Wet Dust Sampler—a Sampling Method for Road Dust Quantification and Analyses

Abstract

In northern countries, the climate, and consequently the use of studded tyres and winter traction sanding, causes accumulation of road dust over winter and spring, resulting in high PM 10 concentrations during springtime dusting events. To quantify the dust at the road surface, a method-the wet dust sampler (WDS)was developed allowing repeatable sampling also under wet and snowy conditions. The principle of operation is flushing high-pressurised water over a defined surface area and transferring the dust laden water into a container for further analyses. The WDS has been used for some time and is presented in detail to the international scientific community as reported by Jonsson et al. (2008) and Gustafsson et al. (2019), and in this paper, the latest version is presented together with an evaluation of its performance. To evaluate the WDS, the ejected water amount was measured, as well as water losses in different parts of the sampling system, together with indicative dust measurement using turbidity as a proxy for dust concentration. The results show that the WDS, when accounting for all losses, have a predictable and repeatable water performance, with no impact on performance based on the variety of asphalt surface types included in this study, given undamaged surfaces. The largest loss was found to be water retained on the surface, and the dust measurements imply that this might not have as large impact on the sampled dust as could be expected. A theoretical particle mass balance shows small particle losses, while field measurements show higher losses. Several tests are suggested to validate and improve on the mass balances. Finally, the WDS is found to perform well and is able to contribute to further knowledge regarding road dust implications for air pollution.

Temporal Variation of Road Dust Load and Its Size Distribution—a Comparative Study of a Porous and a Dense Pavement

“…The validity of the assumption of representative samples from WDS sampling can be discussed, since Lundberg et al (2019a) suggest a variable concentration over the sampling time compared to the assumption of a constant concentration. More particles are possibly collected during the beginning compared to the end of a shot.…”

“…There are different ways to sample road dust, mainly divided into wet methods like cleaning the surface with water as compared to dry methods like using suction, brushing or wind shear to move the particles from the surface to the sample (Amato et al 2009;Etyemezian et al 2007;Lundberg et al 2019a). In Sweden, the road surface is wet (or even snowy) during most of the winter season and the dry methods would not be useable as the wetness of the surface, and not the amount of dust on the road, is the main factor in determining the amount of dust collected.…”

“…Road dust was sampled using the own-developed Wet Dust Sampler (WDS) at both sites (Jonsson et al 2008;Lundberg et al 2019a). The sampling device is placed on the sampling surface, and a small circular area is sealed by the operator standing on the foot plate, pressing a cellular rubber ring into the road surface texture.…”

“…One such procedure will be referred to as a "shot" in the text. Settings used were water delivery stops after 5 s, sample transfer starts after 2 s and the full shot ending at 10 s, as used in previous studies (Gustafsson et al 2019b;Lundberg et al 2019a). Deionized water was used.…”

“…The calculations are based on the assumption, for dense pavements, that the particle concentration is equal in the collected sample and the water potentially retained on the sampling surface, see Lundberg et al (2019a) for more information. These calculations adjust the dust load by considering the water, and thus particles, lost during sampling.…”