Source Characterization of Polycyclic Aromatic Hydrocarbons by Using Their Molecular Indices: An Overview of Possibilities - Reviews of Environmental Contamination and Toxicology - page 97

5.5 Sulfur PAH Indices

5.5.1 Ratios of Alkylated Dibenzothiophenes to Alkylated Phenanthrenes

The methyldibenzothiophene/methylphenanthrene (D1/P1) ratio is an expression of
the relative abundance of alkyl-substituted dibenzothiophenes, and has been used to
apportion diesel and pyrogenic sources in sediments (Wang et al. 2001 ). The D1/P1
was used by Takada et al. ( 1990 ) to distinguish asphalt (0.78), diesel emissions
(0.40) and fuel oil soot (0.05) in street dusts. Used in conjunction with the weather-
ing ratio N2/P2, the D1/P1 ratio was useful for source identification in groundwater
samples having dibenzothiophene concentrations >0.07 ng/cm 3 (Hegazi and
Andersson 2007 ).
Among the most popular ratios in oil spill identification are the D2/P2 and D3/
P3 ratios (D n /P n -alkyldibenzothiophene/alkylphenanthrene). They are source ratios
(almost constant because the compounds degrade at the same rate). They are also
called “the petrogenic source ratios” (because they distinguish different petroleum
sources) and “sulfur to non-sulfur ratios” (Wang et al. 1999a ). Both ratios vary
among products having different sulfur contents (e.g., diesel, crude) (Fig. 16 ; Fig.
S3a, b, Supporting Material) and are useful in identifying such oil sources (e.g.,
distillate fuels from sour or sweet crude) (Hegazi and Andersson 2007 ; Stout et al.
2006 ). Small differences in the crude oil supplied by a refinery may greatly change
these ratios (Hostettler et al. 2007 ; Stout 2007 ).

C 2 - Phenanthrene (ppb) C 3 - Phenanthrene (ppb)

1000000

C 2 -Db/C 2 -Ph=0.15+-0.02

C 2 -Db/C 2 -Ph=0.15+-0.02
( N = 19)

100000

( N = 19)

10000

1000

100

10

C 2 -Db/C 2 -Ph=1.08+-0.14

C 2 -Db/C 2 -Ph=1.08+-0.14

( N = 144) ( N = 144)

1 1

100 10000 1000000 1 100 10000 1000000

C 2 - Dibenzothiophene (ppb) C 3 - Dibenzothiophene (ppb)

Fig. 16 The discriminating power of the D n /P n ratios for different crudes ( (filled square weathered
Exxon Valdez Crude, open circle prespill cores, filled circle Exxon Valdez, multiplication sign
Katalla, open square ANS diesel, open diamond Cook Inlet). Adapted from Wang et al. ( 1999a ),
with permission, © Elsevier Science BV