EFFECT OF SOIL-CONDITIONS ON MODEL PARAMETERS AND ATRAZINE MINERALIZATION RATES

Transformation of pesticides is dependent on soil environmental condit ions and knowledge of this is necessary to improve subsurface fate and transport pesticide models. Laboratory experiments were performed usi ng C-14 ring and isopropyl side-chain labeled atrazine -chloro-4-ethyl amino-6-isopropyl-amino-s-triazine) applied to three Iowa soils incuba ted in batch reactors under different environmental conditions. Minera lization of both the ring and isopropyl side chain carbons was proport ional to the organic matter content of the soils and oxygen content. A trazine ring carbon mineralization also increased with soil water cont ent. Oxygen limitation in soils reduced the bio-transformation rate of atrazine, and mineralization was much slower under denitrifying condi tions. Empirical models were developed to represent the mineralization rate of atrazine ring carbon and isopropyl side-chain carbon for vary ing soil organic matter, soil water content, temperature, and oxygen p artial pressure.