Road Dust PM2 Research Articles

PM10 and PM2.5 chemical source profiles of road dust over China: Composition, spatio-temporal distribution, and source apportionment

The composition, spatio-temporal distribution, and source identification of PM2.5 and PM10 road dust in cities across China were studied. The dominant composition was based on OC, Si, EC, Ca2+, SO42−, K, Al, Mg, Ca, and Fe with a decreasing sequence of elements > total carbon > ions. The correlation coefficient between PM2.5 and PM10 was 0.95 and the coefficient of divergence (COD) was 0.19, indicating that the profiles of the two-particle sizes were similar. The non-parametric test determined that there was no statistically significant difference in the source profiles of road dust in terms of interannual variations. Considerable discrepancies (the COD values all >0.20) demonstrated that the dust profiles in different seasons were different, while they were similar for different road types. Cluster analysis (CA) was conducted to examine the differences between the chemical profiles among the study cities. The chemical composition of road dust PM2.5 and PM10 could be placed into five and six clusters, respectively, with the COD proving an absence of similarity among the different clusters. Principal component analysis (PCA) revealed that there were five principal factors affecting the accumulation of road dust: dust source, vehicular traffic, coal burning, industrial activities, and secondary particle formation.

Explorations of tire and road wear microplastics in road dust PM2.5 at eight megacities in China

Tire and road wear microplastics (TRWMPs) in road dust are a key source of atmospheric particulate matter and have an adverse impact on human health and the environment. In this study, samples of particulate matter with a diameter of 2.5 μm or less (PM2.5) in road dust were collected from eight megacities in China to determine the TRWMP content, including that of natural rubber (NR), styrene–butadiene rubber (SBR), and butadiene rubber (BR). The total abundance of TRWMPs was the highest in Lanzhou (174.7 ± 17.0 μg g−1), followed by Xi'an (169.3 ± 23.8 μg g−1), Beijing (107.5 ± 7.5 μg g−1), Changchun (102.2 ± 8.4 μg g−1), Chengdu (101.6 ± 12.9 μg g−1), Guangzhou (98.8 ± 6.5 μg g−1), Wuhan (96.0 ± 5.3 μg g−1), and Shanghai (86.1 ± 30.1 μg g−1). A considerably higher TRWMP fraction in road dust PM2.5 was observed in the northern cities than in the southern cities and is attributable to the higher frictional resistance of roads subjected to less precipitation. The abundance of TRWMPs in the southern cities was dependent on road type, but this dependence was not observed in the northern cities. In the south, road dust PM2.5 on main roads contained more TRWMPs than that on branch roads. Correlation analysis indicated that TRWMPs were associated with tire, road, and break wear. In relation to intracellular oxidative stress factors, higher correlations were observed between TRWMPs and lactate dehydrogenase (r = 0.83) than between TRWMPs and reactive oxygen species (r = 0.59), possibly because TRWMPs destroy the integrity of the cell membrane, with NR exhibiting a higher cytotoxicity than SBR or BR. This study provides evidence that TRWMPs have an adverse impact on human health by inducing cellular oxidative stress. Therefore, further research on TRWMPs in respirable road dust is required.

Loss of E-cadherin due to road dust PM2.5 activates the EGFR in human pharyngeal epithelial cells.

Exposure to road dust particulate matter (PM) causes adverse health impacts on the human airway. However, the effects of road dust on the upper airway epithelium in humans remain unclear. We investigated the involvement of the epidermal growth factor receptor (EGFR) after PM with an aerodynamic diameter of < 2.5 μm (PM2.5)-induced E-cadherin disruption of human pharyngeal epithelial cells. First, we collected road dust PM2.5 from 10 Chinese cities, including Wuhan, Nanjing, Shanghai, Guangzhou, Chengdu, Beijing, Lanzhou, Tianjin, Harbin, and Xi'an. Human pharyngeal FaDu cells were exposed to road dust PM2.5 at 50 μg/mL for 24 h, cytotoxicity (cell viability and lactate dehydrogenase (LDH)) was assessed, and expressions of the proinflammatory interleukin (IL)-6 and high-mobility group box 1 (HMGB1) protein, receptor for advanced glycation end products (RAGE), occludin, E-cadherin, EGFR, and phosphorylated (p)-EGFR were determined. The E-cadherin gene was then knocked down to investigate EGFR activation in FaDu cells. Exposure to road dust PM2.5 resulted in a decrease in cell viability and increases in LDH and IL-6. Our data suggested that PM2.5 could decrease expressions of occludin and E-cadherin and increase expressions of EGFR and p-EGFR, which was confirmed by E-cadherin-knockdown. Our results showed a negative association between the alterations in E-cadherin and total elemental components in correlation analysis, especially S, Cl, K, Ti, Mn, Fe, Cu, Zn, and Pb. Exposure to metals in PM2.5 from road dust may lead to loss of the barrier function of the upper airway epithelium and activation of the EGFR. Our study showed the adverse effects of road dust PM2.5 on pharyngeal epithelial cells of the human upper airway.

Determination Method and Characteristics of Particle Size Multiplier of PM2.5 in Road Dust

The particle size multiplier is a valuable parameter for depicting the particle size distribution characteristics of road dust and calculating road dust emissions. In order to realize the localization of the particle size multiplier, the AP-42 and TRAKER methods were used for sampling on typical and different types of roads in Baoding in March 2019. Then, the particle size multiplier of road dust PM2.5 (K2.5) was calculated using the correction formula, and the characteristics were analyzed. The results indicated:① The K2.5 obtained separately by AP-42 and TRAKER were 0.21 g·VKT-1 and 0.23 g·VKT-1 on average, which correlated well, with a high correlation coefficient of 0.6. The PM2.5 emission factors calculated using the K2.5 of the different methods were almost at the same value, indicating that TRAKER method based on a laser sensor could measure and calculate the K2.5 and could be directly used to obtain the particle size multiplier or be converted using the fitting equation. ② The characteristics of the K2.5 in Baoding were ranked as:Expressway<Secondary roads<Branch roads<Major Roads. ③ Further study results of K2.5 characteristics demonstrated that the average K2.5 was higher than 0.15 g·VKT-1 (the value recommended by US EPA) in Baoding City, which would cause an underestimate of road dust emissions and increase the uncertainty of the emissions inventory if the recommended value from the EPA were adopted. The K2.5 in Baoding City is relatively high, indicating that the road dust contains a significant number of micro particles, increasing the contribution of road dust to urban atmospheric PM2.5.

Chemical characteristics of road dust PM2.5 fraction in oasis cities at the margin of Tarim Basin

In order to understand the compositions characteristics of particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) fraction in road dust (RD2.5) of oasis cities on the edge of Tarim Basin, 30 road dust (RD) samples were collected in Kashi, Cele, and Yutian in the spring, 2018, and RD2.5 was collected using the resuspension approach. Eight water-soluble ions, 39 trace elements and 8 fractions of carbon-containing species in PM2.5 were analyzed. Ca2+ and Ca were the most abundant ions and elements in RD2.5 (7.1% and 9.5%). Cl- in RD2.5 was affected not only by attributed to saline-alkali soils in oasis cities of the Tarim Basin and dust from Taklimakan Desert but also by human activities. Moreover, the organic carbon/elemental carbon (OC/EC) ratio indicated that carbon components in RD2.5 in Cele town mainly come from fossil fuel combustion, while those in Yutian and Kashi mainly come from biomass combustion. It is noteworthy that high Ca in RD2.5 was seriously affected by anthropogenic emissions, and high Na and K contents in RD2.5 could be derived from soil and desert dust. It was estimated that Cd, Tl, Sn and Cr were emitted from anthropogenic emissions using the enrichment factor. The coefficients of divergence (COD) result indicated that the influence of local emission on road dust emission is greater than that of long-distance transmission. This study is the first time to comprehensively analyze the chemical characteristics of road dust in oasis cities, and the results provides the sources of road dust at the margin of Tarim Basin.

Characteristics and provenance implications of rare earth elements and Sr–Nd isotopes in PM2.5 aerosols and PM2.5 fugitive dusts from an inland city of southeastern China

The chemical profiles of PM2.5 aerosols and PM2.5 fugitive dusts have been widely investigated in many cities; however, the characteristics and provenance implications of rare earth elements (REEs) and Sr–Nd isotopes have seldom been reported for PM2.5 aerosols and PM2.5 fugitive dusts. In this study, PM2.5 aerosol and PM2.5 fugitive (road, construction, and soil) dust samples were collected in Nanchang city, China, and analyzed for the characteristics and provenance implications via REEs and Sr–Nd isotopes. PM2.5 aerosol samples showed significantly higher ΣREE values (510.5 ± 347.4 mg kg−1) than PM2.5 fugitive dust samples (93.83 ± 35.23 mg kg−1 for road dust PM2.5, 185.0 ± 70.90 mg kg−1 for construction dust PM2.5, and 206.5 ± 34.28 mg kg−1 for soil dust PM2.5). Both the REE characteristic parameters and the chondrite-normalized REE distribution patterns indicated LREE enrichment and obvious negative Eu anomalies in both PM2.5 aerosol and fugitive dust samples. As shown in 87Sr/86Sr versus εNd(0) plot and ΣLREE/ΣHREE-Eu/Eu*-εNd(0) plot, the REEs in the PM2.5 fugitive dust samples were mainly affected by coal combustion, steelworks and construction cements and were also influenced by the background soil to some extent, while the REEs in the PM2.5 aerosol samples likely originated from both the investigated local sources and other nonlocal potential sources.

Pollution Characteristics and Potential Ecological Risks of Heavy Metals in Road Dust in Beijing

Based on the concentrations of 21 inorganic elements in particulate matter with diameters less than 10 μm (PM10) in 2004, and PM2.5 in 2004 and 2013 of representative road dust in Beijing, the pollution characteristics and potential ecological risks of heavy metals in this dust were analyzed and discussed. The results showed that the six main elements in road dust in Beijing were Si, Ca, Al, Fe, Mg, and K, and the proportions of the total content of the six elements in PM10 in 2004, PM2.5 in 2004, and PM2.5 in 2013 accounted for 96.51%, 96.42%, and 96.53% of the total content of all elements tested, respectively. The elemental enrichment level and the pollution degree and the potential ecological risk of heavy metal in road dust in Beijing in 2004 were PM2.5>PM10. Se, a characteristic element of coal dust, was highly enriched in PM2.5 in 2004, and Cd was high in PM10 and PM2.5 in 2004 with enrichment factors of 1024.03, 68.15, and 871.55, respectively. Co, Zn, Ca, and Cu were significantly enriched in PM10 and PM2.5 in 2004 with enrichment factors of 12.93, 12.33, 8.30, and 8.07 in PM10 and 17.41, 21.80, 12.83, and 19.73 in PM2.5, respectively; Na and Si were not enriched in the road dust. The pollution load index (PLI) of heavy metals was 3.95 in PM10 and 7.71 in PM2.5 in 2004. Owing to the implementation of dust, motor vehicles, and combustion source control measures in Beijing and the relocation of the Shougang corporation, the elemental enrichment level, pollution degree, and potential ecological risk of heavy metals in road dust PM2.5 in 2013 were significantly lower than those in 2004. The enrichment factors of Cd and Se in PM2.5 in 2013 decreased to 98.47 and 0.95, respectively; those of Cu, Ca, and Zn decreased to 11.90, 8.84, and 8.20, respectively; and PLI decreased to 2.56. The results showed that the total potential ecological risk of heavy metals in road dust in Beijing was extremely strong. Heavy metal Cd was the most significant pollution factor and the main potential ecological risk source; its potential ecological risk index (RI) contribution to the total RI of heavy metals was more than 85%. In 2004, the pollution degree of heavy metals in road dust of main roads was significantly higher than that for other road types. The pollution degree of heavy metals in PM10 was main road > expressway entrance to Beijing > secondary main road > ring road; that for PM2.5 was main road > ring road > expressway entrance to Beijing > secondary main road. For PM2.5 in 2013, however, the order was expressway entrance to Beijing > main road > ring road > secondary main road. The pollution degree of heavy metals in road dust of secondary main roads was significantly lower than that for other road types. In 2013, for road dust PM2.5 in Beijing, the correlation of heavy metals Ti, Zn, V, Cr, Cu, Pb, and Ni was significant owing mainly to traffic-related emissions.

Characteristics and Source Apportionment of Carbon Components in Road Dust PM2.5 and PM10 During Spring in Tianjin Derived by Using the Quadrat Sampling Method

In order to study the characteristics and sources of carbon fractions in PM2.5 and PM10 of road dust in Tianjin, samples of road dust were collected by the quadrat sampling method in April 2015 in Tianjin, and samples were re-suspended on filters by using a NK-ZXF sampler. A Thermal Optical Carbon Analyzer (IMPROVE-TOR) was employed to measure the concentrations of organic carbon (OC) and elemental carbon (EC), and the pollution characteristics and sources were investigated by non-parametric tests and OC/EC ratio, correlation, and cluster analyses. The results showed that ω(total carbon, TC) in PM2.5 of road dust amounted to 4.89% (secondary road) -18.83% (expressway), ω(OC) amounted to 3.57% (secondary road) -15.39% (expressway), and ω(EC) amounted to 1.32% (secondary road) -3.44% (expressway); meanwhile, ω(TC) in PM10 of road dust was 8.14% (secondary road) -19.71% (expressway), ω(OC) was 5.91% (secondary road) -16.28% (expressway), and ω(EC) was 1.96% (main road) -3.43% (expressway). The mass fraction of each carbon component for the expressway was relatively high, and that for the secondary trunk road was relatively low, which may have been due to the large traffic volume on the expressway and corresponding large amounts of exhaust emissions from motor vehicles, whereas there were fewer vehicles on the secondary trunk road. Additionally, ω(OC) was significantly larger than ω(EC) for all types of roads, and ω(EC) did not vary much among the different road types. The non-parametric tests of two related samples showed that there was no significant difference in the mass fraction of each carbon component between PM2.5 and PM10. The correlation analysis showed that the sources of OC and EC in road dust were roughly the same. The OC/EC ratio analysis and cluster analysis showed that the main sources of the carbon components in the dust of roads in Tianjin in spring were coal combustion, motor vehicle exhaust, and biomass burning.

Fugitive Road Dust PM2.5 Emissions and Their Potential Health Impacts.

Fugitive road dust (FRD) particles emitted by traffic-generated turbulence are an important contributor to urban ambient fine particulate matter (PM2.5). Especially in urban areas of developing countries, FRD PM2.5 emissions are a serious environmental threat to air quality and public health. FRD PM2.5 emissions have been neglected or substantially underestimated in previous study, resulting in the underestimation of modeling PM concentrations and estimating their health impacts. This study constructed the FRD PM2.5 emissions inventory in a major inland city in China (Lanzhou) in 2017 at high-resolution (500 × 500 m2), investigated the spatiotemporal characteristics of the FRD emissions in different urban function zones, and quantified their health impacts. The FRD PM2.5 emission was approximately 1141 ± 71 kg d-1, accounting for 24.6% of total PM2.5 emission in urban Lanzhou. Spatially, high emissions exceeding 3 × 104 μg m-2 d-1 occurred over areas with smaller particle sizes, larger traffic intensities, and more frequent construction activities. The estimated premature mortality burden induced by FRD PM2.5 exposure was 234.5 deaths in Lanzhou in 2017. Reducing FRD emissions are an important step forward to protect public health in many developing urban regions.

Characteristics and Interannual Variation of Chemical Components in Typical Road Dust in Beijing

Samples of road dust were collected from selected representative roads in Beijing in September 2004 and May 2013, and then re-suspended on filters using a NK-ZXF sampler to prepare road dust PM10 and PM2.5 samples. The concentrations of the chemical components in the road dust PM10 and PM2.5 were analyzed, and source profiles of the road dust in Beijing in 2004 and 2013 were established. The characteristics and interannual variation of the chemical components in the road dust in Beijing were analyzed and discussed. The results showed that the chemical components in the road dust PM10 and PM2.5 in Beijing were Ca, Si, organic carbon (OC), Al, Fe, K, Mg, SO42-, and elemental carbon (EC). The total content of these chemical components in the PM10 in 2004, PM2.5 in 2004, and PM2.5 in 2013 were 46.7303%, 56.9198%, and 38.7478%, respectively, and the total content of these chemical components accounted for 95.9%, 94.3% and 94.7% of the total content of all components tested, respectively. In 2004, the contents of Si and Al in the road dust of ring road were significantly lower than those of other road types, and the influence of soil dust on the ring road was the smallest. The content of Ca, a characteristic element of construction dust, was the highest in main road, and was the lowest in the expressway entrance to Beijing. The content of EC in the road dust from the expressway entrance to Beijing was significantly higher than that in other road types. However, in 2013, the total content of all components tested and the contents of Si, Al, and Ca in the road dust PM2.5 of secondary main roads were significantly lower than those for other road types. Due to the implementation of dust, motor vehicles, and combustion source control measures in Beijing and the relocation of the Shougang corporation, only the content of SO42- in the road dust PM2.5 in Beijing increased slightly by 2.0% in 2013 compared with in 2004; the contents of the other components decreased significantly. The contents of Ca, Si, OC, Al, Fe, K, EC, and NO3- decreased by 45.1%, 31.5%, 17.5%, 20.3%, 55.6%, 33.3%, 30.0%, and 50.3%, respectively. The results showed that the ratio of[NO3-]/[SO42-] did not accurately reflect the changes in the relative contributions of fixed sources and moving sources. The[OC]/[EC] ratios of PM10 in 2004, PM2.5 in 2004, and PM2.5 in 2013 were 9.77±3.88, 9.36±3.25, and 14.41±10.41, respectively. Secondary organic carbon (SOC) pollution was present in road dust in Beijing, and the SOC was an important component in the road dust PM10 and PM2.5. The source profiles of different urban road dust samples and the source profiles of road dust of different sizes in the same city were not very similar, so the corresponding source profiles should be established and updated in a timely manner.

Characteristics and Source Apportionment of Water-soluble Inorganic Ions in Road Dust PM2.5 During Spring in Tianjin Using the Quadrat Sampling Method

In order to collect comprehensive information regarding the characteristics and sources of the water-soluble inorganic ions in road dust (RD) PM2.5 in Tianjin, samples of road dust were collected in April 2015 in Tianjin, and then re-suspended on filters using a NK-ZXF sampler. The concentrations of the major water-soluble inorganic ions were analyzed by ion chromatography. A correlation analysis, ratio method, and principal component analysis were used to analyze the sources of RD PM2.5. The results showed that the total water-soluble inorganic ion concentration in Tianjin accounted for 6.13%±2.32%, varying with different road types. Na+, K+, Mg2+, and Ca2+ showed high homology. NO3-/SO42- revealed that the main source of PM2.5 was mostly attributed to fixed sources. The principal component analysis showed that the main sources of RD PM2.5 in Tianjin were coal combustion, mobile sources, biomass burning, and construction dust.

Characteristics and Source Apportionment of Water-soluble Inorganic Ions in Road Dust PM2.5 in Selected Cities in Liaoning Province

In order to collect comprehensive information on the characteristics and sources of water-soluble inorganic ions in road dust (RD) PM2.5 in Liaoning Province, samples of road dust were collected in 2014 and 2016 in Anshan and Panjin and then re-suspended on filters using an NK-ZXF sampler. The concentrations of the major water-soluble inorganic ions were analyzed by ion chromatography. A correlation analysis, ratios, and a principal component analysis were used to analyze the sources of RD. The results showed that the total water-soluble inorganic ions in Panjin and Anshan accounted for 5.83%±3.34% and 5.84%±1.15% in RD PM2.5, respectively. NH4+, SO42-, and NO3- in RD PM2.5 coexisted in the forms of (NH4)2SO4, and NH4NO3 in Panjin, and NH4HSO4 and NH4NO3 in Anshan. The average values of NO3-/SO42- were 0.52±0.55 and 0.46±0.13 for Panjin and Anshan, respectively, indicating that the effects of stationary sources (e.g., coal combustion) on PM2.5 were more significant. The main sources of RD PM2.5 in Panjin were biomass burning, sea salt particles, construction dust, and mobile sources, while the main sources of RD PM2.5 in Anshan were coal combustion, biomass burning, sea salt particles, and steel smelting dust.

Associations of PM 2.5 Constituents and Sources with Hospital Admissions: Analysis of Four Counties in Connecticut and Massachusetts (USA) for Persons ≥ 65 Years of Age

Background: Epidemiological studies have demonstrated associations between short-term exposure to PM2.5 and hospital admissions. The chemical composition of particles varies across locations and time periods. Identifying the most harmful constituents and sources is an important health and regulatory concern.Objectives: We examined pollutant sources for associations with risk of hospital admissions for cardiovascular and respiratory causes.Methods: We obtained PM2.5 filter samples for four counties in Connecticut and Massachusetts and analyzed them for PM2.5 elements. Source apportionment was used to estimate daily PM2.5 contributions from sources (traffic, road dust, oil combustion, and sea salt as well as a regional source representing coal combustion and other sources). Associations between daily PM2.5 constituents and sources and risk of cardiovascular and respiratory hospitalizations for the Medicare population (> 333,000 persons ≥ 65 years of age) were estimated with time-series analyses (August 2000–February 2004).Results: PM2.5 total mass and PM2.5 road dust contribution were associated with cardiovascular hospitalizations, as were the PM2.5 constituents calcium, black carbon, vanadium, and zinc. For respiratory hospitalizations, associations were observed with PM2.5 road dust, and sea salt as well as aluminum, calcium, chlorine, black carbon, nickel, silicon, titanium, and vanadium. Effect estimates were generally robust to adjustment by co-pollutants of other constituents. An interquartile range increase in same-day PM2.5 road dust (1.71 μg/m3) was associated with a 2.11% (95% CI: 1.09, 3.15%) and 3.47% (95% CI: 2.03, 4.94%) increase in cardiovascular and respiratory admissions, respectively.Conclusions: Our results suggest some particle sources and constituents are more harmful than others and that in this Connecticut/Massachusetts region the most harmful particles include black carbon, calcium, and road dust PM2.5.Citation: Bell ML, Ebisu K, Leaderer BP, Gent JF, Lee HJ, Koutrakis P, Wang Y, Dominici F, Peng RD. 2014. Associations of PM2.5 constituents and sources with hospital admissions: analysis of four counties in Connecticut and Massachusetts (USA) for persons ≥ 65 years of age. Environ Health Perspect 122:138–144; http://dx.doi.org/10.1289/ehp.1306656