Study of aerosol absorption and hygroscopic properties in the atmosphere of lake Baikal in summer 2024

The paper presents the results of studies of the microstructure and physical-chemical properties of near-water aerosol in the atmosphere of the Lake Baikal in summer of 2024 on board the research vessel "Akademik V.A. Koptyug". It is confirmed that in the absence of smoke plumes from forest wildfires, the spatial distribution of aerosol over the lake surface, as well as the content of black carbon in particles, are determined by arrangement of anthropogenic sources. The characteristics of hygroscopicity and volatility of the aerosol matter in the atmosphere of Lake Baikal, depending on the particle size, are presented for the first time. The enhanced values of the optical parameter of condensation activity were observed in the northeastern part of the lake (clear background areas), and the lowest were in the southwestern part, where the influence of anthropogenic pollution is high. The revealed features of aerosol hygroscopicity in different parts of the Baikal region are in agreement with the data on its chemical composition. The same differences between clear and polluted areas are characteristic of the parameter of condensation activity for the radius of the smallest registered fraction of particles. The dependence of this parameter on the particle radius is characterized by maximum values and the greatest variability in the submicron range and a sharp decrease with increasing radius. The contribution of large particles r>2 μm to the condensation activity is less than 0.05. 

High values of the highly volatile fraction of aerosol matter are observed in the regions with low turbidity, and non-volatile, on the contrary, are observed at high turbidity. A characteristic feature of the dependence of thermal parameters on particle size is a decrease in the relative content of volatile species and, accordingly, an increase in the proportion of non-volatile substances with increasing radius. 

The development of the methods and devices was carried out within the framework of the state assignment of the IAO SB RAS, project No. 121031500342-0; Expedition, processing and analysis of results were carried out with the support of the Russian Science Foundation grant No. 19-77-20058-P.