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Abiotic reduction of dinitroaniline herbicides
1Department of Civil Engineering, University of Minnesota, 500 Pillsbury Dr. SE, Minneapolis, MN 55455, USA.
Water Research
|August 30, 2003
Summary
Abiotic reductive transformations effectively degrade dinitroaniline herbicides like trifluralin. Surface-bound Fe(II) and hydroquinones facilitate nitro group reduction, crucial for understanding herbicide fate in natural systems.
Area of Science:
- Environmental Chemistry
- Soil Science
- Organic Geochemistry
Background:
- Dinitroaniline herbicides are widely used in agriculture.
- Understanding their environmental fate is crucial for risk assessment.
- Abiotic reductive transformations are a potential degradation pathway.
Purpose of the Study:
- To evaluate the significance of abiotic reductive transformations for dinitroaniline herbicides.
- To identify effective abiotic reductants for herbicide degradation.
- To investigate the influence of environmental factors like pH on degradation rates.
Main Methods:
- Incubation of four dinitroaniline herbicides (trifluralin, pendimethalin, nitralin, isopropalin) with representative abiotic reductants.
- Use of surface-bound Fe(II) in goethite suspensions and hydroquinone moieties (mercaptojuglone) in H2S solution.
- Investigation of aqueous iron species and pH effects.
- Development of linear free energy relationships.
Main Results:
- Surface-bound Fe(II) and mercaptojuglone effectively reduced nitro groups on dinitroaniline herbicides.
- Aqueous iron species were effective reductants at pH > 7.0.
- Degradation rates increased with pH in Fe(II) systems.
- Montmorillonite clay did not mediate reduction with Fe(II).
- Aniline and benzimidazole products were observed from trifluralin degradation.
Conclusions:
- Abiotic reductive transformations are significant sinks for dinitroaniline herbicides.
- Fe(II) species and hydroquinones are key reductants in natural environments.
- pH is a critical factor influencing the rate of reductive degradation.