Field-Scale Cleanup of a Pesticide-Contaminated Soil with a Combined Chemical-Biological Approach
Manmeet Waria, University of Nebraska-Lincoln, Lincoln, NE

Abiotic and Biotic Approaches to Remediating Pesticide and Fertilizer-Contaminated Soil and Water

Hardiljeet K. Boparai, University of Nebraska-Lincoln, 255 Keim Hall, Lincoln, NE 68583-0915, Tel: 402-472-6540, Fax: 402-472-7904, Email: hardiljeetboparai@yahoo.com
Manmeet Waria, University of Nebraska-Lincoln, 255 Keim Hall, Lincoln, NE 68583-0915, Tel: 402-472-6540, Fax: 402-472-7904
Tunlawit Satapanajaru, Kasetsart University, Bangkok, Thailand 10900, Tel: (66) 662-942-8036
Steve D. Comfort, University of Nebraska-Lincoln, 256 Keim Hall,Lincoln, NE 68583-0915, Tel: 402-472-1502, Fax: 402-472-7904
Patrick J. Shea, University of Nebraska-Lincoln, 362 Plant Sciences,Lincoln, NE 68583-0915, Tel: 402-472-1533, Fax: 402-472-7904

Spills and inadvertent discharges of agrichemicals at formulating and retail facilities have contaminated soil and water. Impacted soils often contain numerous contaminants (pesticides and inorganic fertilizers), necessitating the need for multiple remedial treatments. This presentation will provide an overview of various abiotic and biotic approaches for degrading pesticides and fertilizers in soil and water. Examples of abiotic approaches include the use of chemical reductants like dithionite, dithionite-reduced sediments, and zerovalent iron (Fe⁰) to transform pesticides. Biotic approaches involve the additions of carbon amendments such as sugar, peat moss and emulsified oils to stimulate biodegradation in contaminated soils. Results from our abiotic approaches indicate that dithionite rapidly transforms chlorinated pesticides in water with a stoichiometric release of chloride. Reducing aquifer and surface soils with dithionite produced reduced solids capable of dechlorinating pesticides and producing more biodegradable products. Laboratory experiments also confirmed that Fe⁰ could dechlorinate pesticides (metolachlor, atrazine and DDT) and reduce nitrate in aqueous solutions and that this process could be enhanced by adding small additions of Al2(SO₄)³, FeSO₄, or acetic acid (CH₃COOH). Field-scale application of zerovalent iron was also attempted and found to successfully remove metolachlor and nitrate but atrazine was more recalcitrant and not completely degraded by Fe⁰. Combining Fe⁰ (abiotic) with various organic amendments (biotic) more effectively degraded atrazine. Results from other previously completed field projects will also be presented.

Field-Scale Cleanup of a Pesticide-Contaminated Soil with a Combined Chemical-Biological Approach

Student Presenter

Manmeet Waria, School of Natural Resources, 255 Keim Hall, University of Nebraska-Lincoln, Nebraska-68583, Tel: 402-560-8854, Fax: 402-472-7904, Email: mwaria1@bigred.unl.edu
Tunlawit  Satapanajaru, Kasetsart University, Bangkok , Thailand 10900, Tel: 662-942-8036
Steve D Comfort, School of Natural Resources, 255 Keim Hall, University of Nebraska-Lincoln, Nebraska-68583, Tel: 402-472-1502, Fax: 402-472-7904

A former agrichemical dealership in North Platte , NE was suspected of having contaminated soil from multiple work-related spills. Dealership property was grid sampled and found to contain high concentrations of atrazine (>300 mg/kg) and cyanazine (>500 mg/kg). The top 60-cm of soil was removed, placed in windrows, and thoroughly mixed with a mechanical high-speed mixer. Mixing homogenized the contaminated soil and lowered pesticide concentrations via dilution. Laboratory investigations were then initiated to determine optimum treatments for pesticide destruction. Using zerovalent iron (Fe⁰) as a chemical reductant along with ferrous sulfate (FeSO_4·7H₂O), we observed greater than 70% destruction of both pesticides within 14 d. We also evaluated emulsified soybean oil (EOS® concentrate 598B42) as a carbon source to stimulate biodegradation and found it was also effective in degrading atrazine and cyanazine (~75%). Combining soybean oil with the chemical amendments resulted in higher destruction efficiencies (80-85 %) and reduced the percentage of FeSO₄ needed. Field treatments were applied (2.5 % Fe0 + 1% FeSO₄·7H₂0 and Oil) to ~360 yd³ of contaminated soil, water was added (0.30 kg water kg^-1 soil) and soil windrows were covered with clear plastic to reduce loss of soil moisture. Temporal sampling through 60 days showed destruction of 75 to 80% for both atrazine and cyanazine. These results provide evidence that both chemical and biological approaches can be used for on-site, field-scale treatment of pesticide-contaminated soil. Investigation of pesticide degradation products are ongoing and will also be presented.  

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