Environmental Forensics Investigation in Sediments near a Former Manufactured Gas Plant Site

Abstract

An investigation of lakebed sediment found elevated polycyclic aromatic hydrocarbon (PAH) levels, and a nearby former manufactured gas plant (MGP) site was identified as the most likely source. Forensic chemistry or “chemical fingerprinting” was conducted on sediment samples from a boat slip in the vicinity of the MGP and on-shore soil samples from the MGP property in order to determine whether or not the former MGP was the origin of the PAHs found in the sediment. An analysis of the data from gas chromatography with flame ionization detection (GC/FID) and mass spectrometry (GC/MS) suggested that the PAH distributions measured in the sediment samples were similar to those measured in samples of tarry soil from the former MGP site. However, because of the urban and industrial land use surrounding the former MGP site, it was also possible that there was a PAH contribution to the sediments from urban runoff or other industrial and municipal discharges. The compound-specific isotope ratios (CSIRs) of carbon in PAHs obtained using a gas chromatograph with an isotope ratio mass spectrometer (GC/IRMS) showed that the CSIRs of the sediment samples were not the same as those of the former MGP site soil samples. The results suggested that the sediment samples most likely contained hydrocarbons from a mixture of sources. Therefore, at least some of the PAH content in the sediments was from a source other than the MGP.