Variability of Concentration of Aerosol Particles, Polycyclic Aromatic Hydrocarbons, and Polychlorinated Biphenyls in the Atmosphere above the Surface of Lake Baikal

This article presents the results of temporal and spatial distribution of aerosol particles and microadmixtures included into them (polycyclic aromatic hydrocarbons and polychlorinated biphenyls) in the near-water layer of the atmosphere above Lake Baikal obtained during a ship expedition from July 18 to July 24, 2022. During the study period, in the lake near-water atmosphere, for the most part, low values of mass and number concentration of aerosol particles and resistant organic pollutants (polycyclic aromatic hydrocarbon (PAHs) and polychlorinated biphenyl (PCBs)) were observed when compared to the fire hazard periods of 2016–2020. During the expedition, the PAHs content in the atmosphere varied from 0.071 to 2.6 ng/m3, which is lower than the concentrations established during the fires (0.22–133 ng/m3). Increased concentrations of the studied components were found only in some areas of southern Baikal, where the formation of aerosol structure occurred due to local pollution sources situated in the populated near-shore areas (namely, Listvyanka, Kultuk, Slyudyanka, and Baikalsk) and at the moment of transfer of polluted air masses northwestward to the lake from Irkutsk and Angarsk. In the aerosol samples from background areas, a PAHs group with two or three benzene rings dominated mainly by naphthalene and phenanthrene. Near local sources in the southern part of Lake Baikal, the proportion of PAHs with four, five, and six benzene rings (fluoranthene > pyrene > benz(b)fluoranthene) increased; they are of pyrogenic origin and are formed at high temperature processes of organic fuel combustion (while combusting coal, wood, and liquid fuel). We revealed a positive correlation between the content of aerosol particles and PAHs. The concentrations of aerosol particles (1.0–13.7 µg/m3) and benz(а)pyrene (0.01–0.22 ng/m3) rated in Russia did not exceed the MAC. Despite the prohibition of production and limited use of PCBs, their traces were found in various industrial and background regions worldwide. It is shown that polychlorinated biphenyls content in Lake Baikal near-water atmosphere (0.48–5.63 pg/m3) is comparable to the concentrations observed in background regions worldwide (0.04–25 pg/m3).