Metal contaminants in the marine sediments could be divided into two groups : less toxic (Fe and Mn) and highly toxic metals (Cd, Cu, Cr, Hg. Ni. Pb and Zn). For less toxic metals, Fe reached its highest concentration in both rainy and winter seasons. followed by Mn in the rainy season. Among toxic elements. Pb and Cr reached the highest in the rainy season (154.28±26.68 mg/kg) and in winter (578.16±126.74 mg/kg), respectively. The amount of metals was slightly higher in winter than in the rainy season due to water dilution. strong wind and waves in the rainy season.. However, the amount of heavy metals did not exceed the standard metals contamination in marine sediments. A high contamination was found at the industrial and shipping areas .
Assessment of radionuclides and heavy metals along the Upper Gulf of Thailand was very important to address the concern about human risk to exposure. The benthic communities could be used as a biological index of a tolerance level guideline for primary producers and consumers. Continuous monitoring of toxic materials not only radionuclides and heavy metals but organic compounds (PAH s,VOCs, pesticides and others) was very important in marine surveillance and could be used as baseline data for management of marine ecology. The amount of toxic substances should be evaluated together with soil parameters: pH and organic matters, to determine the kinetic and thermodynamic parameters.