Road Dust Resuspension Research Articles

Possible sources of ambient PM10 inside Jadavpur University Campus, Kolkata.

High concentration of particulates in the university and research institutional campus can affect cognitive performance of students and researchers. However, studies on ambient particulate concentration in the campus of universities or research institutes are scarce. The ambient concentration of PM10 was measured in the campus of Jadavpur University, Kolkata, during two different seasons (S1: Post-monsoon; S2: Winter) to identify major sources of pollutant here. Significant seasonal variation of ambient PM10 was recorded in the campus. The average ambient PM10 concentration was recorded higher in S2 compared to S1 of the study period. Morphological characteristics of PM10 during the study period suggest that the roundness of particles was in the range of 0.66 to 0.68, whilst the mean spherical diameter suggests most of the PM10 particles were < 2.5 μ diameter. Based on factorial analysis, three factors were generated which includes factor 1: soil, building material and coal burning particles (53.76% of the variance); factor 2: particles from coal combustion (29.89% of the variance) and factor 3: particles from transport emission (16.33% of the variance). The study suggests that it is important to stop burning coal, reduce vehicular emission and reduce road dust resuspension around the campus to maintain the ambient PM10 concentration within the university campus during the post-monsoon and winter months.

Source apportionment modelling of PM2.5 using CMAQ-ISAM over a tropical coastal-urban area

This study aims to explain the role of local emission sources to PM2.5 mass concentration in a tropical coastal-urban area, highly influenced by industrial and urban emissions, located in the Southeast of Brazil. The Integrated Source Apportionment Method (ISAM) tool was coupled with the chemistry and transport Community Multiscale Air Quality (CMAQ) model (CMAQ-ISAM) to quantify the contribution of ten emission sectors of PM2.5. The simulations were performed over five months between spring 2019 and summer 2020 using a local inventory, which was processed by the Sparse Matrix Operator Kernel Emission (SMOKE). The meteorological fields were provided by the Weather Research and Forecasting (WRF-Urban) model. The boundary and initial conditions to the CMAQ-ISAM were performed by the GEOS-Chem model. The simulations results show that the road dust resuspension (36%) and point (17%) emissions sources were the major contributors to PM2.5 mass in the Metropolitan Region of Vitória (MRV). The boundary conditions (BCON), representing the transport contribution from sources outside the domain, were also a dominant contributor in the MRV (20% on average). Furthermore, the primary atmospheric pollutants emitted by the point (14%) and shipping (7%) sectors in the MRV also affected the cities located in the south region of the domain, strengthened by the wind fields that mostly come from the northeast direction.

Spatial Distribution and Chemical Composition of Road Dust in Two High-Altitude Latin American Cities

Road dust (RD) resuspension is one of the main sources of particulate matter in cities with adverse impacts on air quality, health, and climate. Studies on the variability of the deposited PM10 fraction of RD (RD10) have been limited in Latin America, whereby our understanding of the central factors that control this pollutant remains incomplete. In this study, forty-one RD10 samples were collected in two Andean cities (Bogotá and Manizales) and analyzed for ions, minerals, and trace elements. RD10 levels varied between 1.8–45.7 mg/m2, with an average of 11.8 mg/m2, in Bogotá and between 0.8–26.7 mg/m2, with an average of 5.7 mg/m2, in Manizales. Minerals were the most abundant species in both cities, with a fraction significantly larger in Manizales (38%) than Bogotá (9%). The difference could be explained mainly by the complex topography and the composition of soil derived from volcanic ash in Manizales. The volcanic activity was also associated with SO4−2 and Cl−. Enrichment factors and principal component analysis were conducted to explore potential factors associated to sources of RD10. Elements such as Cu, Pb, Cr, Ni, V, Sb, and Mo were mainly associated with exhaust and non-exhaust traffic emissions.

Comparison of resuspended road dust concentration for identifying optimum sampling position on a mobile laboratory vehicle

The accurate measurement of resuspended road dust from driving vehicles is key to assessing its role in air pollution. In this study, we used numerical analysis to investigate the behavior of resuspended road dust and selected the optimum sampling positions for use in a mobile laboratory (ML) to measure resuspended road dust emissions. Transient simulation of vehicle driving was performed by depicting wheel rim shape and tire tread pattern in detail. The resuspended road dust distributions generated around the vehicle wheels and the flow around the vehicle were analyzed according to the vehicle speed. Based on the analysis, four sampling positions with concentrated distributions of resuspended road dust were selected. To verify the simulation results, sampling inlets were installed on a ML in the selected positions, and resuspended road dust was collected at each position using a Teflon filter at vehicle speeds of 30, 40, and 50 km/h. Mass measurements of the resuspended road dust collected at the four locations showed that the most dust was collected at the position at the bottom of the vehicle immediately behind the wheel, and the overall trend was similar to the simulation results. Therefore, when measuring resuspended road dust using a ML, sampling inlets installed at the locations derived in this study are expected to yield more effective measurements for representing the pollution level of the road.Copyright © 2021 American Association for Aerosol Research

Status of Ambient PM2.5 Pollution in the Seoul Megacity (2020)

The Center for Air Quality & Control at the Seoul Research Institute of Public Health and the Environment (SIHE) has monitored changes in the concentration of fine dust in Seoul over the past 10 years and investigated meteorological factors as well as fine particulate matter (PM2.5), sulfur dioxide (SO2), and nitrogen dioxide (NO2) concentrations in northeastern China and its contribution to the PM2.5 concentration in Seoul. The concentration of fine dust in Seoul in 2020 was 21 µg/m3, which is down 16% from 2019 and the lowest since 2010. In 2020, China’s emissions of pollutants such as NO2 have decreased significantly due to regional blockades, social distancing, and factory shutdowns caused by COVID-19. As a results, the concentration of precursors such as SO2 and NO2, and PM2.5 in northeastern China are also decreased, which contributed to the reduction in PM2.5 concentration in Seoul caused by westerly winds blowing. In addition, the ratio of east and south winds that usually contain low concentrations of pollutants was more than 30% of the total air currents into Seoul, which is the highest in the last three years. Moreover, the mean wind velocity and the amount of precipitation were also the highest recorded values of 2.4 m/s and 1651.0 mm, respectively. Calculations using Comprehensive Air quality Model with eXtensions (CAMx)-Particulate Source Apportionment Technology (PSAT) show that the contribution of external inflows to the PM2.5 concentration in Seoul was 65%. We believe that the reasons for the low PM2.5 concentration in 2020 are due to meteorological factors and a decrease in air pollution in northeastern China. Meanwhile, the major contribution of emissions in Seoul (resuspended road dust and non-exhaust dust) was high. When the concentration of PM2.5 was high, the contribution of resuspended road dust was reduced due to an increase of secondary generating materials. Currently, data on emission reduction due to the COVID-19 cannot be assessed, which we believe will enable more accurate contribution calculations in the future.

Source apportionment of SPM by positive matrix factorization and PM2.5 analysis in an urban industrial area

PurposeThe purpose of this study is to monitor suspended particulate matter (SPM), PM2.5 and source apportionment study for the identification of possible sources during the year 2018–2019 at Raipur, India.Design/methodology/approachSource apportionment study was performed using a multivariate receptor model, positive matrix factorization (PMFv5.0) with a view to identify the various possible sources of particulate matter in the area. Back-trajectory analysis was also performed using NOAA-HYSPLIT model to understand the origin and trans-boundary movement of air mass over the sampling location.FindingsDaily average SPM and PM2.5 aerosols mass concentration was found to be 377.19 ± 157.24 µg/m³ and 126.39 ± 37.77 µg/m³ respectively. SPM and PM2.5 mass concentrations showed distinct seasonal cycle; SPM – (Winter ; 377.19 ±157.25 µg/m?) > (Summer; 283.57 ±93.18 µg/m?) > (Monsoon; 33.20 ±16.32 µg/m?) and PM2.5 – (Winter; 126.39±37.77 µg/m³) > (Summer; 75.92±12.28 µg/m³). Source apportionment model (PMF) have been applied and identified five major sources contributing the pollution; steel production and industry (68%), vehicular and re-suspended road dust (10.1%), heavy oil combustion (10.1%), tire wear and brake wear/abrasion (8%) and crustal/Earth crust (3.7%). Industrial activities have been identified as major contributing factor for air quality degradation in the region.Practical implicationsChemical characterization of aerosols and identification of possible sources will be helpful in abatement of pollution and framing mitigating strategies. It will also help in standardization of global climate model.Originality/valueThe findings provide valuable results to be considered for controlling air pollution in the region.

Characterizing the sources, concentrations and resuspension potential of metals and metalloids in the thoracic fraction of urban road dust

Road dust is a sink and source of metals and metalloids of human health concern. To date, many studies have examined the composition of road dust but there remain critical knowledge gaps on the chemistry of thoracic fractions (< 10 μm) and their patterns of deposition and resuspension. The goal of this study is to characterize the elemental concentrations and sources of thoracic fractions of road dust and their resuspension potential for Toronto, Ontario, Canada. Bulk and thoracic road sweepings were acid digested (HF, HClO4, HNO3 and HCl) and the elemental concentrations measured using ICP-MS. Principal component analysis (PCA) was applied to infer source emissions. Annual elemental loadings to roads were estimated using data on total sweepings collected by the City of Toronto. The mass amounts of metals and metalloids (< 10 μm) available for resuspension were calculated assuming a contribution of 10% to total loadings for this fraction.The median trace element concentrations in city sweepings (n = 64) ranged from highest to lowest as follows: Mn > Zn > Ba > Cr > Cu > Pb > V > Ni > Sn > Mo > Co > As > Sb > Cd. Iron, Cr, Ni, Co, Mo and Cu levels were significantly associated with road class, with the highest concentrations measured for the expressway. Most elements, especially Sb and Zn, were enriched in thoracic sweepings. The PCA results demonstrate the importance of non-fossil fuel, traffic-related elemental emissions. Difficulties in identifying sources, given uncertainties regarding overlapping chemical profiles, are also highlighted. Significant elemental loadings to roads were estimated to occur, with the largest amounts identified for Fe, Al, Mn, Zn, Cr and Cu. Road dust resuspension is predicted to be the most important source of emissions for Fe, Al, Mn, Cr, V, Sn, Mo, Co and Sb.

Effect of silt loading on particle concentration in the atmosphere from resuspended road dust through particulate matter dispersion modeling

Particulate matter (PM) is one of the most dangerous pollutants in urban environments, and studies have linked it to many adverse health effects. Resuspended road dust makes up a large portion of PM. Therefore, monitoring and estimating the contribution of resuspended dust to PM is vital. In this study, emission rates of fine and coarse PM from different roads of Vellore City in Tamil Nadu, India, is estimated using silt loading protocol adapted by U.S. EPA. Silt load samples are collected from 8 different roads in the study region. The emission rates estimated using silt loading and fleet weight are then used to model the dispersion of PM throughout the study region using AERMOD. Hotspots of high PM concentration are identified at various locations frequented by commuters in the study region. Areas around educational institutions and hospitals in the region show highly elevated levels of PM. This study illustrates that resuspension of road dust can contribute significantly to PM in urban centers. Fine PM concentration exceeding 500 μg/m3 raises concerns about the health of commuters in the study region. This justifies the need for more regulations aiming at reducing the contribution of PM from resuspended road dust to overall urban PM.

Size distributions and health risks of particle-bound toxic elements in the southeast coastland of China.

Size-fractionated samples were collected at five coastal urban sites in Fujian Province, southeast China, in 2016 and 2017 to determine the trace elements using ICP-MS. Ca, Fe, Al, Mg, and K were the most abundant elements among the studied elements in TSP, much higher than those of heavy metals. The annual mean concentrations of Pb, As, V, Ni, Cd, and Mn were within the acceptable limits of the World Health Organization and the Ministry of Ecology and Environment of China while Cr(VI) exceeded the limits. Most elements exhibited clear seasonal patterns with maxima over the cold season and minima over the warm season. The spatial variabilities in concentrations of the measured elements were not significant except Ni and V. However, the size distribution pattern of each element was quite similar across the region. Characteristic size distributions of elements allowed identification of three main groups: (a) unimodal distribution in the coarse fraction for Ca, Al, Mg, and Ba; (b) unimodal distribution in the fine fraction for Pb, Se, As, Ag, V, Ni, Zn, and Cd; and (c) bimodal or multimodal distribution for Fe, Mn, Cr, K, and Cu. The combination of the size-fractionated concentrations, enrichment factors, correlation coefficients, and factor analysis offered the identification of mixed sources such as vehicular exhaust and wear, heavy fuel oil combustion, and resuspension of road dust. Non-carcinogenic health risks associated with inhalable exposure to airborne metals were higher than the safety threshold (hazard index > 1) across the region, suggesting non-carcinogenic health risks via inhalation. Mn, V, and Ni contributed 74-83% of the total non-carcinogenic risk. The assessment investigation of carcinogenic health risks revealed V and Cr(VI) as elements with the largest carcinogenic risks, accounting for more than 95% of the overall inhalation risk. Nevertheless, the carcinogenic risks for children and adults were between 10-6 and 10-4, within the range considered acceptable by the US EPA. In terms of the size-fractionated risk, PM2.5 contributed 43-50% and 39-44% of the total non-carcinogenic and carcinogenic risks, respectively, indicating the potential health hazard of coarse particle-bound toxic metals was not negligible.

A two-year assessment of particulate air pollution and sources in Kuwait

BackgroundKuwait and the Gulf region have a desert, hyper-arid and hot climate that makes outdoor air sampling challenging. The region is also affected by intense dust storms. Monitoring challenges from the harsh climate have limited data needed to inform appropriate regulatory actions to address air pollution in the region. ObjectivesTo compare gravimetric measurements with existing networks that rely on beta-attenuation measurements in a desert climate; determine the annual levels of PM2.5 and PM10 over a two-year period in Kuwait; assess compliance with air quality standards; and identify and quantify PM2.5 sources. MethodsWe custom-designed particle samplers that can withstand large quantities of dust without their inlet becoming overloaded. The samplers were placed in two populated residential locations, one in Kuwait City and another near industrial and petrochemical facilities in Ali Sabah Al-Salem (ASAS) to collect PM2.5 and PM10 samples for mass and elemental analysis. We used positive matrix factorization to identify PM2.5 sources and apportion their contributions. ResultsWe collected 2339 samples during the period October 2017 through October 2019. The beta-attenuation method in measuring PM2.5 consistently exceeded gravimetric measurements, especially during dust events. The annual levels for PM2.5 in Kuwait City and ASAS were 41.6 ± 29.0 and 47.5 ± 27.6 μg/m3, respectively. Annual PM2.5 levels in Kuwait were nearly four times higher than the U.S. National Ambient Air Quality Standard. Regional pollution was a major contributor to PM2.5 levels in both locations accounting for 44% in Kuwait City and 46% in ASAS. Dust storms and re-suspended road dust were the second and third largest contributors to PM2.5, respectively. ConclusionsThe premise that frequent and extreme dust storms make air quality regulation futile is dubious. In this comprehensive particulate pollution analysis, we show that the sizeable regional anthropogenic particulate sources warrant national and regional mitigation strategies to ensure compliance with air quality standards.

Long-term trends in concentrations and sources of PM2.5–bound metals and elements in central Los Angeles

In this study, we investigated long-term trends in the ambient concentrations and sources of redox-active metals and trace elements in central Los Angeles over the period of 2005–2018. Mass concentrations of PM2.5-bound metals and crustal elements were obtained from the Chemical Speciation Network (CSN) database provided by the US Environmental Protection Agency (US EPA). The recorded metal concentrations showed considerable variations throughout the study period, but they generally followed a descending trend from 2005 to 2018. The decline in annual average concentration of metals was more pronounced for V and Ni. In order to further investigate and interpret the observed decreasing trends, this dataset of 2005–2018 was employed in the positive matrix factorization (PMF) model to determine the contribution of different sources to the total metals’ concentrations and their trends over time. Four major sources were identified by the PMF model, including mineral dust, re-suspended road dust, combustion, and tire wear. Mineral dust (50 ± 8%) and re-suspended road dust (38 ± 13%) were the dominant contributors to total metal concentrations, followed by combustion emissions (9 ± 8%) and tire wear (2 ± 1%). While the PMF results showed generally consistent contributions of mineral dust to total metals concentration throughout the investigation period, the contribution of re-suspended road dust to total metals increased from 2013 to 2018 probably due to the increased road traffic (expressed in the form of vehicle miles traveled, VMT) as well as the growing use of electric vehicles (EVs) (which increases resuspension of road dust particles due to their heavy weight) in the area during the same period. In contrast, the contribution of combustion emissions decreased by almost 88% from 2005 to 2018. Using the PMF-resolved factor profiles, we investigated the contribution of the four identified sources to selected individual metals (i.e., Ba, Br, Fe, Ni, Pb, Ti, V, and Zn). The observed decrease in the mass concentration of V and Ni over time was attributed to the reduction in combustion sources and particularly industrial emissions, further corroborating the effectiveness of aftertreatment and air quality policies in reducing the levels of redox-active metals across Los Angeles.

Required flux tower height for measurement of re-suspended road dust

Concentration of road dust re-suspended by passing vehicles can be measured using fine-dust measuring devices installed at various heights of a flux tower. In this study, simulations were performed to analyze the distribution of dust plumes along the height of a flux tower according to its distance from the center of the road, the vehicle speed, wind direction, and wind speed. Simulation results were compared with field measurements of re-suspended road dust collected by a flux tower during the passage of a van-type mobile laboratory vehicle to confirm the accuracy of the simulation. A parametric study was then conducted using the simulation of the mobile lab vehicle to evaluate the effects of vehicle speed, wind direction, and wind speed. To accurately capture re-suspended road dust concentrations, the flux tower must be at least 4.5, 5.1, 5.8, and 6.2 m high when located 2, 4, 6, and 8 m, respectively, from the road center. The results of this study are expected to serve as guidelines in determining the location and height of flux towers when measuring re-suspended road dust.

Use of Black Poplar Leaves for the Biomonitoring of Air Pollution in an Urban Agglomeration.

Trees are considered to be an effective tool for metal pollution biomonitoring. In the present study, the concentration of metals (Cu, Pb, Zn, Cd, Co, Ni, Fe, Mn, and Al) in black poplar leaves (Populus nigra L.), together with the concentration of PM10, PM2.5, PM1, and total suspended particles (TSP), was used for the air pollution biomonitoring in 12 sites from various areas of Cluj-Napoca city, Romania. The concentration of PM10 in the air was high, but their metal content was low. However, Cu, Pb, and Zn were moderately enriched, while Cd was highly enriched in PM10 due to anthropogenic sources. The average metal concentration in leaves decreased in the order Zn>>Fe>Mn>Al>Pb>Ni>Cu>Co>Cd and increased with the increase of PM10 concentration, indicating that poplar leaves are sensitive to air pollution. The principal component analysis indicated that traffic, waste burning, road dust resuspension, and soil contamination are the main anthropogenic sources of metals in poplar leaves. The results indicated that black poplar leaves are a suitable biomonitoring tool for metal pollution, in urban environments.

PM2.5-bound trace elements in a critically polluted industrial coal belt of India: seasonal patterns, source identification, and human health risk assessment.

The concentration of trace elements like Fe, Mn, Cu, Zn, Ni, Pb, Cd, Cr, Co, and As in atmospheric particulate matter (PM2.5) was estimated to investigate their seasonal variation, potential sources, and health risk at Jharia coalfield, India, during May 2018 to April 2019. Measured PM2.5 (170 ± 45 μg/m3) exceeded the National Ambient Air Quality Standards (2009) by a factor of 4.25, the Clean Air Act, National Ambient Air Quality Standards (40 CFR part 50) by a factor of 11, and Air Quality Guidelines of World Health Organization (2005) by a factor of 16. Mean concentration of the trace elements were observed in the order of Fe > Mn > Cu > Zn > Cr > Pb > Co > Ni > Cd > As, highest being perceived at the monitoring sites affected by coal mine fire. The significantly higher HQ values posed by PM2.5-bound Cd, Cr, Cu, Pb, and As and higher HI values (multi-elemental exposure) indicated potential non-carcinogenic risk to the residents of Dhanbad. Higher ECR values in the coal mining areas of JCF indicated higher carcinogenic risk to the population (adults > children) of Dhanbad due to inhalation of PM2.5-bound Cr. Spontaneous combustion of coal in the mines, active mine fire, associated mining activities, heavy vehicular emission, and re-suspended road dust were recognized as the potential sources of the trace elements from the results of PCA and Pearson correlation analysis.

Personal deposited dose and its influencing factors at several Greek sites: an analysis in respect to seasonal and diurnal variations.

The deposited dose in the human respiratory tract and its influencing factors were investigated for 8 urban/suburban locations within Greek cities. A dosimetry model (ExDoM2) was implemented assuming a 24-h exposure scenario to ambient PM10 whereby regional deposition rates were obtained. Simulations were performed considering three cases (Sahara dust, cold, and warm periods) with seasonal and diurnal variations examining the relative sources and other influencing factors in each case. Health risk indexes such as the relative risk and attributable fraction were also estimated. Overall, higher daily deposited dose was obtained for all urban compared with suburban locations (p < 0.05) and for cold compared with the warm periods (252-820 μg for cold period and 300-686 μg for warm period) for all locations. This finding was associated with increased deposition rate on cold period during evening/night hours, as a result of significant heating emissions. Besides that, most of the urban locations showed relative comparable deposition rates during the day, compared with the daily mean, for the two periods (cold and warm), indicating that urban-associated sources such as exhaust emissions and road dust resuspension contribute similarly to the deposited dose irrespectively of the season. Finally, the highest deposited dose was obtained during Sahara dust events ranged from 1881 to 4648 μg.

Development and evaluation of a mobile laboratory for collecting short-duration near-road fine and coarse ambient particle and road dust samples

ABSTRACT This study used fine and coarse PM concentrator technology in a Mobile Particle Concentrator Platform (MPCP) designed and built to allow the collection of large amounts of ambient PM, enabling time-resolved speciation analysis, which would not be feasible using conventional methods. One hour of sampling yielded sufficient sample loading for trace elemental analysis using X-Ray Fluorescence (XRF). In addition, we developed a novel Road Dust Aerosolizer (RDA) sampler in order to collect PM2.5 and PM10 surface road dust in situ. This sampler aerosolizes dust from the road surface, simulating ambient road dust resuspension, resulting in measured PM composition and size more appropriately (and less labor-intensive) than those obtained from studies using bulk road dust sieved and re-suspended in the laboratory. Overall, our modified fine and coarse particle concentrators yielded good reproducibility between co-located samples and sufficient loading for trace elemental analysis. For particle mass concentration, we observed a relative error of 3% and 4% among pairs of filters for fine and coarse concentrators, respectively; confirming that the mass collected on an unweighted quartz filter in parallel with a Teflon filter will have the same PM mass as the weighed Teflon filter. For samples with elements that are well above the LOD, relative uncertainty values were between 5% and 10% for the fine and 3% and 10% for the coarse. Our results show that the RDA system has an excellent precision for mass and elements as well. The relative error for mass is 7% for PM10 and 3% for PM2.5 within pairs and ranged from 2 to10% for elements. In conclusion, we developed a method for collecting PM10 and PM2.5 near-road air and surface road dust for short durations, which allows investigation of the composition of direct (airborne) and indirect (re-suspended road dust) non-tailpipe vehicular emissions. Implications: The methods we developed in this study allow the collection of one-hour PM10-2.5 and PM2.5–0.2 samples from near-road ambient air at several distances from the same roadway in 1 day, and collection of road dust directly from the road surface, with sufficient loading for trace elemental analysis. This will allow investigation of the composition of direct (airborne) and indirect (re-suspended road dust) vehicular emissions.

A Comparison Study of Chemical Compositions and Sources of PM1.0 and PM2.5 in Hanoi

We simultaneously collected 85 pairs of 24-h PM1.0 and PM2.5 samples from a new urban area in Hanoi, Vietnam, and analyzed their chemical compositions with particle-induced X-ray emission (PIXE) and ion chromatography (IC) to obtain input data for source apportionment via positive matrix factorization (PMF). Sulfate, ammonium, and black carbon (BC) composed the majority of the mass in both size fractions, and the PMF models clearly differentiated the contribution of long-range transport (LRT) aerosols, which accounted for more than two-thirds of the measured PM-bound sulfate and ammonium concentrations, from those of the six in situ sources, viz., resuspended road dust, primary vehicular emissions, coal fly ash, biomass burning emissions, construction dust, and sea salt. Whereas LRT aerosols, coal fly ash, and primary particulate vehicular emissions mainly occurred in the PM1.0, resuspended road dust and biomass-burning fly ash tended to appear in the PM1.0-2.5; hence, we can characterize the anthropogenic emissions in this area by examining the profile of the PM1.0 rather than the PM2.5. Additionally, air masses with inland trajectories originating in northern China and countries northwest and southwest of Vietnam contained more ammonium, sulfate, and BC than those that passed over the East Sea. Finally, the LRT aerosols exhibited high acidity in the PM1.0 but neutrality in the PM2.5.

Chromium and Zinc Speciation in Airborne Particulate Matter Collected in Ulaanbaatar, Mongolia, by X-Ray Absorption Near-edge Structure Spectroscopy

ABSTRACT This study examined the chemical speciation of atmospheric particulate matter (PM) samples collected in Ulaanbaatar, Mongolia. The health effects of atmospheric aerosol depend on the particles’ size distribution, elemental composition and chemical species as well as other factors, which vary according to the pollution sources and meteorological conditions. Employing the International Atomic Energy Agency (IAEA) supported X-ray fluorescence (XRF) beamline at Elettra Sincrotrone Trieste, Italy, we used a small incidence angle for the synchrotron emission radiation in this ultra-high-vacuum environment to analyze the fine and the coarse mode (PM2.5 and PM2.5-10, respectively) through X-ray absorption near-edge structure (XANES) spectroscopy, which was applied to the K-edges of the chromium (Cr) and zinc (Zn) in PM samples selected via energy-dispersive XRF (EDXRF) analysis for their high concentrations of these transition metals. The spectroscopic results identified trivalent chromium sulfate [Cr2(SO4)3] and chromium oxide (Cr2O3) compounds as the major chemical forms of Cr in both the coarse and the fine PM fraction. Furthermore, both fractions contained abundances of sulfate (ZnSO4) and silicate (Zn2SiO4) compounds, but only the fine mode contained Zn oxalate (ZnC2O4), whereas only the coarse mode contained Zn chloride (ZnCl2). These Cr and Zn species seemed to originate from local anthropogenic sources, e.g., combustion products or traffic-related resuspended road dust. Our findings, which are based on the first chemical speciation analysis from Ulaanbaatar, provide insight into the physiochemical characteristics of atmospheric aerosols as well as information on the potential sources of Cr and Zn species bound to fine and coarse PM.

Characterising particulate matter source contributions in the pollution control zone of mining and related industries using bivariate statistical techniques

Na Phra Lan Subdistrict is a pollution control zone with the highest PM10 level in Thailand. Major mobile and industrial sources in the area are related to stone crushing, quarrying and mining. This study used statistical techniques to investigate the potential sources influencing high PM10 levels in Na Phra Lan. Hourly PM10 data and related parameters (PM2.5, PMcoarse and NOx) from 2014–2017 were analysed using time series, bivariate polar plot and conditional bivariate probability function (CBPF). Results of diurnal variation revealed two peaks of PM10 levels from 06:00–10:00 and 19:00–23:00 every month. For seasonal variation, high PM10 concentrations were found from October to February associated with the cool and dry weather during these months. The bivariate polar plot and CBPF confirmed two potential sources, i.e., resuspended dust from mobile sources close to the air quality monitoring station (receptor) and industrial sources of mining, quarrying and stone crushing far from the station on the northeast side. While the industrial source areas played a role in background PM10 concentrations, the influence of mobile sources increased the concentrations resulting in two PM10 peaks daily. From the study results, we proposed that countermeasure activities should focus on potential source areas, resuspended road dust from vehicles and the industrial sources related to quarrying and mining, rather than distributing equal attention to all sources.

Impacts of traffic and street characteristics on the exposure of cycling commuters to PM2.5 and PM10 in urban street environments

Cycling commuters are a large and growing group in China. Cyclists might be exposed to higher than average risks from pollution owing to their proximity to traffic. The factors affecting cyclists' exposure in urban streets include the sources of traffic and the dispersion of pollutants. This study performs cycling mobile monitoring under calm weather conditions in a central business district of Fuzhou, China. Relative exposure concentration (REC) after background correction is proposed to examine exposure level and evaluate the impacts of traffic density and composition and to identify street characteristics (built environment features and roadside vegetation) that determine the exposure level distribution between and within different street segments. The averaged REC of 10 m buffers along the route with a spatial variability between segments ranged from 1.2 to 3.5 μg/m3 and 2.8–4.3 μg/m3 above the background level for PM2.5 and PM10. REC hotspots (>4 μg/m3) not only appeared frequently in wide streets with larger traffic volumes, but also in narrow streets with dense trees owing to the accumulation of particles contributed from emission and road dust re-suspension caused by diesel trucks. In multivariable models, the street aspect ratio H/W and buildings spacing distance are the main factors influencing the REC variation in wide streets, whereas the leaf area index and canopy coverage percentage of the roadside vegetation explained 29–53% of the REC variation in narrow streets with dense trees. Our insights have the potential to inform traffic management and planning strategies designed to reduce cyclists’ exposure to pollution in urban streets.