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

Transformation of pesticides is dependent on soil environmental conditions and knowledge of this is necessary to improve subsurface fate and transport pesticide models. Laboratory experiments were performed using C-14 ring and isopropyl side-chain labeled atrazine (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine) applied to three Iowa soils incubated in batch reactors under different environmental conditions. Mineralization of both the ring and isopropyl side chain carbons was proportional to the organic matter content of the soils and oxygen content. Atrazine ring carbon mineralization also increased with soil water content. Oxygen limitation in soils reduced the bio-transformation rate of atrazine, and mineralization was much slower under denitrifying conditions. Empirical models were developed to represent the mineralization rate of atrazine ring carbon and isopropyl side-chain carbon for varying soil organic matter, soil water content, temperature, and oxygen partial pressure.