IDENTIFYING MICROBIAL DEGRADATION OF PAHS THROUGH COMPOUND SPECIFIC ISOTOPE ANALYSIS OF PHOSPHOLIPID FATTY ACIDS

Polycyclic aromatic hydrocarbons (PAHs) are combustion-derived compounds typically introduced into the environment from natural (wildfires) and anthropogenic (coal tar, vehicle exhaust, fossil fuels) sources. Understanding the fate of potentially carcinogenic and mutagenic compounds within groundwater and subsurface soils is important in assessing the possible impact of these contaminants on an ecosystem. Due to the difficulty of isolating and removing PAHs from the environment, a better understanding of bioavailibility, source apportionment, and degradation of these compounds will facilitate remediation efforts in contaminated areas.

Samples were recovered from the Tennessee Products industrial site located in Chattanooga, TN. The site was occupied by a former coal coking plant where large amounts of coal tar and creosote were discharged onto the site. The soils, surface, and groundwaters are extensively contaminated with this material. This is particularly important since Chattanooga Creek flows adjacent to many residential areas, schools, and research facilities.

The main focus of this project is to assess the degradation of PAHs over time and identify microbial communities controlling this degradation. Key questions we will address are: Is degradation occurring? What is the degradation rate? Can phospholipid fatty acids (PLFAs) identify which microbial communities are causing degradation? A series of microcosm experiments will be conducted to provide insight into the transformation of parent PAHs to alkylated forms (a degradation product). Carbon isotopic composition of PLFAs will help identify microbial communities involved in the degradation process.