№ 1 (2020)

In the aquatic ecosystem of Lake Baikal, global atmospheric transport is regarded as the dominant source of polychlorinated biphenyls (PCBs). Relatively high level of PCB concentration in the southern basin of the lake is associated with PCB influx from local sources. The waters of the tributaries of Southern Baikal, which have watershed basins on the slopes of the Khamar-Daban ridge, possess significant potential as a source of pollutants. The article presents the results of PCBs monitoring in the waters of the rivers Utulik, Solzan, Khara-Murin, Snezhnaya, and Pereemnaya in 2017 and 2019. PCB concentrations in the waters of the tributaries were estimated by the total concentration of seven indicator congeners Nos. 28, 52, 101, 118, 138, 153, and 180 (ƩPCB₇) in water samples taken at the estuaries of the rivers. The ƩPCB₇ level in the waters - from 0.02 to 1.5 ng/L, can be comparable to or exceed that in the littoral zone of the lake. An assessment of the removal of PCBs to the southern part of Lake Baikal indicates a minimal influx of pollutants of this class with tributary waters. In 2017, the number of PCB indicator congeners that entered Lake Baikal with water runoff was estimated to be between 1.7 and 3.1 g in May and between 7.7 and 26 g in September. In extreme conditions, the water runoff of PCBs can reach 40-170 g per month, like in September 2019.

Within the framework of the monitoring of the Baikal endemic sponge fauna, which was started in 2015, we organized field observations. This study is aimed to investigate the dynamics of the disease incidence in sponges and the rate of their degradation/regeneration in the natural environment within a limited space. The observations of the tagged sponges having different shapes were carried out using the photo and video method. Thus, from 2016 to 2018, there was a deterioration dynamics in the state of most control sponges. From 2018 to 2019, the state of some sponges improved owing to the regeneration of the affected areas of the body. In this study, we revealed that Baikal sponges with encrusted and globulous shapes could recover very quickly owing to the regeneration of the affected areas and the rapid growth of the body. After almost complete degradation of the body in the encrusted sponge, the fragments remain, which can subsequently grow as individual specimens. Similar observations are currently being conducted throughout Lake Baikal.

We present the results of long-term (2010-2017) studies of chemical composition of snow cover from the area of the Baikal Region. There is significant pollution of snow cover in the industrial cities of Pribaykalye (Irkutsk and Shelekhov). Some areas are the most subjected to the atmospheric pollution. The emissions from Shelekhov enterprises influence the chemical composition of snow cover in Irkutsk. Transport, fuel and energy complex mainly influence the formation of the chemical composition in snow cover from Irkutsk. In Shelekhov, the source of contaminants is the aluminium smelter (RUSAL-IrkAZ) and power engineering. Based on the data on snow surveys, we estimated the influx of pollutants from the atmosphere to the underlying surface of industrial cities and the water area of South Baikal.