Spatial distribution of DDT in a typical contaminated site

Surface and profile distributions of DDT were studied at a typical pesticide contaminated site.Surface and profile soil samples were collected in and around a plant which had been used for long-term DDT production.The results show that DDT concentrations are higher than 104 mg·kg-1 in surface soil near the original production site,and could even be detected in soil 300 m away from the plant,indicating that this site has been greatly contaminated by DDT.Profile distribution showed that DDT concentration decreases with soil depth,especially from 0.2 to 3 m,and it was lower than 8.89 mg·kg-1 at 10 m.DDD and DDE,the decomposition products of DDT,were also detected in the soil.A relatively low(DDD+DDE)/DDT ratio might indicate that DDT was freshly added to this site.The decomposition rate of DDT varied among soil types,and it was highest in silty sand,followed by clay soil and miscellaneous fill soil.