Heavy metal concentrations in particle size fractions from street dust of Murcia (Spain) as the basis for risk assessment

Nanoparticles of dust as an emerging contaminant in urban environments

Due to very high mobility in the environment and penetration ability into living organisms, nanoparticles (NPs) of urban dust pose a potential threat to human health and urban ecosystems. Currently, data on the chemical composition of NPs of urban dust, their fate in the environment, and corresponding risks are rather limited. In the present work, NPs of deposited urban dust have been comprehensively studied for the first time; NPs isolated from 78 samples of dust collected in Moscow, the largest megacity in Europe, being taken as example. The elemental composition, potential sources as well as environmental, ecological, and health risks of NPs of urban dust are assessed. It is found that dust NPs are extremely enriched by Cu, Hg, Zn, Mo, Sb, and Pb, and can serve as their carrier in urban environments. No regularities in the spatial distribution of elements have been found, probably, due to high mobility of dust NPs. High ecological and health risks caused by dust NPs are demonstrated. Source apportionment study has evaluated one natural and two anthropogenic sources of elements in NPs of urban dust; the contribution of natural and anthropogenic sources being comparable. It is also shown that dust NPs may be considered as an important carrier of trace elements in urban aquatic systems. Additionally, the risks associated with NPs and bulk samples of dust have been compared. The observed risks associated with NPs are significantly higher.

Mechanistic insights into cadmium exacerbating 2-Ethylhexyl diphenyl phosphate-induced human keratinocyte toxicity: Oxidative damage, cell apoptosis, and tight junction disruption

Organophosphate flame retardants 2-ethylhexyldiphenyl phosphate (EHDPP) and cadmium (Cd) are ubiquitous in environmental matrices, and dermal absorption is a major human exposure pathway. However, their detrimental effects on the human epidermis remain largely unknown. In this study, human keratinocytes (HaCaT cells) were employed to examine the toxicity and underlying mechanisms of co-exposure to EHDPP and Cd. Their influence on cell morphology and viability, oxidative damage, apoptosis, and tight junction were determined. The results showed that co-exposure decreased cell viability by >40 %, induced a higher level of oxidative damage by increasing the generation of reactive oxygen species (1.3 folds) and inhibited CAT (79 %) and GPX (90 %) activities. Moreover, Cd exacerbated EHDPP-induced mitochondrial disorder and cellular apoptosis, which was evidenced by a reduction in mitochondrial membrane potential and an elevation of cyt-c and Caspase-3 mRNA expression. In addition, greater loss of ZO-1 immunoreactivity at cellular boundaries was observed after co-exposure, indicating skin epithelial barrier function disruption, which may increase the human bioavailability of contaminants via the dermal absorption pathway. Taken together, oxidative damage, cell apoptosis, and tight junction disruption played a crucial role in EHDPP + Cd triggered cytotoxicity in HaCaT cells. The detrimental effects of EHDPP + Cd co-exposure were greater than individual exposure, suggesting the current health risk assessment or adverse effects evaluation of individual exposure may underestimate their perniciousness. Our data imply the importance of considering the combined exposure to accurately assess their health implication.

Driving factors for distribution and transformation of heavy metals speciation in a zinc smelting site

Heavy metal pollution at an abandoned smelter pose a significant risk to environmental health. However, remediation strategies are constrained by inadequate knowledge of the polymetallic distribution, speciation patterns, and transformation factors at these sites. This study investigates the influence of soil minerals, heavy metal occurrence forms, and environmental factors on heavy metal migration behaviors and speciation transformations. X-ray diffraction analysis revealed that the minerals associated with heavy metals are mainly hematite, franklinite, sphalerite, and galena. Sequential extraction results suggest that lead and zinc are primarily present in the organic-sulfide fractions (F4) and residual form (F5) in the soil, accounting for over 70% of the total heavy metal content. Zinc displayed greater instability in carbonate-bound (16%) and exchangeable (2%) forms. The migration and diffusion patterns of heavy metals in the subsurface environment were visualized through the simulation of labile state heavy metals, demonstrating high congruence with groundwater pollution distribution patterns. The key environmental factors influencing heavy metal stable states (F4 and F5) were assessed by integrating random forest models and redundancy analysis. Primary factors facilitating Pb transformation into stable states were available phosphorus, clay content, depth, and soil organic matter. For Zn, the principal drivers were Mn oxides, soil organic matter, clay content, and inorganic sulfur ions. These findings enhance understanding of the distribution and transformation of heavy metal speciation and can provide valuable insights into controlling heavy metal pollution at non-ferrous smelting sites.

Identification and quantification of trace metal(loid)s in water-extractable road dust nanoparticles using SP-ICP-MS

Resuspension of road dust is a major source of airborne particulate matter (PM) in urban environments. Inhalation of ultrafine particles (UFP; < 0.1 μm) represents a health concern due to their ability to reach the alveoli and be translocated into the blood stream. It is therefore important to characterize chemical properties of UFPs associated with vehicle emissions. We investigated the capability of Single-Particle ICP-MS (SP-ICP-MS) to quantify key metal(loid)s in nanoparticles (NPs; < 0.1 μm) isolated from road dust collected in Toronto, Canada. Water extraction was performed to separate the <1-μm fraction from two different road dust samples (local road vs. arterial road) and a multi-element SP-ICP-MS analysis was then conducted on the samples' supernatants. Based on the particle number concentrations obtained for both supernatants, the metal(loid)-containing NPs could be grouped in the following categories: high (Cu and Zn, > 1.3 × 1011 particles/L), medium (V, Cr, Ba, Pb, Sb, Ce, La), low (As, Co, Ni, < 4.6 × 109 particles/L). The limit of detection for particle number concentration was below 5.5 × 106 particles/L for most elements, except for Cu, Co, Ni, Cr, and V (between 0.9 and 7.7 × 107 particles/L). The results demonstrate that road dust contains a wide range of readily mobilizable metal(loid)-bearing NPs and that NP numbers may vary as a function of road type. These findings have important implications for human health risk assessments in urban areas. Further research is needed, however, to comprehensively assess the NP content of road dust as influenced by various factors, including traffic volume and speed, fleet composition, and street sweeping frequency. The described method can quickly characterize multiple isotopes per sample in complex matrices, and offers the advantage of rapid sample scanning for the identification of NPs containing potentially toxic transition metal(loid)s at a low detection limit.

Exposure risks of lead and other metals to humans: A consideration of specific size fraction and methodology

Particle size is a critical influencing factor in assessing human exposure risk as fine particles are generally more hazardous than larger coarse particles. However, how particle composition influences human health risk is only poorly understood as different studies have different utilised different definitions and as a consequence there is no consensus. Here, with a new methodology taking insights of each size fraction load (%GSFload), metal bioaccessibility, we classify which specific particle size can reliably estimate the human exposure risk of lead and other metals. We then validate these by correlating the metals in each size fraction with those in human blood, hair, crop grain and different anthropogenic sources. Although increasing health risks are linked to metal concentration these increase as particle size decrease, the adjusted-risk for each size fraction differs when %GSFload is introduced to the risk assessment program. When using a single size fraction (250-50 µm, 50-5 µm, 5-1 µm, and < 1 µm) for comparison, the risk may be either over- or under-estimated. However, by considering bulk and adjusting the risk, it would be possible to obtain results that are closer to the real scenarios, which have been validated through human responses and evidence from crops. Fine particle size fractions (< 5 µm) bearing the mineral crystalline or aggregates (CaCO3, Fe3O4, Fe2O3, CaHPO4, Pb5(PO4)3Cl) alter the accumulation, chemical speciation, and fate of metals in soil/dust/sediment from the different sources. Loaded lead in the size fraction of < 50 µm has a significantly higher positive association with the risk-receptor biomarkers (BLLs, Hair Pb, Corn Pb, and Crop Pb) than other size fractions (bulk and 50-250 µm). Thus, we conclude that the < 50 µm fraction would be likely to be recommended as a reliable fraction to include in a risk assessment program. This methodology acts as a valuable instrument for future research undertakings, highlighting the importance of choosing suitable size fractions and attaining improved accuracy in risk assessment results that can be effectively compared.

WITHDRAWN: Trace metals translocation from soil to plants: Health risk assessment via consumption of vegetables in the urban sprawl of a developing country

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Stability of exogenous Cadmium in different vineyard soils and its effect on grape seedlings

Cadmium (Cd) being potentially toxic heavy metal, has become increasingly serious to vineyard soil and grapes in recent years. Soil type is one of the main factors affecting the absorption of Cd in grapes. To investigate the stabilization characteristics and form changes of Cd in different types of vineyard soils, a 90-days incubation experiment was conducted after exogenous Cd addition to 12 vineyard soils from typical vineyards in China. The inhibition of exogenous Cd on grape seedlings was determined based on the pit-pot incubation experiment (200 kg soil per pot). The results demonstrate that Cd concentration in all the sampling sites did not exceed the national screening values (GB15618-2018; i.e., 0.3 mg/kg when pH was lower than 7.5, 0.6 mg/kg when pH was higher than 7.5);. Cd in Fluvo-aquic soil 2, Red soils1, 2, 3 and Grey-Cinnamon soil is dominated by acid-soluble fraction, but was mainly in residual fraction in the remain soils. Throughout the aging process, proportion of the acid-soluble fraction increased and then decreased, while proportion of the residual fraction decreased and then increased, after exogenous Cd was added. The mobility coefficients of Cd in Fluvo-aquic soil 2 and Red soil 1, 2 increased 2.5, 3 and 2 folds, after exogenous Cd addition, respectively. Compared with CK (control), the correlation between total Cd content and its different fractions was relatively weak in the Cdl (low concentration) and Cdh (high concentration) groups. Poor Cd stabilization and strong inhibition of seedling growth rate were observed in Brown soil 1, black soil, red soil 1 and cinnamomic soil. Fluvo-aquic soil 2, 3 and Brown soil 2 showed good Cd stability and small inhibition effect on grape seedlings. These results show that Cd stability in soils and inhibition rate of grape seedlings by Cd are strongly influenced by soil type.

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.

Effects of Road Dust Particle Size on Mineralogy, Chemical Bulk Content, Pollution and Health Risk Analyses

Because of the rising environmental and health concerns associated with atmospheric pollution caused by potentially toxic elements (PTEs), several road dust studies have been performed across the world in recent decades. This paper illustrates the effects of particle size on the PTE contents, mineralogical composition, environmental pollution and health risk assessments in road dust from Barcelona (Spain). The samples were sieved into five size fractions ranging from <45 to 500-800 µm. Although the major mineral contents (tectosilicates, phyllosilicates, and carbonates) were profuse in all fractions, the identified inhalable PTE particles (e.g., Fe, Cr, Cu, Zn, Ni, and REE), with size < 10 µm, were more pervasive in the finest fraction (<45 μm). This is consistent with the concentrations measured: the finest fractions were richer in PTEs than the coarser ones, resulting in a direct correlation with the enrichment factor (EFx), geo-accumulation (Igeo), and non-carcinogenic (HI) and carcinogenic (CRI) values. Igeo and EFx values can be appropriate tracers for some common elements (e.g., Zn, Sb, Sn, Cu, and Cr), but they do not seem adequate for anthropogenic particles accumulated at concentrations similar to the geogenic background. Overall, the HI and CRI values obtained in Barcelona were acceptable, reflecting no serious health impacts in the study area, except for Cr. Our results suggest that fine dust particles are a more suitable fraction to conduct pollution and health risk assessments than coarser ones, although the EFx, Igeo, HI, and CRI threshold values should be redefined in the future to include all emergent pollutants as well. In summary, monitoring programs should include at least the road dust evaluation of <45 µm particles, which can be performed with a simple sieving method, which is both time- and cost-effective.

A comprehensive approach to quantify the source identification and human health risk assessment of toxic elements in park dust

In this research, enrichment factor (EF) and pollution load index were utilized to explore the contamination characteristics of toxic elements (TEs) in park dust. The results exhibited that park dust in the study area was mainly moderately polluted, and the EF values of dust Cd, Zn, Pb, Cu and Sb were all > 1. The concentrations of Cr, Cu, Zn and Pb increased with the decrease of dust particle size. The investigation results of chemical speciation and bioavailability of TEs showed that Zn had the highest bioavailability. Three sources of TEs were determined by positive matrix factorization model, Pearson correlation analysis and geostatistical analysis, comprising factor 1 mixed sources of industrial and transportation activities (46.62%), factor 2 natural source (25.56%) and factor 3 mixed source of agricultural activities and the aging of park infrastructures (27.82%). Potential ecological risk (PER) and human health risk (HHR) models based on source apportionment were exploited to estimate PER and HHR of TEs from different sources. The mean PER value of TEs in the park dust was 114, indicating that ecological risk in the study area was relatively high. Factor 1 contributed the most to PER, and the pollution of Cd was the most serious. There were no significant carcinogenic and non-carcinogenic risks for children and adults in the study area. And factor 3 was the biggest source of non-carcinogenic risk, and As, Cr and Pb were the chief contributor to non-carcinogenic risk. The primary source of carcinogenic risk was factor 2, and Cr was the cardinal cancer risk element.

Overall distribution of tire-wear particles, nano‑carbon black, and heavy metals in size-fractionated road dust collected from steel industrial complexes

Tire-wear particles (TWP) from vehicles serves as a non-exhaust emission source. The mass content of metallic species in road dust may increase owing to the traffic of heavy vehicles and industrial activity; consequently, metallic particles are also present in road dust. Herein, road dust collected from steel industrial complexes with high traffic of high-weight vehicles and the composition distribution of five size-fractioned particle sizes were analyzed. Road dust samples were collected from three areas near steelmaking complexes. The mass distribution of TWP, carbon black (CB), bituminous coal, and heavy metals (Fe, Zn, Mn, Pb, Ni, As, Cu, Cd, and Hg) in different size fractions of road dust was quantified by combining four different analytical techniques. In the magnetic separation for <45 μm fraction, 34.4 wt% and 50.9 wt% was removed for steelmaking and steel-related industrial complexes, respectively. As the particle size decreased, the mass content of Fe, Mn, and TWP increased. The enrichment factors of Mn, Zn, and Ni were higher than two, indicating that they were related to industrial activities in steel complexes. The maximum concentrations of TWP and CB originating from the vehicle varied depending on the region and particle size range: TWP 2.066 wt% at 45-75 μm (industrial complex) and CB 5.559 wt% at 75-160 μm (steel complex). Coal was only found in the steel complex. Finally, to reduce the exposure of the finest particles to road dust, three methods were suggested. Magnetic fraction must be removed from road dust using magnetic separation; the fly dust of coal during transportation must be suppressed, and covers must be used in coal yards; the mass contents of TWP and CB in road dust should be removed by vacuum cleaning instead of water flushing.

Benzo[a]pyrene in Moscow road dust: pollution levels and health risks

Benzo[a]pyrene (BaP) is one of the priority pollutants in the urban environment. For the first time, the accumulation of BaP in road dust on different types of Moscow roads has been determined. The average BaP content in road dust is 0.26 mg/kg, which is 53 times higher than the BaP content in the background topsoils (Umbric Albeluvisols) of the Moscow Meshchera lowland, 50 km east of the city. The most polluted territories are large roads (0.29 mg/kg, excess of the maximum permissible concentration (MPC) in soils by 14 times) and parking lots in the courtyards (0.37 mg/kg, MPC excess by 19 times). In the city center, the BaP content in the dust of courtyards reaches 1.02 mg/kg (MPC excess by 51 times). The accumulation of BaP depends on the parameters of street canyons formed by buildings along the roads: in short canyons (< 500 m), the content of BaP reaches maximum. Relatively wide canyons accumulate BaP 1.6 times more actively than narrow canyons. The BaP accumulation in road dust significantly increases on the Third Ring Road (TRR), highways, medium and small roads with an average height of the canyon > 20 m. Public health risks from exposure to BaP-contaminated road dust particles were assessed using the US EPA methodology. The main BaP exposure pathway is oral via ingestion (> 90% of the total BaP intake). The carcinogenic risk for adults is the highest in courtyard areas in the south, southwest, northwest, and center of Moscow. The minimum carcinogenic risk is characteristic of the highways and TRR with predominance of nonstop traffic.

Health risk assessment of the European inhabitants exposed to contaminated ambient particulate matter by potentially toxic elements

PM₁₀-associated potential toxic elements (PTEs) can enter the respiratory system and cause health problems. In the current study, the health risk indices caused by PM₁₀ inhalation by adults, children, and infants in 158 European cities between 2013 and 2019 were studied to determine if Europeans were adversely affected by carcinogenic and non-carcinogenic factors or not. The Mann-Kendall trend test examined PM₁₀'s increasing or decreasing trend. Random Forest analysis was also used to analyse meteorological factors affecting PM₁₀ in Europe. Hazard quotient and cancer risk were estimated using PM₁₀-associated PTEs. Our results showed a decline in continental PM₁₀ concentrations. The correlation between PM₁₀ concentrations and temperature (-0.40), PBLH (-0.39), and precipitation were statistically strong (-0.21). The estimated Pearson correlation coefficients showed a statistically strong positive correlation between As & Pb, As & Cd, and Cd & Pb during 2013-2019, indicating a similar origin. PTEs with hazard quotients below one, regardless of subpopulation type, posed no noncancerous risk to Europeans. The hazard quotient values positively correlated with time, possibly due to elevated PTE levels. In our study on carcinogen pollution in Europe between 2013 and 2019, we found unacceptable levels of As, Cd, Ni, and Pb among adults, children, and infants. Carcinogenic risk rates were highest for children, followed by infants, adult women, and adult men. Therefore, besides monitoring and mitigating PM concentrations, effective control of PM sources is also needed.

Sequential extraction of selected metals to assess their mobility, pollution status and health risk in roadside soil

Assessment of the mobility and contamination of trace metals in the roadside soil is important to explore the environmental quality and potential risks to the public health. The contents of selected metals (Ca, Mg, Sr, K, Na, Li, Fe, Mn, Zn, Cu, Ag, Co, Ni, Cr, Cd and Pb) in the roadside soil collected from major highways/roadsides of Lahore, Pakistan were quantified employing mBCR sequential extraction. Among the metals, Ca, Sr and Na showed highest contribution in exchangeable fraction, Pb in the reducible fraction and K, Li, Fe, Ag, Ni, Cu and Cr in the residual fraction. However, Mg and Mn exhibited relatively higher contents in exchangeable and residual fractions while Cd, Co and Zn showed relatively higher concentration in all four fractions. Comparatively higher mobility and availability in the soil was shown by Ca followed by Sr, Pb, Na, Cd, Zn, Co, Mn, Cu, Ag and Ni. Principal component analysis demonstrated considerable anthropogenic contributions of the trace metals in the roadside soil. The pollution indices showed that the soil was heavily to extremely polluted by Cd and Ag, followed by significant to very high contamination for Co, Ni and Pb. The modified degree of contamination (4.60 and 3.99 in summer and winter, respectively) revealed an overall high degree of contamination. The health risk assessment revealed that the calculated risks were within the safe limit thereby indicating insignificant non-carcinogenic and carcinogenic heath risk to the populace.

The relationships between fractal parameters of soil particle size and heavy-metal content on alluvial-proluvial fan

The particle size distribution (PSD) of soil is an important factor in determining heavy-metal content, mobility, and transformation. One method of describing the soil PSD is applying fractal theory. This study explored the use of fractal theory to characterize soil PSD in the alluvial-proluvial fan located downstream of the Yangshuo lead‑zinc mine. The relationships between fractal parameters of soil PSD and heavy-metal content were analyzed. The results showed that soil in front of the mountain (FM) had higher clay content than soil on the mountain slope (MS) or in the middle of the alluvial-proluvial fan (MF). Among the different sections of the alluvial-proluvial fan, MS had the largest capacity dimension D(0), information dimension D(1), correlation dimension D(2), single fractal dimension D, spectral width Δα, and D(1)/D(0), whereas MF had the greatest symmetry degree Δf. Soil of MS had the highest ω (Cr) and ω (Fe), while FM had the highest ω (Zn), ω (Mn), ω (Pb), ω (Cu), ω (As), ω (Sb), and ω (Cd). Fractal parameters of soil PSD and soil mechanical composition were significantly correlated, while both variables were correlated with heavy-metal content. Fractal parameters can be used to indicate heavy-metal content when heavy metals migrate due to migration of particle size. This study thus introduces an empirical method for evaluating heavy-metal content in soil and analyzing the mechanisms of their migration, making a strong contribution to developing strategies that limit heavy-metal pollution.

Contamination levels and source apportionment of potentially toxic elements in size-fractionated road dust of Moscow

The distributions of potentially toxic elements (PTEs) among PM₁, PM_1-10, PM_10-50, and PM_50-1000 fractions of the road dust were studied in the western and eastern parts of Moscow, impacted mainly by the road transport and the industrial sector, respectively. The partitioning of PTEs in road dust can provide more precise information on pollution sources and its further interpretation regarding human health risks. The concentrations of PTEs were analyzed by mass and atomic emission inductively coupled plasma spectrometry. Differences in the results between the western and eastern parts of the city were caused by the dissimilarity between traffic and industrial emissions. The source apportionment of the PTEs was carried out using absolute principal component analysis with multiple linear regressions (PCA/APCS-MLR). The contribution from anthropogenic sources was significant to PM₁ and PM_1-10 particles. In coarser fractions (PM_10-50, PM_50-1000), it decreased due to the input with the wind-induced resuspension of soil and rock particles. In the eastern part of the city, the accumulation of PTEs (especially Mo, Sb, Cd, Sn, Bi, Co, and As) is the most active in PM_1-10, while in the western part, it is most pronounced in PM₁ (especially Pb, Cu, Cr, and W) which is associated with differences in the size of particles coming from traffic and industrial sources. In the eastern part of Moscow, in comparison with the western part, the contribution from industrial sources to the accumulation of PTEs in all particle size fractions was higher by 10-30%. In the western part of Moscow, the finest particles PM₁ and PM_1-10 demonstrate the trend of rising pollution levels with the increase in road size, while in the eastern part of the city, only coarse particles PM_50-1000 show the same trend. In the fractions PM₁ and PM_1-10 of road dust, a significant contribution was made by anthropogenic sources; however, its role decreased in the coarse fractions-PM_10-50 and especially in PM_50-1000- due to the influence of roadside soils and their parent material.

Potential application of enhanced phytoremediation for heavy metals treatment in Nepal

Heavy metals contamination in soil and water resources is a great threat to developing countries because of the lack of waste treatment facilities. A majority of wastewater treatment methods are known to be expensive and out of reach for municipalities and small pollution treatment enterprises. Phytotechnology is a promising, sustainable, environment-friendly, and cost-effective technique for domestic and industrial wastewater treatment in places where land is available. However, interest in conventional remediation methods and the lack of information on recent advances in a significant portion of the society in developing countries have restrained the applications of phytoremediation. This review discusses the concept of phytoremediation, mechanisms of heavy metals removal by plants, and the potential application of enhanced phytoremediation technologies in developing countries like Nepal. The authors also review the commercially viable hyperaccumulator species with their native distribution, heavy metals intake capacity, and their availability in Nepal. Those native plants can be utilized locally or introduced strategically in other parts/countries as well. Thus, for a flora-rich country like Nepal, this study holds great potential and presents enhanced phytoremediation as an effective and sustainable strategy for the future.

Effects of soil aging conditions on distributions of cadmium distribution and phosphatase activity in different soil aggregates

Aging behaviors of metals in the field differ from those in a controlled laboratory environment. Whether aging conditions influence the fates of metals in soil remains unclear. In this study, distributions of cadmium (Cd) and phosphatase activity were compared in soil aggregates (i.e., >2, 1-2, 0.25-1, and <0.25 mm) along a profile (0-5, 5-10, and 10-15 cm) at the end of 500-day aging experiments under both controlled laboratory and field conditions. Cd concentration in the 0-5 cm layer was lower and Cd concentration in the 5-10 cm layer was higher in field-aged soil compared to laboratory-aged soil. 25.26-35.62% of soil Cd was loaded in >2 mm aggregates of field-aged soils, and 58.41-66.95% was in laboratory-aged soils. Higher loadings of Cd in 0.25-1 and <0.25 mm aggregates were found in field-aged soil. A higher proportion of exchangeable Cd fraction (20.93% of total soil Cd) was found in the 0-5 cm layer of field-aged soil than in laboratory-aged soil (17.63%), while the opposite tendency was found in deeper soil layers. Soil phosphatase activities in field-aged soils were 1.13-1.26 times higher than in laboratory-aged soils. Phosphatase loadings in the >2 mm aggregates were lower and loadings in both the 1-2 and 0.25-1 mm aggregates were higher in field-aged soils than in laboratory-aged soils. Furthermore, correlation analysis and principal component analysis indicated that available Cd fractions accounted for most of the variations in phosphatase activities. In summary, the fates of the exogenous metal Cd differed between field and controlled laboratory conditions. To better understand the behaviors of heavy metals in soil, especially in a seasonal freeze-thaw area, further field studies are needed.

Metal biomonitoring using fractioned dust to investigate urinary and oxidative stress biomarkers among occupationally exposed chromite mine workers

Exposure to heavy metals has been associated with the generation of reactive oxygen species (ROS) among exposed individuals in occupational and environmental settings. Dust is considered a significant contributor to airborne metal exposure, and previous data suggest that their levels in dust may vary based on its particle sizes. However, no biomonitoring study has been reported so far to address the metal-induced oxidative stress using different dust fractions, particularly in occupational settings. We designed a systematic cross-sectional study involving 110 chromite mine workers stratified into loaders (n = 28), extractors (n = 47) and operators (n = 35), and controls (n = 30) to find out the association between dust-bound metal exposure and oxidative stress using urinary creatinine-adjusted metal level as a biomarker of metal exposure. Results suggested elevated urinary levels of Cr 51.34 ± 8.6 along with Pb 34.29 ± 4.39, Cd 21.1 ± 2.6, and Ni 18.98 ± 3.01 µg/g creatinine in exposed (extractor group) workers. Correlating metal levels with oxidative stress revealed elevated malondialdehyde (MDA) levels of 62.28 ± 5.52 nM/dl among the extractors showing high levels of lipid peroxidation. Furthermore, blood superoxide dismutase (SOD) was also found significantly correlated (P = 0.000) with urinary toxic metal levels among exposed workers. We report the association between metal exposure and oxidative stress in exposed mining workers that may give rise to workers' susceptibility towards genetic and non-genetic health implications. The current study emphasized on the need for exposure control measures in the chromite ore mining activity areas.

Geochemistry of street dust in Tyumen, Russia: influence of traffic load

This study investigates the elemental composition, organic carbon content, pH values, and particle size characteristics in 50 road dust samples collected from Tyumen, a large city in Western Siberia (Russia). The content of 62 major and trace elements was studied using atomic emission spectrometry (ICP-AES) и inductively coupled plasma spectrometry (ICP-MS). It was revealed that the dust has an alkaline reaction pH = 7.4-10.2 and low organic carbon content (0.07-2.9%). The grain size distribution of the road dust samples revealed that the predominant grain size fraction was of 100-250 μm. The content of small particles (PM₂ and PM₁₀) representing the greatest environmental hazard is minimal on roads with an average traffic intensity. Studies have shown that the main road dust pollutants in Tyumen are Ni, Sb, Cr, Zn, and Co. The average geoaccumulation index (Igeo) values are ranked as Ni (2.2) > Sb (1.5) > Cr (1.3) > Zn (0.4) > Co (0.4) > Cu (0.2). The contamination evaluation through enrichment factor (EF) calculation showed that road dust is highly enriched in Ni and significantly in Cr and Sb. More than 80% of Zn, Co, and Cu and more than 90% of Ni, Sb, and Cr come from anthropogenic sources. The average concentration of Ni and Cr in the road dust of Tyumen is one order of magnitude higher than in other cities of the Earth where similar studies were carried out. The high Ni content is associated with the composition of local soils and roadways, increased content in vehicle exhaust gasses, and abrasion of metal parts. Calculations of the total enrichment index Ze showed that the level of road dust pollution in most of Tyumen's territory is hazardous.

Interactive effects of biochar amendment and lead toxicity on soil microbial community

This study determined the interactive effects of biochar and lead toxicity on the soil microbial community in a phytoextraction experiment. Arranged with a completely randomized design in a greenhouse, banana liners were planted singly in a sandy soil spiked with Pb(NO3)2 at 0, 400 and 1200 mg kg-1 and amended with bamboo biochar (pyrolyzing at 600 °C) at 0, 1, 3%. Soil samples were taken from triplicated pots five months after planting and measured for (i) content of lead and organic carbon; (ii) lead speciation; and (iii) microbial community composition through 16S rRNA gene sequencing. DNA sequencing results showed that lead and biochar treatments had significant individual and interactive effects on soil microbial dissimilarities from taxonomic levels of phyla to genera. While some specific taxa were lead resistant, biochar addition apparently alleviated lead toxicity and increased their richness (e.g., Alkanibacter, Muciaginibacter, Burkholderiaceae, and Beggiatoaceae). Soil analysis data indicated that biochar not only helped retain more lead in the soil matrix but created a soil environment inducive for transformation of lead into highly insoluble pyromorphite. This study highlights the effectiveness of biochar for lead remediation and the sensitivity of soil microorganisms in sensing changes in soil environment and lead bioavailability.

Arsenic and lead in soil: impacts on element mobility and bioaccessibility

Long-term brown coal mining contributes to risk element contents in soils surrounding coal basins. However, there is a lack of bioaccessibility characterization of the risk elements in the soils at the impacted locations for estimation of the potential health risk, in relation to the effects of soil particle size and element origin. In this study, soils from different geological areas (geogenic vs. anthropogenic) were sampled around the Most brown coal basin, Czech Republic. These soils were passed through sieves to obtain seven aggregate size fractions. For an estimation of the oral bioaccessibility of As and Pb in the size fractions, the physiologically based extraction test was applied, whereas the potential pulmonary bioaccessibility of the elements was estimated by using both Gamble's and Hatch's tests. The results showed that the geochemical pattern of the investigated elements clearly separates the soil samples collected from the mountain region (mineralization from geogenic processes) from those of the basin region (extensive coal mining). For As, the results indicated that it poses higher risks in the anthropogenically affected basin region due to its higher gastro-intestinal and pulmonary bioaccessibility in soil samples in this area. A higher bioaccessibility of As in the soils was recorded in the finer grain size fractions, which are usually air-borne and can be easily ingested and/or inhaled, leading to potential health risks to humans and livestock. The opposite pattern, with a higher content on coarse particles, was recorded for Pb, indicating a potential risk of livestock in the non-forest mountainous areas.

Pollution Level, Partition and Spatial Distribution of Benzo(a)pyrene in Urban Soils, Road Dust and Their PM10 Fraction of Health-Resorts (Alushta, Yalta) and Industrial (Sebastopol) Cities of Crimea

Polycyclic aromatic hydrocarbons (PAHs), in particular benzo(a)pyrene (BaP), are priority organic pollutants coming from various anthropogenic sources. The levels of accumulation and the spatial distribution of BaP in urban soils, road dust and their PM10 particles (with a diameter of less than 10 microns) were for the first time determined for various land use zones and roads of different size in the cities of Crimea—Alushta, Yalta and Sebastopol. The average content of BaP in soils and road dust in Alushta is 60 and 97 ng/g, in Yalta—139 and 64 ng/g, in Sebastopol—260 and 89 ng/g, respectively, which considerably exceeds the background level (1 ng/g). The BaP concentrations in PM10 particles of soils and dust are up to 11 and four times higher, respectively, than the total contents; they concentrate 35–70% of amount of the pollutant. The accumulation of BaP in soils and dust depends on the type of land use and size of roads. The exceedance of BaP standards in soils and road dust indicates a hazardous environmental situation in three cities of Crimea. The most dangerous are PM10 particles, which form anomalies with extreme levels of BaP contamination.

Concentrations, spatial distribution, sources and environmental health risks of potentially toxic elements in urban road dust across China

Potentially toxic element (PTE) pollution is widespread in road dust across China, and the effects of PTEs in road dust on health cannot be ignored. In this study, the concentrations of six PTEs (Pb, Cd, Cr, Cu, Zn and Ni) in 4336 road dust samples from 58 cities in 31 provincial regions of China taken after 2000 were obtained from the literatures. Based on these data, the spatial distribution, pollution sources, and ecological and human health risks of PTEs in road dust were comprehensively assessed and the main pollution factors and areas of high risk were identified. The results revealed that PTE levels are generally higher in eastern cities than western cities in China. The key driving factors are socioeconomic factors, including those related to transportation, industry, and population, for which the contribution rates are 57.80%, 55.39% and 37.19%, respectively. PTEs in the road dust with high ecological risks are mainly distributed in the southeastern coastal areas and the Beijing-Tianjin-Hebei region. No obvious noncarcinogenic risk was found for PTEs in road dust, but Cd and Pb may have potential noncarcinogenic risk, mainly distributed in cities in western China. Therefore, regions and pollution sources contributing to Pb and Cd levels should be monitored. The control of PTE pollution in China is a priority for ecological and environmental protection.

Evaluation of pollution indices, health hazards and source identification of heavy metal in dust particles and storm trajectory simulation using HYSPLIT model (Case study: Hendijan center dust, southwest of Iran)

Atmospheric dust is one of the most recent environmental pollutions in Iran. This study examines the concentration of heavy metals and the assessment of environmental and human health risk in the dust samples of Hendijan region as one of the most important centers of wind erosion in the southwestern of Iran. ICP-MSS analysis was performed on 18 samples of fine dust to specify the concentration of heavy metals. Studies showed that the highest concentrations of metals in these fine dust samples belong to Cr, Ni, Zn, Cu, As, Pb and Cd, respectively. Examining fine dust's pollution assessment showed that the highest enrichment and geo-accumulation index belong to As, Ni and Cr metals. Environmental risk assessment shows the low environmental risk of these fine dusts. The hazard quotient in children and adults belongs to Cr, As and Ni, respectively. Human health risk assessment also showed that the highest absorption of metals in both children and adults is through ingestion. The non-carcinogenic risk of heavy metals of dust samples in children is about 9 times more than adults. The highest risk of cancer in the adult group belongs to Ni metal and in the group of children belongs to As and Ni metal. PCA analysis showed that As, Cu, Cd, Cr and Ni are of anthropogenic origin and Zn and Pb are of geogenic origin. The source of the dust phenomenon with the HYSPLIT model and the backward method indicates the tracking of this dust mass through Iraq, and its probable origin was assessed in the centers of northern Iraq and southeastern Syria.

The Content and Sources of Potentially Toxic Elements in the Road Dust of Surgut (Russia)

The chemical and particle size composition of road dust in Surgut, which is a rapidly developing city in Western Siberia, was studied for the first time. Contents of major and trace elements were determined using ICP-MS and ICP-AES, respectively. It was found that the road dust had an alkaline pH (from 7.54 to 9.38) and that the particle size composition was dominated by the 100–250-μm fraction. The contamination assessment based on calculations of the enrichment factor (EF) showed that the road dust was significantly enriched in Sb and Cu and moderately enriched in Zn, Pb, Mo, Ni and W. The sources of these elements are probably associated with the abrasion of car tires and brake pads. Based on calculations of global pollution index (PIr) and total enrichment factor (Ze), the road dust of Surgut was characterized by a generally low level of potential ecological risk, except for stretches of road subject to regular traffic jams, where a moderate ecological risk level was identified. In comparison to the other Russian cities (Moscow, Chelyabinsk, Tyumen, etc.) where studies of road dust composition have been carried out, Surgut had similar contents of Cr and Cu and relatively lower contents of Sb, Cd, As and Pb.

Quantification and Characterization of Metals in Ultrafine Road Dust Particles

Road dust is an important source of resuspended particulate matter (PM) but information is lacking on the chemical composition of the ultrafine particle fraction (UFP; <0.1 µm). This study investigated metal concentrations in UFP isolated from the “dust box” of sweepings collected by the City of Toronto, Canada, using regenerative-air-street sweepers. Dust box samples from expressway, arterial and local roads were aerosolized in the laboratory and were separated into thirteen particle size fractions ranging from 10 nm to 10 µm (PM10). The UFP fraction accounted for about 2% of the total mass of resuspended PM10 (range 0.23–8.36%). Elemental analysis using ICP-MS and ICP-OES revealed a marked enrichment in Cd, Cr, Zn and V concentration in UFP compared to the dust box material (nano to dust box ratio ≥ 2). UFP from arterial roads contained two times more Cd, Zn and V and nine times more Cr than UFP from local roads. The highest median concentration of Zn was observed for the municipal expressway, attributed to greater volumes of traffic, including light to heavy duty vehicles, and higher speeds. The observed elevated concentrations of transition metals in UFP are a human health concern, given their potential to cause oxidative stress in lung cells.

Advanced mineral magnetic and geochemical investigations of road dusts for assessment of pollution in urban areas near the largest copper smelter in SE Europe

This study aims to evaluate the urban pollution by combined magnetometric and geochemical analyses on road dusts from three towns in the vicinity of Cu-smelter and ore mining. A collection of 117 road dust samples was investigated for their magnetic characteristics (magnetic susceptibility (χ), frequency dependent susceptibility, anhysteretic and isothermal (IRM) remanences), IRM step-wise acquisition and thermal demagnetization. Coarse grained magnetite and hematite were identified as major iron oxides in the emissions from ore spills and smelter, while traffic-related magnetic minerals were finer magnetite grains. Degree of pollution is assessed by geo-accumulation index, enrichment factor and Pollution Load Index (PLI) for a set of potentially toxic elements (PTEs). Using the geochemical data, we evaluate the carcinogenic and non-carcinogenic health risks for the population. Our results show that dust emissions from the industrial facilities likely pose significant health hazard for adults and children caused largely by Arsenic pollution in "hot spots". Based on the strong correlation between χ and most of the PTEs, detailed variations in pollution degree inside the urban areas are inferred. Strong linear regression between χ and PLI allows designating limit susceptibility values, corresponding to the PLI categories. This approach can be successfully applied for monitoring and mapping purposes at high spatial and temporal resolution.

Mineralogy and geochemistry of clay fractions in soils developed from different parent rocks in Limpopo Province, South Africa

This study investigates the mineralogical and geochemical characteristics of clay fractions in soils developed from different parent rocks in Limpopo Province, South Africa using the X-ray diffraction (XRD), X-ray Fluorescence (XRF) Spectrometry, Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS), Fourier Transform Infrared (FTIR) Spectrophotometry, Thermogravimetric Analysis and Differential Scanning Calorimetry (TGA-DSC) analytical techniques. Health risk associated with the presence of some trace elements was also investigated. The results revealed that the clay fractions had kaolinite as the dominant clay component occurring with other weatherable minerals. The crystallinity based on FTIR for the soil kaolinites correspond to partially - poorly ordered structures. The geochemical data showed appreciable accumulation of trace elements in the clay fractions. The absence of negative Ce anomaly in the chrondrite-normalised rare earth elements (REE) pattern in the clay fractions suggest the alteration of the primary minerals took place under suboxic conditions. The average non-carcinogenic hazard index (HI) were 1.52, 1.08, and 2.01 for children and 0.18, 0.13, and 0.24 for adults in the clay fractions from basalt, granite, and arkosic sandstone, respectively. The HI > 1 for children suggest non-carcinogenic health risk to children with ingestion pathway contributing the highest. The average carcinogenic risk index values were >10-3 for children and adults with respect to Cr, Ni, and Pb in the clay fractions. This suggests very high carcinogenic risk to children and adult population in decreasing order from clay fractions in arkosic sandsone > basalt > granite, respectively.

Spatial distribution and sources of potentially toxic elements in road dust and its PM10 fraction of Moscow megacity

For the first time, the contents of potentially toxic elements (PTEs) in road dust and in its PM₁₀ fraction were studied in Moscow from June 09 to July 30, 2017 on roads with different traffic intensities, inside courtyards with parking lots, and on pedestrian walkways in parks. The contents of PTEs in road dust and PM₁₀ fraction were analyzed by ICP-MS and ICP-AES. The main pollutants of road dust and its PM₁₀ fraction included Sb, Zn, W, Sn, Bi, Cd, Cu, Pb, and Mo. PM₁₀ was a major carrier of W, Bi, Sb, Zn, Sn (accounts for >65% of their total contents in road dust); Cu (>50%); and Cd, Pb, Mo, Co, Ni (30-50%). PM₁₀ fraction was 1.2-6.4 times more polluted with PTEs than bulk samples. Resuspension of roadside soil particles accounted for 34% of the mass of PTEs in road dust and for 64% in the PM₁₀ fraction. Other important sources of PTEs were non-exhaust vehicles emissions (~ 20% for dust and ~14% for PM₁₀) and industrial emissions (~20% and ~6%). The road dust and PM₁₀ particles were most contaminated in the central part of the city due to the large number of cars and traffic congestions. Local anomalies of individual PTEs were observed near industrial zones mainly in the west, south, and southeast of Moscow. In the yards of residential buildings the total enrichment of road dust and PM₁₀ with PTEs was only 1.1-1.5 times lower than that on major roads which poses a serious danger to the population spending a significant part of their lives in residential areas. The spatial pattern of the PTEs distribution in road dust and its PM₁₀ fraction should assist in more efficient planning of washing and mechanical cleaning of the road surface from dust to minimize the risk to public health.

The characteristics of atmospheric particles and metal elements during winter in Beijing: Size distribution, source analysis, and environmental risk assessment

In order to investigate the pollution characteristics of size-segregated particles and metal elements (MEs) after the Chinese Air Pollution Prevention Action Plan was released in 2013, an intensive field campaign was conducted in the suburban area of Chaoyang District, Beijing in winter 2016. The size distributions of particle mass concentrations were bimodal, with the first peak in the fine fraction (0.4-2.1 µm) and the second peak in the coarse fraction (3.3-5.8 µm). Moreover, the proportion of fine particles increased and the proportion of coarse particles decreased as the pollution level was more elevated. It was found that the composition of coarse particles is as important as that of fine particles when pollution of aerosol metals in the atmosphere in 2016 were compared to 2013. In addition, according to the size distribution characteristics, 23 MEs were divided into three groups: (a) Fe, Co, Sr, Al, Ti, Ba, and U, which concentrated in coarse mode; (b) Zn, As, Cd, Tl, and Pb, which concentrated in fine mode; and (c) Na, K, Be, V, Cr, Mn, Ni, Cu, Mo, Ag, and Sn, showing bimodal distribution. Under clean air, slight pollution and moderate pollution conditions, most elements maintained their original size distributions, while under severe pollution, the unimodal distributions of most MEs became bimodal distributions. The factors analysis combined with size distributions indicated that Na, Zn, Mo, Ag, Cd, and Tl, showing the moderate to severe contamination on environment, were significantly influenced by diffuse regional emissions or anthropogenic source emissions (vehicle exhaust emissions and combustion process). The environmental risk assessment revealed that the heavy metal loading in the atmospheric particles collected had a high potential for ecological risk to the environment during sampling period because of the high contribution of Cd, Tl, Zn and Pb.

Pollution effect assessment of industrial activities on potentially toxic metal distribution in windowsill dust and surface soil in central China

Boundaries between industrial and urban areas in developing countries are not clearly defined, but pollution effect assessment of industrial activities on potentially toxic metal (PTM) distribution in these areas has rarely been investigated. Fifteen villages and eight communities surrounding the industrial areas from Anyang, China, were chosen as research objects in this study. A total of 78 windowsill dust and 78 surface soil samples were collected to determine the pollution levels, spatial distribution and risk indices of nine PTMs. PTM concentrations (expect Cr, Mn and Ni in surface soil) in the surveyed region were higher than the local soil background values. Amongst these PTMs, serious Cd and As pollution was discovered, and Cd and As in windowsill dust and surface soil exceeded the background value by 73.00 and 9.59, 9.74 and 10.92 times, respectively. Compared with the I_geo in surface soil, a large degree of variation in I_geo for the different PTMs was found in windowsill dust. The interpolated spatial distribution of dust Cr, Zn, Pb, Cd and soil Mn, Ni and Cu had a gradually decreasing pollution trend from the south to the north due to the prevailing wind directions in winter in the study area. Results of multivariate statistics reflected that industrial production and traffic emission affected the concentration of PTMs in windowsill dust and surface soil. The non-carcinogenic risks for children (soil: 12.4; dust: 19.2) were larger than those for adults (soil: 1.02; dust: 1.51). This finding suggested that industrial activities caused serious harm to the residents around industrial areas.

Distribution of metal(loid)s in particle size fraction in urban soil and street dust: influence of population density

Assessment of street dust is an invaluable approach for monitoring atmospheric pollution. Little information is available on the size distribution of contaminants in street dusts and urban soils, and it is not known how the population density would influence them. This research was carried out to assess the size distribution of trace metal(loid)s in street dust and urban soil, and to understand how population density might influence the size-resolved concentration of metal(loid)s. Three urban areas with a high, medium and low population density and a natural area were selected and urban soil and street dust sampled. They were fractionated into 8 size fractions: 2000-850, 850-180, 180-106, 106-50, 50-20, 20-10, 10-2, and < 2 µm. The concentration of Pb, Zn, Cu, Cd, Cr, Ni, As, and Fe was determined, and enrichment factor and grain size fraction loadings were computed. The results indicated that the concentration of Pb, Zn, Cu, Cd, and Cr was highly size dependent, particularly for particles < 100 µm, especially for street dust. Low concentrations of Ni and As in street dust and urban soil were size and population density independent. Higher size dependency of the metals concentration and the higher degree of elemental enrichment in the street dust fractions than the urban soils indicate higher contribution of human-induced pollution to the dust. Findings also confirm the inevitability of size fractionation when soils or dusts are environmentally assessed, particularly in moderately to highly polluted areas. Otherwise, higher concentrations of certain pollutants in fine-sized particles might be overlooked leading to inappropriate decisions for environmental remediation.

Geochemical fractionation and mineralogy of metal(loid)s in abandoned mine soils: Insights into arsenic behaviour and implications to remediation

Trace element contamination from abandoned mine sites is a major threat to the environment. The distribution of trace elements in various particle size fractions of soils from abandoned mine sites plays a critical role in designing remediation approaches. This study investigated the geochemical distribution of trace element enrichment and mineralogical composition in various particle size fractions from contrasting abandoned mine sites (Webbs Consols, Halls Peak and Mole River, Australia). Results revealed that arsenic and other element concentrations increased with decreasing particle size for samples from Webbs Consols and Halls Peak. The highest arsenic (3.05%), lead (3.23%) and zinc (1110 mg/kg) were found in the finest fraction (<0.053 mm). In Mole River, the highest concentration of arsenic (10.8%), lead (209 mg/kg) and zinc (351 mg/kg) were observed in coarse fractions. Arsenic fractionation by sequential extraction showed that arsenic was strongly associated with the amorphous and crystalline iron phases. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies revealed that tooeleite (a ferric arsenite mineral, also confirmed by Transmission electron microscopy (TEM)), arsenopyrite, scorodite and arsenolite were the dominant arsenic minerals. The study showed elevated levels of arsenic bearing minerals across particle sizes which has significant implications for remediation approaches at abandoned mine sites.

Comprehensive Urumqi screening for potentially toxic metals in soil-dust-plant total environment and evaluation of children's (0-6 years) risk-based blood lead levels prediction

Environmental contaminations by potentially toxic metals (PTMs) are associated with energy exploitation and present a significant problem in urban areas due to their impacts on human health. The PTMs status in Urumqi total environment inevitably impacted by extensive development of coal and oil industries has been lack of understanding comprehensively. A series of PTMs (As, Ba, Ce, Co, Cr, Cu, Ga, La, Mn, Ni, Pb, Rb, Sr, Th, U, V, Y, Zn, Zr) in the soil-dust-plant (foliage of Ulmus pumila L.) system of Urumqi (NW China) were screened by XRF and ICPMS. Multivariate statistics, risk models, GIS-based geostatistics, Positive Matrix Factorization (PMF) receptor modelling and blood lead levels of 0-6 aged children evaluated by IEUBK model are used to determine the priority pollutants, sources and health effects of the investigated elements. The spatial distribution of PTMs in soil-dust-plant system significantly coincides with coal combustion, traffic emission, and industrial activity. Although all PTM toxicants in soil, dust and tree foliage show some effects, the priority contaminants are observed for Cu, Pb and Zn as single element. The total carcinogenic and non-carcinogenic risks from PTMs are beyond the tolerance range of 0-6 year's old children, and the dust (TCR = 1.07E-04) PTMs pose approximatively equivalent carcinogenic risk to soil PTMs (TCT = 1.09E-04). The predicted BLLs (75-83 μ g·L^-1) of 1-2 years children are most strongly influenced by Pb in soil and dust, and therefore more attention should be focused on sources of Pb to support the primary health care of the toddlers in Urumqi.

Investigation of road dust characteristics and its associated health risks from an urban environment

Globally, road dust is a major source of inhalable particulate matter in any urban environment. This research seeks to assess the elemental composition of road dust at Vellore city, India, and to evaluate its health risks. For this, dust samples are collected from 18 locations in the study region. The collected samples are digested and analysed for about 25 elements using inductively coupled plasma-optical emission spectroscopy, of which 19 elements have concentration greater than the detection limit of the instrument (Al, Ba, Ca, Mg, Sr, Co, Cr, Cu, Fe, Ga, Zn, In, K, Li, Mn, Na, Ni, Pb and Rb). The highest mean concentration is noted for Fe (22,638.23 mg/kg) followed by Ca (13,439.47 mg/kg), Al (8445.89 mg/kg) and Mg (3381.20 mg/kg). Enrichment factor (EF) and contamination factor (CF) are calculated for 10 trace elements: Cu, Co, Cr, Ga, Mn, Ni, Pb, Rb, Sr and Zn. Elements Ga and Zn show the highest EF and CF. Source identification recognized that crustal material and traffic as the major sources of potentially toxic elements (PTEs). Further, the health risk assessment is performed for nine PTEs and identifies that Fe, Pb, Cr and Co are elements with the highest health index. Health index of these elements suggests a possible health risk. Ingestion is the major pathway, and children are found to be at a higher risk compared to adults.

Variation of the chemical composition of street dust in a highly industrialized city in the interval of ten years

Street dust can be re-suspended into the atmosphere by wind and vehicle passage in an urban area. Street dust is affecting the environmental quality of the atmosphere and human health. A detailed study was conducted to determine the changes in concentrations of heavy metals and magnetic susceptibility by comparison of samples of street dust obtained in the years 2008 and 2018 at the same localities. An amount of dust per m² of road area was highly variable for individual localities (47 g/m² - 1.37 kg/m²), with arithmetic mean (229.7 ± 85.97 g/m²) in the year 2018. Silt particles in street dust (<0.063 mm) represented approx. 15-20%, sand particles approx. 63-70% and gravel 10-20%. Iron (5-6%) has significant concentrations in street dust. The highest concentrations are represented by the series Mn ˃ Zn ˃ Cr ˃ Cu ˃ Pb ˃ Ni. Comparison of metal concentrations in the years 2008 and 2018 showed a comparable level of iron and a lower level of lead. The significant enrichment was found for Cu, Cr and Zn expressed by enrichment factor in the range from 5 to 20. High values of magnetic susceptibility of street dust are caused by metallurgy. Metals except Cu are bound in magnetic particles and have a high correlation coefficient with magnetic susceptibility.

Lead distribution in urban street dust and the relationship with mining, gross domestic product GDP and transportation and health risk assessment

Lead (Pb) is an important pollutant and it is of significance to explore the Pb distribution, influencing factors and health risk. Pb concentration and mass load per unit area in 385 street dust samples collected from 19 cities in China were determined during 2011-2013. The results show that the Pb concentration are 68.8, 105.4, 41.7, 49.7, 75.6, 81.7, 131.9, 67.5, 109.3, 164.1, 74.8, 66.4, 99.8, 58.4, 114.0, 59.6, 103.7, 55.4 and 80.4 for Beijing, Chengdu, Daqing, Harbin, Jilin, Jinan, Kunming, Lanzhou, Luoyang, Panzhihua, Qingdao, Yinchuan, Guangzhou, Tangshan, Xi'an, Guangyuan, Nanjing, Taiyuan and Tianjin, respectively. The Pb pollution level of urban street dust varies among cities in the range of 1.72-5.56 times higher than soil background values. The allometric function can fit the change in Pb concentration with particle size well. The medium-sized (38-120 μm) particles contributed 60.2%-80.4% to the Pb load and should be highlighted when selecting street dust management techniques. Influenced by the distribution of Pb ore, the Pb concentration of urban street dust in China shows obvious regional differences, with value in the south 112% higher than that in the north. Among all kinds of mining types, metal-related mining activities discharge a large amount of Pb dust in the process of crushing and smelting, thus contributing most to the Pb load. The Pb load was also affected by transportation. The relationship between Pb load and gross domestic product (GDP) was described with the environmental Kuznets curve (EKC) model, which indicated that the Pb emissions of most cities were still increasing. Finally, the human health risk assessment model with adjusted parameters showed that the Pb risk of all cities was below the threshold. Despite all this, given the EKC law of Pb emission, long-term follow-up assessments are needed.

Bioaccessibility of metals/metalloids in willow catkins collected in urban parks of Beijing and their health risks to human beings

Air pollution and its resulting health risks in Beijing City have been widely investigated by scientists and administrators. However, the health risks caused by willow and poplar catkins in April and May (known as "spring snow") have been rarely reported. Poplar and willow are the two common trees in Beijing City that generate many whirling catkins in the air. The chemical composition of catkins remains unknown. In this study, catkins and dust samples were collected in several parks in Beijing. The total concentrations of metals/metalloids in catkins measured through inductively coupled plasma mass spectrometry were generally lower than those of the corresponding dust samples, and they were lower than the risk control standard for soil contamination of development land. The simulated rain and lung fluid extraction rates of catkin samples were significantly higher than those of the dust samples. The concentration of extracted Pb and Zn using simulated rainwater exceeded the environmental quality standards for surface water (0.1 and 2.0 mg/L for Pb and Zn, respectively), indicating the possibility of runoff pollution. Scanning electron microscopy images showed that fine particles (<10 μm) are attached to the surface of catkins. Therefore, the metals/metalloids in fine particles adsorbed by the catkin samples possess higher bioaccessibility than that in the dust samples based on different sizes of particles. A significant correlation is found between Pb in catkin and Pb in dust. Therefore, attention should be paid to the possible increase in metal/metalloid concentrations in catkins planted in contaminated areas.

Distribution and Bioavailability of Heavy Metals in Soil Aggregates from the Fenhe River Basin, China

Accumulation, bioavailability and potential ecological risk of seven heavy metals - chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb) - have been analyzed in agricultural soil aggregates with particle size of > 1 mm, 0.25-1 mm, 0.05-0.25 mm, and < 0.05 mm from the Fenhe River Basin (FRB). Accumulation factor (AF) analysis demonstrated that heavy metals tend to be enriched in < 0.05 mm soil aggregate. The bioavailability to plants of Cu, Zn, and Cd was higher than that of other metals and increased with the decrease in soil aggregate particle sizes. Risk assessment code (RAC) of Ni, Cu, Zn and Cd were 13.84%-21.08%, 7.13%-13.74%, 32.08%-51.82% and 29.38%-43.82%, indicating that Cu, Zn, Cd and Ni had a low to very high risk to other ecosystems, and the smaller the particle size (0.05-0.25 mm and < 0.05 mm), the greater ecological risk.

A preliminary study of heavy metals pollution in the sandy dust storms and its human risk assessment from middle and south of Iraq

Sandy dust storms in Iraq represented a serious problem for human health, not only in Iraq but also extended to be in other countries. Therefore, this study has assessed five heavy metals (Cd, Ni, Zn, Pb, and Fe) in the sandy dust storms from ten locations in the middle and south of Iraq. Contamination levels in the dust were evaluated by using various pollution indices. Heavy metals recorded a high pollution load index (PLI) that considered as baseline pollution in the dust. The geo-accumulation index (Igeo) values were moderately contaminated for Cd, and Pb, in case of potential ecology risk ([Formula: see text]), was a considerable risk for Cd. Based on multivariate analysis which is performed by principal component analysis (PCA), correlation analysis (r²) and cluster analysis (CA) revealed that heavy metals in sandy dust storms were possible from anthropogenic activities. The Cd, Ni, Zn, and Fe were from the same pollution sources, while Pb element was from the different pollution sources. Therefore, this data will be useful as sources to the Quality Control Department in Iraq to establish perfect qualitative standards and also to acquire a better quality of the atmosphere in Iraq and the region.

Endogenous release of metals with dissolved organic carbon from biochar: Effects of pyrolysis temperature, particle size, and solution chemistry

Metals are released from biochar (BC) in either the free or dissolved organic carbon (DOC)-combined form. The complexation of metals with DOC influences their toxicity and bioavailability in the environment. The endogenous release of metal species with heterogeneous DOC from BC is very complex; this process has been neglected and remains unaddressed in the literature to date. In this study, the yield and chemical properties of labile DOC from BC were characterized, and the release of endogenous metal/metalloid elements (K, Mg, Mn, Fe, Al, Cu, and Si) and their species from BC with various pyrolysis temperatures and particle sizes were systematically investigated under various solution chemistries. The results showed that pyrolysis temperature of BC significantly influenced the yield and composition of DOC and DOC-metal/metalloid complexes, while particle size had lower impact. The yield of BC-derived DOC significantly decreased and the components gradually changed from low-molecular weight and low-aromaticity hydrophilic humic acid-like substances to complex high-molecular weight and high-aromaticity hydrophobic substances as pyrolysis temperature increased from 200 to 700 °C. The release of total dissolved metals decreased with increasing pyrolysis temperature, while the highest total dissolved Si was released from BC with the moderate pyrolysis temperature (500 °C). The metal elements were mainly released in the DOC-combined form, while the released Si was mainly in the free form in the neutral water environment. The release of DOC increased while that of dissolved metals decreased with increasing solution pH. The release of total dissolved metals/metalloids increased but the ratio of the DOC-combined metals/metalloids decreased with increasing solution ionic strength. These results provide new insight into the understanding of endogenous metal/metalloid release from BC in the natural environment.

The upper size limit of the dust samples in road dust heavy metal studies: Benefits of a combined sieving and air classification sample preparation procedure

The concentrations of heavy metals and other components in road dust from a Polish coal mining district were investigated. The sample was split into eight size fractions ranging from <5 μm to 1-2 mm applying the combined classification procedure of dry sieving and air classification. For most elements, significantly higher concentrations were found in the finest size fractions. In combination with the mass fractions of the various size fractions the concentrations of the components were calculated for this road dust assuming different upper size limits. The results demonstrate the important influence of the upper size limit applied on the composition of road dust. An analysis of the composition of road dust by particle size, instead of analysing whole road dust samples, proves to have several advantages. On the one hand, a reliable comparison of the results with the concentration data available in the literature is possible and on the other hand, the results can be used in assessments, for example resuspension or wash-off by rainfall, which require different upper size limits. Upper size limit applied in road dust sampling significantly influences the results. Combined sieving and air classification sample preparation procedure allows flexible use of the results.

Environmental impact assessment of industrial activities on heavy metals distribution in street dust and soil

Street dust and soil are important materials for evaluating the contaminants level in industrial areas. Detailed size-resolved distribution of metal(loid)s in street dusts and soils influenced by industrial activities has rarely been investigated. This study was carried out to understand how industrialization might affect the size distribution of metal(loid)s concentration and contamination level in the street dust and soil from Murcia, southern Spain. An industrial and a natural areas were selected and surface soil and street dust samples were taken. They were fractionated into eleven size classes and total concentrations of Pb, Zn, Cu, Cd, Cr, Ni, As and Fe were determined in both the bulk samples and their fractions. Enrichment factor, geoaccumulation index, and mass loading of different heavy metal(loids) were calculated. The results indicated that the street dust from natural and industrial areas had almost the same particle size distribution, both containing higher percentage of coarse-sized particles than the soil. Industrialization seems to have only slightly affected the concentration of most elements studied in the soil. In contrast, the concentrations of the heavy elements in bulk industrial dust samples and all their size fractions were extremely higher than those from the natural area. This means that the industrial activities only affected the size dependency of the concentration (contamination level) of certain elements (Pb, Zn, Cu, Cd, and Cr) in the street dust, but not in the soil.

Composition and risk assessment of roasted pyrite ash from fertiliser production

Pyrite ash is a residue from the roasting of pyrite ores to obtain sulphuric acid used in the fertiliser industry and its production is widely extended worldwide. The mismanagement of this waste may result in environmental and health damages due to its physico-chemical characteristics. The main objective of this study was to examine the physico-chemical and mineralogical composition of roasted pyrite ash from an abandoned fertiliser company, and to evaluate the environmental risk caused by the wind and water dispersion of metals posed by this waste. In order to achieve these objectives, a sequential extraction procedure and a physical fractionation into six size fractions: >100, 100-50, 50-20, 20-10, 10-2.5 and < 2.5 μm were applied. Results showed that pyrite ash is composed mainly of iron-oxides such as hematite (46%) and secondary minerals as anglesite and shows high concentrations of Pb (7464 mg kg^-1), Zn (2663 mg kg^-1) and Cu (585 mg kg^-1). The highest Risk Assessment Code (RAC) values were found for Cd, Pb and Zn, bound to the more labile fractions. Conversely, Pb showed the lowest water solubility due to the covering effect provided by a coating of anglesite in the pyrite ash surface. Most of the metals were associated to both the coarsest (>100 μm) and the finest (2.5-10 μm) fractions, although none represented an environmental risk according to the ecological risk index results. However, 30% of the metals were bound to the respirable fraction (≤100 μm) posing a potential risk for human health and a high potential dispersion by wind to the surrounding areas.

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).

Use of multivariable and redundancy analysis to assess the behavior of metals and arsenic in urban soil and road dust affected by metallic mining as a base for risk assessment

The vicinity of abandoned mining ponds to populated areas may suppose a high environmental and health risk being necessary evaluate unreclaimed ponds as source of metal(loid)s. In order to evaluate the behaviour of metals and arsenic from tailing ponds and their effects in urban areas, 10 mine wastes samples, 10 urban soil and 10 urban road dust samples were collected from two mining districts (La Unión and Mazarrón, SE Spain). Physicochemical properties and total, available and water-soluble concentration of metals (Cd, Co, Cr, Cu, Fe, Ni, Mn, Pb, Zn) and As were analyzed. Results suggest enrichment in Fe, Mn, Pb and Zn of urban soil and road dust in both studied towns. Multivariable analysis indicated that Cd, Mn, Pb and Zn in La Unión urban soil, and As, Cd, Cu, Pb and Zn in soil and Fe in road dust of Mazarrón come from mining districts. In addition, redundancy analysis showed that mobility of metal(loid)s related to mining sources were more influenced by their total concentration, while metals with a lithogeny origin were more affected by physicochemical properties.

Elemental Concentrations in Roadside Dust Along Two National Highways in Northern Vietnam and the Health-Risk Implication

There is a need to assess the risk of exposure to metals via roadside dust in Vietnam where many people live along the road/highways and are constantly exposed to roadside dust. In this study, we collected dust samples at 55 locations along two major Highways in north-east Vietnam, which passed through different land use areas. Samples were sieved into three different particle sizes and analyzed for concentrations of eight metals using a X-ray fluorescence instrument. The concentrations and environmental indices (EF, I _geo) of metals were used to evaluate the degree of pollution in the samples. Among different land uses, industrial areas could be highly polluted with heavy metals in roadside dust, followed by commerce and power plants. Additionally, the traffic density probably played an important role; higher concentrations were observed in samples from Highway No. 5 where traffic is several times higher than Highway No. 18. According to the risk assessment, Cr poses the highest noncarcinogenic risk even though the health hazard index values of assessed heavy metals in this study were within the acceptable range. Our assessment also found that the risk of exposure to heavy metals through roadside dust is much higher for children than for adults.