THESIS APPROVAL

4. Distribution in the Aquatic Environment
PAHs entering water from various sources quickly become adsorbed on
organic and inorganic particulate matter in water, and large amounts are deposited in
bottom sediment. Herbes (1977) said that organic particles tend to adsorb PAHs more
readily than clay particle. Once deposited on the bottom, the PAHs are much less
subject to photochemical, chemical or biological degradation than they were in the
water column (Neff, 1985). However, leaching or biological activities in the
sediments may return a small fraction of these PAHs to the water column. The
composition and relative concentrations of the PAH assemblage in the sediment may
be differed from those in the PAHs source because of differential partitioning of
PAHs between sediment and aqueous phases (Hase and Hites, 1977). The distribution
of PAHs in aquatic environment is described in Figure 9.
PAHs
Evaporation Photo-oxidation
Dissolution
Water surface
Water column
Photo degradation Biodegradation
Chemical degradation
Bioaccumulation
Sedimentation
Attachment to particulate matter
Figure 9 Distribution of PAHs in aquatic environment.
Bioaccumulation
Biodegradation
Chemical degradation
Bottom sediment
Most of the PAHs entering the aquatic environment are localized in rivers,
estuaries and coastal marine waters. Table 3 and Table 4 show the concentration of
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