Chemical Composition of the Hydro-Cryogenic System of Lake Baikal: “Snow on Ice–Ice–Water Under-Ice”

The results of studies of the chemical composition and the basic regularities of migration of macro- and microelements within the hydro-cryogenic system “snow on ice–ice–water under ice” obtained in the winter of 2016/17 in the waters of Lake Baikal are presented. Such investigation over the Lake area was carried out for the first time. It has been found that due to climatic conditions, dates of freeze-up (formation of the ice on the Lake) differ by 7–10 days from North to South, and the depth of snow on ice and its density change over the Lake area by 2 times, however there are some parts without snow. It was found that the changes in the pH indexes were identical across the whole Lake area – minimum pH values are present in the snow (from 5.59 to 7.39), average values – in the ice (6.01–7.50), and maximum values are noted in the water under ice (7.42–8.50). For the most part, increased quantities of suspended matter and an increase in the pH of snow were recorded near settlements, which is obviously a result of the anthropogenic influence. It was determined that the concentration of ions in the ice in relation to their content in the initial solutions decreases within the series: \({\text{NO}}_{2}^{ - }\) > Cl^– > \({\text{SO}}_{4}^{{2 - }}\) > \({\text{HCO}}_{3}^{ - }\). Among the cations, K⁺, Na⁺ ions are involved into the ice intensively, while the Ca²⁺ and Mg²⁺ – weakly. The ice phase is enriched with ammonium ions outside the settlements. Near settlements and in shallow water, quantity of salts in the ice may be close to or equal to their concentration in the water under ice. The coefficient of migration in the water (Kx) divide the chemical elements into two groups – the mobile ones and slow-moving elements. The first group includes Ca, Cu, Sr, Mg, Co, Zn, and Cd (Kx >1), the second one contains Ba, Mn, Si, Fe, Al, Ti, Ni, Cr, P, and K.