Dicofol application resulted in high DDTs residue in cotton fields from northern Jiangsu province, China

Dicofol with high impurity of DDT compounds is still widely used in agricultural practice such as cotton cultivation and becomes an important source of DDT pollution in China. In this study, investigations on the DDT residues in cotton fields from northern Jiangsu province, China were conducted. The results showed that DDTs in cotton soil were much higher than other mode of land use. The DDTs levels ranged from 4.2 to 678.6 ng g−1, with a mean concentration of 190.4 ng g−1, of which the most abundant compounds were p,p′-DDE (mean of 129.38 ng g−1), p,p′-DDT (mean of 26.57 ng g−1) and o,p′-DDT (mean of 16.92 ng g−1). The concentrations of o,p′-DDT and o,p′-DDE were significantly higher (p < 0.05) in topsoil (0-10 cm) than in subsoil (10-20 cm), while other DDT compounds were not. Source apportionment showed that dicofol-type DDT accounted for up to 80% of the DDTs residue. All the results indicated that dicofol applications resulted in serious DDT pollution in cotton fields. Our work provided implications for reasons why there was no apparent decrease of DDT level in China.