Evaluation of rate coefficients for consecutive reactions of pesticides in soil
Abstract A short computation model was used to derive reaction rate coefficients from measured concentration‐time relationships reported in the literature for parent compounds and important conversion products. For the pesticides aldicarb, phorate and disulfoton, description was attempted of the formation and decline of the sulfoxide and of the sulfone with first‐order rate equations. This involved the approximation of the contribution of simultaneous reactions in the decline of the parent compound and of the sulfoxide. For some well‐defined experiments, good descriptions of the concentration‐time relationships could be obtained, so the corresponding rate coefficients could be derived. In some of the instances, the measuring period was too short to evaluate the rate coefficients for the sulfone. Between results of different experiments, great deviations sometimes showed up, which could be related to the experimental design. Lack of recovery percentages for conversion products and of checks on transformati...