Geoscience Reference
In-Depth Information
Table 8.3
Concentrations of PAHs in waters from remote sites (mean ± standard
deviation). (From Vilanova
et al
. 2001b; Fernandez
et al
. 2005.)
PAH particulate
(Units in ng/L)
PAH dissolved
(Units in ng/L)
PAH total
(Units in ng/L)
Location
Ladove Lake Sept. 2000
8.5 ± 0.7
3.4 ± 0.4
12 ± 1.0
Lake Redon May 2001
0.18 ±0.03
0.58 ± 0.2
0.77 ± 0.20
Lake Redon (1996-8)
0.41 ± 0.13
0.27 ± 0.19
0.70 ± 0.21
Lake Gossenkölle (1996-7)
0.57 ± 0.34
0.35 ± 0.19
0.86 ± 0.44
Øvre Neådalsvatn (1998)
0.50 ± 0.08
0.56 ± 0.06
1.1 ± 0.1
Esthwaite Water Lake
92 ± 32
Raritan Bay (New Jersey)
7.0-7.1
3.2-7.4
10-15
Hamilton Harbour (Lake Ontario)
45 ± 4
Niagara River
17 ± 5
Danube Estuary
0.13-1.25
0.18-0.21
Northern Chesapeake Bay
8.7-14
Southern Chesapeake Bay
Hampton (urban)
2.9
3.2
York River (semiurban)
5.2
5.2
Elizabeth River (industrial)
23
43
Baltic Sea
0.07-0.33
0.57-0.74
0.64-1.08
Polycyclic aromatic hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) do not contain chlorine atoms; they
are formed by fused aromatic (benzene-type) rings. Due to this fusion, PAHs are
very stable and, therefore, exhibit properties of POPs. However, they are more
sensitive to photolysis and environmental oxidation. These compounds are
primarily generated during combustion (e.g. from cars, thermal plants and forest
fires) and are also present in petroleum. Hence, PAHs, in contrast to OCs, have
always been present in nature: ever since the earth has had an oxygenated
atmosphere they have been introduced into the environment by forest fires and
geochemical processes.
Organisms have been exposed to PAHs over the course of evolution. Current
concentrations in remote European water bodies range between 0.1 and 10 ng l
−1
(Table 8.3). This continued exposure has resulted in the development of metabolic
mechanisms for their efficient elimination. Therefore, PAHs do not bioaccumulate
in higher organisms. However, this does not mean that PAHs do not negatively
affect human health; indeed, some of these compounds are well known to be
highly carcinogenic (IARC 1983). The main difference between PAHs and OCs
is that the former exert their effects more strongly through direct exposure,
whereas the latter tend to affect health over the long term. Nonetheless, as a
consequence of the extensive use of combustible fossil fuels as energy sources
starting in the mid 19th century, the levels of these compounds in ecosystems
have risen by several orders of magnitude (Fernandez
et al
. 2000). Furthermore,
humans live in areas where PAHs are constantly being emitted, such as cities.
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