Particulate air pollution in cities is caused by a variety of sources. One of the less-studied contributors is wind-induced particle resuspension. As the wind speed increases, particles are removed from surfaces. These particles cause an increase in the total concentration in the air. It is known that particles of 10-2.5 μm in size can be resuspended (PM10-2,5). Modern emission monitoring in cities also allows the monitoring of fine particles of 10, 2.5 and 1 μm in size. The size fractions can then be sorted into PM10-2,5, PM2,5-1 and PM1. When breathed in, particles of different sizes cause various serious health risks. This paper focuses on the identification of the resuspension process of different particle size fractions by a data processing method. Data measured by automatic emission monitoring are used. It is confirmed that the concentration increase can be dominated by the fraction PM10-2,5. However, a concentration increase of fractions PM2,5-1 and PM1 is also evident with increasing wind speed. Although the increase in the PM1 fraction is smaller than PM10-2,5, it is more severe due to the respiratory deposition dose. The resuspension of particles of different fractions has different behaviours during the year. PM10-2,5 particles are dominantly resuspended in the summer months. In winter, on the other hand, the proportion of PM2.5-1 and PM1 particles increases, which may be related to the heating season
Air pollution by particulate matter (PM) in urban environment is an ongoing problem with increasing severity. With the gradual evolution of electromobility and lowemission heat sources, the focus is shifting to non-exhaust PM emissions. Wind induced PM resuspension is one of them. This source is hardly amenable to mitigation measures. It was assumed, that only coarse PM (PM10-2,5) can be lifted from the ground by the wind. By the evaluation of the long-term data series, we can divide the PM10 concentration to its fractions PM10-2,5, PM2,5-1, PM1 and evaluate their behaviour. The aim of the work was to evaluate the data in order to recognize the resuspension process, even with a fine fraction, PM1. The data were then compared with the NOx values to determine if the PM originated from combustion processes. The original assumption of a correlation between NOx and PM1 was not confirmed in most cases. The results show that in some cases coarse PM are dominantly associated with NOx. The correlation of fine and coarse particles with NOx in resuspension process depends primarily on the time period of the day.
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.
Air pollution caused by particulate matter (PM) is a current problem in many cities. With the introduction of strict emission limits and electric cars, lower particle production is expected in the future. However, there are sources of particles that cannot be easily influenced. These include resuspension, where particles deposited on surfaces re-enter the air, causing pollution multiple times. Resuspension can account for up to 18% of the total emissions in some cases. The present paper focuses on the use of the computational fluid dynamics (CFD) tools to describe the flow in a street canyon where resuspension by wind occurs. Based on the calculated flow, a resuspension model is applied to see where resuspension occurs and how far the particles can travel. The shear stresses on the surfaces and the character of the flow field in the boundary layer are evaluated. Different building configurations and flow parameters are tested using a simple 2D model. The model makes it possible to see in which parts of the street canyon resuspension can occur. It shows that the particles leave the street canyon only from the surfaces where the conditions are suitable for resuspension. These particles then enter the mainstream. However, most of the particles stay in the canyon, which can cause resuspension to pollute the air repeatedly. This effect can have a severe impact on human health. The total dispersion of particles in the urban environment is evaluated. The results may be useful for cities that clean the streets, as it is clear which areas will benefit most from the cleaning.
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