ИСТИНА

The first data on the heavy metals and metalloids (HMM) content in aquatic systems of the Lake Baikal main tributaries were obtained by the Baikal Expedition of Russian Geographical Society in July and August of 2017 (fig. 1). Water and suspended sediment were sampled in river mouths of Barguzin, Chivyrkuy, Malaya Cheremshana, Bol’shaya Cheremshana, Sosnovka, Bolshaya, Yazovka, Kabanya, Shegnanda, Turali, Frolikha, Holodnaya, Kichera, Tyya and Verkhnyaya Angara rivers. The enrichment factor was calculated for the suspended and dissolved forms of chemical elements as follows: EF = [X]/[WA], where [X] represents the measured concentration of element X and [WA] – its average concentration in world rivers. Both dissolved and suspended HMM content in the rivers were found rather low. Only dissolved Zn and Mo at most sampling stations exceeded average concentrations for non-contaminated world river waters (Gaillardet et al., 2003) 3 times and more. Dissolved Cu, Li, Ba, Pb and W were slightly higher than world average values only in few points related to Holodnaya (Cu), Kichera (Li, Ba), Yazovka (Li, W), Malaya Cheremshana (Ba) and Frolikha (Pb) rivers. Suspended forms of HMMs were found much higher than the world average (Viers et al., 2009). Thus, Mn, Li, Na, Sn, Sb, Ba were found in rather high concentrations (EF > 3,5) at the most stations. Extremely high amounts were found for Cd and U (EF > 100), Mn, Te, W, Sn, Ba, Sb, Zn, Na, Fe, Pb (50 > EF > 10). Highest concentrations were revealed in Shegnanda (U, Te, Sn, Ba, W, Sb with 100 > EF > 10), Holodnaya (Sn, Te, Na, Ba, W, Pb, U with 35 > EF > 10) and Tyya (Na, Pr, Nd, Sm, La, Li with 10 > EF > 5) rivers. Whereas chemical elements in these rivers migrate mostly in dissolved forms, another group with prevailing suspended forms can be defined: Al, Ti, Mn, Fe, Zr, La, Ce, Pr, Nd, Sm, Gd. The third group consists of elements with a quite changeable predominant form of migration. The share of suspended forms for Be, Ga, Y, Nb, Cs, Yb, Th varies from 6 to 98%.