Source Characterization of Polycyclic Aromatic Hydrocarbons by Using Their Molecular Indices: An Overview of Possibilities - Reviews of Environmental Contamination and Toxicology - page 51

urban and industrial areas that often have multiple point sources of release (Boll
et al. 2008 ; Elmquist et al. 2007 ).
PAHs are potentially toxic and mutagenic to many living organisms, such as
marine plants and animals (Boehm et al. 2007 ; Guo et al. 2007 ; Swietlik et al. 2002 ).
The lower molecular weight PAHs (LMW PAHs) are acutely toxic but non-
carcinogenic to many aquatic organisms, whereas the high molecular weight PAHs
(HMW PAHs) are strongly carcinogenic and mutagenic (Karlsson and Viklander
2008 ; Laane et al. 2006 ; Ou et al. 2004 ). Different PAH priority lists have been
compiled by different environmental or statutory bodies, such as the
U.S. Environmental Protection Agency (EPA), the Dutch ministry of housing, spa-
tial planning and the environment (VROM) and the so called “Borneff-6” PAHs
(e.g., European Commission 2001 ; Laane et al. 1999 ; Table 2 ).
PAH source characterization defensibly links the contaminants with their sources
for the purpose of finding parties that are liable for the contamination. Source appor-
tionment quantifies the amount of contamination contributed by each party involved,
so that regulators can make accountability decisions (relating to, e.g., cleanup costs,
mitigation, etc.). If a strategy for characterizing PAHs is to succeed, knowledge of
the sources, chemistry and fate of each individual PAH is crucial, and the PAHs to
be analyzed must be carefully selected (Peters et al. 2005 ).
PAHs are classified according to the temperature at which they form, or their
origin. An example is the threefold classification espoused by Boehm et al. ( 2007 )
and Mitra et al. ( 1999 ): i) pyrogenic PAHs, which originate from different pyrolysis
substrates, such as fossil fuels and biomass, ii) petrogenic PAHs from petroleum-
related sources, and iii) natural PAHs of biogenic or diagenetic origin.
In the history of determining the PAH contaminating source and the contami-
nants themselves, it was realized that petroleum and its products, as well as combus-
tion byproducts, included quite complicated mixtures of PAHs (Farrington et al.
1977 ; Giger and Blumer 1974 ; Windsor and Hites 1979 ; Youngblood and Blumer
1975 ). However, it was observed that the distribution of PAHs varied among differ-
ent PAH sources (Grimmer et al. 1981 , 1983 ; Laflamme and Hites 1978 ; Youngblood
and Blumer 1975 ). Since then, there has been an ongoing effort to find the proper
molecular indices of a PAH distribution that would allow source characterization of
contaminated areas.
Our approach on reviewing PAH molecular indices that are used for source
characterization is twofold. Firstly, we review indices of a PAH distribution
(ubiquitous PAH markers, PAH abundance, modes of distribution, etc.) which are
characteristic for pyrogenic and petrogenic sources. The possible modifications
that a PAH distribution undergoes on its way from source to receptor are also
reported. Secondly, we review a selection of certain indices of a PAH distribution
(PAH ratios and some of their combinations) in a quantitative way and evaluate
their use in source characterization. Finally, we address the following questions
in this review:
• What are the most important PAH sources in the aquatic environment, and which
PAH indicators can be used to unequivocally identify them?