Spatial variability of organochlorine pesticides (DDTs and HCHs) in surface soils from the alluvial region of Beijing, China

The spatial variability in the concentrations of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) and 1,1,1-trichloro-2, 2-bis-(p-chlorophenyl) ethane (DDT) in surface soils was studied on the basis of the analysis of 131 soil samples collected from the surface layer (0–20 cm depth) of the alluvial region of Beijing, China. The concentrations of total HCHs (including a-, (β-, y-, and 6-isomers) and total DDTs (including p, p′-DDT, p, p′-DDD, p, p′-DDE, and o, p′-DDT) in the surface soils tested were in the range from nondetectable to 31.72 μ/kg dry soil, with a mean value of 0.91, and from nondetectable to 5910.83 (μg/kg dry soil, with a mean value of 32.13, respectively. It was observed that concentrations of HCHs in all soil samples and concentrations of DDTs in 112 soil samples were much lower than the first grade (50 μg/kg) permitted in “Environment quality standard for soils in China (GB15618–1995)”. This suggests that the pollution due to organochlorine pesticides was generally not significant in the farmland soils in the Beijing alluvial region. In this study, the spatial distribution and trend of HCHs and DDTs were analyzed using Geostatistical Analyst and GS+(513). Spatial distribution indicated how these pesticides had been applied in the past. Trend analysis showed that the concentrations of HCHs, DDTs, and their related metabolites followed an obvious distribution trend in the surface soils from the alluvial region of Beijing.