Superfund Research Program
Beyond Parent Compound Disappearance in the Bioremediation of PAH-Contaminated Soil
Project Leader: Michael D. Aitken
Grant Number: P42ES005948
Funding Period: 1995-2018
Final Progress Reports
The paradigm for risk assessment and remediation decisions at sites contaminated with polycyclic aromatic hydrocarbons (PAHs) is based on only 16 compounds, but the sources of PAH contamination (e.g., tars or creosote) are complex mixtures containing thousands of co-contaminants that remain unregulated. Furthermore, remediation processes can form uncharacterized byproducts whose toxicity is not understood. An emerging approach to elucidating the presence of unknown chemicals in complex systems (such as soil) is non-target analysis, which relies on both high-resolution mass spectrometry and advanced informatics tools. Last year Michael Aitken, Ph.D., and his research team reported using non-target analysis to identify a previously unknown, genotoxic metabolite of pyrene resulting from bioremediation of PAH-contaminated soil. They also used a non-target method to demonstrate the presence in PAH-contaminated soils of more than 200 azaarene compounds, a poorly studied class of chemicals similar to PAHs, except that a nitrogen atom is incorporated into one of the rings. The diversity and abundance of azaarenes that the researchers uncovered was unrecognized prior to their work. In a third example of non-target analysis, Aitken and his team adapted a technique called stable isotope-assisted metabolomics to identify biotransformation products of several four-ring PAHs in microcosms of contaminated soil. They discovered several metabolites not previously observed, including sulfate conjugates of pyrene and benzo[a]anthracene that suggested fungal metabolism of the parent compounds. Collectively, the researchers demonstrated the power of using non-target analysis for discovering previously unknown contaminants in soil whose contributions to the toxicity of contaminated soil also remain unknown.