PERSISTENCE, METABOLISM AND BINDING OF P,P'-DDT IN SOIL IN DELHI, INDIA

The persistence, metabolism and binding of C-14-p,p'-DDT in soil were studied for two years under field sub-tropical conditions in Delhi, In dia. Two experiments were conducted at initial concentrations of 3.7 a nd 12.8 ppm and it was shown that about 80% of the DDT was lost from t he soil in two years. The half life of DDT was 319 and 343 days in the two experiments. At zero-time p,p'-DDT accounted for 93-95% of the ex tractable residues. Gradually, the proportion of p,p'-DDT declined wit h time to 58-71% of the extractable residues after two years. In addit ion to DDT, the extractable residues contained DDE and DDD. DDE was th e major metabolite of DDT in soil and accounted for about 22% of the e xtractable residue after 245 days and 37% after 18 months. DDD account ed for only 5% of the extractable residues after 18 months. Initially, the amount of bound residues was very small, but it gradually increas ed reaching a maximum of about 8% after one year. However, the bound r esidues declined thereafter to 4.5-5.45% after 1.5 years and to 3.4-4. 2% after 2 years. The soil-bound residues were chemically released by sulfuric acid treatment and were found to consist of DDT, DDE and DDD.