STUDIES ON DISSIPATION AND DEGRADATION OF C-14 DDT AND C-14 DDE IN PAKISTANI SOILS UNDER FIELD CONDITIONS

Dissipation and degradation of C-14-p,p'-DDT (Faisalabad and Peshawar locations) and C-14-p,p'-DDE (Faisalabad location) were studied for one year in soils under field conditions. Both DDT and DDE dissipated more rapidly under the Pakistani subtropical climate than reported for temperate regions. More binding to soil of C-14-DDT was observed at Peshawar than that at Faisalabad. Overall halflives were 144 and 313 days in Faisalabad and Peshawar respectively. The main degradation products of p,p'-DDT extracted from soils at the two locations were p,p'-DDE and p,p'-DDD. C-14-DDE showed an overall halflife of 191 days under Faisalabad field conditions. Since the degradation of both DDT and DDE was not substantial, it is maintained that dissipation of both chemicals was largely due to volatilization/codistillation. About 68-92% of bound C-14-residues from soils previously treated with C-14-DDT were released by sulphuric acid treatment. Fresh soil inoculum also released up to 77% after three months. The residues released consisted of p,p'-DDT, p,p'-DDE and p,p'-DDD.