The fate and dissipation of surface applied 14C‐DDE in a tropical soil

Abstract

The results of a study conducted to follow the dissipation, distribution and fate of 14C‐p,p'‐DDE in a tropical soil under field conditions are reported. 14C‐DDE was applied to soil columns in PVC cylinders (of lengths: 15 cm and diameters: 10.4 cm) inserted in an agricultural field. The climatic factors and soil characteristics that were likely to influence the behaviour of this compound in soil are given. Volatilization resulted in 13.4% loss of the pesticide from the soil within 12 hours after application. During this short period there was rapid distribution of 14C‐DDE in the soil matrix and 9% of all recovered residues were in form of bound residues. A graph showing the % recovered 14C‐residues over a period of 189 days gave a fast rate of disappearance of the pesticide during the first 7 days. No rainfall was recorded during this period. In the second phase of the experiment, rainfall was recorded. During this phase, the level of extractable residues continued to decrease slowly but this was compensated by higher levels of bound residues. After 189 days, only 34.9% of the radioactivity applied to the soil was recovered and composed of 17.7% extractable and 17.2% bound residues. DDE was found to stable in this soil and only p,p'‐DDE was detected by GC and TLC analysis of the soil samples.