Source Characterization of Polycyclic Aromatic Hydrocarbons by Using Their Molecular Indices: An Overview of Possibilities - Reviews of Environmental Contamination and Toxicology - page 73

4 Analytical Approach for PAH Source Characterization

It is often complicated to define the sources of PAH contamination in waterways
and coastal areas that have limited water circulation, particularly where multiple
point sources co-occur with persistent non-point sources (i.e., urban areas or areas
that have high ambient background levels). In such situations, the potential contri-
butions of all possible point or non-point sources should be considered (De Luca
et al. 2004 ; O'Reilly et al. 2012 , 2014 ; Stout et al. 2003 ).
The major approaches used in source identification are pattern recognition, spa-
tial and temporal analysis (sources, historic records, etc.), source-specific diagnostic
ratios of PAH analytes, and principal component analysis (PCA) or positive matrix
factorization (Battelle Memorial Institute et al. 2003 ; Burns et al. 1997 ; Johnson
et al. 2007 ; Stout and Graan 2010 ). If the types of sources and the relative abun-
dances of contributing PAHs are known, then the most useful tools for distinguishing
pyrogenic from petrogenic hydrocarbons are the PAH distributions (patterns, boiling
ranges and fingerprints of alkylated and non-alkylated PAHs) and diagnostic ratios
(Benner et al. 1995 ; Elmquist et al. 2007 ; Neff et al. 2005 ; Wang and Brown 2009 ).
Successful inference and/or differentiation of sources depends on many factors,
such as sampling plan design, sample collection, chemical analysis methods and
knowledge of historical industrial processes (Johnson et al. 2007 ). Problems often
exist in establishing unique organic “tracer” compounds for a given combustion
source, and such problems include variability in the composition of emissions from
the same types of source, degradation of the “tracer”, and general lack of source
composition data for all but a few classes of compounds (Johnson et al. 2007 ).
There are three main steps (tiers) in characterizing the sources of PAHs (Fig. 6 ).
First, inexpensive rapid screening techniques like gas chromatography (GC)—flame
ionization detection (FID), are applied to identify trends, background concentra-
tions, “hotspots”, and key samples (Page et al. 2006 ; Stout et al. 2003 ; Wang et al.
1999a ). Second, if initial screening results allow defensible decision-making,
advanced chemical fingerprinting (e.g., GC-MS, 2 GC-FID, use of diagnostic ratios,
etc.) helps to reveal and identify distinct source “fingerprints” (Boehm et al. 1995 ;
Page et al. 2006 ; Stout et al. 2003 ; Wang and Fingas 2003 ; Wang et al. 1999a ). 3
Third, tier results are explored and explained by using statistical tools. In this review,
we emphasize the use of molecular indices (PAH ratios) as the basis for character-
izing PAH sources.

2 Mass Spectrometry.
3 For guidelines on how to perform a fingerprinting analysis of PAH sources (assessment of historic
records, sampling considerations, climatic conditions, background pollution, quality assurance,
etc.) see Christensen and Tomasi ( 2007 ), Christensen et al. ( 2004 ), Saber et al. ( 2006 ), Stout et al.
( 2001b , 2003 ), Wang et al. ( 1999a ).