DISSIPATION AND DEGRADATION OF C-14 P,P'-DDT AND C-14 P,P'-DDE IN TANZANIAN SOILS UNDER FIELD CONDITIONS

C-14-labelled p,p'-DDT and p,p'-DDE were used to study the dissipation and degradation rates in soil under tropical field conditions in two locations. Dissipation of DDT was more rapid at Magugu (with hot and wet climate) than at Arusha (with cool and wet climate). After 350 days the methanol-extractable residues declined to 14.44% and 33.76% for Magugu and Arusha respectively; while the bound residues gradually increased to a maximum of 10.03% after 106 days in Magugu and 11.99% after 286 days in Arusha. The overall half-life for C-14-dissipation was 174 days for Magugu and 335 days for Arusha. DDT degraded mainly to DDE and to a smaller extent to DDD. The dissipation rate of C-14-DDE in Arusha was little higher than DDT under similar field conditions, with an overall half life of 233 days.