The article analyzes the chemical composition (ions, elements, and polycyclic aromatic hydrocarbons) of the atmospheric aerosol in the near-water layer of the atmosphere above Lake Baikal during wildfires in Siberia. Aerosol deposition affects the aquatic environment of the watershed basin and the lake itself. The current law on Lake Baikal limits the activity of the permanent stationary anthropogenic sources of the aerosol in the central ecological zone, and they do not have a significant negative impact. Wildfires can have a much greater impact on the environment. Smoke emissions entering the area of Lake Baikal due to wildfires change the chemical properties of the atmospheric aerosol and increase its mass and number concentration. The concentrations of NH₄⁺, K⁺, NO₃⁻, and SO₄²⁻, which enter with submicron aerosol fraction, increase in the ionic composition of the aerosol. The composition of polyaromatic compounds changes, and their concentrations increase. Elevated concentrations of B, Mn, Zn, As, Sr, Cd, and Pb in the composition of aerosol indicate the influx of air masses from the areas prone to wildfires. Despite the sporadic effects of these natural factors, they affect the pollution of various Baikal ecosystems, especially small tributaries of the lake, whose main supply is atmospheric.

The results of long-term routine measurements of the concentration of major ions in the water of the Lake Baikal pelagic zone, the Angara River source, and main tributaries of the lake are analyzed....

Recent studies have revealed how the freshwater biota of Lake Baikal responds to climate change and anthropogenic impacts. We studied phyto- and zooplankton, as well as phyto- and zoobenthos, in the open coastal waters of the southern basin of the lake and of Listvennichny Bay. A total of 180 aquatic organism taxa were recorded. The response of the Baikal ecosystem to climate change can be traced by changes in the species composition of planktonic communities of the lake’s open coasts in summer. The key species were thermophilic the Anabaena lemmermannii P. Richt. (F_ij = +0.7) blue-green algae, the Asplanchna priodonta Gosse (F_ij = +0.6) rotifers in 2016, the Rhodomonas pusilla (Bachm.) Javorn. (F_ij = +0.5) cold-loving algae, and the Cyclops kolensis Lilljeborg (F_ij = +0.9) copepods in the past century. The proportion of Chlorophyta decreased from 63% to 17%; the Cyanophyta increased from 3% to 11% in the total biomass of phytoplankton; and the proportion of Cladocera and Rotifera increased to 26% and 11% in the biomass of zooplankton, respectively. Human activity makes an additional contribution to the eutrophication of coastal waters. The Dinobryon species, the cosmopolitan Asterionella formosa Hass. and Fragilaria radians Kütz., dominated phytoplankton, and filamentous algae, Spirogyra, dominated at the bottom in the area with anthropogenic impact. The trophic level was higher than at the unaffected background site: the saprobity index varied from 1.45 to 2.17; the ratio of eutrophic species to oligotrophic species ranged from 1:2 to 3:1, and the ratio of mesosaprobiont biomass to endemics biomass ranged from 2:1 to 7:1. Currently, the boundaries of eutrophication zones of shallow waters in Lake Baikal are expanding, and its coastal zone has acquired features typical of freshwater bodies of the eutrophic type.

Eutrophication is a major ecological problem and affects and endangers freshwater bodies, making assessment of the trophic status of water bodies crucial for their restoration and sustainable use. Lake Baikal is affected by a number of environmental stressors, including coastal eutrophication. Daily measurements of concentrations of nutrients, dissolved oxygen (DO), chlorophyll-a (Chl-a), weekly measurements of algae abundance and biomass in the open water season in June-December 2020, and measurements of concentrations of nutrients at 2–7-day intervals in June-October 2021 were made in the littoral of the South Baikal for the first time. It was shown that nitrate and phosphate concentrations decreased by July-August, their minimum content was maintained until September, concentrations began to increase in October and reached a maximum in December. The maximum abundance and biomass of algae and chlorophyll concentrations were only observed in early July. Storm situations increased the content of nitrogen, phosphorus and DO in water, the duration of their influence was not more than 2 days. A correlation matrix revealed significant positive correlations of NO₃⁻-DO, phosphate (SPR)-NO₃⁻, SRP-DO and biomass-Chl-a and strong negative correlations between water temperature (Tw)-DO, Tw-NO₃⁻, Tw-total nitrogen (TN) and Tw-SRP. Based on SRP and NO₃⁻ concentrations and TN:TP ratios, it was concluded that algal development was limited to nitrogen and phosphorus in summer. The trophic status of the Southern Baikal littoral zone was assessed using classifications based on TN, TP, NO₃⁻, SRP, Chl-a content and algal biomass, as well as the Carlson index (TSI) and probabilistic assessment. The results of assessments using different methods of trophic status determination showed that the Baikal littoral zone in the study area belongs to the oligotrophic type with minor elements of mesotrophy. According to the saprobity index, water purity of littoral waters varies within the oligosaprobic and β-mesosaprobic zones and corresponded to quality classes II and III (clean and moderate purity); the system demonstrates a high capacity for self-purification.

The aim of this study was to identify particulate matter (PM) sources and to evaluate their contributions to PM in the snowpack of three East Siberian cities. That was the first time when the PM accumulated in the snowpack during the winter was used as the object for source apportionment study in urban environment. The use of long-term integrated PM samples allowed to exclude the influence of short-term weather conditions and anthropogenic activities on PM chemistry. To ascertain the real number of PM sources and their contributions to air pollution the results of source apportionment using positive matrix factorization model (PMF) were for the first time compared to the results obtained using end-member mixing analysis (EMMA). It was found that Si, Fe and Ca were the tracers of aluminosilicates, non-exhaust traffic emissions and concrete deterioration respectively. Aluminum was found to be the tracer of both fossil fuel combustion and aluminum production. The results obtained using EMMA were in good agreement with those obtained using PMF. However, in some cases, the non-point sources identified using PMF were the combinations of two single non-point sources identified using EMMA, whereas the non-point sources identified using EMMA were split by PMF into two single non-point sources. The point sources were clearly identified using both techniques.

Atmospheric deposition is the process of migration of pollutants from the atmosphere to the land surface. The data on it can be used to assess the ways of