Source Characterization of Polycyclic Aromatic Hydrocarbons by Using Their Molecular Indices: An Overview of Possibilities - Reviews of Environmental Contamination and Toxicology - page 72

Retene has other anthropogenic sources, such as fresh oil, diesel, exhaust emissions
from heavy-duty diesel fuels, pulp/paper mill effluents, and emissions from coals
(Mandalakis et al. 2004 ; Yan et al. 2005 ).

3 Factors Influencing PAH Distribution in Aquatic Systems

Sediments are sensitive indicators of natural and anthropogenic origin, such as PAH
contamination (De Luca et al. 2004 ; Klamer et al. 1990 ). Variables such as OC,
particle size and depositional environment are important for discovering and char-
acterizing the source, transport and bioavailability of PAHs in sediment (e.g.,
Dickhut et al. 2000 ; Morillo et al. 2008b ; Soclo et al. 2000 ; Wang and Fingas 2003 ).
In the different environmental matrices (atmosphere, water column, oil, sedi-
ments), easily degradable LMW PAHs (i.e., two- and three-ringed) are relatively
soluble and predominate in the water phase, whereas the more recalcitrant and more
lipophilic alkylated and/or HMW PAHs are more often associated with particulate
matter, and thus are better protected from degradation (Budzinski et al. 1997 ;
Cailleaud et al. 2007 ; De Luca et al. 2005 ; Karlsson and Viklander 2008 ; Page et al.
1996 ; Stout et al. 2001a , b ). This fact has implications that need to be taken into
consideration when dealing with PAH distributions:

a. It is difficult to distinguish certain weathered pyrogenic sources (e.g., severely
weathered coal tar) from urban background, which is also dominated by HMW
four- to six-ringed PAHs (Battelle Memorial Institute et al. 2003 ).
b. Lack of oxygen (that fosters biodegradation) in deeper sediment layers and also
the physical-chemical association of PAHs with the sediment matrix can result in
long-term PAH stability (Page et al. 1996 , 1999 ; Short et al. 2007 ).
c. Small molecules, such as three-ringed/LMW PAHs, are selectively depleted by
physical mixing and tend to be enriched in the fine sand fraction, whereas the
larger PAHs (six-ringed) are enriched in the fine silt fraction (Karlsson and
Viklander 2008 ; Mitra et al. 1999 ). Partitioning of PAHs into different sediment
fractions has been reported in the literature (Johnson-Restrepo et al. 2008 ; Magi
et al. 2002 ; Micic et al. 2011 ). Sediment particle size affects the oxygenation of
sediments, as well (Jeanneau et al. 2008 ).
d. Climatic conditions may affect the distribution of PAHs in different environmental
compartments, particularly in the atmosphere and consequently may determine
what constitutes the final sink. For example, fluctuations in temperature directly
affect the particle and vapor phase distributions of retene, a common softwood
combustion marker (Benner et al. 1995 ; Gogou et al. 2000 ; Stout 2007 ; Yunker
et al. 2002 ). Accordingly, retene's diagnostic reliability for softwood combustion in
aqueous environments has been doubted (Bucheli et al. 2004 ; Gogou et al. 2000 ).
e. The sorption and desorption of PAHs to the organic carbon (OC) content of sedi-
ments can be used to interpret the source of PAH contamination (Boehm et al.
2001 , 2002 ; De Luca et al. 2004 , 2005 ; Mitra et al. 1999 ; Morillo et al. 2008b ;
Zakaria et al. 2002 ).