Beyond parent compound disappearance in the bioremediation of PAH contaminated soil

Project 5 Leader: Michael Aitken, UNC-Chapel Hill

Project Description

Among the chemicals of most concern at Superfund sites are polycyclic aromatic hydrocarbons (PAHs), major contaminants in both soil and groundwater. Bioremediation is an established technology for removing PAHs from contaminated soil, but previous studies have shown that it does not always lead to a reduction in toxicity. The causes of toxicity and the mechanisms by which toxicity might be avoided or diminished are not well-understood.

Project 5
This project will fill key gaps in knowledge that will inform and improve field applications of bioremediation, leading to true reductions in risk.
Michael Aitken, PhD
Project 5 Leader, Professor and Chair, ESE
Dr. Aitken hypothesizes that metabolites produced by PAH-degrading bacteria, which have been observed to accumulate in field-contaminated soil and sediment, are responsible at least in part for the toxicity that can result from bioremediation. Dr. Aitken also hypothesizes that bioremediation conditions influence the community of PAH-degrading microorganisms in contaminated soil, which in turn influences both PAH removal and the extent to which metabolites might accumulate. His research team will explore the effects of bioremediation conditions on PAH removal and soil toxicity.

Among the conditions to be evaluated is the addition of a hydrophobic surfactant at a low dose, which Aitken’s research group recently demonstrated can improve the bioavailability and biodegradation of PAHs that remained in a field-contaminated soil after conventional bioremediation. Furthermore, his team will identify the PAH-degrading bacteria most likely to influence PAH removal, metabolite accumulation, and toxicity in the treated soil. Genomes of these organisms will be sequenced to identify genes associated with PAH metabolism, and the key genes will be expressed. Differences in the ability to metabolize various PAHs will be correlated to sequence differences in these genes so that genetic determinants of metabolite accumulation can be identified. In parallel, Dr. Aitken and his research team will identify compounds responsible for toxicity of the treated soil. Finally, variables that can be controlled during bioremediation will be evaluated for their ability to preclude or mitigate toxicity