A field site was established and instrumented in Amana, Iowa to investigate the fate and transport of the pesticides alachlor and atrazine in the unsaturated zone adjacent to a drainage lake. The pesticides were applied to a barren plot, a plot planted with corn, and a plot planted with deep-rooted poplar trees (Populus spp.) to study the characteristic behaviors of a typical agricultural environment (corn plot) and a novel pollutant interception technique (poplar plot) in comparison to unmanaged land (barren plot). A mass balance model was developed and solved for the pesticides on each of the three plots. While the majority of alachlor and atrazine adsorbed to the soil and eventually degraded or accumulated in the unsaturated zone, portions of the pesticides remained in the aqueous phase and subsequently were transported in the surface runoff and to the water table. Alachlor was found to be more mobile and more quickly transformed than atrazine. Plant uptake was an important process in the fate of the pesticides, and hence, vegetative buffer strips hold promise for protecting water supplies.
