Dissipation and degradation of DDT and DDE in Philippine soil under field conditions

Abstract

Abstract Dissipation and degradation of 14C‐p,p'‐DDT in soil was studied under field conditions in the Philippines for two consecutive years. Extractable radioactivity decreased with time while there was a gradual increase of bound activity. Half‐life of dissipation of total 14C was 261 days and 210 for the two field trials while the half‐life of extractable radioactivity was 173 and 134 days. p,p'‐DDE was the major metabolite in the extracts and the half‐life of extracted DDT was 105 days. In the laboratory, the soil mineralized 70% of 14C‐DDT at 35°C in six weeks, while organic volatiles contributed < 1%. Almost 80% of soil‐bound 14C was released by addition of fresh soil; presumably through the action of microflora. Under field conditions, 14C‐DDE dissipated with a halflife of 151 days, and bound 14C residues accounted for 40% of the terminal residue after one year. The results indicate that p,p'‐DDT and p,p'‐DDE dissipate from Philippine soils at rates which may preclude accumulation of residues.