ИСТИНА

The Selenga River, which originates in Mongolia, contributes about 50 % of the total inflow into Lake Baikal. Together with the Angara and Yenisey rivers it forms the longest river network in Eurasia. Mining, industrial and agricultural activities within the Selenga drainage basin affect the sediment influx and transport along the river and its tributaries. Novel screening campaigns were conducted in June–August 2011-2012 in both the Russian and the Mongolian parts of the Selenga river basin. Discharge and suspended sediment concentration (SSC) data were combined to yield estimates of daily and monthly suspended load averages at more than 150 locations. The chemical analysis of large number of chemical elements (heavy metals et al.) in water, sediments (riverbed and suspended) and aquatic plants was done mainly by ICP method. The conducted monitoring and modeling characterize the spatial variations of suspended load and its characteristics (SSC, grain size, organic matter) over river basin summer season. The increasing human activities (mining and pastures) increases the portion of fine-grained clay particles in total sediment load. Empirical data and modeling results showed that flow peaks carry very high sediment loads. Main sources of sediment pollution of Selenga river are related to industrial and mining centers. Main output of the work is that the rapid urbanization and clear cutting of forests, open gold- and other metal-mining activities that are typical for Central Asia have a profound impact on suspended sediment load of the Selenga river.