Conference Paper

Particulate Matter from Non-exhaust Sources

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Abstract

Air pollution is an important issue worldwide. Solid components in air (particulate matter, PM) originate from a variety of natural or anthropogenic sources and have different morphological, physical, and chemical properties. Their presence in the air also depends on meteorological conditions, such as humidity, rainfall, and wind speed. PM pollution has adverse effects on environment and human health. Therefore, it is very important to address sources and processes involved in PM generation. Among the existing sources, a special attention must be paid to PM emissions from road traffic, i.e., exhaust sources (e.g., fuel combustion) and non-exhaust sources (e.g., road, tyre, brakes). These traffic-related sources contribute to PM concentrations in cities, and this calls for research into new possible systems and/or mitigation measures. In light of the facts above, the objectives of this study are 1) To evaluate the contribution to PM emission from traffic-related sources. 2) To evaluate existing mitigation measures and to identify new ones to reduce PM production. First results show that: 1) Non-exhaust sources have a different role in PM generation and they differently affect PM10, PM2.5, and PM0.1. 2) Even if emissions-related regulations have led to reductions in exhaust emissions from road traffic, other mitigation measures could reduce the non-exhaust part of emissions (e.g., brakes wear, road wear, and tyre wear). 3) New technologies could be developed to reduce PM from non-exhaust sources.

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... For pollution, note that road traffic is one of the most significant sources of air pollution (cf. Figure 1), where meteorological conditions, fossil fuels, gas emissions, and vehicles interact (mechanical components of cars, brakes, pads, speeds, operating conditions of the vehicle, vehicle weight [6]). Polluting particles can be divided into exhaust Ca [18] emissions and non-exhaust emissions [12,13], where primary particles are directly released into the atmosphere by human or natural sources, and secondary particles are generated by mechanical or chemical reactions and can be classified in terms of aerodynamic diameter [13]. Non-exhaust traffic emissions are the major source of dust load [12]. ...
... For pollution, note that road traffic is one of the most significant sources of air pollution (cf. Figure 1), where meteorological conditions, fossil fuels, gas emissions, and vehicles interact (mechanical components of cars, brakes, pads, speeds, operating conditions of the vehicle, vehicle weight [6]). Polluting particles can be divided into exhaust Ca [18] emissions and non-exhaust emissions [12,13], where primary particles are directly released into the atmosphere by human or natural sources, and secondary particles are generated by mechanical or chemical reactions and can be classified in terms of aerodynamic diameter [13]. Non-exhaust traffic emissions are the major source of dust load [12]. ...
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Physicochemical properties of pure tire wear particles (TWPs) were investigated in a laboratory. A tire simulator installed in an enclosing chamber was employed to eliminate artifacts caused by interfering particles during the generation and measurement of TWPs. TWP particulate matter (PM2.5 and PM10) was correlated with tire speed (r > 0.94) and load (r > 0.99). Their mass size distributions showed that TWP mode diameters ranged between 3 and 4 μm (unimodal). Tire wear caused by slip events resulted in an increase in the number concentration (ca. 8.4 × 10⁵ cm–3) of particles (mainly ultrafine particles (UFPs)) at low PM2.5 and PM10 values (1 and 2 μg m–3, respectively). During braking events, UFPs were emitted at an early stage, with an increase in number concentration (up to 1.1 × 10⁷ cm–3); a high mass concentration (3.6 mg m–3) was observed at a later stage via the coagulation of early emitted UFPs and condensation. On the basis of morphology and elemental composition, TWPs generally had elongated (micron-scale) and round/irregular (submicron-scale) shapes and they were classified into C/Si-rich, heavy metal-containing, S-containing, and mineral-containing particles. This study determined that TWP emissions can vary with changes in driving condition.
Article
The design of a braking system involves a delicate balance between the friction pair, the disc and pad, where the pad is a complex blend of constituents to provide predictable characteristics, typically, a known and consistent friction level. In its base form the brake has to absorb the vehicle kinetic energy by converting it into heat. This heat absorption by the friction pair can result in chemical and physical interactions with the release of debris about which we know little. Other than environmental concerns, brake dust causes unnecessary problems with wear, thermal gradients (hot banding) and NVH. This paper is concerned with the removal and collection of brake debris from the friction interface - the debris being regarded as solids and airborne particles, the latter less than 10μm in size. The test procedure consisted of a Burnish program followed by 8 different drive cycles. The overall effects of debris removal is then reported for each test. It will be shown that, by careful design of air circulation within a collection system, over 92% of dust generated may be removed and collected. It will also be shown that debris collection results in reduced rotor and pad wear and that the brake temperatures during the braking event are not significantly affected. The impact on brake cooling and brake operating temperatures during a customer usage-based braking schedule are under study. The implementation of providing a solution “at source” may provide the automotive industry with a system to meet current U.S. legislative requirements. It will also help to satisfy future costly global legislation. In addition the module will serve as a “real life” mobile laboratory where the OEMs may gather data from the filters to gain a greater understanding of the characteristics of the debris generated during braking - saving time and money on research. This is the first paper in a series which introduces the benefits of using the on-vehicle CBPModular brake wear debris collection system.
Article
The author formalises and examines a physical-based model to estimate the loudness for a specified geometric context with an assigned pavement. Different functions to analyse optimum variable domains are then proposed.
Article
With regard to airborne particles with an aerodynamic diameter of less than 10 μm (PM10), in countries in the European Union, the mass of brake emissions equals approximately 8–27% of the total traffic-related emissions. Using a research methodology combining tests at different scale levels with contact mechanics simulations and PM10 chemical characterization, the REBRAKE EU-financed project had the following aims: i) to demonstrate the possibility of reducing the PM10 fraction of the airborne particulate from brake wear by 50 wt.%; ii) to enhance the general understanding on the physical and chemical phenomena underlying the brake wear process. The results achieved so far indicate that it is possible to design a disc brake system for a European standard car affording at least a 32 wt.% PM10 emission reduction using a standard European pad and a heat-treated rotor. A further reduction to 65 wt. % PM10 emission could be achieved with NAO pad material and the same heat-treated disc.
Article
For the past 45 years, the EPA has set uniform national ambient air quality standards for common pollutants pursuant to the mandate of the Clean Air Act. The pollutant that has been the most difficult to control is ozone. Much of the nation’s population lives in areas that fail to meet the health-based standards for this pollutant. Ozone nonattainment areas include most of California and the Northeast corridor from Northern Virginia to New York, as well as many of the largest metropolitan areas throughout the nation. Over the years, updated ozone standards have become increasingly stringent, which is resulting in a backlash over the cost of compliance. The compliance requirements are particularly challenging for rural areas in the West, where imported pollution and less than ideal meteorological conditions make compliance difficult and costly. Costs have not been used when determining air quality standards, but this may not be the best policy decision. The EPA is ratcheting down the ozone standards and this will add many new nonattainment areas with new responsibilities for controlling air emissions. This can be expected to lead to more confrontation between the regulated states and the EPA.
Chapter
Particulate matter (PM) accounts for a complex group of air pollutants with properties and impacts that vary according to its composition and size. The emission rates, size and composition of primary PM emissions are challenging to determine since they depend not only on the sector considered, but also on the fuel properties, technology and other characteristics of the emission process. At the European level, fine carbonaceous particles are generally the dominant components of primary PM emissions, the most important sources of organic and black carbon being residential biomass combustion and diesel vehicle engines, respectively. On the other hand, soil particles generated by wind erosion processes, traffic resuspension, mining and construction operations, and agricultural land management activities are large contributors to the coarse fraction of primary PM emissions. European PM emissions are decreasing as a result of implemented EU legislation mainly focused on road transport and large point sources. Nevertheless, emissions released by residential solid fuel appliances have been increasing due to a lack of regulations, a tendency that is expected to change with the eco-design directive. The decrease of traffic PM exhaust emissions has also increased the importance of traffic non-exhaust emissions, a major source of metals in urban areas.
Article
This work evaluates the effectiveness of on-road primary particulate matter emission reductions that can be achieved by long-term vehicle scrappage and retrofit measures on regional and global levels. Scenario analysis shows that scrappage can provide significant emission reductions as soon as the measures begin, whereas retrofit provides greater emission reductions in later years, when more advanced technologies become available in most regions. Reductions are compared with a baseline that already accounts for implementation of clean vehicle standards. The greatest global emission reductions from a scrappage program occur 5 to 10 years after its introduction and can reach as much as 70%. The greatest reductions with retrofit occur around 2030 and range from 16-31%. Monte Carlo simulations are used to evaluate how uncertainties in the composition of the vehicle fleet affect predicted reductions. Scrappage and retrofit reduce global emissions by 31-60% and 15-31%, respectively, within 95% confidence intervals, under a mid-range scenario in the year 2030. The simulations provide guidance about which strategies are most effective for specific regions. Retrofit is preferable for high-income regions. For regions where early emission standards are in place, scrappage is suggested, followed by retrofit after more advanced emission standards are introduced. The early implementation of advanced emission standards is recommended for Western and Eastern Africa.
Article
Acoustic-based mix design is still far from achieving a clear and accepted rationale. The three main dominions (generation, absorption, propagation) which affect pavement acoustic performance involve a number of acoustic parameters. Their relationship with pavement properties is scarcely or insufficiently known. In more detail, the parameters that define the acoustic coupling between the two phases that comprise a porous material are: porosity, resistivity, tortuosity, and viscous and thermal factors. Consequently, the spectrum of a pavement absorption coefficient depends, in particular, on tortuosity, whose relationship with HMA (hot mix asphalt) bulk properties is still an issue.
Article
Fine and coarse fraction PM was simultaneously sampled with Dichotomous Stacked Filter Units at a road site and at an urban background site during both summer and winter periods. The collected mass was determined gravimetrically, and the contents of 26 elements were measured by Proton-Induced X-ray Emission (PIXE). NOx was monitored continuously at both sites. The road increments (road concentrations minus urban background concentrations) of PIXE elements, PM and NOx were analysed using the Constrained Physical Receptor Model (COPREM). Good agreement between the measured data and the model was achieved in both size fractions using four well-separated source profiles representing the emissions from exhaust, road/tyres, brakes and road salt. The analysis showed that the particles created by brake abrasion have aerodynamic diameters in the inhalable size range around 2.8μm. This particle diameter is common mass median for a long list of heavy metals that are apportioned to the brakes source: Cr, Fe, Cu, Zn, Zr, Mo, Sn, Sb, Ba and Pb. Other significant contributions of Al, Si, K, Ca, Ti, Mn, Fe, Zn and Sr, mostly in the coarse particle fraction, are apportioned to the road/tyres source.
Article
Wear at the interface between flexible pavements and tires influences pavement life, pavement cycle costs, and tire consumption, and is a source of environmental harm. Wear-related processes evolve over time and are affected by a number of boundary conditions, such as interface fluids, water and fuels. We develop a model explaining and predicting mass losses in flexible pavements under carefully controlled conditions, and with estimation of the related environmental costs. We also employed an accelerated loading test. Under normal conditions, the environmental impact of pavement wear is not greatly influenced by mix type or volumetrics. Indeed, the presence of hazmat materials, traditional, dense mixes have an environmental impact that is appreciably lower than that of porous European mixes.
Article
In addition to industrial facilities, fuel combustion, forest fires and dust erosion, exhaust and non-exhaust vehicle emissions are an important source of ambient air respirable particulate matter (PM10). Non-exhaust vehicle emissions are formed from wear particles of vehicle components such as brakes, clutches, chassis and tires. Although the non-exhaust particles are relatively minor contributors to the overall ambient air particulate load, reliable exposure estimates are few. In this study, a global sampling program was conducted to quantify tire and road wear particles (TRWP) in the ambient air in order to understand potential human exposures and the overall contribution of these particles to the PM10. The sampling was conducted in Europe, the United States and Japan and the sampling locations were selected to represent a variety of settings including both rural and urban core; and within each residential, commercial and recreational receptors. The air samples were analyzed using validated chemical markers for rubber polymer based on a pyrolysis technique. Results indicated that TRWP concentrations in the PM10 fraction were low with averages ranging from 0.05 to 0.70 μg m−3, representing an average PM10 contribution of 0.84%. The TRWP concentration in air was associated with traffic load and population density, but the trend was not statistically significant. Further, significant differences across days were not observed. This study provides a robust dataset to understand potential human exposures to airborne TRWP.
Article
We investigated the physical and chemical properties of non-exhaust coarse and fine particles generated by on-road driving and in a laboratory setting using a mobile sampling system. The on-road driving and laboratory measurements performed under constant speed driving revealed that particles produced by tire wear had a size distribution in the range of 2-3μm, while roadway particles (RWPs) measured behind the front tire during on-road driving largely comprised crustal materials such as road surface wear particles and road dust as well as tire wear particles (TWPs). The mode diameters of particles obtained from on-road driving under cornering conditions were similar to those obtained under constant speed conditions, but with higher concentrations of crustal elements. Under braking conditions, the particulate matter (PM) concentrations of brake wear particles (BWPs) sampled near the brake pad increased significantly and were much higher than the concentration of RWPs during deceleration, indicating that BWPs are one of the main sources of non-exhaust emissions. In addition, BWPs observed from on-road and laboratory measurements had a broader PM size range (1-10μm) than RWPs. Size-segregated chemical analysis of PM samples indicated that the concentrations of Fe and Ca were highest in the coarse fraction emitted under constant speed and cornering conditions, while Fe, Ba, and Ti were most abundant in the fine fraction emitted during braking events.
Article
While emissions control regulation has led to a substantial reduction in exhaust emissions from road traffic, currently non-exhaust emissions from road vehicles are unabated. These include particles from brake wear, tyre wear, road surface abrasion and resuspension in the wake of passing traffic. Quantification of the magnitude of such emissions is problematic both in the laboratory and the field and the latter depends heavily upon a knowledge of the physical and chemical properties of non-exhaust particles. This review looks at each source in turn, reviewing the available information on the source materials and particles derived from them in laboratory studies. In a final section, some of the key publications dealing with measurements in road tunnels and the roadside environment are reviewed. It is concluded that with the exception of brake dust particles which may be identified from their copper (Cu) and antimony (Sb) content, unequivocal identification of particles from other sources is likely to prove extremely difficult, either because of the lack of suitable tracer elements or compounds, or because of the interactions between sources prior to the emission process. Even in the case of brake dust, problems will arise in distinguishing directly emitted particles from those arising from resuspension of deposited brake dust from the road surface, or that derived from entrainment of polluted roadside soils, either directly or as a component of road surface dust.
Article
A comprehensive organic compound based receptor model is developed that can simultaneously apportion the source contributions to atmospheric gas phase organic compounds semivolatile organic compounds fine particle organic compounds and fine particle mass The model is applied to ambient data collected at four sites in the south coast region of California during a severe summertime photochemical smog episode where the model determines the direct primary contributions to atmospheric pollutants from 11 distinct air pollution source types The 11 sources included in the model are gasoline powered motor vehicle exhaust diesel engine exhaust whole gasoline vapors gasoline headspace vapors organic solvent vapors whole diesel fuel paved road dust tire wear debris meat cooking exhaust natural gas leakage and vegetative detritus Gasoline engine exhaust plus whole gasoline vapors are the predominant sources of volatile organic gases while gasoline and diesel engine exhaust plus diesel fuel vapors dominate the emissions of semivolable organic compounds from these sources during the episode studied at all four air monitoring sites The atmospheric fine particle organic compound mass was composed of noticeable contributions from gasoline powered motor vehicle exhaust diesel engine exhaust meat cooking and paved road dust with smaller but quantifiable contributions from vegetative detritus and tire wear debris In addition secondary organic aerosol which is formed from the low vapor pressure products of gas phase chemical reactions is found to be a major source of fine particle organic compound mass under the severe photochemical smog conditions studied here The concentrations of secondary organic aerosol calculated in the present study are compared with previous fine particle source apportionment results for less intense photochemical smog conditions.
Article
Mineral matter is an important component of airborne particles in urban areas. In northern cities of the world, mineral matter dominates PM10 during spring because of enhanced road abrasion caused by the use of antiskid methods, including studded tires and traction sanding. In this study, factors that affect formation of abrasion components of springtime road dust were assessed. Effects of traction sanding and tires on concentrations, mass size distribution, and composition of the particles were studied in a test facility. Lowest particle concentrations were observed in tests without traction sanding. The concentrations increased when traction sand was introduced and continued to increase as a function of the amount of aggregate dispersed. Emissions were additionally affected by type of tire, properties of traction sand aggregate, and driving speed. Aggregates with high fragmentation resistance and coarse grain size distribution had the lowest emissions. Over 90% of PM10 was mineral particles. Mineralogy of the dust and source apportionment showed that they originated from both traction sand and pavement aggregates. The remaining portion was mostly carbonaceous and originated from tires and road bitumen. Mass size distributions were dominated by coarse particles. Contribution of fine and submicron size ranges were approximately 15 and 10% in PM10, respectively.
Article
Particle emissions from residential wood combustion in small communities in Northern Sweden can sometimes increase the ambient particle concentrations to levels comparable to densely trafficked streets in the center of large cities. The reason for this is the combination of increased need for domestic heating during periods of low temperatures, leading to higher emission rates, and stable meteorological conditions. In this work, the authors compare two different approaches to quantify the wood combustion contribution to fine particles in Northern Sweden: a multivariate source-receptor analysis on inorganic compounds followed by multiple linear regression (MLR) of fine particle concentrations and levoglucosan used as a tracer. From the receptor model, it can be seen that residential wood combustion corresponds with 70% of modeled particle mass. Smaller contributions are also seen from local nonexhaust traffic particles, road dust, and brake wear (each contributing 14%). Of the mass, 1.5% is explained by long-distance transported particles, and 2% derives from a regional source deriving from either oil combustion or smelter activities.
Article
There is a growing body of evidence for serious health consequences of exposure to ambient air pollution. The general question of who is susceptible is one of the most important gaps in current knowledge regarding particulate matter (PM)-related health effects. Who is susceptible depends on the specific health endpoint being evaluated and the level and length of exposure. Here, we restrict the review on the impact of fine particle exposure on children's health to the following outcomes: infant death, lung function, respiratory symptoms and reproductive outcomes. This is a strategic review of children's susceptibility to ambient fine particles and characteristics of infant and children which underlie their increased susceptibility to PM. Ambient fine PM is associated with intra-uterine growth retardation, infant mortality; it is associated with impaired lung function and increased respiratory symptoms, particularly in asthmatics. Concerning infant mortality, exposure to PM is strongly and consistently associated with postneonatal respiratory mortality and less consistently with sudden infant death syndrome. Although most of the studies reported adverse effects for this health outcome, the evidence is weaker than for infant death. Exposure to fine PM has been associated with impaired lung function and lung function growth. Most of the studies reported increased prevalence of symptom with increased exposure to fine PM. Fine PM is a major threat to children, because of their higher exposure to PM compared to adults, the immature state of the lung in childhood and also of the immune function at birth. The first months of life might be a period of particular sensitivity. Although the mechanisms of air pollution effects have not yet been completely understood, pregnant women, infants and children need specific protection against exposure to fine particles.
LIFE11/ENV/ES/584 - Testing and development of air quality mitigation measures in Southern Europe. Air quality mitigation measures in urban areas from Southern Europe
  • Airuse Project
AIRUSE Project. (2016). LIFE11/ENV/ES/584 -Testing and development of air quality mitigation measures in Southern Europe. Air quality mitigation measures in urban areas from Southern Europe. https://ec.europa.eu/environment/life/project/Projects/index.cfm?fuseaction=search.dspPage&n_proj_id=4253&docType=p df
Non-exhaust traffic related emissions. Brake and tyre wear PM. Literature review
  • T Grigoratos
  • G Martini
Grigoratos, T., & Martini, G. (2014). Non-exhaust traffic related emissions. Brake and tyre wear PM. Literature review. https://doi.org/10.2790/21481
Road traffic tyre wear. Emission estimates for diffuse sources. Netherlands Emission Inventory Road
  • H Ten Broeke
  • J Hulskotte
  • H Denier Van Der Gon
ten Broeke, H., Hulskotte, J., & Denier van der Gon, H. (2008, September). Road traffic tyre wear. Emission estimates for diffuse sources. Netherlands Emission Inventory Road.
Emission of microplastics and potential mitigation measures. Abrasive cleaning agents, paints and tyre wear
  • A Verschoor
  • L De Poorter
  • R Dröge
  • J Kuenen
  • E De Valk
Verschoor, A., de Poorter, L., Dröge, R., Kuenen, J., & de Valk, E. (2016). Emission of microplastics and potential mitigation measures. Abrasive cleaning agents, paints and tyre wear. National Institute for Public Health and teh Environment.
Potential measures against microplastic emissions to water
  • A J Verschoor
  • E De Valk
Verschoor, A. J., & de Valk, E. (2018). Potential measures against microplastic emissions to water. National Institute for Public Health and teh Environment.
Emission of inhalable particles from studded tyre wear of road pavements. A comparative study (VTI rapport 867A)
  • M Gustafsson
  • O Eriksson
Gustafsson, M., & Eriksson, O. (2015). Emission of inhalable particles from studded tyre wear of road pavements. A comparative study (VTI rapport 867A).
Non-exhaust emissions from road traffic. Air quality expert group
  • P Monks
  • J Allan
  • D Carruthers
  • D Carslaw
  • G Fuller
  • R H Obe
  • M Heal
  • A Lewis
  • E Nemitz
  • M Williams
  • C Reeves
Monks, P., Allan, J., Carruthers, D., Carslaw, D., Fuller, G., OBE, R. H., Heal, M., Lewis, A., Nemitz, E., Williams, M., & Reeves, C. (2013). Non-exhaust emissions from road traffic. Air quality expert group.