Factors influencing the spatial distribution of organochlorine pesticides in soils surrounding chemical industrial parks.

Topsoil samples (n = 105) were collected to study the distribution of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) residues in the vicinity of chemical industrial parks in Tianjin, China. The occurrence and distribution of target organochlorine pesticides (OCPs) were mapped to identify the spatial variation using Geographical Information System (GIS). In general, the concentrations of OCPs were higher in soils near the industrial parks, even some hotspots showed very high OCP contaminations which could cause ecological risk. The relationships between contaminant concentrations and other factors (land use and soil properties) were discussed. Significant correlations (P < 0.01) between TOC contents and the concentrations of DDTs, alpha-HCH, and beta-HCH indicated the effect of organic carbon on OCP distribution. Soil pH levels had no obvious effect on the OCP distributions. Except for the effects of the industrial parks, the capacities of biodegradation and dissipation of soils under different land uses were the important factors that affected the HCH distribution, but the distribution of DDTs was mainly influenced by the TOC levels. The results of this study can provide some evidences and data on the long term effects of industrial activities in the environment even after the cease of operations for a long time.