An index for estimating the potential metal pollution contribution to atmospheric particulate matter from road dust in Beijing

Evaluating city road dust emission characteristics with a dynamic method: A case study in Luoyang, China

Road dust, a significant contributor to non-exhaust particulate matter emissions in urban transport, poses considerable health risks, necessitating accurate and high-resolution data for effective control. The traditional AP-42 method offers data on point-specific dust emissions, while vehicle-based testing ascertains the relative emission intensity in the road network. However, a clear mathematical relationship between these measurements has been elusive, limiting efficiency in emission control. By integrating the On-board Conventional Pollutant Monitoring System with the AP-42 method, we devised a dynamic link between the concentration of particles in vehicle plumes and actual road dust emissions. This relationship is substantiated by a notable correlation (R2 = 0.91) between our emission factors and those calculated using the AP-42 method. Significant variations emerged in dust emission factors across road types, with changes between -30.1 % to +57.79 % from the average (0.05 g·vehicle-1·km-1), in tandem with traffic flow fluctuations of approximately ±90 %. Meteorological factors, except for continuous rainfall, showed minimal impact on dust emissions. However, our findings revealed a significant underestimation (58.87 %) of road dust PM10 emissions by the AP-42 method. Intriguingly, we found that short-range emission hotspots substantially contribute to total emissions, suggesting a potential 50 % reduction by controlling merely 8.8 % ± 2.5 % of the total road length. Our research elucidates the interplay between road dust emissions, road types, and human activities. The application of a dynamic, high-resolution assessment method enhances our understanding of the impacts of road dust on urban particulate pollution, allows accurate hotspot identification, and aids in developing efficacious strategies for air quality enhancement.

Temporal-spatial distributions of road silt loadings and fugitive road dust emissions in Beijing from 2019 to 2020

Road silt loading (sL) is an important parameter in the fugitive road dust (FRD) emissions. In this study, the improved Testing Re-entrained Aerosol Kinetic Emissions from Roads (TRAKER) combined with the AP-42 method was firstly developed to quickly measure and estimate the sLs of paved roads in Beijing, China. The annual average sLs in Beijing was 0.59±0.31 g/m² in 2020, and decreased by 22.4% compared with that in 2019. The seasonal variations of sLs followed the order of spring > winter > summer > autumn in the two years. The seasonal mean road sLs on the same type road in the four seasons presented a decline trend from 2019 to 2020, especially on the Express way, decreasing 47.4%-72.7%. The road sLs on the different type roads in the same season followed the order of Major arterial ∼ Minor arterial ∼ Branch road > Express road, and Township road ∼ Country highway > Provincial highway ∼ National highway. The emission intensities of PM₁₀ and PM_2.5 from FRD in Beijing in 2020 were lower than those in 2019. The PM₁₀ and PM_2.5 emission intensities at the four planning areas in the two years all presented the order of the capital functional core area > the urban functional expansion area > the urban development new area > the ecological conservation and development area. The annual emissions of PM₁₀ and PM_2.5 from FRD in Beijing in 2020 were 74,886 ton and 18,118 ton, respectively, decreasing by ∼33.3% compared with those in 2019.

A Comprehensive Exploration on Occurrence, Distribution and Risk Assessment of Potentially Toxic Elements in the Multi-Media Environment from Zhengzhou, China

Road dust (RD), roadside soils (RS) and river surface sediments (sediments) are important materials for evaluating contaminant levels in urban areas. This study aims to investigate the contaminant characteristics, pollution levels and ecological risks of RD, RS and sediments of potentially toxic elements (PTEs), including Cr, Ni, Cu, Zn, As, Cd, Hg and Pb, in the central urban area of Zhengzhou. Results reveal that RD shows a higher concentration of PTEs when compared to the other two environments. The spatial distribution characteristics suggest that PTEs in RD, RS and sediments may come from different sources. The geo-accumulation index (I_geo) was used to describe that the RD was moderately to extremely contaminated with Cd and Hg, while both RS and sediments were significantly enriched with Cd and Hg. For RD, RS and sediments, the potential ecological risk (RI) demonstrates a high potential ecological risk from Cd and Hg. Overall, PTEs in Zhengzhou road dust present a moderate risk.

Effects of Heavy Metals on the Metabolome of Pinus sylvestris (Pinaceae)

The effects of Cu, Ni, and Cd on the Pinus sylvestris metabolome was studied in experimental conditions by gas chromatography-mass spectrometry (GC-MS). Structural changes in plant metabolite network became detectable on day 6 of exposure to the metals, 3-6 days earlier than visual signs of toxicity developed. Differences at the metabolome level arose earlier in a control group of plants, and specific effects of particular metals on the plant metabolome became distinct on day 9. Both nature and concentration of a metal equally contributed to the plant metabolome clustering. Plant responses (changes in concentrations of individual metabolites) to metal exposure substantially differed depending on the metal concentration (1 or 5 mM) and nature. The effects of Cd and Cu were generally similar, while the effect of Ni was often different. Dynamic changes visualized in plant metabolite matrix reflected the changes in its correlation structure, rather than depending on the set of particular compounds.

Impact of particle sizes on health risks and source-specific health risks for heavy metals in road dust

To analyze the impact of particle sizes on sources and related health risks for heavy metals, road dust samples in Beijing were collected and sifted into five particle sizes. The positive matrix factorization (PMF), human health risk assessment model (HHRA), and Monte Carlo simulation were used in the health risk assessment and source apportionment. Results showed that mass of particles < 74 μm occupied about 50% of the total particles, while only 8.48% of the particles were > 500 μm. Mass distribution and concentrations of heavy metals in each particle size changed in temporal. Over 85.00% of carcinogenic risks (CR) were from particles <74 μm, whereas CR from particles >250 μm were ignorable. Sources for health risks in each particle size were traffic exhaust, fuel combustion, construction, and use of pesticides and fertilizers. Proportions of sources to CR differed among particle sizes. Traffic exhaust and fuel combustion contributed over 90% to CR in particles <74 μm, whereas construction contributed the highest (31.68-54.14%) among all sources in particles 74-250 μm. Furthermore, the difference between health risks based on sifted road dust and that based on unsifted road dust was quantitatively analyzed. Source-specific health risk apportionment based on unsifted road dust was not presentative to all particle sizes, and true value of health risks could be over 2.5 times of the estimated value based on unsifted road dust, emphasized the importance of sifting of road dust.

Road sediment, an underutilized material in environmental science research: A review of perspectives on United States studies with international context

Road sediment is a pervasive environmental medium that acts as both source and sink for a variety of natural and anthropogenic particles and often is enriched in heavy metals. Road sediment is generally understudied in the United States (U.S.) relative to other environmental media and compared to countries such as China and the United Kingdom (U.K.). However, the U.S. is an ideal target for these studies due to the diverse climates and wealth of geochemical, socioeconomic, demographic, and health data. This review outlines the existing U.S. road sediment literature while also providing key international perspectives and context. Furthermore, the most comprehensive table of U.S. road sediment studies to date is presented, which includes elemental concentrations, sample size, size fraction, collection and analytical methods, as well as digestion procedure. Overall, there were observed differences in studies by sampling time period for elemental concentrations, but not necessarily by climate in the U.S. Other key concepts addressed in this road sediment review include the processes controlling its distribution, the variety of nomenclature used, anthropogenic enrichment of heavy metals, electron microscopy, health risk assessments, remediation, and future directions of road sediment investigations. Going forward, it is recommended that studies with a higher geographic diversity are performed that consider smaller cities and rural areas. Furthermore, environmental justice must be a focus as community science studies of road sediment can elucidate pollution issues impacting areas of high need. Finally, this review calls for consistency in sampling, data reporting, and nomenclature to effectively expand work on understudied elements, particles, and background sediments.

Seasonal source identification and source-specific health risk assessment of pollutants in road dust

Humans who are exposed to metals in road dust may have potential health risks through touching, ingesting, and inhaling the suspended road dust. There were limited studies to link seasonal emission sources to health risks from metals in road dust. In this study, metals in road dust from different functional areas were seasonally monitored. The contributions of the pollutant sources in study areas varied with seasons. By combining the source apportionment model (PMF), road dust emission model, and health risk models (HI: hazard index and ILCR: incremental lifetime carcinogenic risk), industrial and construction activity was identified as the crucial source of both the pollutants in road dust (29-47%), and the HI for adults (27-45%) and children (41-50%) in different seasons. The traffic non-exhaust emission dominated in the carcinogenic risks for children in spring (45%) and summer (36%). Factors such as seasons, particle size, metal bioavailability, human exposure time, and exposure area were all taken into consideration to avoid overestimating or underestimating health risks. The carcinogenic risks for children (1.6 E-06) and adults (2.8 E-06) exposed to Cr both exceed the minimum threshold (10-6). It means that the potential risks were acceptable but could not be completely neglected. Measured metals mainly posed hazard to human health through ingestion route. Pb and Mn, Fe and Mn were the main harmful elements that induced non-carcinogenic risks for adults and children, respectively. Effectively identifying the source-specific health risks in different seasons will help in the formulation of adaptive strategies to diminish the potential risks.

Heavy metal accumulation characteristics and physiological response of Sabina chinensis and Platycladus orientalis to atmospheric pollution

Heavy metal (Cu, Mn, Zn, Pb, and Cd) concentrations were measured in the leaves of Sabina chinensis and Platycladus orientalis collected from urban, suburban, and rural sites in Tianjin, China. Photosynthetic pigment contents, reactive oxygen species content, malondialdehyde (MDA) content and antioxidant enzyme activity were investigated, providing physiological response parameters. Our comparison of the sites revealed that urbanization significantly influenced the heavy metal concentrations in both plant leaves. At the rural site, both plant leaves exhibited the lowest heavy metal accumulation. The highest Cu, Mn, and Zn concentrations were found in S. chinensis leaves from the urban site; the highest Pb and Cd concentrations were found in P. orientalis leaves from the urban site. These results indicate that the urban site contained larger heavy metal concentrations in the plant leaves that may reflect the anthropogenic emission gradient. It is also found that S. chinensis may be used to monitor airborne heavy metal pollution because it is highly quick response to heavy metals, while P. orientalis may be used for mitigation due to its high resistance. The results of this study can contribute to the development of monitoring and environmental management plans by providing information on sensitive and resistant tree species for city greening in North China.

Characteristics of potentially toxic elements and multi-isotope signatures (Cu, Zn, Pb) in non-exhaust traffic emission sources

Non-exhaust emissions (e.g., particles from brake pads, asphalt, curb, road paint, tire) are important sources of potentially toxic elements (PTEs) pollution in urban environments and are potential causes of PTEs pollution in road dust. We present the PTEs concentrations (Cr, Ni, Cu, Zn, As, Cd, Sn, Sb, Pb) of non-exhaust emission sources and pollution degree of PTEs. Isotopic signatures of Cu, Zn, and Pb were also analyzed to distinguish these sources. Among PTEs, the Cu concentration in all brake pads was significantly high and brake pads from Korea showed remarkably high Sb concentrations. Asphalt had a higher Pb concentration than other non-exhaust emission sources. Mean of δ⁶⁵Cu_AE647, δ⁶⁶Zn_IRMM3702, and ²⁰⁶Pb/²⁰⁷Pb values of non-exhaust emission sources in this study ranged from -0.49‰ to +0.19‰, -0.24‰ to +0.16‰, and 1.1535 to 1.4471, respectively. Non-exhaust emission sources could be discriminated by plotting the concentration and isotopic composition of Cu. Cu isotopic compositions (δ⁶⁵Cu_AE647) were clearly distinguished between brake pads including domestic and imported products and tires. Zn isotope values (δ⁶⁶Zn_IRMM3702) of brake pads, tires, and asphalt overlapped, but discriminated from road paint and curb. Our results indicate that the combination of Cu and Zn isotopic signatures can distinguish various non-exhaust traffic emissions, especially brake pads and tires.

Effectiveness of road dust suppressants: insights from particulate matter-related health damage

Although dust suppressants are widely applied to control road dust pollution, a consensus on their effectiveness has not been reached. To evaluate the effectiveness of dust suppressants (a calcium-magnesium complex) from health risks and health damage, spraying and sampling activities were conducted at four sites in Beijing. Using inhalation risk model and health damage assessment, health risks of PM_x for three sensitive occupational groups were calculated and converted to life and economic loss. Results revealed that dust suppressants can indeed mitigate PM pollution and its accompanying health risks and health damage in road dust, but at a limited efficiency. By spraying dust suppressants, the total PM-related life loss reduced by 1.60E-02 years and 2.50E-04 years in urban and suburban areas on average, and the total willingness to pay (WTP) values decreased by 120 and 50 US$ for PM_2.5 and PM₁₀, indicating a more considerable environmental gain if dust suppressants were sprayed in additional regions when necessary. Overall, our study demonstrated that the effectiveness of dust suppressants cannot be pictured only by the variations of pollutant concentrations, and indicators with practice and economic value should be more useful for traffic-related pollution management.

Human Health Risk Assessment of Heavy Metals in the Urban Road Dust of Zhengzhou Metropolis, China

The goal of this research is to assess hazardous heavy metal levels in PM2.5 fractioned road dust in order to quantify the risk of inhalation and potential health effects. To accomplish this, Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) was used to determine concentrations of eight heavy metals (Cr, Cu, Ni, Zn, Cd, As, Pb, and Hg) in the PM2.5 portion of road dust samples from five different land use areas (commercial, residential, industrial, parks, and educational) in Zhengzhou, China. The following were the average heavy metal concentrations in the city: Cr 46.26 mg/kg, Cu 25.13 mg/kg, Ni 12.51 mg/kg, Zn 152.35 mg/kg, Cd 0.56 mg/kg, As 11.53 mg/kg, Pb 52.15 mg/kg, and Hg 0.32 mg/kg. Two pollution indicators, the Pollution Index (PI) and the Geoaccumulation Index (Igeo), were used to determine the degree of contamination. Both PI and Igeo indicated the extreme pollution of Hg and Cd, while PI also ranked Zn in the extreme polluted range. The US Environmental Protection Agency (USEPA) model for adults and children was used to estimate health risks by inhalation. The results identified non-carcinogenic exposure of children to lead (HI > 0.1) in commercial and industrial areas. Both children and adults in Zhengzhou’s commercial, residential, and park areas are exposed to higher levels of copper (Cu), lead (Pb), and zinc (Zn).

Is the Urban Form a Driver of Heavy Metal Pollution in Road Dust? Evidence from Mexico City

Environmental pollution is a negative externality of urbanization and is of great concern due to the fact that it poses serious problems to human health. Pollutants, such as heavy metals, have been found in urban road dust; however, it is unclear whether the urban form has a role in its accumulation, mainly in cases where there is no dominant unique source. We collected 482 samples of road dust, we determined the concentrations of five heavy metals (Cr, Cu, Pb, Zn, and Ni) using inductively coupled plasma optical emission spectrometry (ICP-OES), and then we derived the pollution load index (PLI). After estimating the mostly anthropogenic origin of these pollutants based on global levels of reference, there were two main aims of this study. Firstly, to analyze the spatial correlation of heavy metals, and secondly, to identify the main factors that influenced the heavy metal concentrations in the road dust of Mexico City. We did this by using a spatial autocorrelation indicator (Global Moran’s I) and applying ordinary least squares (OLS) and spatial regression models. The results indicated low levels of positive spatial autocorrelation for all heavy metals. Most variables failed to detect any relationship with heavy metals. The median strip area in the roads had a weak (significance level of 90%) but consistent positive relationship with Cr, Cu, Ni, Pb, and the PLI. The distance to the airport had a weak (significance level of 90%) and inverse relationship with Pb. Manufacturing units were associated with an increase in Cu (significance level of 95%), while the entropy index was associated with an increase in Ni (significance level of 95%).

Source apportionment and source-specific health risk assessment of heavy metals in size-fractionated road dust from a typical mining and smelting area, Gejiu, China

Source-specific health risk apportionment for heavy metals is critical for pollution prevention and risk management in mining and smelting areas. An integrated method combining health risk assessments with the positive matrix factorization model was proposed to evaluate source-specific health risks for adults and children. A typical mining and smelting area was taken as an example in the present study to apportion the source-specific health risks to humans. A total of 37 road dust samples collected from the industrial (IA) and residential areas (RA) of Gejiu (China) were analyzed for heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn). The results indicated that road dust in the study area was mainly contaminated with Cd, Cu, Pb, and Zn. Three potential sources, including atmospheric deposition, industrial waste, and natural sources, were identified and quantified, with contributions of 43.32%, 30.83%, and 25.85%, respectively. For non-carcinogenic risks, a similar trend of the source contribution was found for adults and children under the same land use; atmospheric deposition made the greatest contribution to the non-carcinogenic risk in both IA and RA. However, for carcinogenic risk, natural sources were the greatest contributor to human health risks in both IA and RA, followed by atmospheric deposition and industrial waste. The investigation in this study allowed the evaluation of health risks from potential contamination sources and the results provide valuable information on health risk mitigation strategies for environmental managers.

Particulate matter exchange between atmosphere and roads surfaces in urban areas

The deposition and the re-suspension of particulate matter (PM) in urban areas are the key processes that contribute not only to stormwater pollution, but also to air pollution. However, investigation of the deposition and the re-suspension of PM is challenging because of the difficulties in distinguishing between the resuspended and the deposited PM. This study created two Bayesian Networks (BN) models to explore the deposition and the re-suspension of PM as well as the important influential factors. The outcomes of BN modelling revealed that deposition and re-suspension of PM10 occurred under both, high-traffic and low-traffic conditions, and the re-suspension of PM2.5 occurred under low-traffic conditions. The deposition of PM10 under low-volume traffic condition is 1.6 times higher than under high-volume traffic condition, which is attributed to the decrease in PM10 caused by relatively higher turbulence under high-volume traffic conditions. PM10 is more easily resuspended from road surfaces compared to PM2.5 as the particles which larger than the thickness of the laminar airflow over the road surface are more easily removed from road surfaces. The increase in wind speed contributes to the increase in PM build-up by transporting particulates from roadside areas to the road surfaces and the airborne PM2.5 and PM10 increases with the increase in relative humidity. The study outcomes provide a step improvement in the understanding of the transfer processes of PM2.5 and PM10 between atmosphere and urban road surfaces, which in turn will contribute to the effective design of mitigation measures for urban stormwater and air pollution.

Concentrations, Speciation, and Bioavailability of Heavy Metals in Street Dust as well as Relationships with Physiochemcal Properties: A Case Study of Jinan City in East China

A total of 77 street dust samples were collected from Jinan City in East China and were analyzed for the concentrations, speciation, bioavailability, and influencing factors of ten heavy metals. The results showed that the average concentrations of Ba, Co, Cr, Cu, Cd, Mn, Ni, Pb, Zn, and V in the street dust were 642.77, 8.24, 114.09, 87.71, 1.08, 517.04, 30.29, 80.32, 497.84, and 51.76 mg/kg, and the concentrations of Ba, Cr, Cu, Cd, Ni, Pb, and Zn exceeded the local soil element background values. In the street dust, Ba, Co, Cr, Mn, Ni, and V were mainly in the residual; Cu and Pb were controlled by the oxidizable; Cd mainly existed in the acid extractable; and Zn was dominated by the reducible. According to the ratios of the acid extractable to the sum of four forms, Cd (39.85%) presented a high environmental risk; Mn and Zn (24.29% and 27.78%) exhibited a medium risk; and V, Cu, Pb, Ba, Co, Ni, and Cr had no environmental risk. The order of mobility or potential risk of heavy metals was Cd ( 85.8%) > Zn (77.1%) > Cu (64.3%) > Pb (62.0%) > Mn (51.7%) > Ba ( 38.9%) > Co (31.2%) > Ni (30.1%) > V (25.8%) > Cr (23.1%), suggesting that Cd, Zn, Cu, Pb, and Mn presented relatively high movability and risk. The bioavailability order of heavy metals was Cd (82.7%) > Zn (63.6%) > Mn (40.4%) > Ni (20.4%) > Pb (11.7%) > Cu (11.1%) > V (7.8%) > Cr (3.7%) in the gastric phase and Cu (24.6%) > Cd (19.9%) > Mn (16.2%) > Ni (6.6%) > Pb (5.7%) > Zn (4.4%) > Cr (3.0%) > V (2.3%) in intestinal phase, implying that Cd, Zn, Mn, and Cu were highly bioavailable in the gastrointestinal environment, which coincided with the risk of speciation. The speciation of heavy metals in street dust had certain correlations with their bioavailability. The physiochemical properties of street dust had significant effects on the concentrations, speciation, and bioavailability of heavy metals in street dust. The simple, fast, and nondestructive magnetic measurements could be used as indicators of the concentrations, speciation, and bioavailability of heavy metals in street dust.

Health Risk Assessment of Heavy Metals Accumulated on PM2.5 Fractioned Road Dust from Two Cities of Pakistan

The aim of this study is to identify and investigate levels of toxic heavy metals in PM2.5 fractioned road dust to better understand the associated inhalation risk and potential health impacts. To achieve this aim, concentrations of seven traffic generated heavy metals (Cu, Pb, Zn, Cd, Ni, Sb, and Cr) were determined in the PM2.5 fraction of road dust samples from four different locations (offices, residential, hospital, and school) in two cities (Karachi and Shikarpur) of Pakistan using ICP-MS. The average concentration values of heavy metals in Karachi were as follows: 332.9 mg/kg Cu, 426.6 mg/kg Pb, 4254.4 mg/kg Zn, 62.3 mg/kg Cd, 389.7 mg/kg Ni, 70.4 mg/kg Sb, 148.1 mg/kg Cr, whereas the average concentration values of heavy metals in Shikarpur were 245.8 mg/kg Cu, 538.4 mg/kg Pb, 8351.0 mg/kg Zn, 57.6 mg/kg Cd, 131.7 mg/kg Ni, 314.5 mg/kg Sb, 346.6 mg/kg Cr. The pollution level was assessed through two pollution indices enrichment factor (EF) and geoaccumulation index (Igeo). These indices showed moderate to extreme level pollution in studied areas of both cities. The health risk assessment through inhalation contact was conducted according to the United States Environmental Protection Agency's (USEPA) model for children and adults. Both non-cancerous and cancerous risks were characterised in the road dust samples for each location. As yet, there is not a single study on the concentrations of heavy metals in PM2.5 fractions of road dust in Karachi and Shikarpur, findings of this research will facilitate researchers for further investigations in current field.

Risks related to heavy metal pollution in urban construction dust fall of fast-developing Chinese cities

Urban construction is a major contributor to air pollution, but few studies have examined heavy metal pollution in urban areas caused by construction dust fall. We measured the concentrations of Cr, Ni, Cu, Zn, Pb, Cd, and Hg and particle size distribution in dust fall from various construction activities in seven fast-developing cities in China and conducted a health risk assessment. Mean metal concentrations in construction dust fall were on the order of Zn (246.3 mg/kg) > Cr (94.2 mg/kg) > Pb (56.5 mg/kg) > Cu (53.6 mg/kg) > Ni (22.8 mg/kg) > Cd (0.68 mg/kg) > Hg (0.08 mg/kg). Cu and Zn were positively correlated in areas of subway and building construction, and Pb and Cd were positively correlated in areas of road construction, likely because of the materials specific to these activities. Enrichment factors for heavy metals at all sampling sites were on the order of Cd (10.4) > Zn (6.37) > Cu (4.25) > Pb (3.84) > Hg (2.41) > Cr (2.02) > Ni (1.32). The enrichment factors for all metals except Zn indicated that heavy metal pollution was highest in road construction, followed by building and subway construction. Non-carcinogenic risks to children (hazard index >1) were 1.01-1.08 in four of the seven sampling sites, indicating possible risk from deposition of construction dust fall. In contrast, the hazard index for adults was <1 at the seven cities and total carcinogenic risks (<1 × 10^-6) were at acceptable levels. An integrated ecological risk assessment demonstrated that heavy metal particles in construction dust fall in two of the cities (Shijiazhuang and Qingdao) were likely to be suspended in the atmosphere. Our study of heavy metal pollution in construction dust fall provides data on ecological and human health impacts and suggests that extensive measures are required to control construction dust fall in China.

Speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry

In this work, a methodology for chemical speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry is proposed. Doehlert design and desirability function were used to find the optimum conditions for hydride generation (1.0 mol L^-1 HCl and 0.9% m v^-1 NaBH₄). The accuracy of the analytical method was evaluated by analysis of reference material fly ash (BCR 176R), addition and recovery tests for inorganic As species, and comparison of independent methods for Sb determination in urban dust samples. The determination of the total concentrations of As and Sb and their inorganic species presented good accuracy, between 80 ± 1 and 101 ± 6%. Precision was expressed as the relative standard deviation and was better than 4.7% (n = 3). The limit-of-quantification values were 0.23 and 1.03 mg kg^-1 for As and Sb, respectively. The methodology was applied to eight samples of dust collected in an urban area of Salvador and Jaguaquara cities, Bahia, Northeast, Brazil, with an aerodynamic size lower than 38 μm. Concentrations of pentavalent inorganic species (iAs⁵⁺ and iSb⁵⁺) in relation to trivalent species (iAs³⁺ and iSb³⁺) were found in urban dust collected in the city of Salvador, which are regarded as more toxic for both elements. The enrichment factor and geoaccumulation index (I_geo) values showed that for some samples, the concentrations of iAs and iSb presented strong enrichment and, and regarding environment, strong to moderately polluted by iAs and iSb, with an indication of anthropogenic contributions. The occurrence of these inorganic constituents in the urban area of Salvador can be related with intense industrial activities and vehicular traffic.

A mineralogical and chemical investigation of road dust in Philadelphia, PA, USA

Road dust was investigated within Philadelphia, a major United States city with a long history of industrial activities, in order to determine pollution levels. Almost all of the investigated minor elements were enriched relative to the continental crust. Furthermore, mean concentrations of Cr, Co, Cu, and Pb were high compared with those reported in cities in other countries. Lead pollution should be investigated further in Philadelphia, where 8 of the 30 sample sites, including those heavily trafficked by civilians, were at or above the EPA's child safety threshold for Pb in bare soil. High Spearman correlations between Zn and Cu, Zn and Cr, Cu and Cr, and Sn and V, as well as factor analysis of minor elements suggests that the primary sources of these elements were anthropogenic. Potential sources included the breakdown of alloys, non-exhaust traffic emissions, paint, smelting, and industry. We found that higher organic content in road dust may be related to higher traffic densities, which could be due to tire-wear particles. Additionally, higher mean concentrations of Fe, Cr, Cu, and Zn were found at sites with elevated traffic densities. Land use impacted some of the elements not influenced by traffic density, including Co, Sn, and Pb. Bulk mineral content was similar across different land uses and traffic densities and, thus, did not appear to be influenced by these factors. Our research emphasized the complexity of road dust and utilized a more comprehensive approach than many previous studies. This study established fundamental groundwork for future risk assessment in Philadelphia, as it identified several key pollutants in the city. Overall, this assessment serves as an informative reference point for other formerly heavily industrialized cities in the USA and abroad.

Contribution of road dust from Low Impact Development (LID) construction sites to atmospheric pollution from heavy metals

The re-suspension of road dust due to intense Low Impact Development (LID) construction activities may be a major contributor to atmospheric metal pollution. However, the distribution characteristics, mobility potential, and pollutant load of atmospheric particles at LID construction sites are not clear. Consequently, management practices to mitigate air pollution from LID construction are lacking. We investigated the atmospheric metal pollution from road dust produced during different construction stages of rain gardens and porous pavements and estimated the ecological risks posed by the heavy metals. Although concentrations of heavy metals in road dust at LID construction sites were lower than at sites without LID construction, the ecological risks posed by the atmospheric heavy metals at LID construction sites were generally higher due to the greater mass of road dust produced during LID construction. Hence, LID management practices should focus on the removal of road dust, especially finer particles (<44 μm) produced during early construction stages. In roads, the zones influenced by LID construction is related to road types based on traffic volume; these road types in descending order of zone influenced by LID construction are: arterial road (400-600 m) > collector road (100-150 m) > access road (50-100 m) > laneway (30-50 m). Based on the study sites, we estimate LID construction in China will contribute 2.31 and 6.23 times as much as the current load of atmospheric particles by 2020 and 2030; and we project atmospheric heavy metals will be 1.45-2.18 and 2.82-4.73 times greater than the current load by 2020 and 2030 from the intense LID construction. Based on our results, several regulatory recommendations are presented to mitigate air pollution at LID construction sites.

Occurrence of heavy elements in street dust from sub/urban zone of Tianjin: pollution characteristics and health risk assessment

Main purpose of this study was to determine the concentrations of selected heavy elements (As, Cd, Pb, Cu, Co, Cr and Ni) in the street dust samples (n = 49) collected from seven districts located in suburban/urban zone of Tianjin in order to estimate their possible sources and degree of environmental pollution as well as human health risk. Mean concentrations (mg kg^-1) of As (19.3), Cd (0.60), Pb (28.4) and Cu (62.7) were above their corresponding soil background values. According to the results of multivariate statistical analysis, the accumulation of As, Cd, Pb, Cu and Cr in street dust was affected by anthropogenic activities, while the contents of Ni and Co were associated with natural sources. Pollution degree by geo-accumulation index had the following trend: Cd > Cu > As > Pb > Cr > Ni > Co. Dust contamination with Cd ranged from unpolluted to highly polluted. Potential ecological risk indicated low (Pb, Cu, Cr, Co and Ni) to high (Cd) risk, while potential risk index showed moderate and very high risks. Non-carcinogenic risk of the studied elements was below safe level (<1). Data obtained in this investigation gave the additional values to the knowledge needed for future monitoring and risk assessment, relating the presence of heavy elements studied in suburban/urban areas.

Fine road dust contamination in a mining area presents a likely air pollution hotspot and threat to human health

The road dust found in mining areas is composed of dust from multiple sources, including wind transported mineral dust from mines and tailings as well as uncovered trucks leakage. Collectively, these are then distributed via wind and traffic activity, becoming an important source of particulate matter (PM) and subsequently inhaled by pedestrians. A common practice in previous road dust risk assessments has regarded them as soil, which likely led to a significant underestimation of the actual inhaled amount. To more accurately understand the inhalation risk presented by road dust in mining areas, the study applied a detailed pollution analysis and dust dispersion model to assess the inhaled amount of road dust. Road dust samples located at different distances to the mine and tailings were collected and sieved to 10 μm (RD10). Enrichment factors (EFs) of Ce, As, Cd, and Mo exceeded 20 across most sampled sites, suggesting extreme pollution. Source analysis indicated that most of the collected RD10 had greater than half of its mass originating from the mine. To assess the risk presented by inhalation exposure to local populations, we built a method using Gaussian diffusion model and two exposure scenarios for both adults and children were considered. The level of simulated particle concentrations was comparable to that described in the literature; the inhalation of potential toxic elements (PTEs) in RD10 led to health risks for both adults and children (adult and child HI > 1, with adults CR in industrial areas >10^-4). Results also indicated that a ten-fold reduction of silt load resulted in a >4-fold decrease in risk. Collectively, the results suggest that fine road dust is a potential hotspot for mineral exposure in populations living around a mine and its tailings; moreover, that effective prevention measures like road cleaning and truck regulation are urgently needed.

Chemical speciation, pollution and ecological risk of toxic metals in readily washed off road dust in a megacity (Nanjing), China

Pollution of potentially toxic metals (PTMs) in road dust (RD) is becoming an important threat to the urban environmental quality and human health. The chemical speciation of PTMs is an important index charactering the risks, which may also closely relate to the pollution level and source but it was poorly understood. In this study, the chemical speciation of Cd, Cr, Cu, Ni, Pb and Zn in the RD of a megacity (Nanjing), China was determined following an optimized BCR (proposed by the European Community Bureau of Reference) sequential extraction procedure to assess their pollution and potential eco-risk and to explore the variations of metal chemical speciation with the pollution levels and sources. Total concentrations of the PTMs in the RD were enriched 1.4- to 123-fold relative to the subsoil with median contamination factors (CF) of 6.7 (Pb), 6.0 (Cu), 5.5 (Cd), 4.0 (Zn), 2.0 (Cr) and 1.9 (Ni). Pollution of the PTMs should be mainly from industrial and traffic emissions and showed high CF values in the northern industrial zone. Whereas, the chemical percentages of each metal showed relatively narrow spatial variations and were not statistically correlated with the pollution levels (p = 0.05). Comparing of similar studies indicates that no regular patterns existed in chemical percentages for each metal in RD polluted by the traffic and/or both the industrial and traffic sources. In the RD of Nanjing, Pb was mostly associated with reducible phase, Cd and Zn were mainly present in acid-soluble phase, Cu was mostly concentrated in oxidizable phase, while Cr and Ni were predominantly present in residual phase. As the typical pollutants, anthropogenic Cd, Cu, Pb and Zn were mostly associated with the potential mobile phases but also with the residual phase in the RD of Nanjing, causing 1.4- to 3.0-fold increase in the mobility. Combining the assessments from eco-risk index, risk assessment code and sediment quality guidelines with the pollution levels and chemical speciation, we deduced that Cd, Cu, Pb and Zn may pose certain eco-risk upon transport into the aquatic system and soil, and Cd should be primarily concerned.

Vehicular contribution of PAHs in size dependent road dust: A source apportionment by PCA-MLR, PMF, and Unmix receptor models

This study focuses on the source apportionments of polycyclic aromatic hydrocarbons (PAHs) in road dust (RD) with four size fractions through three receptor models of principal component analysis with multiple linear regression (PCA-MLR), positive matrix factorization (PMF) and Unmix. The concentrations of total PAHs range from 0.45 to 2.03μgg^-1. Results show that the concentrations of PAHs increased with a decreasing size fraction. Similar potential sources to PAHs in RD were extracted by three models with a little difference in numbers and percent load contributions of each identified sources. The overall proportion of the identified sources were ranked as vehicular emission>coke oven>surface pavement>others in each size fractions. In terms of risk assessment, the mean values of incremental lifetime cancer risk (ILCR) of the total cancer risk of PAHs in RD were lower than the baseline value of an acceptable risk. However, PAHs in smaller size fraction prone to have a higher adverse effect on children via ingestion. Furthermore, the ecological risk assessment of hazard quotients and mean hazard quotients indicated that PAHs in RD had a 9% probability of being toxic to the benthic organisms and aquatic environment.

Source and path identification of metals pollution in a mining area by PMF and rare earth element patterns in road dust

To better assess pollution and offer efficient protection for local residents, it is necessary to both conduct an exhaustive investigation into pollution levels and quantify its contributing sources and paths. As it is the biggest light rare earth element (REE) reserve in the world, Bayan Obo deposit releases large amounts of heavy metals into the surrounding environment. In this study, road dust from zones located at different distances to the mining area was collected and sieved using seven sizes. This allowed for subsequent analysis of size-dependent influences of mining activities. A receptor model was used to quantitatively assess mine contributions. REE distribution patterns and other REE parameters were compared with those in airborne particulates and the surrounding soil to analyze pollution paths. Results showed that 27 metals were rated as moderately to extremely polluted (2<geo-accumulation index<6) in both mine processing and residential areas. REEs are the most polluted elements, followed by Mo, Cd, Pb, and Ag. Although mining contribution to pollution levels increased with decreasing distance and size, 35% of REEs and 6% of other polluted metals in residential area road dust originated directly from the mine. The provenance index (PI) calculated using the REE parameters confirmed this result. While the REE distribution pattern showed that airborne particulates may not be the path for mining-derived particles, they may be one for other sources.

Tracing source, distribution and health risk of potentially harmful elements (PHEs) in street dust of Durgapur, India

Street dust samples from Durgapur, the steel city of eastern India, were collected from five different land use patterns, i.e., national highways, urban residential area, sensitive area, industrial area and busy traffic zone during summer, monsoon, and winter to analyze the pollution characteristics, chemical fractionation, source apportionment and health risk of heavy metals (HMs). The samples were fractionated into ≤ 53 µm and analyzed for potentially harmful elements (PHEs) viz. Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. Summer season indicated higher concentrations of PHEs when compared to the other two seasons. Mean enrichment factor (EF), geo-accumulation index (Igeo), and contamination factor (CF) were high for Cd followed by Pb during all the three season in Durgapur. Chemical fractionation was executed in order to obtain distribution patterns of PHEs and to evaluate their bioavailable fractions in street dust samples. Mn was found to be highly bioavailable and bioavailability of the PHEs were in the order of Mn > Zn > Pb > Ni > Cd > Cu > Fe > Cr. Principal Component Analysis (PCA), cluster analysis, correlation analysis indicated the main sources of PHEs could be industrial, especially coal powered thermal plant, iron and steel industries and cement industries and vehicular. Multivariate analysis of variance (MANOVA) indicated that sites, seasons and their interaction were significantly affected by different PHEs as a whole. The health risk was calculated with total metal as well as mobile fraction of PHEs, which indicated that the actual non-carcinogenic risk due to bioavailable PHEs was less (HI < 1) when compared to total concentrations of PHEs. Carcinogenic risk was observed for total Cr in street dust (Child: 4.6E-06; Adult: 3.6E-06).

Status, source identification, and health risks of potentially toxic element concentrations in road dust in a medium-sized city in a developing country

This study aims to determine the status of potentially toxic element concentrations of road dust in a medium-sized city (Rawang, Malaysia). This study adopts source identification via enrichment factor, Pearson correlation analysis, and Fourier spectral analysis to identify sources of potentially toxic element concentrations in road dust in Rawang City, Malaysia. Health risk assessment was conducted to determine potential health risks (carcinogenic and non-carcinogenic risks) among adults and children via multiple pathways (i.e., ingestion, dermal contact, and inhalation). Mean of potentially toxic element concentrations were found in the order of Pb > Zn > Cr(IV) > Cu > Ni > Cd > As > Co. Source identification revealed that Cu, Cd, Pb, Zn, Ni, and Cr(IV) are associated with anthropogenic sources in industrial and highly populated areas in northern and southern Rawang, cement factories in southern Rawang, as well as the rapid development and population growth in northwestern Rawang, which have resulted in high traffic congestion. Cobalt, Fe, and As are related to geological background and lithologies in Rawang. Pathway orders for both carcinogenic and non-carcinogenic risks are ingestion, dermal contact, and inhalation, involving adults and children. Non-carcinogenic health risks in adults were attributed to Cr(IV), Pb, and Cd, whereas Cu, Cd, Cr(IV), Pb, and Zn were found to have non-carcinogenic health risks for children. Cd, Cr(IV), Pb, and As may induce carcinogenic risks in adults and children, and the total lifetime cancer risk values exceeded incremental lifetime.

Contamination and health risks of heavy metals in street dust from a coal-mining city in eastern China

We collected street dust from Huainan, a typical coal-mining city in China, to investigate the contamination features and health risks of heavy metals. Concentrations of Co, Cr, Cu, Pb, As, and Sb were generally low to moderate, while pollution levels of Cd and Hg were moderate to high. Concentrations of Cd and Hg were associated with considerable health risks at 64.3% and 58.6% of sites, respectively. In particular, about a fifth of samples had associated high risks as a result of Hg contamination levels. Relative to other urban areas, the street dust from the mining area had no more severe metal pollution, which might be partly attributed to the deposition of coal dust onto street dusts. A source assessment indicated that metals in dust form Huainan were mainly derived from vehicular-related activities, industrial emissions, weathering of coal dust and natural soils, and coal combustion. Although the health risk levels from exposure to individual metals in dusts were low, the non-carcinogenic risks from multiple metals to local children exceeded the acceptable level (1.0), suggesting that the overall risk from exposure to multiple metals in dust is concerning.

Accumulation of heavy metals and antioxidant responses in Pinus sylvestris L. needles in polluted and non-polluted sites

The purpose of this study was to determine the concentrations of heavy metals (cadmium, iron, manganese, lead and zinc) in current-year, 1-year old and 2-year old needles of Pinus sylvestris L. Trees were from three heavily polluted (immediate vicinity of zinc smelter, iron smelter and power plant) and three relatively clean sites (nature reserve, ecologically clean site and unprotected natural forest community) in southern Poland. Analysis also concerned the antioxidant response and contents of protein, proline, total glutathione, non-protein thiols and activity of guaiacol peroxidase (GPX) in the needles. Generally, in pine needles from the polluted sites, the concentrations of the metals were higher and increased with the age of needles, and in most cases, antioxidant responses also were elevated. The highest levels of Cd, Pb and Zn were found in 2-year old pine needles collected near the polluted zinc smelter (respectively: 6.15, 256.49, 393.5 mg kg(-1)), Fe in 2-year old pine needles in the vicinity of the iron smelter (206.82 mg kg(-1)) and Mn in 2-year old needles at the ecologically clean site (180.32 mg kg(-1)). Positive correlations were found between Fe, Mn and Pb and the content of proteins and NPTs, between Cd and non-protein -SH groups, and between Zn and proline levels. The activity of GPX increased under the influence of Mn, while glutathione levels tended to decrease as Mn levels rose. The data obtained show that the levels of protein and non-protein -SH groups may be useful in biological monitoring, and that these ecophysiological parameters seem to be good evidence of elevated oxidative stress caused by heavy metals.