Along with house heating and industry, emissions from road traffic (exhaust and tire, brake, car body or road surface abrasions) are one of the primary sources of particulate matter (PM) in the atmosphere in urban areas. Though numerous regulations and vehicle-control mechanisms have led to a significant decline of PM emissions from vehicle exhaust gases, other sources of PM remain related to road and car abrasion are responsible for non-exhaust emissions. Quantifying these emissions is a hard problem in both laboratory and field conditions. First, we must recognize the physicochemical properties of the PM that is emitted by various non-exhaust sources. In this paper, we underline the problem of information accessibility with regards to the properties and qualities of PM from non-exhaust sources. We also indicate why scarce information is available in order to find the possible solution to this ongoing issue.

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Road dust is an important inexhaustible source of particulate matter from traffic and the resuspension of finer particles carried by wind and traffic. The components of this material are of both natural and anthropogenic origin. Sources of particulate pollution are vehicles and road infrastructure. The work aimed to analyze the mass fraction of the finest fractions of road dust (<0.1 mm) collected from highways and expressways with asphalt and concrete surfaces. Sampling points were located in the central and southern parts of Poland. The research material was sieved on a sieve shaker. It has been proven that concrete pavement is less susceptible to abrasion than asphalt pavement. Particles formed under the influence of the erosion of asphalt and concrete belong to the fraction gathering coarser particles than the critical for this research fraction (<0.1 mm). It was found that limiting the area with sound-absorbing screens leads to the accumulation of fine road dust in this place, contrary to the space where are strong air drafts that remove smaller particles from the vicinity of the road. In general, the mass fraction of particles smaller than 100 μm in road dust was from 12.8% to 3.4% for asphalt surfaces and from 12.0% to 6.5% for concrete surfaces.

Based on literature data, the percentage contribution of road traffic to concentrations of particulate matter (PM) and PM-bound elements, separately for PM2.5-10 and PM10-100 fractions were assessed. The data on the PM2.5-10 and PM10-100 concentrations examined simultaneously at two locations (the 1 st outside the direct impact of the road emission; the 2 nd next to a crossroads or highway) were used in the analysis. There were clear differences in the concentrations of PM and its components between these locations (a crossroads vs. background; highway vs. background). Both PM concentrations and concentrations of the majority of the PM2.5-10-and PM10-100-bound elements had higher values in the traffic site. The percentage increase of PM concentrations was in the range from 25 (PM2.5-10; highway) to 606% (PM10-100; crossroads). The highest percentage increase in the concentration of elements was noted at the crossroads, where concentrations of PM10-100-bound Si, Sc, Fe and Pb were 12, 22, 25 and 71 times higher than at the urban background site, respectively. The measurable results of this paper are elemental profiles of two coarse fractions of PM in the vicinity of the road and crossroads and at sites far apart from the big road traffic sources. The collected information can be an important source of knowledge in identifying the origin of PM in the receptor.