Loss of Chlorinated Hydrocarbon Insecticides from Soil Surface in the Field1

Abstract

Four chlorinated hydrocarbon insecticides, namely, DDT, endrin, aldrin, and Shell Development Company SD-4402 (1,3,4,5,6,7,8,8-octahcloro-3a,4,7,7a-tetrahydro-4,7-methanophthalan) were applied to the surface of the soil in the field and exposed at least for sometime to relatively high surface temperatures. The rate of loss of activity owing to physical, chemical, and biological processes was measured by bioassay procedure against an eye gnat Hippelates collusor (Townsend) and larvae of the mosquito Culex quinquefasciatus Say. After 24 hours of exposure the biological activity of all materials except DDT as measured against eye gnats, had decreased considerably. Approximately 50% of endrin was lost after a 24-hour exposure period as determined by both bioassay methods. The loss of DDT during the same period was about 10%. The overall loss of DDT determined by the gnat bioassay was greater than that obtained by the mosquito larvae bioassay. Greater loss of activity was recorded for Compound SD-4402 by both the mosquito and gnat bioassay procedure than for aldrin. The loss of activity of aldrin and DDT measured by mosquito bioassay method was lower than that measured by the eye-gnat bioassay method for each material. A partial explanation of this phenomenon is offered.