Reduction of Herbicides in Wetland SedimentsEPA Grant Number: U915365
Title: Reduction of Herbicides in Wetland Sediments
Investigators: Klupinski, Theodore Paul
Institution: The Ohio State University
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 1998 through August 1, 2001
Project Amount: $89,126
RFA: STAR Graduate Fellowships (1998) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Chemistry and Materials Science
The objective of this research project is to determine the factors that control the abiotic transformation of herbicides in wetland sediments.
Two common classes of herbicides, nitroaromatic compounds (e.g., Trifluralin) and chloroacetanilides (e.g., Alachlor), have been selected for the project. The functional groups present on these compounds (i.e., nitro- and chloro-) are susceptible to reductive transformations. In freshwater wetlands, dissolved Fe(II) and iron oxide minerals are frequently found in the sediment phase. These conditions create a natural reducing environment that can induce transformations in some organic compounds. Natural organic matter (NOM) found in wetland sediments may influence the chemistry of these environments by complexing with Fe(II) or adsorbing on mineral surfaces. Laboratory studies will explore the fate of herbicides in iron-based reducing systems, with NOM content varied as an independent parameter. Analytical techniques available for studying the reactions include high performance liquid chromatography and gas chromatography/mass spectrometry. The laboratory experiments will identify what chemical factors influence an herbicide’s fate, but they may not accurately predict kinetic behavior in an actual wetland. Field studies will be performed at several locations to investigate the diversity of reducing conditions found in natural wetlands, as affected by Fe(II) concentration, NOM structural composition, and other parameters. In addition, herbicide reductions can be performed in microcosm studies using actual sediments and/or sediment porewaters extracted from selected wetlands. The results of these experiments will be used to determine the quantity and reactivity of natural reductants that degrade the target herbicides. Further studies will be pursued, as necessary, to examine the effects of other components found in the wetland sediments.
Although the reduction of nitroaromatic compounds in natural sediments previously has been observed, the details of the transformation pathways are still unknown. This project may lead to an elucidation of the abiotic reaction mechanisms, and provide an assessment of the numerous parameters that can influence the fate of these chemicals. Furthermore, the results will contribute to the general understanding of naturally mediated reductive transformations, which may occur for a wide variety of common environmental contaminants.