Environmental Engineering Reference
In-Depth Information
• What are the inherent uncertainties in these indicators and how does the value of
the indicator change after undergoing biogeochemical processes (i.e., photo-
chemical oxidation, degradation, volatilization, etc.) in the aquatic environment?
• Can the Borneff-6, 16 EPA, and 10 VROM PAHs be used to calculate the pro-
posed indicator—and, if so, which uncertainties are introduced by utilizing this
approach?
2
Source Profiles of PAHs
If source inventories are lacking or incomplete, the first task is to clarify whether the
known or unknown sources of PAHs are petrogenic, pyrogenic or natural. This is
usually accomplished by observing PAH fingerprints that show the relative PAH
abundances (Douglas et al.
2007a
). For example, the relative distribution of PAHs
in each homologous family is used to differentiate compositional changes during
the degradation of oil spills (Wang et al.
1999a
). Characteristic PAH fingerprints of
petrogenic and pyrogenic sources from the literature are shown in Figs. S1-S32
(Supporting Material).
Once released to the environment, the PAHs are prone to a wide variety of
degradation processes, including evaporation, dissolution, dispersion, emulsifi-
cation, adsorption on suspended materials, microbial degradation (biotic or bio-
degradation), photo-oxidation, and interaction among the contaminants and
sediments (Gogou et al.
2000
; Kim et al.
2009
; Page et al.
1996
; Wang et al.
2004
). Degradation substantively changes the physicochemical properties and
relative abundances of even the highest MW PAHs, and such changes must be
considered when identifying and quantifying PAH sources (Page et al.
1996
;
Wang et al.
2004
).
2.1
Petrogenic
Petrogenic substances (petrogenics) are defined as the substances that originate
from petroleum, including crude oil, fuels, lubricants, and their derivatives (Saber
et al.
2006
). Petrogenic PAHs are introduced into the aquatic environment through
accidental oil spills, discharge from routine tanker operations, municipal and urban
runoff, etc. (Zakaria et al.
2002
). There have been no observations of widespread,
and continuous (i.e., nationwide and non-accidental) input of petrogenic PAHs
(Zakaria et al.
2002
).
Petroleum is a complex mixture of different organic compounds formed dur-
ing different geological ages and under different geological conditions. The dif-
ferent depositional environments during oil formation are reflected in different
PAH distributions (e.g., dibenzothiophenes: D
n
) in crudes from different sources
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