APPLICATION OF 2-SITE 2-REGION MODELS FOR STUDYING SIMULTANEOUS NONEQUILIBRIUM TRANSPORT AND DEGRADATION OF PESTICIDES

Quantitative laboratory study of pesticide sorption and degradation during transport can provide insight into the basic processes affecting pesticide fate in field soils. Accordingly, we demonstrate the application of analytical solutions of two-site two-region transport models useful in studying simultaneous pesticide sorption and degradation. Soil-column displacement experiments involving 3H2O, Cl, and atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) were conducted during steady-state water flow at two pore-water velocities and two pesticide concentrations. Data collected elsewhere for 2,4,5-T(2,4,5-trichlorophenoxyacetic acid) herbicide transport were used as an additional example of the application of the model with degradation. Strengths and weaknesses of the models, and suggestions for further study, are presented.