When polycyclic aromatic hydrocarbons (PAHs) are released into the environment, they exist initially as “parent compounds”. There’s been an assumption that when parent compounds can no longer be detected, there is no longer a danger. Researchers at OSU SRP challenged that assumption because in reality, the parent compounds are not the whole story. Environmental processes and remediation, or clean up, break down parent compounds into what are known as “transformation” or “breakdown” products. Remediation engineers must consider how parent PAHs are broken down, and what compounds they’re broken down into.

The goal of this research was to identify and recommend remediation technologies that minimize the formation of hazardous PAH breakdown products. SRP researcher Staci Simonich led an effort to help stakeholders at the Wyckoff/Eagle Harbor Superfund site to select the most effective remediation technologies for their sites. She and her team learned which transformation products were produced by specific remediation technologies and soil conditions.

Working collaboratively with other SRP researchers at PNNL and OSU, they were able to compare several remediation approaches and evaluate toxic transformation products that formed from them. They used computational modeling to predict the structures produced, and experimentally tested their toxicity to identify which toxic breakdown products result from specific remediation strategies.

They found that biodegradation, or natural breakdown of parent PAHs, can actually increase their toxicity. For example, a specific PAH parent compound, called phenanthrene (PHE), was not found to be toxic in embryonic fish tests. However, after PHE was biotransformed by bacteria (Mycobacterium), some of the breakdown products did lead to toxicity in embryonic fish. This is significant –it means that any future selection of remediation techniques should include the evaluation of breakdown products that can result from treatment, as well as their potential toxicity.

Aerial photo of Wycoff / Eagle Harbor SRP site, Bainbridge Island, WA