Total mercury in seawater and sediment of the Gulf
of Thailand is shown in Table 6. Considering the data
obtained from several surveys, it can be found that the
mercury concentration in seawater during the period
1974–1980 is comparable to natural level as suggested by
Kothny (1973), i.e. in the range of 0.01–0.38 ppb. High
mercury concentrations (44.7–847 ppb) nevertheless
were reported during 1983–1987. The levels were even
higher than those detected in Minamata Bay, Japan
(1.6–3.6 ppb). Whether these reported data are valid or
not, there is a need for clarification both on sample
collection and analytical methods. Most mercury concentrations
in the sediments were still within the acceptable
limit of 0.3 ppm (Ministry of Transport, Japan,
1976), except certain locations such as the Chao Phraya