Technical Report No. 9
BEHAVIOR OF SELECTED PESTICIDES WITH PERCOLATING WATER IN OAHU SOILS
Marshall A. Eto, Nathan C. Burbank, Jr., Howard W. Klemmer, and L.Stephen Lau
August 1967
ABSTRACT
This study investigated the ability of two Oahu soils, Wahiawa and Lahaina, to prevent chlorinated hydrocarbon pesticides; DDT and Lindane, in acetone solutions from percolating through the soils. The study was prompted by the possibility of contamination of Oahu’s domestic groundwater source by the two widely used insecticides. Wahiawa and Lahaina soils were effective in withholding DDT under saturated and intermittent flow conditions. Breakthrough of Lindane was noted in Wahiawa and Lahaina soil under saturated flow, and under intermittent flow conditions in Wahiawa soil only. Breakthrough concentrations were generally in the order of 0.3 ppm or lower. Breakthrough of Lindane and concentrations in the percolate were in direct proportion to soil volume. Column analysis showed that, in most cases, Lahaina soil held both pesticides in the upper three inches while Wahiawa soil held only DDT in the same region. Lindane was evenly distributed through the Wahiawa columns with a slightly greater count held at the surface. Pesticide loss through volatility in Lahaina soil was 60 to 80% of that noted in Wahiawa soil. Overall losses were as high as 50% for DDT and 25% for Lindane in the Wahiawa soil. Resistance to loss through volatility and retention of pesticides in soil appear to be directly related to organic matter content. Five Oahu soils tested to determine their ability to absorb pesticides from water-acetone solutions effectively removed pesticides in solute concentrations up to 1OO ppm. DDT and Lindane were removed in the order of 90 to 100% by swirling the soils in the pesticide solutions. No desorption occurred with water, but both pesticides were absorbed with benzene. Data obtained may be described by the Freundlich adsorption isotherm X/M = KC1/n where X/M = amount of pesticide sorbed per unit weight of soil, C = concentration of pesticide solution, and K = constant. values of K and n for Lindane sorption were in the range of 0.1 and 0.9, respectively, and for DDT they were in the order of 2.0 and 1.0, respectively.