Source Characterization of Polycyclic Aromatic Hydrocarbons by Using Their Molecular Indices: An Overview of Possibilities - Reviews of Environmental Contamination and Toxicology - page 108

particularly in non-trivial cases, e.g., when urban background has to be discrimi-
nated from a petrogenic or, more often, a pyrogenic source. Using PMF in conjunc-
tion with PCA for the EPA16 PAHs and advanced chemical fingerprinting, Stout
and Graan ( 2010 ) differentiated between creosote and urban background runoff.
One confounding factor contributing to PAH contamination was two four-ringed
parent PAHs (FP0). The other factor was eight HMW PAHs (BaA, C0, BbF, BjF,
BaP, IP, DA, ghi ). An increase in the abundance of the eight PAHs was attributed not
to weathering, but to increased urban contribution.
Walker and Dickhut ( 2001 ) intrigued by abundances of FP0 (MW = 202) or of
the isomer sum BbF + BkF + BeP + BaP + PER (MW = 252), plotted ratios of these
sums to the parent compounds that have MW = 202-276 (i.e., FL0 + PY0 + BbF + Bk
F + BeP + BaP + PER + IP + DA). Using double PAH ratio plots and PCA, they
showed that both isomer-sum ratios (ʣPA H 202 /ʣPA H 202-276 and ʣPA H 252 /ʣPA H 202- 276 )
explained a significant proportion of the variability (1st principal component).
These results show that parent PAH compilations (e.g., fluoranthene-pyrene pair
and HMW PAHs) are suitable for discriminating pyrogenic sources. However, it
remains important to consider the influence of weathering or urban background
when interpreting the results, in order to attribute the explained variability to the
correct source factor (Stout et al. 2003 ; Walker and Dickhut 2001 ).

5.8.2 Low Versus High Molecular Weight Parent PAHs

A numeric index related to the pyrogenic-petrogenic differentiation into LMW and
HMW PAHs is the ratio of these PAH fractions (De Luca et al. 2004 ; Fig. 22 ; Magi
et al. 2002 ; Soclo et al. 2000 ):

PA FP
BaAC BkFBaP IP DA ghi

+
++++++

0 0

LH / =

0

Others (Boonyatumanond et al. 2007 ; Zakaria et al. 2002 ) add P1 to “L”, and
B[ b + j ]F, BeP, and optionally, Cor and PER to “H”, without the DA.
In some studies (De Luca et al. 2004 ; Karlsson and Viklander 2008 ; Mathieu and
Friese 2012 ), the EPA 16 are divided into low molecular weight (LPAH, i.e., naph-
thalene to anthracene, 2-3 rings) and high molecular weight PAHs (HPAH, i.e.,
fluoranthene to indeno[ 1 , 2 , 3 - cd ]pyrene, 4-6 rings):

++++
+ +++++ +

N EAYF PA 0 0 0

LPAH HPAH / = .

FP 0 BC 0 BbFBkF BaPIPDA ghi

Chen and Chen ( 2011 ) add 2-P1 to the numerator. Stout et al. ( 2003 ) used all
quantified compounds, including alkylated ones. The LPAH/HPAH ratio has been
reported for several substances, including gasoline, diesel fuel, used lubricating oil
and bitumen (Fig. 23 ; Karlsson and Viklander 2008 ). The ratio can differ for differ-
ent brands of gasoline, diesel, and oil, depending on the differences in the crude oil
properties and refinery processes.