Abiotic Reductive Transformations
Problem:
Reductive transformation is the dominant reaction pathway for many organic pollutants in anoxic environments. Although the understanding of the classes of organic chemicals that are subject to reduction in anoxic environments has been significantly advanced in recent years, it is not yet possible to predict the rates of reductive transformations quantitatively. Consequently, models used in regulatory decision-making do not incorporate this reaction pathway. The general goal of our project is to describe the reaction kinetics for the reductive transformation of organic chemicals in anoxic environments to develop useful predictive models.
Approach:
A dual approach is being pursued involving (1) mechanistic studies in well-defined systems designed to address specific questions concerning the identification of naturally occurring reductants and electron transfer pathways and (2) laboratory measurements of the reaction kinetics for a series of nitroaromatics, aromatic azos and halogenated aliphatics in a large number of well-characterized anoxic sediments and groundwater aquifers. The mechanistic studies are designed to (1) determine the role of iron oxides and sulfides in the reduction of organic chemicals, (2) clarify the role of natural organic matter in reductive transformations, and (3) determine whether electron transfer from environmental reductants to organic chemicals is facilitated by electron-transfer mediators and, if so, determine the identities of these electron-transfer mediators. Measuring reduction kinetics for a series of probe molecules in a substantial number of well-characterized sediments and aquifer materials will provide the opportunity to delineate the properties of the reaction systems and probe chemicals that are useful for predicting reaction rates. The successful completion of the proposed research will significantly enhance our ability to predict half-lives for the reduction of organic chemicals containing reducible functional groups.
Projects:
- Iron Oxide and Iron Sulfide Mediated Reductive Transformations
- Column Studies: Reduction Kinetics as a Function of Redox Zonation
- Identification of Chemical Reductants: Measuring Reactivity Patterns of Probe Chemicals
- Redox Characterization of Sediments and Aquifer Materials
- Natural Attenuation of Chlorinated Solvents in Wetlands
- Field Demonstration and Validation of Novel Attenuation Analytical Technologies