L. Somasundaram

Application of the Microtox System to Assess the Toxicity of Pesticides and Their Hydrolysis Metabolites

In this study, we used the Microtox analyzer to determine the relative microbial toxicities of some pesticides and their metabolites. Because hydrolysis is a significant step in the chemical and microbial degradation of pesticides in soil, the principal focus of this investigation was on hydrolytic metabolites

Fate of major degradation products of Atrazine in Iowa soils

Abstract Five Iowa soils, sampled at two depths each were treated with 14C‐deethylatrazine (DEA) and 14C‐hydroxyatrazine (HYA) and incubated for nine and 17 weeks. 14CO2 evolution was monitored over this period. The degradation of DEA was influenced by both soil type and soil depth. For each soil studied, the degradation of DEA was much higher in the surface layer compared to the respective subsurface layer. The major degradation products from DEA included CO2, soil bound residues, and polar metabolites. Deethylhydroxyatrazine (DEHYA) and didealkylatrazine (DAA) were detected in minor quantities. Increased mineralization of DEA in the extended incubations confirmed the susceptibility of DEA to microbial degradation. In the complete metabolism studies with HYA, the major components identified included HYA, soil bound residues, and CO2. Deethylhydroxyatrazine deisopropylhydroxyatrazine and ammeline were found in smaller quantities. The relatively long persistence (45 to 69% remaining) of HYA was observed in...

Degradation of pesticides in soil as influenced by the presence of hydrolysis metabolites

Abstract The degradation of 8 pesticides was evaluated in a soil pretreated with their respective hydrolysis metabolites. 2,4‐Dichlorophenol, p‐nitrophenol, and salicylic acid conditioned the soil for enhanced degradation of 2,4‐dichlorophenoxyacetic acid (2,4‐D), parathion, and isofenphos, respectively. Repeated application of carbofuran phenol, 2‐isopropyl‐4‐methyl‐6‐hydroxypyrimidine, methyl phenyl sulfone, thiophenol, isopropyl salicylate, and 2,4,5‐trichlorophenol had no effect on the rate of degradation of their parent pesticides. Prior exposure of soil to 3,5,6‐trichloro‐2‐pyridinol resulted in increased persistence of its parent compound, chlorpyrifos. Results indicate that pesticide hydrolysis metabolites can effect the induction or inhibition of enhanced microbial degradation of some soil‐applied pesticides.