Submitted to: International Association of Environmental and Analytical Chemistry
Publication Type: Abstract Only
Publication Acceptance Date: 9/13/1999
Publication Date: N/A
Technical Abstract: Herbicides are one of the most common classes of nonpoint-source pollutants in the Midwestern United States. Among several management practices, grass riparian buffer strips are recognized as one of the most cost-effective bioremediation approaches to alleviating nonpoint sources of agricultural pollutants from adjacent crop lands. Thirty-six 1-m wide and 0.5-m deep lysimeters with 6 different ground covers (bare ground, tall fescue, smoot bromegrass, orchardgrass, timothy, and switchgrass) were established in 1998 to evaluate the bioremediation capacity of the vegetated ground cover on Balance and atrazine removal. Herbicides were uniformly applied to each lysimeter with irrigation of 3L solutions containing atrazine (500 ppb) or Balance (80 ppb). The effluent of each lysimeter was sampled as a function of time. The concentrations of atrazine, Balance, and their metabolites in the leachate will be determined by solid phase extraction and HPLC-UV methods. Balance (isoxaflutole) is a new herbicide that has received conditional registration from the EPA and is scheduled for commercial introduction in 1999 in some corn producing states. It is being marketed as a potential atrazine replacement which the manufacturer claims has similar broad spectrum weed control to that of atrazine with the advantage of low applications rates (64 g/ha). Balance has a very short soil half- life (<7days) degrading to a biologically active diketonitrile metabolite that is more stable than the parent and moderately water soluble. Further degradation of the diketonitrile metabolite produces a non-biologically active benzoic acid derivative, a highly stable and water soluble metabolite. These two metabolites pose potential contamination threats to surface and ground waters.