The behavior and environmental impact of mercury released through the human activity

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The chemical forms of mercury in water and sediment in Idrijca river were investigated. Fresh river water and sediment samples were collected from 4 locations in 2003, and 5 locations in 2004.T-Hg, RHg and Hg^0 concentrations in water were 4.8 - 312 ng/l, 0.77 - 164 ng/l and 0.13 - 66.5 ng/l, respectively. The highest concentrations of the individual species were recorded in the sample taken from the nearest point of the mine and their concentrations decreased with distance from the mine. MeHg concentration in river water was 0.058 - 0.588 ng/l and the highest MeHg concentration was observed at a point about 1 km lower leaches of the mine. In order to estimate the release of mercury from sediment into water, sediment was taken from 5 locations with river water in plastic bottles. The bottles were filled with the sample at the sites, brought back to laboratory and stored at room temperature. After 5days, the water overlying sediment in the bottle was separated into three parts, that is, supernatant layer, suspended layer and pore water. Water in suspended layer was used for mercury determination after centrifugation. The supernatant layer and pore water were filtered (0.45 μm Millipore filters) to determine dissolved T-Hg and MeHg. T-Hg and MeHg concentrations in the waters were 2 - 119 times and 19 - 1357 times higher than that in fresh river water, respectively. The observation suggested that the river sediment could become significant source of mercury in river water. To understand the different behavior between MeHg and other mercury species in the river, kinetic investigations will be required.