Physicochemical Properties of Road Dust in Moscow

Abstract

Road dust is a composite substance formed due to wear of different components of transport infrastructure and motor vehicles. In 2017, 214 road dust samples were collected in Moscow to analyze pH, electrical conductivity (EC), and organic carbon (Cоrg) content that controls the ability of dust to fix pollutants. The road dust was dominated by sand and silt size particles (the share of PM10 particles varies from 2.3% to 39%) and had alkaline pH (6.4–8.1), high EC (33–712 μS/cm) and Cоrg (0.17–6.7%). The road dust is alkalinized by detergents and particles formed by abrasion of roadways and blown out from construction sites. A three-fold excess of the EC over the background values (dust in parks) is mainly due to the use of the de-icing agents and roadway maintenance. But the concentration of Cоrg in the Moscow’s road dust is on average 2 times lower compared to the background values; the increased content of Cоrg in the courtyards is associated with the application of organic fertilizers. The most significant factor that determines the physicochemical properties of the dust was the type of a road. The dust on large roads including the Third Ring Road had higher pH (7.0–8.0) and EC (98–712 μS/ cm); it contained higher proportions of the fine particle-size fractions compared to other roads. The Cоrg content in the road dust was minimum on Moscow’s major radial highways due to the insignificant contribution of soil particles. The spatial trends in variability of the physicochemical properties of the dust in Moscow were not evident as they were to a large extent masked by other factors: proximity to industrial zones and large forest parks, differences in the de-icing agents used, unequal frequencies of road cleaning, and the various contribution of soil particles that vary in composition and genesis in different parts of Moscow.