Assessment of sources, environmental, ecological, and health risks of potentially toxic elements in urban dust of Moscow megacity, Russia

Metals and metalloids pollution levels, partitioning, and sources in the environmental compartments of a small urban catchment in Moscow megacity

This study examines the contamination levels and sources of 32 metals and metalloids (MMs) in environmental compartments (roadside soil, road dust, and river suspended sediments) of a small urbanized river catchment located in Moscow megacity. MMs partitioning between particle size fractions (PM1000, PM1-10, and PM1) was analyzed by ICP-MS and ICP-AES methods. The pollution level of particle size fractions with MMs decreases in the following series: road dust > suspended sediments > soils. Absolute principal component analysis with multiple linear regression (PCA/APCS-MLR) shows that in both relatively coarse (PM1-10) and fine (PM1) fractions, traffic emissions are the primary contributors to pollution, whereas natural sources are dominant providers of chemical elements in bulk samples (PM1000). The predominance of fractions with a diameter over 10 μm in all three studied compartments indicates that the mineral matrix of all compartments is formed predominantly by natural material. Across all compartments and their fractions, Sb, Cd, Zn, Mo, W, Sn, Cu, Pb, and Bi are consistently accumulated. PM1 and PM1-10 particles of road dust and suspended sediments also absorb Ni and Cr, suspended sediments retain Mn and As, and soils additionally accumulate As. Anthropogenic influence is more pronounced in PM1 and PM1-10 particles compared to bulk samples due to a large impact of industrial sources, traffic, construction activities, and waste storage. Polluted soils are an additional source of MMs to PM1 and PM1-10 of road dust and PM1-10 of suspended sediments, and road dust acts as a source of MMs to PM1-10 of soils.

Spatial and ecological health impacts of potentially toxic elements in road dust from long-term mining activities: A case study of the Bayan Obo deposit

The long-term impacts of mining activities at the Bayan Obo deposit on potentially toxic elements (PTEs) in road dust remain insufficiently understood. This study aims to enrich knowledge in this area by investigating the spatial and eco-health impacts of PTEs in both bulk road dust (BRD) and resuspended road dust (RRD) from mining. An integrated approach combining Monte Carlo simulations with multiple statistical and geostatistical methods was used to quantify mining-related impacts. The findings revealed that Cd was the most polluted element. Concentrations of Cd, Mo, Pb and Zn were notably higher near the mine and decreased with increasing distance, with mining activities directly contributing over 20 % to these PTEs. Moderate and considerable eco-risks were identified for BRD and RRD, respectively, primarily driven by Cd and Mo, with higher risks closer to the mine. While non-carcinogenic risks were negligible, carcinogenic risks for adults required attention. Mining-related sources accounted for over 30 % of eco-risks but less than 10 % of health risks. This research integrates multiple methods, providing a more comprehensive understanding of the spatial and eco-health impacts of mining activities on PTEs in road dust. These findings offer critical insights and guidance for managing similar environmental challenges in other mining regions.

Source apportionment, ecological and health risks of potentially toxic elements in street dusts across different land uses in city of Kermanshah, Iran

In this study, the contamination, ecological and human health risks as well as source apportionment of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn, and V in street dusts of different land-uses in Kermanshah, Iran were investigated. A total of 192 dust samples were taken from 16 sites and were analyzed for their elemental contents using ICP-OES. The computed mean values for the geo-accumulation index (I-geo) and the pollution index (PI) ranged from - 6.07 to 2.67 and from 0.023 to 9.58, respectively, indicating 'unpolluted' to 'moderately to heavily polluted', and 'slight to very high polluted' pollution levels, respectively. The pollution load index (PLI) with a cumulative mean value of 1.03 reflected moderate pollution levels across the entire study area. Moreover, the ecological risk (RI) of 135 indicated moderate ecological risks throughout the study region. The mean hazard index (HI) values for the analyzed potentially toxic elements (PTEs) for both adults and children were all within the safe limit (< 1). Furthermore, the total carcinogenic risk (TCR) values showed that the carcinogenic risks associated with As, Cd, Cr, and Ni for both target populations were at tolerable to unacceptable levels. The positive matrix factorization (PMF) model identified traffic emissions and sources, fossil fuel combustion and natural sources, and industrial emissions as the major sources of tested elements. Hence, a thorough investigation into the sources of ecological health risks associated with dust contamination from potentially toxic elements (PTEs) is recommended for future studies.

Separation and preparation of nanoparticles of urban dust for biological studies

Nanoparticles (NPs) of urban dust pose a potential threat to public health. Nevertheless, this issue remains largely unexplored due to a lack of biological research related to these NPs. This may be attributed to the complexity of the separation, characterization, analysis, and subsequent preparation of NPs of urban dust for biological studies. In the present work, the methodology for the separation and preparation of NPs of urban dust for biological assays has been developed. The isolation of NPs from bulk samples of urban dust has been carried out using coiled tube field-flow fractionation, which allows one to recover a fraction of NPs, which is sufficient for further research. The weight of the recovered fraction of NPs was 0.42 ± 15 mg; the mean size of particles in the fraction was 220 nm. Albumin was employed as a stabilizing agent for NPs, a phosphate buffer solution simulated physiological salt concentrations. The isolated NPs were found to contain microorganisms, and a sterilization procedure was therefore applied. A 5 min UV treatment ensured sterilization of the suspension of NPs. Ultrafiltration was used to pre-concentrate NPs of urban dust required for biological studies; the ultrafiltration procedure did not affect the stability of the NPs suspension. The concentrations of toxic elements like Cu, Zn, As, Mo, Cd, Sn, Sb, Hg, Pb and Bi in the obtained NPs were found to be up to 10 times higher than in the bulk dust samples, indicating a potential health threat. The proposed procedure for the separation and preparation of NPs of urban dust can serve as a reliable basis for further biological studies.

Comprehensive assessment of potential toxic elements in surface dust of community playgrounds in Xi'an, China

To identify the key factors for managing and controlling potential toxic elements (PTEs) in surface dust of urban community playgrounds, this study comprehensively analyzed the content, pollution characteristics, eco-health risks, and sources of commonly concerned PTEs in surface dust of Xi'an community playgrounds. The average levels of Cd, Hg, Cu, Cr, Ba, Zn and Pb in the dust were 2.2, 0.27, 1.4 × 102, 2.1 × 102, 1.7 × 103, 2.9 × 102, 1.5 × 102 mg kg-1, respectively, exceeding the soil background values. The main sources of PTEs in the dust were natural source, mixed source of construction and weathering of entertainment facilities, traffic source, and industrial source, accounting for 24.9%, 45.7%, 18.1%, and 11.3%, respectively. The contamination and ecological risk of PTEs in the dust were elevated, and Cd and industrial source were identified as the primary contributors. The non-carcinogenic risks for different age groups were within a safe range, but the cancer risk was high, especially for toddlers and the elderly. It is worth noting that the cancer risk based on the minimum values of key exposure parameters for toddlers, preschool children, children, and teenagers has exceeded the acceptable level. According to the results of source-oriented health risk assessment, the traffic source was identified as the main contributors of health risk, and Ni was a particularly concerned PTE. These findings can provide the scientific basis for controlling PTEs pollution in urban community playgrounds and the guidance for protecting residents' health.

Contamination assessment and source identification of metals and metalloids in submicron road dust (PM1) in Moscow Megacity

The content of 39 metals and metalloids (MMs) in submicron road dust (PM1 fraction) was studied in the traffic zone, residential courtyards with parking lots, and on pedestrian roads in parks in Moscow. The geochemical profiles of PM1 vary slightly between different types of roads and courtyards but differ significantly from those in parks. In Moscow, compared to other cities worldwide, submicron road dust contains less As, Sb, Mo, Cr, Cd, Sn, Tl, Ca, Rb, La, Y, U, but more Cu, Zn, Co, Fe, Mn, Ti, Zr, Al, V. Relative to the upper continental crust, PM1 is highly enriched in Sb, Zn, Cd, Cu, W, Sn, Bi, Mo, Pb. In the courtyards, where contact between pollutants and the population is most frequent and occurs over an extended period, the level of PM1 pollution with MMs (from strong to extreme) is comparable to that on large roads. Source identification was conducted using correlations, elemental ratios, and absolute principal component analysis with multiple linear regression (APCA-MLR). In the traffic zone, non-exhaust and exhaust vehicle emissions contribute significantly to the MM concentrations in PM1 (especially for Bi, Sb, Sn, V, Fe, Cu, W, Mo); soil particles, abrasion of steel surfaces, industrial emissions, tire and road wear with carbonate dust resuspension contribute less. In the courtyards, the contribution of the road wear with carbonate dust resuspension and soil particles increases by up to 16% due to the poor condition of the road surface, frequent construction works, and large contact areas of roads with soils. In parks, the contribution of anthropogenic sources sharply decreases by 20-48% due to the increased soil resuspension rate. The spatial distribution pattern of MMs in submicron road dust should aid in the development of more effective road surface washing strategies, ultimately minimizing the risk to public health.

Vertical distribution patterns and ecological risk assessment of heavy metal(loid)s pollution in a sediment profile from Bohai Sea

The sedimentary records of heavy metal(loid)s contamination and their potential risks from the Bohai Sea are still very lacking. In this study, a sediment profile B18 was collected in the Bohai Sea to explore the contamination status and vertical distributions of heavy metal(loid)s as well as their potential risks. The heavy metal(loid)s contents showed an upward increasing trend towards the surface, and the heavy metal(loid)s concentrations in the upper layer are significantly higher than those of the middle layer and bottom layer. Obvious enrichment of Sb, As, Pb and Cd was observed and the ecological risk assessment results also revealed potential ecological risks of As, Ni and Cd. Moreover, the vertical distributions of pollution status (PLI) and ecological risk (RI) all increased steadily towards the surface for sediment profile B18. Based on comprehensive analysis of the above results, the gradually increasing trend of heavy metal(loid)s contents, pollution status, and potential ecological risks could be linked to anthropogenic influence in recent years, and could be regarded as a potential geological fingerprint for anthropogenic influence over the past few decades. This study could provide important insights to the geochemical distributions, sources and potential risks of heavy metal(loid)s in Bohai Sea sedimentary records.

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.

An explicit review and proposal of an integrated framework system to mitigate the baffling complexities induced by road dust-associated contaminants

Road dust-associated contaminants (RD-AC) are gradually becoming a much thornier problem, as their monotonous correlations render them carcinogenic, mutagenic, and teratogenic. While many studies have examined the harmful effects of road dust on both humans and the environment, few studies have considered the co-exposure risk and gradient outcomes given the spatial extent of RD-AC. In this spirit, this paper presents in-depth elucidation into the baffling complexities induced by both major and emerging contaminants of road dust through a panorama-to-profile up-to-date review of diverse studies unified by the goal of advancing innovative methods to mitigate these contaminants. The paper thoroughly explores the correlations between RD-AC and provides insights to understand their potential in dispersing saprotrophic microorganisms. It also explores emerging challenges and proposes a novel integrated framework system aimed at thermally inactivating viruses and other pathogenic micro-organisms commingled with RD-AC. The main findings are: (i) the co-exposure risk of both major and emerging contaminants add another layer of complexity, highlighting the need for more holistic framework strategies, given the geospatial morphology of these contaminants; (ii) road dust contaminants show great potential for extended prevalence and severity of viral particles pollution; (iii) increasing trend of environmentally persistent free radicals (EPFRs) in road dust, with studies conducted solely in China thus far; and (iv) substantial hurdle exists in acquiring data concerning acute procedural distress and long-term co-exposure risk to RD-ACs. Given the baffling complexities of RD-ACs, co-exposure risk and the need for innovative mitigation strategies, the study underscore the significance of establishing robust systems for deep road dust contaminants control and future research efforts while recognizing the interconnectivity within the contaminants associated with road dust.

Pine needles as bioindicator and biomagnetic indicator of selected metals in the street dust, a case study from southeastern Iran

Among the different approaches currently being used to evaluate the contamination level of street dust, the magnetic susceptibility of dust and urban tree leaves has received little attention. The key objectives of this study were: (i) to investigate the feasibility of using pine needles as a bioindicator and biomagnetic indicator for estimating the concentration of selected metals in street dust, and (ii) to predict the contamination level of street dust by selected metals using magnetic susceptibility. Street dust and pine tree needle samples were taken from 60 locations in three adjacent cities in Kerman province (Kerman, Rafsanjan, and Sirjan), southeastern Iran. The total concentrations of selected metals, including Cu, Zn, Fe, Mn, Ni, and Pb, and the magnetic susceptibility (χlf and χhf) values of both pine tree needles and street dust samples were determined. Among the three cities studied, samples from Kerman showed the highest magnetic susceptibility and metal concentration values. This could be attributed to the larger size and much higher population density of this city, with more industrial activities and urban traffic than the other two cities investigated. The results also showed that the concentrations of metals in pine needles were strongly correlated (p < 0.01) with those in street dust. The magnetic susceptibility of pine needles and the concentrations of Fe, Pb, Zn, Cu, Ni, and Mn in street dust showed a statistically significant correlation (p < 0.01). A strong and statistically significant correlation (p < 0.01) was also found between magnetic susceptibility and the concentration of metals in pine needles. In conclusion, strong relationships between magnetic properties and metal concentrations of pine needles with those of street dust samples seem to make pine needles a good bioindicator and biomagnetic estimator of the contamination level of metals in street dust.

Geospatial patterns and geochemical compositional characteristics of molybdenum in different mediums of an urban environment

Urban areas are characterized by the presence of certain potentially toxic elements including molybdenum (Mo). Therefore, compositional data analysis combined with geospatial mapping was applied in this study to reveal the spatial distribution characteristics of Mo in courtyard surface dust (dust), soils, and river sediments (sediments), to identify potential sources of Mo, and to reveal Mo geochemical associations in different urban environmental mediums. The mean contents of Mo decreased in the following order: dust (11.9 mg/kg) - soil (5.84 mg/kg) - sediment (4.87 mg/kg). The highest maximum Mo content among the studied mediums (61.8 mg/kg) was detected in dust. It was the only investigated medium where a very high level of Mo enrichment was observed (4.4% of samples). Moreover, a significant level of enrichment predominated in dust (47% of samples) whereas in soil, moderate enrichment prevails (68.5%). A significant correlation of Mo contents was observed with Zn contents in all the studied mediums, and with Ca contents in soil and sediments. A significant negative correlation was observed only between Mo contents in dust and sampling site altitudes suggesting that high-rise buildings might play the role of geochemical barriers. Principal component analysis, k-means and hierarchical clustering showed that in the geogenic elements soil group Mo showed an affinity to be bound by Fe/Mn oxide/hydroxides whereas the Mo coprecipitation, complexation and absorption by carbonates predominated in the Mo-related soil group (geochemical compositional association of Mo, Zn, Cu, Pb, and Ca) under anthropogenic influence. For dust, the geochemical compositional association was the same, but in the geogenic-related group, Cu was the most closely associated element instead of Zn. The spatial location of the Mo-related group of samples identified by k-means clustering indicates that Mo concentrate processing plant may be a potential source of Mo introduction into the urban environment.

Elemental composition of atmospheric PM10 during COVID-19 lockdown and recovery periods in Moscow (April-July 2020)

Changes in the concentrations of PM10-bound potentially toxic elements (PTEs) during the COVID-19 lockdown period and after the revocation of restrictions were analyzed using the data received at the Aerosol Complex of Moscow State University in April-July 2020. During the lockdown, the input of biomass combustion products enriched in PTEs from the Moscow region hindered the decrease in pollutant concentrations. After the introduction of the self-isolation regime, lower concentrations of most PTEs occurred due to the decrease in anthropogenic activity and the rainy meteorological conditions. After the revocation of restrictive measures, the PTE concentrations began to increase. Multivariate statistical analysis (APCA-MLR) identified the main sources of atmospheric pollutants as urban dust, non-exhaust traffic emissions, and combustion and exhaust traffic emissions. PM10 particles were significantly enriched with Sb, Cd, Sn, Bi, S, Pb, Cu, Mo, and Zn. The total non-carcinogenic and carcinogenic risks, calculated according to the U.S. EPA model, decreased by 24% and 23% during the lockdown; after the removal of restrictions, they increased by 61% and 72%, respectively. The study provides insight into the PTE concentrations and their main sources at different levels of anthropogenic impact.

Source-specific risk judgement and environmental impact of potentially toxic elements in fine road dust from an integrated industrial city, North China

The contamination of potentially toxic elements (PTEs) in road dust of large industrial cities is extremely serious. Determining the priority risk control factors of PTE contamination in road dust is critical to enhance the environmental quality of such cities and mitigate the risk of PTE pollution. The Monte Carlo simulation (MCS) method and geographical models were employed to assess the probabilistic pollution levels and eco-health risks of PTEs originating from different sources in fine road dust (FRD) of large industrial cities, and to identify key factors affecting the spatial variability of priority control sources and target PTEs. It was observed that in FRD of Shijiazhuang, a typical large industrial city in China, more than 97% of the samples had an INI > 1 (INI_mean = 1.8), indicating moderately contaminated with PTEs. The eco-risk was at least considerable (NCRI >160) with more than 98% of the samples, mainly caused by Hg (E_{i (mean)} = 367.3). The coal-related industrial source (NCRI_(mean) = 235.1) contributed 70.9% to the overall eco-risk (NCRI_(mean) = 295.5) of source-oriented risks. The non-carcinogenic risk of children and adults are of less importance, but the carcinogenic risk deserves attention. The coal-related industry is a priority control pollution source for human health protection, with As corresponding to the target PTE. The major factors affecting the spatial changes of target PTEs (Hg and As) and coal-related industrial sources were plant distribution, population density, and gross domestic product. The hot spots of coal-related industrial sources in different regions were strongly interfered by various human activities. Our results illustrate spatial changes and key-influencing factors of priority source and target PTEs in Shijiazhuang FRD, which are helpful for environmental protection and control of environmental risks by PTEs.