Assessment of Mercury Contamination in the Kahayan River, Central Kalimantan, Indonesia

From 2004 to 2007 we studied the contamination of the Kahayan and Rungan Rivers in Central Kalimantan, Indonesia, by mercury used in the processing of mined gold. Water, sediments and fish species were collected from both rivers. Total mercury concentration was determined by cold vapor atomic absorption spectrometry (CVAAS). In the Kahayan River and its tributaries, the highest total mercury concentration in water samples was 2260 ng/l. In sediment samples, the concentration ranged from 0.002 to 0.095 ng/mg dry wt. In the Rungan River, the total mercury concentration in water samples ranged from 16 to 117 ng/l and in sediment samples from 0.003 to 0.253 ng/mg dry wt. The highest total mercury concentration in a water sample came from a tributary of the Kahayan River; the level was higher than Indonesia's drinking water standard for total mercury (1000 ng/l). However, total mercury concentrations in water samples from both main rivers were lower than the standard. The sediment sample mercury concentrations from both rivers were lower than the USEPA quality guideline. Total mercury concentrations in fish obtained from both rivers ranged from 0.02 to 0.48 ng/mg wet wt. Mystus nemurus had a total mercury concentration close to the USEPA guideline value for fish for human consumption.