15 - Mercury distribution in the bottom and stream sediments of Lake Baikal,water reservoirs of the Angara river cascade, and adjacent drainage basins

Abstract

The anthropogenic mercury input into the global environment is comparable in scale with the natural flows of the pollutant in recent biosphere wheels, and the primary concern in this regard are the atmospheric fluxes and pollution of aquatic systems by industrial sources. The pollution of aquatic systems is especially harmful to people and wildlife because of the greater methyl mercury accumulation. This chapter summarizes data on mercury (Hg) distribution in the bottom and stream sediment of Lake Baikal and adjacent areas of Siberia that are strongly endangered in terms of technogenic Hg emission into the environment. Cold vapor atomic absorption spectrometry was used to make the measurements (detection limit 2: ppb). The silt fractions with particles smaller than 0.04 mm were the main Hg concentrators in sediments and suspended matter in waters. In polluted waters, their Hg concentration was one order higher (up to 3,500–4,500,000 ppb) than in the sand–aleurite fractions. The relatively weakly bound portion of Hg in polluted sediments and suspended matter was much greater than in natural sediments and suspensions. In general, the region can be considered a low Hg pollution area, except for the basins downstream of the Irkutsk dam, where the Hg pollution problem is very real. The available data highlighted the problem of Hg pollution in the regional environment, and provide key topics for the further scientific investigations, the mode of Hg occurrence in the main natural and manmade reservoirs and routes of migration, Hg balance in particular geochemical cycles, and approaches to conserve and rehabilitate extremely polluted sites.