Hexachlorocyclohexane, DDT, parathion and toxaphene, each mixed at several concentrations with sandy loam, clay loam and muck, were leached with water and aged in a greenhouse. Bioassays, using Drosophila adults or mosquito larvae, showed that rate of decomposition was most rapid with parathion, followed in turn by hexachlorocyclohexane, wettable DDT, toxaphene, p-p' DDT. Rate of decomposition varied with the soil, generally being quicker at low than at high dosages, and more rapid at the top of the soil column than at the bottom with toxaphene and hexachlorocyolohexane while the reverse was true with DDT. Bioassays showed small quantities of insecticide in the leachates. Aging reduced phytotoxicity of hexachlorocyclohexane, but increased that of DDT.

Morrison, Frank O. (Supervisor)