P44

BIOREMEDIATION OF PESTICIDE-CONTAMINATED SOILS: HERBICIDE INTERACTIONS AND PHYTOREMEDIATION STUDIES

Treated soils were incubated at 24 °C in the dark for 0, 21, 63, and 160 d, and soil moisture tension was maintained at -33 kPa. Germination and survival of kochia, giant foxtail, birdsfoot trefoil, canola, and soybean were evaluated using subsamples of the treated soils at the end of each incubation period. Plant survival was very good for soybean and canola, but quite poor for kochia.

Concentrations of each herbicide were determined by gas chromatography at day 0, 21, 63, and 160. The degradation of atrazine was rapid with less than 6 (g/g remaining after 63 d. There was no significant difference among the treatments. Pendimethalin showed no degradation in any of the treatments after 160 d. Preliminary findings indicate that metolachlor degradation was greater when applied with atrazine than with the other treatments.

Soil respiration was measured by infrared gas analysis for 10 d at the end of each incubation period. Respiration levels were elevated for the first 6 d immediately following treatment, and then declined to very low levels. At the end of day 21, 63, and 160, soil respiration remained at very low levels.

Additional studies were carried out in the greenhouse, using pesticide-contaminated soils from the same location to determine the influence of vegetation on aged pendimethalin residue and freshly applied atrazine, metolachlor, and trifluralin mixtures. Plant species included in this study were natural prairie grasses, woody rose, multiflower rose, and cocklebur. Results will be presented.

Key words: atrazine, metolachlor, pendimethalin, trifluralin, phytoremediation