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Abstract. The results of direct observations of fine mineral dust aerosol (0.15-15 µm) were carried out on extensive sand areas in desertificated lands of Kalmykia in 2007Kalmykia in , 2009Kalmykia in , and 2010 under conditions of weak wind and strong heating of the surface, almost in the absence of saltation processes. These results show that the fine mineral dust aerosol (0.15-0.5 µm) in the region under consideration contributes considerably to the total aerosol content of the atmospheric surface layer. Data on the mass concentrations of fine aerosol are treated on the basis of physical model estimates obtained for fluid dynamic parameters in the viscous thermal boundary layer near the ground surface. Deviations of these mass concentrations from their background values are related to a temperature drop in the thermal layer at the surface and from the values of friction velocity. For small and moderate values of friction velocity, these mass concentrations increase proportionally to a temperature drop with an exponent of about 0.5, and, for high friction velocities, this exponent becomes negative (∼−0.5), which implies a decrease in these concentrations with an increase in a temperature drop.

The results of an intensive complex experiment carried out from March 25 to May 3, 2020, to study the composition and time variability of urban aerosol in the atmosphere in the center of Moscow include data on daily mean concentrations of both РМ 10 and РМ 2.5 particles and 65 chemical elements. The concentrations of all components did not exceed the maximum permissible concentration (MPC) for residential areas. The exception was increased РМ 10 concentrations recorded on March 27–29, when air masses from neighboring regions with biomass fires arrived in the city. The coefficients of correlation between values of the concentrations and enrichment factors of the elements confirmed the anthropogenic/local origin of some heavy metals (Cd, Sb, Pb, Se, Th) and the terrigenous/global origin of elements such as Mn, Mg, Zn, Co, Fe, Al, and Cr. The elements S, P, K, Na, Ca, Ni, Cu, Mo, Sn, W, Bi, and U, for which no significant correlation between their concentrations and enrichment factors has been found, apparently, have a mixed origin from both natural and anthropogenic sources competing with each other from day to day. The first studies of the weekly cycle of the relative elemental composition of surface aerosol in Moscow have shown the leading role of meteorological conditions (in particular, air pressure and humidity) in variations of aerosol pollution levels.

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