Source Characterization of Polycyclic Aromatic Hydrocarbons by Using Their Molecular Indices: An Overview of Possibilities - Reviews of Environmental Contamination and Toxicology - page 65

bell-shaped distribution of volatilized LMW PAHs (2-4 rings). In such cases, the
destruction efficiency of PAHs decreased as the MW increased. The newly diesel-
combustion-generated PAHs (mainly HMW) were in the range of 0.5-1.5‰ of the
destroyed/combusted PAHs (mainly LMW) (Fig. S16, Supporting Material; Wang
et al. 1999b ).
The most abundant pyrogenic PAHs are fluoranthene, pyrene, and, to a lesser
extent, phenanthrene (Page et al. 1999 ). Predominance of P0, FL0 and PY0 indi-
cates the pyrolytic origin of the contamination (Morillo et al. 2008a ). Like phenan-
threne, anthracene is also common to pyrogenic sources (De Luca et al. 2004 ;
Gogou et al. 2000 ). In sediments, absence of IP has been interpreted as the absence
of pyrogenic PAHs (De Luca et al. 2004 ). Moreover, it has been shown that the use
of HMW PAHs (e.g., MW=252, benzo[ k ]luoranthene, benzo[ b ]luoranthene,
benzo[ a ]pyrene, benzo[ e ]pyrene, benzo[ j ]luoranthene, and perylene) is adequate
to discriminate between different high-temperature processes, e.g., carbonization
and coking in manufacturing gas plants, and combustion in motor vehicle engines
(Boll et al. 2008 ; Costa and Sauer 2005 ; Costa et al. 2004 ; Ollivon et al. 1999 ; Stout
and Graan 2010 ).
The HMW pyrogenic PAHs emitted at high temperatures as gases condense on
particulates when cooled (Tobiszewski and Namiesnik 2012 and references therein).
Accordingly, LMW pyrogenics are more abundant in the gaseous phase.
The pyrogenic PAHs (especially parent PAHs) associate with small soot-rich
particles (Sicre et al. 1987 ; Yunker et al. 2002 ). As a result, pyrogenic PAHs are
more often associated with sediments and become more resistant to microbial deg-
radation than PAHs of petrogenic origin (De Luca et al. 2004 ). Nevertheless, weath-
ering also causes pyrogenic products to increasingly be dominated by four- to
six-ringed PAHs, producing a pattern very similar to what appears in urban runoff
(see below), rendering it more difficult to identify the source (Stout et al. 2003 ).
The pyrogenic PAHs are subject to differential photodegradation (first order
kinetics). The isomer pairs of phenanthrene-anthracene, fluoranthene-pyrene and
indeno[ 1 , 2 , 3 - cd ]pyrene-benzo[ ghi ]perylene degrade photolytically at about the
same rate in the atmosphere (Behymer and Hites 1988 ; Yunker et al. 2002 ). By con-
trast, BaP is photolyzed in the atmosphere at much faster rates than are its isomers
(Behymer and Hites 1988 ; Gogou et al. 2000 ; Sicre et al. 1987 ; Yunker et al. 2002 ).
On the other hand, Brenner et al. ( 2002 ) used BaP as a normalization constant to
calculate PAH losses in a weathered creosote site. Despite not being listed as a prior-
ity pollutant (Table 2 ), benzo[ e ]pyrene (BeP) has been included in many studies
(especially of iron and steel plant emissions) because of its chemical stability in the
atmosphere and the additional information it can provide (Daisey et al. 1986 ; Ollivon
et al. 1999 ; Soclo et al. 2000 ; Yang et al. 2002 ). PAH photodegradation also takes
place in other environmental matrices (e.g., water), which preferentially protect cer-
tain isomers (Bertilsson and Widenfalk 2002 ; Tobiszewski and Namiesnik 2012 ).
Motor vehicles are a major source of potential carcinogenic HMW PAHs (such as
benzo[ a ]pyrene, benz[ a ]anthracene, and benzo[ b ]luoranthene), especially in highly
populated areas (Dickhut et al. 2000 ; Simoneit 1985 ). Marr et al. ( 1999 ) reported
unburned fuel, lubricating oil, and pyrosynthesis as possible sources for PAHs from