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Long-term dynamics of total mercury in surficial bottom sediments of the Volga River’s reservoir in central Russia

Udodenko, YuryG., Komov, ViktorT., Zakonnov, ViktorV.
Environmental monitoring and assessment 2018 v.190 no.4 pp. 198
mercury, organic matter, rivers, runoff, sediments, watersheds, Russia
The long-term dynamics of mercury in bottom sediments of Uglich Reservoir were examined. Samples of the 0–5-cm surface layer of bottom sediment collected during research expeditions in 1958, 1977, 1991, and 2012 were analyzed. An increase in the average mercury concentration from 1958 to 1977 (0.440 ± 0.039 and 0.668 ± 0.065 mg/kg d.w., respectively) was followed by a decrease in 2012 (0.260 ± 0.021 mg/kg d.w.). During all years except 1991, a significant correlation was found between mercury content and the amount of organic matter in the sediments (r = 0.54–0.87, p < 0.01), flow velocity (r = 0.38–0.53, p < 0.01), and the rate of sedimentation in the reservoir (r = − 0.51 to − 0.69, p < 0.01). Calculations based on these results and previously published data from the study region on the density of atmospheric mercury precipitation showed that the watershed as a whole received 2.4–3.0 t on an annual basis, and in the same period, the water surface received 9.7–12.8 kg of mercury. The bottom sediment contained 4.31 (2012)–7.40 (1977) tons of mercury. Thus, most of the mercury in the Uglich Reservoir is assumed to originate from runoff and terrigenous sources within the watershed.