I'r - Memorial University of Newfoundland

After release by the primary sources, PAM can be affected by different degradative
processes which can eventually result in alteration ofthe assemblage. The IItOst
important among them are photooxidation. chemical and physical degradation. and
microbiological transfonnations (Neff. 1979). The photooxidation is generally
considered to be the most important mode of PAH decomposition in the atmosphere and
the photic zone ofwater column. This process result s in transformations ofparental PAM
through a variety ofphoto-Induced reactions with oxygen. ozone. HO radical, and other
oxidizing agents. The processes ofvolatilization across the air-water interfa ce and
reactions with a variety oforgani c andinorganic oxidants, including peroxides, nitrogen
oxides. sulfur oxides. etc.• bring about physical and chemical transformations ofthe PAH
assemblage through removal or alteration of more mobile compounds. In addition,
biological degradation which primarily occurs in the upper layer ofsediments.,close to
the water-sediment interface. results in preferential cons umption of less stable
compounds by microorganisms that inhabit the substrate.
Thus PAH predominantly emanating from different anthropogenic activities are
transported by rivers and streams and through the atmosphere to become eventually
deposited in lacustrine and marine sediments. During the transport and after deposition.
the initial PAH assemblage can be significantly altered by a variety of different processe s.
Disciplinary and regional contest: Studies ofPAH contamination in lacustrine and
marine sediments and its original sources are important. This importance is substantiated
by the fact that most of the compounds have toxic properties. They tend to fonn
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