Water Chemistry in Small Tributaries and the Coastal Zone of Lake Baikal in the Period of Environmental Crisis

In the context of the environmental crisis observed in recent years in some areas in Baikal coastal zone, water chemistry was studied in June 2018 in seven points in this zone at different distances from populated localities and in six small tributaries of the lake. To compare data on different biological seasons lake water sampling was repeated in August–September 2019 in four previous and five additional points. Water mineralization was found to be minimal in the southern Baikal. The total mineralization of Baikal water remained relatively low, not exceeding the background values in previous decades; the concentration of environmentally hazardous elements is also low, except for the higher concentration of strontium in the thermal water of the Goryachinskii Creek. On the other hand, Baikal water in most points showed higher nitrogen content, and anomalously high phosphate concentration (0.413–0.941 mg/L) was recorded in the middle part of the lake (Barguzin Bay at Maksimikha Settl., at Svyatoi Nos Peninsula, and at Bol’shoi Ushkanii Isl.). Considerable enrichment of Baikal water by nutrients, which can provoke extremely high values of alga biomass in late summer and early autumn, was recorded not only near populated localities but also far from them and was not caused by inflow of these elements from tributaries. The sources of these pollutants are to be identified. In the late August–early September 2019, in the period of active consumption of phosphorus by summer phytoplankton and bottom algae, the concentration of phosphates in Middle Baikal decreased, remaining elevated (0.09 mg/L) near Maksimikha, but it abruptly rose (1.33 mg/L) in the thermal Goryachinskii Creek. In that period, water near Slyudyanka City (the southern part of the lake) was rich in nitrates (1.67–1.94 mg/L); their concentration was highest near Maksimikha (2.39 mg/L). The high concentration of nutrients in Baikal water requires extensive comprehensive measures to be taken to reduce the anthropogenic load onto lake ecosystem.