W11 AM Environmental Chemical Forensics
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in 343-344

(BOC-1117-813031) Fingerprinting of polycyclic aromatic hydrocarbons in environmental samples, a weight of evidence approach.

Bock, M¹, Barber, T², ¹ ARCADIS, Portland, ME, USA² ENVIRON, Burton, OH, USA

ABSTRACT- Polycyclic aromatic compounds (PAHs) are ubiquitous in urban settings as a result of their presence in petroleum hydrocarbons and their formation during the combustion of organic materials. Although thousands of different PAHs exist, in most environmental investigations only the 16 priority pollutant PAHs are quantified. Methods such as high resolution gas chromatography mass spectrometry analysis (HR GCMS), quantify many more PAHs, including parent and alkylated isomers. Many of these additional PAHs are resistant to weathering and are present in proportions diagnostic of the original source or alternatively non-point source urban background. Forensic analysis or "fingerprinting" can be used to differentiate multiple potential sources of PAHs in environmental samples (e.g., urban runoff, manufactured gas plant residues, lubricating oils, fuel oils). Differentiating PAH sources requires a mixture of graphical and statistical methods including: simple comparisons of the total priority pollutant or benzo[a]pyrene equivalent concentrations, the PAH composition, an examination of the levels of alkylation of the homologue groups, correlation analysis, double-ratio plots, hierarchal tree clustering analysis, and principal components analysis (PCA). The valid application of some these techniques requires careful normalization of the data, for example the use of the proportion of the total concentration rather than the raw concentration of individual isomers. This paper describes the application and interpretation of multiple techniques using a weight of evidence approach. The weighting is based on the power of the various lines of evidence to resolved differences in the PAH composition. If there is general concordance among multiple lines of evidence then there is a high confidence in the determination of sources. We will present cases studies illustrating how the results of a weight of evidence evaluation can be used differential multiple sources of PAHs and used to support environmental management decisions.

Key words: fingerprinting, PAH