The paper examines the features of aerosol optical depth (AOD) variations over the Baikal region. The data from expeditionary measurements conducted between 2018 and 2022 were used, obtained using a portable photometer called SPM, developed at the Institute of Atmospheric Optics of the SB RAS. The study analyzes the AOD optical characteristics, the fine and coarse AOD components, the Ångström parameters, and the retrieved aerosol microstructure parameters. It is demonstrated that aerosol pollution during the summer season is caused by an increase in the concentration of fine aerosol particles. The mean/modal AOD values in the short-wavelength range of the spectrum exceed the mean AOD values for the Baikal region by a factor of 3-8.