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University of North Carolina-Chapel Hill

Superfund Research Program

Factors Influencing the Biodegradation of High Molecular Weight PAHs in Contaminated Soil

Project Leader: Michael D. Aitken
Grant Number: P42ES005948
Funding Period: 1995-2018

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Project Summary (2000-2006)

The purpose of this project is to develop approaches by which the factor(s) that limit the degradation of polycyclic aromatic hydrocarbons (PAHs) can be identified and, eventually, overcome. These factors include the absence of significant numbers of microbes able to degrade these compounds; the inherently low rates of degradation of the compounds by all organisms; loss of growth substrates for the microorganisms over time and consequent loss of PAH-degrading activity; and accumulation of products of incomplete metabolism that may inhibit the degradation of one or more of the PAHs. Specifically, researchers are quantifying rates of degradation of high-molecular weight PAHs by bacteria isolated from a variety of contaminated soils and the effect of other PAHs in mixtures on these rates. Actual contaminated soil from an industrial site is being treated in a bench-scale bioreactor to study the degradation of one or more apparently recalcitrant PAH. The factor(s) that govern the degradation of these compounds will be elucidated by quantifying the organisms in the treated soil that are capable of degrading the recalcitrant PAHs; evaluating the effects of adding readily-degraded, naturally occurring compounds known to stimulate PAH degradation; examining whether the liquid phase in the bioreactor is inhibitory to PAH-degrading bacteria as a result of metabolite accumulation; and examining the role of bioavailability in the apparent recalcitrance of these compounds. With knowledge of the factor(s) most responsible for limited degradation of the target compound(s), project investigators will then explore methods of stimulating biodegradation either directly in the bioreactor or in treated soil removed from the bioreactor.

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