We discuss here data on the near-ground aerosol particle number density collected from a whole day round measurement in Barnaul under unfavorable meteorological conditions of the early October, 1997. The atmospheric situation in Barnaul during this period was characterized by high pollution of the atmosphere with smoke aerosol from the forest fires. The results obtained are indicative of aerosol accumulation in the central part of the city, on the side of the river valley, under conditions of inversion layer formation at night. The data collected enabled us to calculate the median diameter of aerosol particles and the polydispersity parameter of the aerosol. Their connection with the processes in the ground atmospheric layer is discussed.