Road dust resuspension

To date, research on non-exhaust emissions has been rather limited due to the difficulties encountered by experimentalists and modellers to characterise and describe the complex phenomenon of road dust resuspension and wear emissions. 

Thorpe et al. [116] proposed the roadside incremental concentration of coarse particles above the urban background as a first estimate of the sum of source strength road dust resuspension and the coarse fraction of wear emissions. Other studies succeeded in separating different traffic emissions by means of multivariate receptor models applied to PM size distribution data ([84, 117]. 

In dry climates such as South European countries, the low and infrequent precipitations hamper the wash-out and the moistening of road surface, favouring road dust resuspension by traffic-induced turbulence. Moreover additional inputs of dust come from the urban soil resuspension due to the little vegetal covering and from sporadic intensive deposition of Saharan dust outbreaks or uncontrolled construction/demolition activities. 

Modelled contributions were validated against mineral dust observations across Europe, revealing a significant improvement in spatial variation when compared to the mineral dust modelling without emission without road dust resuspension. The temporal variation needs improvement as the dependency of resuspension source strength on day-to-day meteorology is crudely parameterized. 

With the abovementioned technique Hendriks et al. [30] estimated that road dust resuspension contribute around 10-15% of modelled PM10 on a European scale and up to 30% in densely populated area of South Europe (Fig. 5). These estimates are relative to the modelled concentrations, which are lower than observed ones due to uncertainties in primary organic emissions and the lack of secondary organic compounds. However, this overestimate is probably compensated by the fact that in the model, peak contributions (in cities) are not captured due to the model resolution (25 x 25 km). 

Amato F, Pandolfi M, Escrig A, Querol X, Alastuey A, Pey J, Perez N, Hopke PK (2009) Quantifying road dust resuspension in urban environment by Multilinear Engine a comparison with PMF2. Atmos Environ 43 2770-2780... 

Amato F, Karanasiou A, Moreno T, Alastuey A, Orza JAG, Lumbreras J, Borge R, Boldo E, Linares C, Querol X (2012) Emission factors from road dust resuspension in a Mediterranean freeway. Atmos Environ 61 580-587... 

Mineral dust sources in urban areas include road dust resuspension and demolition and construction activities. There is no apparent reason why the unknown part should also be higher or lower at urban or rural sites. A possible cause may be the amount of water attached to SIA which appears increased. Hygroscopic salts on particles, like ammonium nitrate and ammonium sulphate in the fine fraction, and sodium nitrate and sodium sulphate in the coarse fraction attract water erroneously, increasing the PM mass. 

Tsai, J.-H., Wu, Y.-L., 1995. Contributions of road dust resuspensions to the airborne particle concentrations in Taipei. Part. Sd. TechnoL 13, 55—67. 

Soil resuspension has the capability of entraining significant volumes of Pb into the air of urban areas. Harris Davidson (2005) calculated that resuspension of soil is responsible for generating 54,000 kg of airborne Pb each year in the South Coast Air Basin of California (SOCAB) and will remain a major source well into the future. Similarly, Lankey et al. (1998) concluded that 43% of Pb emissions in the South Coast Air Basin in California resulted from the resuspension of soil and road dust. 

Receptor models are widely used tools for apportioning concentrations of pollutants to different sources. They can be factor analytical methods (PMF, PCA, UNMIX, etc.) or chemical mass balance (CMB). On the one hand, these methods revealed to be very valuable to identify the main sources/categories of PM pollution (road traffic, secondary particles, fuel oil combustion, sea salt, etc.) but on the other hand they experienced difficulties in separating the contributions of collinear sources such as mineral dust (natural resuspension) and road dust (anthropogenic) or co-variant sources such as vehicle exhaust and road dust [34, 44, 45, 49, 55, 58, 110-113]). Significant improvements were made with the use of combination of models or constrained models such as the Multilinear Engine (ME-2). 

In dry and hot seasons, road vehicles enhanced dust resuspension, making traffic a major contributor to PM elevated levels in the region. 

Additionally to these combustion derived emissions a motor vehicle also produces so called non-tailpipe emissions, which result from wearing of tires and brakes (Rogge et al. 1993 Garg et al. 2000), abrasion of road pavement (Kupiainen et al. 2005) and from the resuspension of road dust churned up by cars (Nicholson et al. 1989 Sternbeck et al. 2002 Rogge et al. 1993). Though brake and tire wear are... 

K Resuspension of road dust and fugitive soil Lough et al. (2005)... 

Mn Brake wear resuspension of road dust and fugitive Allen et al. (2001), Gillies et al. 

Kupiainen et al. 2005). Iron emissions originate from the resuspension of road dust as well as from the abrasion of road construction material additionally particles liberated from processes such as engine and brake wear have to be considered (Garg et al. 2000). These supplementary iron sources are responsible for the different size distribution of iron emissions compared to the results for Ca, Mg and Si, Al emissions. 

Dusts resuspended in localized atmospheres reflect both the distribution of lead species and particulate sizes in the dusts or soils serving as the source and the main mechanisms producing the resuspension. Street dusts have a bimodal distribution, the fine particle sizes arising from the tailpipes directly and the coarse materials from such mechanisms as smaller particle distribution. Al-Chalabi and Hawker (1997) reported that with increasing resuspension, the lead levels decreased, consistent with either coalescing small and coarser particles or increasing dispersion from the source. Similarly, Abu-Allaban et al. (2003) reported that road dust had most of its lead content in the coarse fraction. 

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