MERCURY CONTAMINATION IN THE NORTHERN PANTANAL REGION MATO-GROSSO, BRAZIL

In gold mining areas around the world, mercury is used to separate gol d by amalgamation. This often causes mercury contamination. Such a sit uation near the goldmines in the Pocone area, Mato Grosso, Brazil was investigated. Concentrations of mercury were determined in water, sedi ment and air. The results obtained in water showed elevated mercury co ncentrations of between 18 and 160 ng/1 (filtered) compared to 25 +/- 0.9 ng/1 in a reference site. In sediments, total mercury concentratio ns were in the range from 23 to 198 ng/g (dw). Results of speciation a nalyses in water and sediment samples from two small rivers showed tha t only 10 to 50% of the mercury is easily reducible. At the beginning of the rainy season, volatile mercury concentrations of up to 8 ng/l r esulted from leaching the tailings by the rain. In the ambient air nea r the gold mine region, concentrations of up to 6 ng/m3 mercury were d etected. Two meters above contaminated tailings, the values found were ten times higher. These results provide first information on transfor mations of mercury species and their pathways under tropical condition s.