Breakdown of Lindane and Aldrin in Soils1

Abstract

A muck soil, Miami silt loam and a sandy loam were treated in 1954 with lindane at rates of 10 and 100 pounds per 6-inch acre and aldrin at rates of 2,20, and 200 pounds per 6-ineh acre. Laboratory experiments were conducted, where a Miami silt loam was treated with either lindane or aldrin at a rate of 10 p.p.m. Lindane was found to break down within 2 weeks after application to a nontoxic compound, which was still detected by the colorimetric method for lindane, but not by bioassay. Two weeks after treatment the quantity estimated by bioassay amounted to 66% of that obtained by chemical analysis. Even after 3 years the same ratio was found between bioassay and chemical results. When field samples were analyzed, 3½ years after treatment, the quantity estimated by bioassay amounted to 46% of that obtained by chemical analysis. Aldrin was found to be converted into dieldrin, which first was indicated by higher recoveries obtained by bioassay. Chemical analysis for dieldrin proved the presence of this insecticide in soils. It was found that relatively more dieldrin was formed in a sandy loam and in soils which had been treated at lower concentrations and which were held at higher temperatures. Experiments conducted in the laboratory showed that 2 weeks after treatment no dieldrin was formed in a loam having; been held at 7° In soils, having; been held at 26° C. or 46° C., 4 to 8% of the recovered insecticides were found to be dieldrin. The peak of dieldrin formation was reached 56 days after treatment, followed by a decrease.