Persistence and Degradation of Heptachlor in Some Soils1

Abstract

The persistence and degradation patterns of heptachlor applied in 3 different formulations to 2 fine sandy-loam soils of similar nature at Plum Coulee (Manitoba) and Taber (Alberta) were studied. Determinations of heptachlor and heptachlor epoxide residues in samples taken on the 20th, 60th, and 120th day after applications showed that the persistence and degradation patterns of heptachlor and heptachlor epoxide were independent of the formulations employed, and that the patterns for Plum Coulee soil differed from those for the Taber soil. A comparison between these 2 soils and 4 reported in the literature with regards to persistence and degradation of heptachlor and heptachlor epoxide showed that these 2 compounds were less persistent in sandy loam soils than in silt loam soils. An unknown substance, possibly a degradation product of heptachlor or chlordane, was found in Taber soil samples taken on the 120th day after applications. Fractions containing this substance were nontoxic to Drosophila melanogaster Meigen.