FATE OF C-14 P,P'-DDT IN KENYAN TROPICAL SOILS

The dissipation and degradation of C-14-p,p'-DDT in tropical soils of Nairobi were studied under field and laboratory conditions for a perio d of six months. DDT was found to dissipate much more rapidly from the soil under field conditions than reported for temperate regions. The dissipation curve was found to be biphasic; a rapid phase from 0-37 da ys after application and a slower phase from 51-172 days. Based on fir st order kinetics an overall halflife of 65 days was calculated. The b ound residues initially constituted a very small percentage (1.3%) of the applied pesticide and gradually increased to 5.9% after 64 days. T he main degradation products extracted from the soil were p,p'-DDE and a small percentage of p,p'-DDD. While the amount of p,p'-DDT decrease d with time, there was a slow increase in the amount of pIp'-DDE extra cted from the soil. The effects of solar radiation on the dissipation of C-14-p,p'-DDT from non-sterile soil was also studied under laborato ry conditions by quantifying the volatilization and mineralization of C-14-p,p'-DDT. It was found that volatilization was the major dissipat ion process and the dissipation rate was significantly increased by so lar radiation.