Polycyclic aromatic hydrocarbons in Louisiana Rivers and Coastal environments: Source fingerprinting and forensic analysis

Polycyclic aromatic hydrocarbons (PAHs), many of which are toxic and recalcitrant compounds, are ubiquitous in rivers and coastal environments. Anthropogenic introduction of these chemicals into the environment compromises the assessment of cleanup responsibility and environmental damage liability. Natural background and anthropogenic PAHs in Louisiana coast and major rivers were differentiated based on PAH profiles in samples selected from a pool of 3,540 samples collected over a 3-year period. Several groupings of 2- to 6-ring parent and their C1-C4 alkylated PAH homologs were quantified by gas chromatography/mass spectrometry. Sampling stations were delineated in terms of pyrogenic, petrogenic, and biogenic/diagenetic source PAHs. Fragmentograms indicated that petrogenic inputs generally dominated at more stations than pyrogenic and diagenetic inputs. Most of the results reflected multiple sources of contamination, as would be expected. Preexisting environmental forensic techniques were selected and applied to compare several different source differentiation and allocation methods to evaluate PAH sources in samples from a wide geographical coastal system influenced by myriad sources and complex mixing dynamics. This article covers diagnostic ratios and plots utilizing petroleum biomarker constituents, ratios within homologous PAH categories, pollution indices, and qualitative comparisons to reference profiles suspected as PAH sources.