The Research On The Residue And Bioavailability Of Organochlorine Pesticides In Typical Agricultural Soils

Dichlorodiphenyltrichloroethane(DDTs) and Hexachlorocyclohexane(HCHs) pollution concentration in typical agricultural soil for scientific research in Hohhot in Inner Mongolia were investigated with three types of samples-surface soils, section soils and planting by improving pick-up method. Statistical methods were used to study the distribution and contamination of these pollutants in the soils and the relationship between pollutant residues and environmental factors were also analyzed. The transport and transformation of HCHs and DDTs in soil vertical profile during the plant growing stage were studied.The enrichment and bioavailability of HCHs and DDTs in soil were decided. Furthermore,their environmental risk and quality grade was estimated according the toxic data and Chinese Environmental Quality Standard for Agricultural Soils, which can offer a basic statistics for the soil risk assessment of OCPs in scientific research region in Hohhot. The results are as follows:(1) The soil samples were collected from the surface of farmland in Hohhot and the analyzing results showed the concentration of HCHs and DDTs in the soils were 65.64-622.57 ng.g^-1 and 166.96-1599.09 ng.g^-1 respectively, and the mean were 272.06 ng.g^-1 and 696.77 ng.g^-1'.The distribution of HCHs and DDTs and isomers were not uniform mainly for the residue in the history. But we didn't conclude that there was no new input of pollution in this area, for instance lindane.(2) HCHs and DDTs were detected in the deep soil samples. The contents of HCHs and DDTs were decreased with the increased depth obviously. The vertical distribution of HCHs and DDTs were not uniform and it revealed transport and transformation of isomers were also different. The soil utilization was the key factor affecting the concentrations of HCHs and DDTs in surface,while the organic carbon content showed a strong relativity with the section residues.(3) The bioavailability and plant enrichment of HCHs and DDTs during plant growth period were studied, and the results showed that the residual HCHs and DDTS in soils was absorbed and enriched in some crops's roots, and the enrichment in the wheat was less than in the corn. HCHs was transfered more easily than DDTs. The quantity of residual OCPs was that root >leaf> fruit.(4) The concentrations of HCHs and DDTs in most soil samples were more than the standard quality of soil environment. Especially DDTs concentrations in some samples (20 out of 100) exceeded Chinese Environmental Quality Standard for Agricultural Soils(DDT>1000ng.g^-1). In conclusion,the organochlorine pollution is severe in this area and the biological risk is high.