THESIS APPROVAL

oil and asphalt may contain several percent PAHs (Guerin et al., 1978). These PAHs
include naphthalene, phenanthrene, fluorine, fluoranthene, benzo (a) anthracene,
benzo (a) pyrene, benzo (e) pyrene, dibenzo (c, d) pyrene and perylene.
2.3 Biosynthesis
PAHs are also directly synthesized by organisms particularly bacteria,
fungi and higher plants. Many of these compounds are not true PAHs since they
contain oxygen, nitrogen, or sulfur substituents. Most of these synthesize are wide
variety of polycyclic quinine pigment. Naphthoquinones are common in flowering
plants. The largest group of natural occurring polycyclic quinines is the
anthraquinones (Gerarde and Gerarde, 1962).
3. Routes of Entry into the Aquatic Environment
PAHs may reach the aquatic environment by a variety of routes including
biosynthesis and human activities (Andelman and Snodgrass, 1972). PAHs emitted to
the atmosphere during pyrolysis of organic matter are absorbed on microscopic
particles and deposited into water (Suess, 1976). Accidental spillage and natural
seepage of petroleum represents a quantitatively important input of PAHs to the
aquatic environment. Treated and untreated liquid sewage is nearly always
discharged to water. Solid residues from activated sludge treatment of wastes may be
disposed of in the ocean or in landfills. The estimated total annual input of PAHs to
the aquatic environment from the sources discusses above is approximately 230,000
metric tons (Neff, 1979). Liquid domestic sewage usually contains less than 1µg/l
total PAHs, industrial sewage 5-15 µg/l (Borneff and Kunte, 1965) and sewage sludge
1-30 mg/kg (Nicholls et al., 1979). Surface runoff from land and fallout from the air
appear to be the main sources of high molecular weight PAHs in the aquatic
environment while petroleum spillage is the main source of total PAHs (Neff, 1985).
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