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In
order to cover both temporal and spatial trends in Total
DDT and TBT contamination of local marine waters, sediment
samples were collected four times (December 1998, January,
June and August 1999) from ten stations located throughout
Hong Kong waters (DS3, ES2, MS15, MS5, NS4, PS6, SS3,
TS2, VS3 and WS1). In addition to the sediment samples,
marine biota were collected from four stations (Mirs
Bay, Port Shelter, Southern Waters and Deep Bay) in
December 1998, January, August and September 1999 and
analysed for Total DDT, TBT, Total PCBs and Total PAHs
concentrations that had been accumulated in their tissues.
A
summary of the major sources in the marine environment
and toxic effects attributed to Total PCBs, Total PAHs,
Total DDT and TBT is presented in Table 5.0a.
| Table
5.0a Summary of PCB, PAH, DDT and TBT Major Sources
in the Marine Environment and Toxic Effects |
| Toxic
Pollutant |
Major
Sources |
Effect
of Toxicity |
| PCB |
Insulating
fluids used in the electricity industry (such as
in transformers) and as plasticisers. |
Immumo-suppression.
Reproductive failure.
Carcinogen. |
| PAH |
Hydrocarbon
combustion such as emissions from vehicles and coal-fired
power stations |
A
diverse group of similar compounds (congeners) which
can be bioaccumulated and stored in body fats. Toxicity
increases with molecular weight and lipophicity.
Some congeners undergo photo-oxidation in presence
of UV and become more toxic.
Some congeners are carcinogens. |
| DDT |
Run
off from agricultural land when applied as a pesticide. |
Temperature-dependent
toxicity (less toxic at higher temperatures).
Accumulates in body fats.
Interferes with reproduction and fertility.
Neuronal toxcity. |
| TBT |
Antifouling
paints (major input to the marine environment is
from paint applied to ship hulls) |
Interferes
with sex hormones in molluscs inducing the imposition
of male genitalia in female snails.
Growth abnormalities and immumo-suppressant. |
|
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