Background concentrations Hg in lakes Khanty-Mansi Autonomous Area, Russia

Abstract

The materials of the study: the background concentrations of mercury dissolved in water and precipitated in bottom sediments of the 95 lakes. Methods: a total of 332 samples of lake sediments and 37 samples of lake water were collected during the background ecological monitoring of petroleum deposit areas between 2007–2011. Results: The mean background concentration of mercury had values of 0.046±0.012 mg/kg and 0.025±0.014 mg/kg in lake bottom sediments and waters, respectively. The highest concentrations of Hg were found in the eluvial and transeluvial positions, the lowest – in superaqual landscapes. The highest concentration of Hg in lake bottom sediments was found in string bogs (ridge-hollow-pool complex bogs) and the lowest – in mineral soils. There is a general tendency to for an increase the concentration of mercury in the bottom sediments of lakes from the tundra zone through the northern taiga to the middle taiga subzone. However, the middle taiga was characterized by a significant (R = 0.4) increase in Hg concentrations in the bottom sediments from the south to the north due to an increase in the proportion of string bogs in the same direction. Dissolved mercury concentrations significantly (R=0.6) increased from the west to the east The assessment of seasonal dynamics of mercury contents showed that Hg concentrations in bottom sediments significantly increased during the winter.