PREDICTING ALACHLOR MOBILITY USING BATCH SORPTION KINETIC DATA

The ability to accurately predict the mobility of a soil-applied herbi cide is important to product registration and recommendations for envi ronmentally safe use. Commonly, mobility is affected by time-dependent sorption processes. Parameters for such nonequilibrium sorption may b e conveniently determined from batch kinetic studies; however, applica bility of these parameters for subsequent use in transport modeling mu st be verified. The objective of this study, therefore, was to determi ne whether batch kinetic data were appropriate for predicting nonequil ibrium sorption during alachlor N-(2,6-diethylphenyl)-N-(methoxymethyl )-acetamide] transport in Dundee silt loam soil. Batch (solution and e xtraction) data previously generated in this laboratory were used to d etermine sorption parameters for two- or three-site equilibrium/kineti c sorption models. Predictions of alachlor mobility generated from the corresponding transport models were then compared with miscible displ acement data. Use of sorption parameters determined from batch solutio n data alone resulted in only qualitative predictions of alachlor move ment. However, more accurate predictions were obtained if sorption par ameters were based on both soil extraction and soil solution data.