Submitted to: Environmental Toxicology and Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2005
Publication Date: October 3, 2005
Citation: Zao, S., Arthur, E.L., Moorman, T.B., Coats, J.R. 2005. The evaluation of microbial inoculation and vegetation to enhance the dissipation of atrazine and metolachlor in soil. Environmental Toxicology and Chemistry. 24(10):2428-2434.
Interpretive Summary: Pesticide spills on farmsteads and agricultural chemical dealership sites can require remediation. Phytoremediation is an inexpensive treatment strategy that uses plants to stimulate the microbial populations degrading the pesticides in soil. This research examined the degradation of two herbicides, atrazine and metolachlor, in soils with or without prairie grasses or herbicide-degrading bacteria co-applied with the grasses. Both grasses and inoculation with bacteria increased the degradation of atrazine in one soil, but not in another. Aging of residues (time before treatment) also decreased the effectiveness of grasses and bacteria. Vegetation increased the remediation of metolachlor, but the bacterial treatment was ineffective. This information will be useful to engineers and consultants engaged in remediation of these contaminated sites and to state and EPA officials engaged in regulating cleanup of these sites.
Four greenhouse studies were conducted to evaluate the effects of native prairie grasses and two pesticide-degrading bacteria to remediate atrazine and metolachlor in soils from agricultural dealerships (Alpha and Bravo). The Alpha soil contained a low population of atrazine-degrading microorganisms relative to the Bravo soil. The atrazine- degrading bacterium, Agrobacterium radiobacter strain J14a, and a mixture of three native prairie grasses, big bluestem (Andropogon gerardii Vitman), yellow Indian grass (Sorghastrum nutans (L.) Nash), and switchgrass (Panicum virgatum L.) significantly reduced the concentration of atrazine in Alpha soil when the soil treated with atrazine and metolachlor was aged for 13 days before inoculation and vegetation. However, these treatments had no effect when the soil was aged for 213 days before inoculation and vegetation or on atrazine in Bravo soil. Inoculation with a metolachlor-degrading bacterium, Pseudomonas fluorescens strain UA5-40 did not enhance metolachlor dissipation in either soil, but vegetation did increase metolachlor dissipation. Our results indicate that the dissipation of atrazine by J14a is affected by the presence of indigenous atrazine-mineralizing microorganisms and probably by the bioavailability of atrazine in the soil.