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PAH Forensics in the Penobscot River, ME Sediment

META conducted extensive laboratory testing of NAPL and sediment to characterize sources of PAHs in the Penobscot River in Bangor, Maine. 

Forensic chemistry, using selected PAH ratios, demonstrated that the NAPL in the source area was stratified with older coal-derived tar at deeper depths and more recent oil-derived tar in the shallower zones. This corresponded well with the operational history of the former MGP that discharged to the River.

Additionally, the organic sulfur content of the NAPL changed with depth in the source area. More organic sulfur was present in the shallower zones, correlating with the use of high sulfur petroleum products late in the MGP’s operational history.

Finally, the concentrations of PAHs in sediment away from the source area were found to vary greatly even though the sediments were visually similar. No sheens or chemical odors were observed in the samples with high PAH concentrations. Using a combination of microscopy and GC fingerprints, META showed that severely weathered tar particles, i.e., those where most of the light hydrocarbons were absent, were the source of the high PAH concentrations in some samples.