Rt€@lll

- 245
Upper Gutf of Thailand, rnainly fine mud, in ppm dry weight (ldthikasem' l98l):
cd 0.05 - 0.21
Co 4.0 - I8
Cu 1.8 - 2t
Hg 0.I - 0.I)
Pb L7 -t5
Zn 5.8 - lI5
Middle and Lower GuIf of Thailand (Hungspreugs, 1983)
cd 0.rl - 0.61
Cr 24.8 - 48.0
Cu 9.0 - 14.0
Pb 10.5 - 2r.0
Zn 22.9 - 42.O
The Andaman Sea (Hungspreugs and Yuangthong, 1982)
cd 0.I0 - 0.17
Cu 5.41 - 8.99
Pb o.7r - 19.25
Zn L2.62 - 77.50
In the study of sediments for pollution, it is not enough to analyse only the surface
sediment. The history of sedimentation must also be studied to detect any increase over the
natural level caused by anthropogenic sources. This is done by analysing the metal contents
of various strsta in the sediment core, coupled with radioactive geochronology of the core.
Examples of such studies done elsewhere are Goldberq et al. (f979), Bentine (1978)' etc
Windom et g. (f982) made one such study in the Upper Gulf of Thailand and found the
sedimentation rate to be between J.J and 8.9 mm/year with the highest rate at the mouth o'
the Chao Phnya River.
Marine organiems
A few euthors have reported on the heavy nretal contamination of marine organisms it
Thai waters, namely Huschenbeth and Harms (I975), Wattayakorn et eL (L979) anl
Hungspreugs and Siriruttanaehai (1981). Menasveta and Cheevaparanapiwat (f9Bf) 8D'
Siwareksa et aL (f98I) worked on mercury in marine animals. Both groups found mercur
content in-Tish to be mostly below 0.1 ppm in agneement with the nesults of Huschenbeth an
Harms (1975). However, the local workers' values for cadmium and lead must be regarded a
rather high, due to the inferior instrunent in use up to 1980. In the case of lead in th
oyster Crasgotrea commercialis, Hungspreugs (1981), using an AAS with flameless graphit
furnace-arxl cleuterium background correction, found a much lower value of around 0.)5 ppt
dry weight for lead and 0.26 ppm for cadmium instead of the former high values of 15.0 an
8.9 ppm respectively. The most recent values for cadmium and lead in economically importar
bivalves are (in pS/S dry weight):
Perna viridis
PapnA--""0"t"t"
Anadare qranosa
Cressostrea commercialis
Amusium pleuronectes
Cd pg/g
0.49
o.42
o.77
o.26
0.48
Pb rrg/q
which are all within the limits set by the Australian Nationel Heatth and Medical Researr
Council in 1979 (1.0 for Cd and 2.5 for Pb).
Fo fish, Huschenbeth and Harms (1975) found a range of 0.001 to 0.25 ppm f
cadmium, 0.20 to 1.25 ppm for copper, 0.01-0.22 ppm for lead and 2.9 to 19.9 ppm for zinc
marine fish from all major areas.
Brown and Holley (f98]) made a study of the effect of tin dredging and smelting on t
marine animals nearby and found no increase in metal levels in those animals. The dissolv
netal content of the water did not change significantly. They explained that perhaps the
0.48
o.26
o.47
a.t6
0.4I