ACCUMULATION OF HEAVY METALS AND THEIR BIOAVAILABILITY IN SEDIMENTS FROM BANDON BAY, SURAT THANI PROVINCE

Abstract

This research aimed to investigate the accumulation of heavy metals and their bioavailability in sediments collected from the Bandon Bay, Surat Thani Province. The samples were randomly collected from 10 sampling locations in coastal area of Bandon Bay. The samples were digested by a microwave system followed by elemental quantitation using inductively coupled plasma-optical emission spectrometry (ICP-OES). The total amounts found in the sediment, in descending order were: Zn > Pb > Cu > Cd with the mean concentrations of 59.520, 8.163, 2.838 and 0.216 mg/kg dry weight, respectively. When compared to the quality standards for coastal marine sediment and the standards set by the Environmental Protection Agency of the United States, it was found that the levels of all four heavy metals found in the sediment are below the specified standards. Therefore, it can be concluded that the sediment from the mentioned source has an environmentally safe level of heavy metal accumulation. In studying the bioavailability of heavy metals in sediment, the sequential extraction method is employed to assess the potential release of each type of heavy metal from the sediment into water sources and its uptake into the cells of aquatic organisms. It was found that the levels can be ranked in descending order as follows: Cd > Zn > Cu > Pb. Cadmium (mostly 70.6-78.4%) is predominantly in forms soluble in water/exchangeable ions/capable of forming complexes with carbonate. For zinc and copper, they are in forms soluble in water/exchangeable ions/capable of forming complexes with carbonate, with percentages of 33.6-50.4 and 10.5-26.5, respectively. Meanwhile, lead fraction in the sediment is mostly in forms ready to be released into the water in the smallest quantity (3.9-9.9%).