Source Characterization of Polycyclic Aromatic Hydrocarbons by Using Their Molecular Indices: An Overview of Possibilities - Reviews of Environmental Contamination and Toxicology - page 58

25

Interpretation

MDL A: Jet Fuel

20

MDL B:
MDL C:
MDL D:

Low Sulfur Diesel

Diesel
Crude Oil

15

10

MDL A

5

MDL B

MDL C

M DL D

0

Fig. 2 How the method detection limit (MDL) affects the interpretation of fingerprinting. Shown
here is a comparison of fingerprints of crude and its refined products (crude fractions). EPA16
priority PAHs are shown in black . See Table 1 for PAH abbreviations, except for HOP : hopane.
Adapted from Douglas et al. ( 2007a ), with permission, © Elsevier Academic Press

ment or the degree of degradation to which they were subjected (Ou et al. 2004 ;
Yan et al. 2005 ).
Distilling crude oil does not produce significant amounts of new PAHs in the
crude fractions (Stout et al. 2001b ). As a result, all refined petroleum products
mainly contain PAHs that were present in the original crude oil. Nevertheless, frac-
tionation among refined products (Fig. 2 ), and different crude oil feedstocks, make
the PAH compositions of the refined crude products distinguishable (Stout et al.
2001b ; Wang and Fingas 2003 ). Lighter products, such as jet fuel, tend to contain
the more volatile LMW PAHs (e.g., phenanthrene). In crude and heavier fractions
(higher distillation temperature), the higher MW PAHs become more abundant
(Fig. 2 ; and note boiling points and vapor pressures of the PAHs in Table 2 ).
For example, because methylphenanthrene isomers all boil in the same temperature
range, they pass unchanged from the crude oil feedstock into a straight-run distillate
(Stout and Wang 2007 ). Nevertheless, during the refining process, alkylated chry-
senes are removed from diesel (Bence et al. 1996 ). Other heavily alkylated three-
and four-ringed homologues are impoverished in fuel #2 PAH distributions
(Figs. S3 vs. S5, Supporting Material). Similarly, the abundances and distributions
of sulfur-bearing compounds, such as dibenzothiophenes, are altered during
hydrodesulfurization processing of crude oil or middle distillate blending stocks
(Page et al. 2006 ; Stout et al. 2006 ).