Conditions Affecting Wind-Induced PM10 Resuspension as a Persistent Source of Pollution for the Future City Environment

Abstract

Air pollution by particulate matter (PM) in cities is an ongoing problem with increasing severity. The biggest PM contributors are traffic and domestic fire burning. With the shift towards electromobility and the use of low-emission fuels, attention should be shifted to less mentioned sources of pollution. Such sources of pollution include wind-induced resuspension. This study focuses on determining the threshold wind speed causing the resuspension of particulate matter (TWSR) with aerodynamic diameter smaller than 10 µm. A methodology is introduced that examines how data could be treated to identify its characteristics (for locations where only PM10 data are available). The most significant monitored parameters are air humidity, wind direction, time of the day, and surface type. The characteristic wind speeds causing resuspension are identified in four locations for different times of day. It was proven that at times of intense human activity, particles are lifted by wind more easily. The mean threshold wind speed causing resuspension in the studied urban environment was identified as 1.58 m/s at a height of 2 m above the surface. The wind speeds were also compared with experimental studies of resuspension. The results proved correspondence between the identified wind speeds and the experimental results.

Identification of Wind-Induced Particle Resuspension in Urban Environment Using CFD Modelling

“…Ref. [6] reports a value of u * t = 0.11 − 0.21 m/s (specifically 0.11, 0.21, 0.16, 0.13 m/s). Similar values were also derived by [7,9].…”

“…The adhesion force in multilayer deposits is different from smaller particle clusters [62]. To determine the value of the threshold friction velocity, studies such as [6,27] can be used. The average threshold friction velocity is then u * t = 0.142 m/s.…”

“…The other increases, with its source being the particle resuspension [9]. The threshold wind speed causing resuspension was 1.58 m/s at a 2 m height [6].…”

“…The production of particles in cities, in combination with suitable surfaces, creates ideal conditions for this process. From roads, paved surfaces, and roofs, particles are lifted more easily than in the case of bare soil or green surface [6]. The contribution of wind-induced resuspension to the total pollution is difficult to determine.…”

“…Wind-induced resuspension was previously studied in a city environment by [6][7][8]. By evaluating long-term data series, these studies can determine when this process starts.…”