Elemental composition of sediments on exterior window surfaces along vertical gradient in Moscow

Despite numerous studies on the spatial distribution of pollutants in urban environments, little is known about their vertical profile. The presented research aims to analyze loadings and concentration of elements sedimented on exterior glass window surfaces of a high-rise building in Moscow city. The roadside part of a typical 17-level building was examined. Window sediments were collected along vertical from the 2nd to the 17th level using the novel instrumental approach of wet vacuum dust collection. A clear declining trend of sediment weight distribution was observed along the height increase. The values decreased by six times within 40-m vertical, from the 3rd (386 mg m^-2) by the 17th level (63 mg m^-2), driven by a decline of coarse dust fraction. Organic matter, Si, and Ca were the key contributors to the window sediments, providing 40%, 15%, and 4% in total weight, respectively. Among other elements, the highest proportions (over 1%) were identified for S, Fe, and Al, whereas little less (0.5-1%), for Mg, K, and Na, individually. Other element concentrations decreased in the following order P > Zn > Mn > Cu > Ba > Sr > Cr > V > Ni > Pb > Co > As>Cd. Element concentrations did not differ along vertical gradient due to the constant proportion of the finest dust fraction. Window sediments were characterized by 2-4 times higher concentrations of most of the studied elements than the road dust, being enriched by S, Na, Zn, and Cu - 27, 15, 10, and 6 times higher, respectively. Based on the strong correlation between the composition of road dust and window sediments, we consider resuspension of the road dust as a predominant source of particles sedimented on window glass surfaces and its enrichment by non-exhaust traffic-related elements. The research proved the validity of the suggested instrumental technique for sediment collection from window glass surfaces. Elemental analysis of window sediments was considered as a promising approach for environmental studies.