Shawnee A



J.C. Anhalt, E.L. Kruger, D.L. Sorensen, B. Nelson, S. Zhao, and J.R. Coats, Insectary Building, Pesticide Toxicology Laboratory, Department of Entomology, Iowa State University, Ames, Iowa 50011 Degradation studies were carried out in pesticide-contaminated soils from an Iowa agrochemical dealer site to look at interaction of herbicide mixtures. Atrazine, metolachlor, and pendimethalin were applied individually and in all possible combinations to soil. The rate of application for each chemical was 50 (g/g, representative of contamination problems at mixing and loading areas of agrochemical dealer sites.

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

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Tuesday, May 20, 1997

Metals Kansa A

Remediation of Munitions Compounds Kansa B

Analytical Methods Kansa C/D

General Topics Kansa B

Wednesday, May 21, 1997

Metals Kansa A

Zero-Valent Metals Kansa A

Remediation Kansa A

Vegetation-based Remediation Kansa B

Partnerships & Innovative Technologies Kansa C/D

Nonaqueous Phase Liquids Kansa C/D

Thursday, May 22, 1997

Biofilms & Barriers Kansa A

Bioremediation Kansa B

Partnerships & Technology Innovations Kansa C/D

Remediation Kansa C/D


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