DEGRADATION IN SOILS OF CIODRIN AN ORGANOPHOSPHATE INSECTICIDE

The rates of ciodrin degradation in soils followed first-order kinetics and were related to the extent of initial insecticide adsorption by the soils. Rates of the reactions were slower in electron-beamsterilized soils; however, this rate decrease was due to decreased ciodrin adsorption resulting from the irradiation treatment and not from retardation of microbial degradation processes. Firstorder rate constants for ciodrin degradation were related directly to adsorption and were the same for sterile and nonsterile soils for constant adsorption in a given soil. Between soils, even at constant adsorption, the rates of ciodrin degradation were variable, ranging from a t1/2 value of 2.0 hours in a Poygan silty clay loam (66% adsorption) to 71 hours in an Ella loamy sand (53% adsorption). In aqueous soil-free systems t1/2 values for ciodrin degradation were 180, 410, and 540 hours at pH 9.6, and 2, respectively. © 1969, American Chemical Society. All rights reserved.