Chemistry Reference
In-Depth Information
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Benz[a]anthracene
Chrysene
Benzo[b]fluoranthene
Benzo[k]fluoranthene
Benzo[a]pyrene
Dibenz[ah]anthracene
Indeno[123-cd]pyrene
Benzo[ghi]perylene
Fig. 6 Molecular structures of PAHs
10
5
Pa (Table
1
) which are in the range of phase changes at ambient temperatures.
In this way, POPs tend to evaporate with rising ambient temperatures and condense,
or adsorb to surfaces, at decreasing temperatures. These temperature-dependent
processes have been described using the concept of “global distillation” taking as
example a gas chromatography process [
41
] (Fig.
7
). Other concepts used to define
this process have been “global” or “latitudinal fractionation,” “cold condensation”
or “selective trapping” [
2
,
29
,
42
,
43
]. These effects have allowed to explaining the
changes in POP composition in different environmental matrices in relation with
latitude [
43
-
46
] and altitude [
2
,
44
,
47
,
48
].
Atmospheric POPs are distributed between the gas and particulate phases and, as
mentioned above, the distribution rates are temperature-dependent [
35
]. However,
other atmospheric processes such as photochemical oxidation and deposition are
also relevant for the ultimate value of POPs in the air compartment (Fig.
7
).
Once the compounds have been deposited on land or water surfaces, they can be
incorporated into these compartments and the organisms living in them (Fig.
7
).
Soils and sediments can be considered as final POP sinks. However, the retention
