This paper presents the results of measurements of the optical characteristics of aerosol particles using a solar photometer and nephelometer from 2016 to 2021 obtained at the atmospheric monitoring station in Peterhof (59.88° N, 29.83° E). The measurements are compared with the MERRA-2 reanalysis data. It is
shown that interseasonal variability is observed in the region, characterized by low values of the Angstrom exponent in winter and high values in the warm season. The backscatter fraction has a similar—but less pronounced—seasonal cycle. The average value of the turbidity coefficient for the period is less than 0.10, which makes it possible to determine the observation station as a background one. Using the HYSPLIT model, the origin of air masses forming the atmospheric air state at the observation station is determined when the limiting
values of the measured scattering coefficients (<10 and >70) and the Angstrom exponent (<1) are realized. Air masses coming from the northwest correspond to clean and humid air from the marine area and are manifested in the minimum values of the measured parameters. The maximum values of the scattering coefficient are associated with fine aerosol entering the atmosphere both from regional emissions sources (urban pollution from the territory of St. Petersburg) and as a result of transboundary transport from southwestern directions.