Poranee Pataranawat,Ph.D1. Andrew J. Englande, Jr., Ph.D2, Preeda Parkpian, Ph.D,3

1Sopa Chinwetkitvanich, Ph.D.

1Mahidol University, Bangkok Thailand, 2Tulane University, United State of Amerika, 3Asia Institute of Technology, Thailand

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OBJECTIVE - This study was conducted to investigate the total mercury (THg) in aquatic systems (water column, sediment, and aquatic biota) in the Buladu River and the Sulawesi Sea as well as terrestrial systems (dry deposition, surface soil, food stuffs, and shallow well water) in the area surrounding the Buladu gold mine and vicinity. Hg mass balance and the assessment of potential environmental and health risks both in summer and the rainy season were also investigated.


RESULTS- Results showed by an assessment that the average ratio of Hg:Au was approximately 1.3 g of Hg in the open burning process was released into the atmosphere to produce 1 g of  gold. THg in the water column, sediment, and shellfish (Bellamnya javanica and Mya arenaria) in the contaminated track were 41µg L-1, 5238 µg kg-1dw, 215 µg kg-1ww, and 397µg kg-1ww during summer, respectively. During the rainy season, lower THg concentrations were found to be  24 µg L-1, 5077 µg kg-1dw, 141µg kg-1ww, and 180 µg kg-1ww, respectively. However, in the contaminated track, significantly elevated THg levels were found; about 123 µg L-1, 5612 µg kg-1dw, 1455 µg kg-1ww, and 1745 µg kg-1ww for water, sediment and shellfish, respectively. Also, in the rainy season, the elevated THg concentrations were 165 µg L-1, 6950 µg kg-1dw, 1250 µg kg-1ww, and 1745 µg kg-1ww for those categories, respectively. Highly elevated THg levels in Thunnus sp. was found at Station A1 in large tuna (762 µg kg-1ww) whereas the highest concentration of Hg in sea water was found at Station A7 as a large tuna live in the area within about a 10 km radius. Those elevated THg levels were significantly different between the two seasons in terms of bioaccumulation levels.  In addition, the estimated weekly intake (EWI) of Hg for B. javanica, M. arenaria, and T sp. exceeded the acceptable maximum tolerable weekly intake of 0.005 µg kg-1 bw. Nevertheless, they were not at risk as the target hazard quotient (THQ) values were less than 1 at  maximum levels of 0.1, 0.1, and 0.7 in the summer, respectively.

In addition, the elevated THg concentrations in rice fields for dry deposition, surface soil (0-10 cm depth), and grains of rice (Oriza sativa), both brown (once milled) and white grains (twice milled), were 322µg m-2 day-1, 4244 µg kg-1dw, 1812 µg kg-1ww, and 1084 µg kg-1ww, respectively. The highest HQ values for dry deposition and surface soil were 7 and 42, respectively; whereas, THQ for brown and white rice grains for 70 kg bodyweight were 2 and 1, respectively. THQ values after brown rice consumption in some areas that exceeded the guideline (>1) indicated that those who eat the rice grains from this area are at risk for their whole life span.

Likewise, the concentrations of THg in summer were higher than those in the rainy season. In communities, the magnitude of THg concentrations for dry deposition, surface soil, cocoa meat and seed (Theobroma cacao), coconut meat and milk (Cocos nucifera L.), corn seed (Zea mays), and shallow well water were 501 µg m-2 day-1, 4765 µg kg-1dw, 1335, 1743, 1581 µg kg-1ww, 477 µg L-1, 327 µg kg-1ww, and 2.0 µg L-1, respectively. The highest values of HQ for dry deposit, surface soil, and shallow well water were 10, 48, and 3, respectively. All values exceeded the standard accepted by EPA (>1) whereas the highest THQ values of edible cocoa and coconut meat as well as corn seed for mercury consumption were lower, at 0.2, 0.2, 0.1, respectively. Thus, the foodstuffs in these areas were apparently safe for over whole life span of consumption.