ABSTRACT
This chapter focuses on the environmental fate of herbicides which could receive increased usage from the adoption of herbicide-resistant crop (HRC) varieties. The key processes controlling the fate of herbicides in the environment include retention in the soil; the chemical and biological degradation in air, soil, and water; and the transport processes in air and soil. Runoff and leaching of herbicides and the resulting contamination of water resources are complex processes that are dependent upon pesticide physical and chemical properties, soil properties and processes, climate, and farming practices. Volatilization and drift are the principal mechanisms for herbicide entry into the atmosphere. Volatilizations refer to loss of herbicide from soil surfaces, crop residues, or live vegetation, whereas drift refers to movement of herbicide in aerosols created during spray applications. Atrazine degradation in soil is an example of the complexity in biological and chemical reactions that contribute to atrazine fate in the environment.
