecological impact on the studied area.