Project Summary (2000-2006)

The objective of this project is to quantify the relationship between contaminant exposure history and regulation of microbial biodegradative capabilities in natural porous media under flowing conditions representative of field scale plume contamination scenarios (low substrate concentrations and low levels of mixed electron acceptors [oxygen and nitrate]). Researchers are focusing on the processes influencing the natural attenuation of four model compounds, representing three classes of priority contaminants (fuel hydrocarbons, chlorinated solvents, and polynuclear aromatic hydrocarbons). Well-characterized microbial/contaminant/porous media systems are being used to develop validated mathematical tools for the description of pollutant evolution, transport, and microbial transformation. Specific studies are: 1) evaluating the influence of substrate composition, porous media characteristics, and concentration exposure history on biodegradative gene expression under natural attenuation conditions; 2) investigating links between contaminant exposure history and regulation of biodegradative functions; 3) evaluating the influence of surface attachment on expression of biodegradative capabilities under natural attenuation conditions; and 4) developing state-of-the-art mathematical models to validate conceptual models, test hypotheses, and explore the implications of laboratory findings at the field scale. This knowledge will provide the foundation for improved Superfund site remediation and characterization methods for assessment and monitoring of intrinsic remediation at chlorinated solvent and hydrocarbon contaminated sites.