Mercury Distribution and its Potential Environmental and Health Risks in Aquatic Habitat at Artisanal Buladu Gold Mine in Gorontalo Province, Indonesia

摘要

Total mercury (THg) in water column, sediment and aquatic biota as well as environmental and health risks at artisanal Buladu gold mine and vicinity areas of Gorontalo Province, Indonesia were investigated both in summer and rainy seasons. THg was determined by CV-AAS (Cold Vapor Atomic Absorption Spectrophotometer; Spectr. AA6200) after NabH4 (Sodium Borohydride) reduction, with detection limit was of 0.001 ??g/L. Site-specific exposure parameters such as body weight (bw) and consumption rate of fish and shellfish were determined and calculated using target hazard quotient (THQ) formulation for health risk assessment. This study showed that the assessment of average balance of Hg: Au ratio forecasted that approximately 1.3 g of Hg in open burning process was released to atmosphere to produce 1 g of gold. Likewise, 15.88 g of Hg is lost to produce 1 g of gold during amalgamation process in particular equipment, the tromols. Moreover, the highest levels of THg concentrations in water column, sediment and shells in uncontaminated track were 41 ??g/L, 5238 ??g/kg dw, 215 ??g/kg dw for Bellamnya javanica and 397 ??g/kg dw for Mya arenaria in summer season, respectively, whereas in rainy season the lower THg concentration were 24 ??g/L, 5077 ??g/kg dw, 141 ??g/kg dw for Bellamnya javanica and 180 ??g/kg dw for Mya arenaria, respectively. However, in contaminated track, the significant elevated THg were found about 123 ??g/L, 5612 ??g/kg dw, 1455 ??g/kg dw for Bellamnya javanica and 1745 ??g/kg dw for Mya arenaria in summer season, respectively, whereas in rainy season the highest concentration were 165 ??g/L, 6950 ??g/kg dw, 1250 ??g/kg dw for Bellamnya javanica and 1745 ??g/kg dw for Mya arenaria, respectively. THg elevated in Thunnus sp. was also found at station one in big tuna with the value of 762 ??g/kg dw. Those elevated THgs were consistent and significantly different between those two seasons in term of bioaccumulation level. In addition, the estimated weekly intake (EWI) of Hg for B. javanica, M. arenaria and Thunnus sp. exceeded the accepted maximum tolerable weekly intake of 0.005 ??g/kg bw. Nevertheless, THQ values were still less than 1 with the maximum levels of 0.06, 0.11 and 0.69 in summer season, respectively. These results suggested that Hg containing wastewater discharged into the Buladu River and the atmospheric fallout from Hg emission were the major sources of Hg in the areas of interest. Consequently, Hg, resulting from Hg released from the gold mine that has been operated for 30 years more, has gradually accumulated in the aquatic ecosystems of the Buladu River and the Sulawesi Sea.