Spatial-temporal characteristics, source-specific variation and uncertainty analysis of health risks associated with heavy metals in road dust in Beijing, China

Exploring the environmental risks and seasonal variations of potentially toxic elements (PTEs) in fine road dust in resource-based cities based on Monte Carlo simulation, geo-detector and random forest model

The environmental pollution caused by mineral exploitation and energy consumption poses a serious threat to ecological security and human health, particularly in resource-based cities. To address this issue, a comprehensive investigation was conducted on potentially toxic elements (PTEs) in road dust from different seasons to assess the environmental risks and influencing factors faced by Datong City. Multivariate statistical analysis and absolute principal component score were employed for source identification and quantitative allocation. The geo-accumulation index and improved Nemerow index were utilized to evaluate the pollution levels of PTEs. Monte Carlo simulation was employed to assess the ecological-health risks associated with PTEs content and source orientation. Furthermore, geo-detector and random forest analysis were conducted to examine the key environmental variables and driving factors contributing to the spatiotemporal variation in PTEs content. In all PTEs, Cd, Hg, and Zn exhibited higher levels of content, with an average content/background value of 3.65 to 4.91, 2.53 to 3.34, and 2.15 to 2.89 times, respectively. Seasonal disparities were evident in PTEs contents, with average levels generally showing a pattern of spring (winter) > summer (autumn). PTEs in fine road dust (FRD) were primarily influenced by traffic, natural factors, coal-related industrial activities, and metallurgical activities, contributing 14.9-33.9 %, 41.4-47.5 %, 4.4-8.3 %, and 14.2-29.4 % to the total contents, respectively. The overall pollution and ecological risk of PTEs were categorized as moderate and high, respectively, with the winter season exhibiting the most severe conditions, primarily driven by Hg emissions from coal-related industries. Non-carcinogenic risk of PTEs for adults was within the safe limit, yet children still faced a probability of 4.1 %-16.4 % of unacceptable risks, particularly in summer. Carcinogenic risks were evident across all demographics, with children at the highest risk, mainly due to Cr and smelting industrial sources. Geo-detector and random forest model indicated that spatial disparities in prioritized control elements (Cr and Hg) were primarily influenced by particulate matter (PM10) and anthropogenic activities (industrial and socio-economic factors); variations in particulate matter (PM10 and PM2.5) and meteorological factors (wind speed and precipitation) were the primary controllers of seasonal disparities of Cr and Hg.

Assessment of potentially toxic elements (PTEs) in atmospheric dry deposition of Hamedan Metropolis, west of Iran: pollution status, spatiotemporal variation, health risk implications, and source identification

The present study was designed to assess concentrations, contamination levels, spatiotemporal variations, health hazards and source apportionment of potentially toxic elements (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn, and V) of atmospheric dry deposition (ADD) in Hamedan Metropolis. In so doing, a total of 144 atmospheric dry deposition samples were collected from 12 sites during four seasons in 2023. The concentrations of the analyzed PTEs in dry deposition samples were determined using ICP-OES after samples were digested with acid. The results illustrated that the average contents of As, Cd, Cr, Cu, Ni, Pb, and Zn with 4.52, 0.591, 4.01, 36.5, 42.5, 10.9, 84.6, 69.6, 178, and 3.91 mg/kg, respectively, were higher than those in the background samples reported for Iran, which could indicate the anthropogenic origin of these PTEs. The highest quantities of the tested PTEs in various seasons were observed in summer and/or fall samples and their highest amount in various functional regions pertained to the samples collected from the commercial or industrial regions, showing the effect of seasonal changes on emission sources and human inputs. Values of average contamination factor (CF), geo-accumulation index (I-geo), and enrichment factor (EF) ranged from 0.013 to 4.45, - 7.07 to 1.56, and 0.120 to 41.3, respectively, showing 'slight to high' pollution, 'unpolluted to moderately polluted', and 'no enrichment to very severe enrichment' levels, respectively. The pollution load index (PLI) with an average value of 0.680 reflected slight pollution levels in the entire study area. The average hazard index (HI) values of the tested PTEs for the residents were all within the safe limit (< 1). Additionally, the total carcinogenic risk (TCR) values showed that the carcinogenic risk of As, Cr and Ni for both target groups were at an acceptable level. Based on the positive matrix factorization (PMF) model, non-exhaust emissions and natural sources, fossil fuel combustion and industrial emissions, and traffic sources were identified as the primary contributors to ADD pollution, accounting for 26%, 38%, and 36%, of the total pollution respectively. In conclusion, further research is recommended to investigate the source-oriented ecological and health risks associated with atmospheric dry deposition pollution.

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.

Determination of high-risk factors and related spatially influencing variables of heavy metals in groundwater

Identifying high-risk factors (heavy metals (HMs) and pollution sources) by coupling receptor models and health risk assessment model (HRA) is a novel approach within the field of risk assessment. However, this coupled model ignores the contribution of spatial differentiation to high-risk factors, resulting in the assessment being subjective. Taking Dongting Plain (DTP) as an example, a coupling framework by jointly using the positive matrix factorization model (PMF), HRA, Monte Carlo simulation, and geo-detector was developed, aiming to identify high-risk factors in groundwater, and further explore key environmental variables influencing the spatial heterogeneity of high-risk factors. The results showed that at least 82.86 % of non-carcinogenic risks and 97.41 % of carcinogenic risks were unacceptable for people of all ages, especially infants and children. According to the relationships among HMs, pollution sources, and health risks, As and natural sources were defined as high-risk HMs and sources, respectively. The interactions among Holocene thickness, oxidation-reduction potential, and dissolved organic carbon emerged as the primary drivers of spatial variability in high-risk factors, with their combined explanatory power reaching up to 74%. This proposed framework provides a scientific reference for future studies and a practical reference for environmental authorities in developing effective pollution management measures.

Road dust exposure and human corneal damage in a plateau high geological background provincial capital city: Spatial distribution, sources, bioaccessibility, and cytotoxicity of dust heavy metals

Ocular surface diseases are common in the plateau city, Kunming China, the continued daily exposure to heavy metals in dust may be an important inducement. In this study, the 150 road dust samples from five functional areas in Kunming were collected. The concentrations, distribution, possible sources, and bioaccessibility of heavy metals were analyzed. The adverse effects of dust extracts on human corneal epithelial cells and the underlying mechanisms were also assessed. The concentrations (mg·kg-1) of As (19.1), Cd (2.67), Cr (90.5), Cu (123), Pb (78.4), and Zn (389) in road dust were higher than the soil background, with commercial and residential areas showing the highest pollution. Their bioaccessibility in artificial tears was As (6.59 %) > Cu (5.11 %) > Ni (1.47 %) > Cr (1.17 %) > Mn (0.84 %) > Cd (0.76 %) > Zn (0.50 %) > Pb (0.31 %). The two main sources of heavy metals included tire and mechanical abrasion (24.5 %) and traffic exhaust (21.6 %). All dust extracts induced cytotoxicity, evidenced by stronger inhibition of cell viability, higher production of ROS, and altered mRNA expression of antioxidant enzymes and cell cycle-related genes, with commercial- areas-2 (CA2)-dust extract showing the greatest oxidative damage and cell cycle arrest. Our data may provide new evidence that dust exposure in high geological background cities could trigger human cornea damage.

Risk assessment of heavy metals in agricultural soil based on the coupling model of Monte Carlo simulation-triangular fuzzy number

Soils in areas wherein agriculture and mining coexist are experiencing serious heavy metal contamination, posing a great threat to the ecological environment and human health. In this study, heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) in agricultural soil samples from mining areas were analyzed to explore pollution status, bioavailability, potential sources, and ecological/health risks. Particularly, the coupling model of Monte Carlo simulation-triangular fuzzy number (MCS-TFN) was established to quantify ecological/health risks accurately. Results showed that Cd was heavily enriched in soil and had the highest bioavailability based on both geo-accumulation index (Igeo) and chemical speciation analysis. Pollution sources apportioned with the absolute principal component score-multiple linear regression (APCS-MLR) model demonstrated that heavy metals were mainly derived from agricultural activities, followed by mining activities and natural sources. The MCS-TFN ecological risk assessment classified Cd into the high-risk category with a probability of 40.96%, whereas other heavy metals were categorized as the low risk. Cd was regarded as the major pollutant for the ecosystem. Moreover, the MCS-TFN health risk assessment indicated that As showed high noncarcinogenic risk (0.07% probability) and moderate carcinogenic risk (1.87% probability), and Cd presented low carcinogenic risk (80.19% probability). As and Cd were identified as the main heavy metals that pose a threat to human health. The MCS-TFN risk assessment is superior to the traditional deterministic risk assessment since it can obtain the risk level and the corresponding probability, and significantly reduce the uncertainty in risk assessment.

Contamination and source-specific health risk assessment of polycyclic aromatic hydrocarbons in soil from a mega iron and steel site in China

The iron and steel industry has always been a key and difficult point of environmental pollution control. In the present study, 493, 175, 153, 72, and 42 soil samples were collected from the soil depths of 0-0.5, 0.5-2, 2-3, 3-4, and 4-5 m (herein called the layers) of the Shougang Steel site, respectively. Compared with the evaluation criteria, the Shougang Steel surface soil was severely polluted by polycyclic aromatic hydrocarbons (PAHs). Inverse distance-weighted interpolation and the Kruskal-Wallis H test revealed that the soil PAH pollution in the iron-making area, especially the coking area, was severer than those in other areas. The PAH concentrations first decreased, and then, increased with the increase of depth. With the increase in depth, the contributions of 2- and 3-ring PAHs increased, while those of 4-, 5-, and 6-ring PAHs decreased. The bivariate local indicators of spatial association (LISA) analysis was used to identify the areas prone to soil PAH pollution due to atmospheric deposition of industrial waste gas and traffic emissions. The method could be used to analyze the impact of anthropogenic activities on soil's PAH pollution for other contaminated sites. Three main pollution sources of soil PAHs, the backfill source, the combustion of coal, and the traffic emissions, were identified based upon three diagnostic ratios, positive matrix factorization and the bivariate LISA analysis, and accounted for 53.8%, 23.5%, and 22.7%, respectively. The combination of bivariate LISA analysis and other source analysis methods could improve the accuracy of source analysis. Benzo[a]pyrene contributed the most to the total health risk among sixteen PAHs. The health risks related to the three pollution sources decreased in the order of backfill sources > coal combustion > traffic emissions. The incremental life-time carcinogenic risks were all below 10-4, indicating negligible or acceptable risks.

Bioavailability-based risk assessment of various heavy metals via multi-exposure routes for children and teenagers in Beijing, China

Assessing the health risks of sensitive population, such as children and teenagers, through multiple exposure routes (MERs) such as ingestion, inhalation, and dermal contact is critical for policy creation that protects or reduces exposure to pollutants for all populations. Heavy metal (HM) contents in food and environmental media in Beijing, capital of China, were collected. Furthermore, on the basis of considering the bioavailability of HMs, we evaluated the multiple environmental routes and health risks to HMs in children and teenagers of eight age groups (2-<3, 3-<4, 4-<5, 5-<6, 6-<9, 9-<12, 12-<15, and 15-<18) in Beijing, China by Monte Carlo simulation approach. The main findings are as follows: lead exposure in children aged 2-<3 years exceeds the exposure dose (0.3 μg·kg-1·d-1) of 0.5 point reduction in intelligence quotient. Moreover, children aged 2-<3 and 6-<9 years have relatively high non-carcinogenic risk (NCR) of 1.32 and 1.30, respectively. The carcinogenic risk (CR) for children aged 6-<9 and 9-<12 years is 2.73×10-6 and 2.39×10-6, respectively. Specifically, the contributions of oral ingestion, dermal contact, and inhalation to the NCR were 69.5%, 18.9%, and 11.6%, respectively. Moreover, the combined NCR contributions of copper, cadmium, mercury, and arsenic (As) were about 69.4%. The contributions of the above three routes to the CR were 93.4%, 4.1%, and 2.5%, in that order, with the largest CR contribution of As being about 92.0%. This study can provide new ideas for accurately assessing the exposure and health risks of HMs in the population, and we believe that it is necessary to update the national standards for food and soil based on the bioavailability of HMs.

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.

Ascertaining priority control pollution sources and target pollutants in toxic metal risk management of a medium-sized industrial city

Re-suspended surface dust (RSD) often poses higher environmental risks due to its specific physical characteristics. To ascertain the priority pollution sources and pollutants for the risk control of toxic metals (TMs) in RSD of medium-sized industrial cities, this study took Baotou City, a representative medium-sized industrial city in North China, as an example to systematically study TMs pollution in RSD. The levels of Cr (242.6 mg kg-1), Pb (65.7 mg kg-1), Co (54.0 mg kg-1), Ba (1032.4 mg kg-1), Cu (31.8 mg kg-1), Zn (81.7 mg kg-1), and Mn (593.8 mg kg-1) in Baotou RSD exceeded their soil background values. Co and Cr exhibited significant enrichment in 94.0 % and 49.4 % of samples, respectively. The comprehensive pollution of TMs in Baotou RSD was very high, mainly caused by Co and Cr. The main sources of TMs in the study area were industrial emissions, construction, and traffic activities, accounting for 32.5, 25.9, and 41.6 % of the total TMs respectively. The overall ecological risk in the study area was low, but 21.5 % of samples exhibited moderate or higher risk. The carcinogenic risks of TMs in the RSD to local residents and their non-carcinogenic risks to children cannot be ignored. Industrial and construction sources were priority pollution sources for eco-health risks, with Cr and Co being the target TMs. The south, north and west of the study area were the priority control areas for TMs pollution. The probabilistic risk assessment method combining of Monte Carlo simulation and source analysis can effectively identify the priority pollution sources and pollutants. These findings provide scientific basis for TMs pollution control in Baotou and constitute a reference for environmental management and protection of residents' health in other similar medium-sized industrial cities.

Assessment of Potentially Toxic Elements Pollution and Human Health Risks in Polluted Farmland Soils around Distinct Mining Areas in China-A Case Study of Chengchao and Tonglushan

This research study investigates the extent of heavy metal pollution and pollution trends in agricultural soil in mining areas during different time periods. A total of 125 soil samples were collected from two mining areas in China, the Chengchao iron mine and Tonglushan ancient copper mine. The samples were analyzed for various potentially toxic elements (PTEs). The index of geoaccumulation (Igeo), pollution index (Pi), potential ecological risk index (Eri), and hazard index (HI) were calculated to evaluate the pollution status of PTEs in the farmland around the two mining areas. The sources of PTEs were inferred by pollution distribution, and the pollution conditions of the two mining areas were compared. The results showed that the pollution of ancient copper mines was relatively severe. The main pollution elements were Cu, Cd, and As, and their average Pi values were 3.76, 4.12, and 1.84, respectively. These PTEs mainly came from mining and transportation. There are no particularly polluted elements in the Chengchao iron mine and the average Pi of all PTEs were classified as light pollution and had a wide range of sources. The findings suggest that the ancient copper mine, due to outdated mining techniques and insufficient mine restoration efforts, resulted in the spread and accumulation of PTEs in the soil over an extended period, making the farmland soil around the ancient copper mine more polluted compared to the Chengchao iron mine. In the two mining areas, there is no risk of cancer for adults and children. However, the RI values of Cr in adults and children are higher than 10^-4, which indicates that the carcinogenic risk of Cr in these soils is very high. The non-carcinogenic effects of PTEs on the human body in the soil of ancient copper mine are also higher than that of the Chengchao iron mine.

Contamination and source apportionment of metals in urban road dust (Jinan, China) integrating the enrichment factor, receptor models (FA-NNC and PMF), local Moran's index, Pb isotopes and source-oriented health risk

Contamination and source identifications of metals in urban road dust are critical for remediation and health protection. Receptor models are commonly used for metal source identification, whereas the results are usually subjective and not verified by other indicators. Here we present and discuss a comprehensive approach to study metal contamination and sources in urban road dust (Jinan) in spring and winter by integrating the enrichment factor (EF), receptor models (positive matrix factorization (PMF) and factor analysis with nonnegative constraints (FA-NNC)), local Moran's index, traffic factors and Pb isotopes. Cadmium, Cr, Cu, Pb, Sb, Sn and Zn were the main contaminants, with mean EFs of 2.0-7.1. The EFs were 1.0-1.6 times higher in winter than in spring but exhibited similar spatial trends. Chromium contamination hotspots occurred in the northern area, with other metal contamination hotspots in the central, southeastern and eastern areas. The FA-NNC results indicated Cr contamination primarily resulting from industrial sources and other metal contamination primarily originating from traffic emissions during the two seasons. Coal burning emissions also contributed to Cd, Pb and Zn contamination in winter. FA-NNC model-identified metal sources were verified via traffic factors, atmospheric monitoring and Pb isotopes. The PMF model failed to differentiate Cr contamination from other detrital metals and the above anthropogenic sources, largely due to the model grouping metals by emphasizing hotspots. Considering the FA-NNC results, industrial and traffic sources accounted for 28.5 % (23.3 %) and 44.7 % (28.4 %), respectively, of the metal concentrations in spring (winter), and coal burning emissions contributed 34.3 % in winter. Industrial emissions primarily contributed to the health risks of metals due to the high Cr loading factor, but traffic emissions dominated metal contamination. Through Monte Carlo simulations, Cr had 4.8 % and 0.4 % possibilities posing noncarcinogenic and 18.8 % and 8.2 % possibilities posing carcinogenic risks for children in spring and winter, respectively.

Source-oriented ecological and resistome risks associated with geochemical enrichment of heavy metals in river sediments

Heavy metals (HMs) pose ecological and resistome risks to aquatic systems. To efficiently develop targeted risk mitigation strategies, apportioning HM sources and assessing their source-oriented risks are essential. Although many studies have reported risk assessment and source apportionment of HMs, yet few have explored source-specific ecological and resistome risks associated with geochemical enrichment of HMs in aquatic environments. Therefore, this study proposes an integrated technological framework to characterize source-oriented ecological and resistome risks in the sediments of a plain river in China. Several geochemical tools quantitatively showed Cd and Hg had the highest pollution levels in the environment, with 19.7 and 7.5 times higher than their background values, respectively. Positive matrix factorization (PMF) and Unmix were comparatively used to apportion sources of HMs. Essentially, the two models were complementary and identified similar sources including industrial discharges, agricultural activities, atmospheric deposition and natural background, with contributions of 32.3-37.0%, 8.0-9.0%, 12.1-15.9% and 42.8-43.0%, respectively. To analyze source-specific ecological risks, the apportionment results were integratively incorporated into a modified ecological risk index. The results showed anthropogenic sources were the most significant contributors to the ecological risks. Particularly, industrial discharges majorly contributed high- (44%) and extremely high (52%) ecological risk for Cd, while agricultural activities posed a greater percentage of considerable-(36%) and high- (46%) ecological risk for Hg. Furthermore, the high-throughput sequencing metagenomic analysis identified abundant and diverse antibiotic resistance genes (ARGs), including some carbapenem-resistance genes and emerging genes such as mcr-type in the river sediments. Network and statistical analyses displayed significant correlations between ARGs and geochemical enrichment of HMs (ρ > 0.8; P-value <0.01), indicating their important impacts on resistome risks in the environment. This study provides useful insights into risk prevention and pollution control of HMs, and the framework can be made applicable to other rivers facing environmental challenges worldwide.

A review on toxic metal pollution and source-oriented risk apportionment in road dust of a highly polluted megacity in Bangladesh

Heavy metal enrichment in road dust has resulted from intensive anthropogenic activity, particularly urbanization, industrial activities and traffic emission, posing a hazard to urban ecosystems and human health. To promote optimal road dust management in urban environments, it is necessary to assess the possible ecological and health impact of toxic elements in road dust. In a heavily populated megacity like Dhaka, Bangladesh, large-scale risk assessments of contamination in road dust with heavy metals are limited. The present study aims at presenting a concentration of twenty-five metals in road dust (Na, K, Cs, Rb, Mg, Ca, Sr, Ba, Al, Zn, Cd, Pb, As, Sb, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr and W) in Dhaka megacity. We used a critical source-based positive matrix factorization model, source-oriented potential ecological risks and health risks. Out of the studied metals, Na, Ca, Zn, Cd, Cu, Zr and W exceeded the shale value. About 73%, 48%, 29% and 32% of sampling sites showed a higher level of pollution based on PLI, NIPI, PER and NIRI, respectively. PMF model identified that Cd (85.3%), Cr (62.4%), Ni (58.2%), Zn (81.8%) and Mn (65.9%) in road dust were primarily attributed to traffic emission, fuel combustion, metal processing, transport sources and natural sources, respectively. Fuel combustion and metal processing posed considerable and high risks based on modified potential ecological risk and NIRI. Based on health hazards, traffic emission posed a high cancer risk in adult males (29%), whereas transport sources contributed to females (21%) and children (23%).

A comprehensive study of potentially toxic element contamination and source quantitative assessment by positive matrix factorization model: risk from the fine road dust of Chehe mining area, China

Extreme mining activities can risk human life and the environment via potentially toxic elements (PTEs) in road dust, thus making their quantification and assessment unavoidable. For this purpose, we collected 50 fine road dust samples from the Chehe mining area, China, to quantify the level of contamination and ecological and health risks of PTEs comprising As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, and Zn, and their quantitative source apportionment using the positive matrix factorization model (PMF). Results indicated that the average values of Cd, Sb, As, Zn, Pb, and Cu in road dust were 1555.21, 586.78, 429.68, 429.43, 72.88, and 26.61 times higher than their background values. Pollution indices of PTEs revealed a strong level of contamination by Cd, Sb, As, Zn, and Pb, which were extremely polluted in the study area. The average values of the Nemerow integrated risk index (NIRI) and potential ecological risk index (RI) were 104.09 and 86.49 times the highest risk limit, respectively, which are extremely high ecological risks. Based on PMF for quantitative source identification, mining activities and fuel combustion were the main sources of PTEs in road dust contributing 57.25% and 35.95%, respectively. Furthermore, the health risk assessment indicated that Sb, As, Cr, Cd, and Pb in the Chehe road dust could lead to significantly serious carcinogenic and non-carcinogenic risks to both children and adults. The results of this study could be used to opt for strategies to mitigate the ecological and human health risk in the mining area of Hechi, China.

Multi-element features and trace metal sources of road sediment from a mega heavy industrial city in North China

As the primary carrier of harmful elements, road sediment poses severe hazards to human health and ecological environment, especially in megacities. Based on the industrial cities in North China, this research focused on the multi-element features and the pollution levels, sources, and spatial distributions of trace metals in road sediment of Shijiazhuang. The mean levels of P (928.4 mg kg^-1), S (1446.2 mg kg^-1), Cl (783.9 mg kg^-1), Br (5.3 mg kg^-1), Na₂O (2.0%), CaO (9.9%), Co (36.0 mg kg^-1), Pb (38.0 mg kg^-1), Cu (34.7 mg g^-1), Zn (149.1 mg kg^-1), Ba (518.1 mg kg^-1), and Sr (224.9 mg kg^-1) in road sediment were greater than their soil background values. Trace metals in most samples was moderately (75%) and heavily contaminated (15.6%). The industrial areas, congested roads, and residential areas in the northeast, middle and south of Shijiazhuang are the hotspots of trace metals pollution. A comprehensive analysis of trace metals sources indicated that Ni, V, Ga, Rb, Y, Sc, La, Ce, Zr, and Hf were mainly from natural source, which contributed to 34.2% of the total trace metals concentrations. Cu, Pb, Zn, Cr, Ba, Sr, and Mn primarily originated from mixed source, which accounted for 46.5%. Co principally came from building source, which accounted for 19.3%. This study shows that industrial discharges, construction dust and traffic emissions are the primary anthropogenic sources of trace metals in road sediment in the study area.

Morphological characterization, hazardous metal contamination, source identification, and health risk assessment of the fine road dust from Dachang mining area, China

Dachang mining area in China is known as "paradise for mineralogists" due to its most reserves of Sn, Sb, Pb, and Zn non-ferrous metal resources; thus, its evaluation for heavy metal assessment and consequent health risk is unavoidable. Sixty road dust samples were collected from study area to explore pollution level, ecological, and health risks from heavy metals and were analyzed by an inductively coupled plasma optical emission spectrometer and atomic fluorescence spectrometer. The results showed that average concentration of all the heavy metals in road dust in both mining and residential areas were remarkable higher than its corresponding background values, the former being more severe, except for Cr and Co. The morphological investigation showed that most of the particles were much less than 100 μm illustrating fine part of the road dust samples. Based on integrated pollution indices, Cd, Sb, As, Zn, and Pb were extremely contaminated and exceeded hundred times of the maximum risk value. The health risk assessment revealed substantially higher carcinogenic and non-carcinogenic risks to children and adult. Highest non-carcinogenic risk resulted from arsenic in mining and residential area with HQ_ing of 644.56 and 267.94 respectively (standard HQ ≥ 1) while carcinogenic risk to children (1.94E + 00) which greatly exceeded from the threshold value of (1.0E-4). Sb, Cd, and Pb also posed carcinogenic and non-carcinogenic risk in road dust which is caused by excessive mining activities and heavy vehicle movement in the study area.

In Vitro Bioaccessibility and Health Risk Assessment of Arsenic and Zinc Contaminated Soil Stabilized by Ferrous Sulfate: Effect of Different Dietary Components

Iron-based materials have good stability in reducing the mobility and toxicity of heavy metals, but the behavior and human health risks of heavy metals could be affected by dietary components. This study investigated the effect of typical diets (lettuce, cooked rice and apples) on the bioaccessibility and morphological changes of arsenic (As) and zinc (Zn) in contaminated site after stabilization by ferrous sulfate (FeSO4). The results showed that the bioaccessibility of As and Zn were increased in a co-digestion system of food. The augmented effect on As bioaccessibility mainly occurred in the gastric phase: apple > lettuce > cooked rice (p < 0.05), while the augmented effect on Zn bioaccessibility mainly occurred in the intestinal phase: lettuce > apple > cooked rice (p < 0.05). FeSO4 weakened the dissolution effect of dietary components on As bioaccessibility, and reduced As bioaccessibility in the gastric and intestinal phases by 34.0% and 37.9% (p < 0.05), respectively. Dietary components and Fe fractions influenced the speciation and distribution of As and Zn. FeSO4 reduced the hazard quotient (HQ) and carcinogenic risk (CR) values of the contaminated soil by 33.97% and 33.59%, respectively. This study provides a reference for a better understanding of more realistic strategies to modulate exposure risks of heavy metal-contaminated sites.

Variation in Road Dust Heavy Metal Concentration, Pollution, and Health Risk with Distance from the Factories in a City-Industry Integration Area, China

Road dust samples around three typical factories, F1, F2, and F3, in the National Zhengzhou Economic and Technology Development Zone (ZETZ), China, were collected to study the variation in heavy metal concentration (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn), pollution, and health risk with distance from the factories. The results indicated that the concentrations of all the elements near F1 were higher than near both F2 and F3. Apart from Co, Mn, and Cu in some dust samples, all the element concentrations were higher than the corresponding background values (BCs), to varying degrees. The spatial distributions of the heavy metals surrounding the factories followed the normal distribution. The peak values of element concentrations occurred at 300~400 m away from the factories, except for Hg, which continued increasing more than 500 m away from the factories. The fluctuation curves of the pollution load index value calculated according to the BCs for F1, F2, and F3 all had two peaks, a "small peak" and a "large peak", appearing at about 30 m and 300 m, respectively. For the hazard index and the total carcinogenic risk, the peak values all appeared at 400 m, with the curves following the normal distribution. Exposure to road dust containing non-carcinogenic and carcinogenic elements around F1 was greater than around F2 or F3. In conclusion, our results provide a reference for pursuing effective prevention of dust heavy metal pollution around modern manufacturing factories.

Bioaccessibility, source and human health risk of Pb, Cd, Cu and Zn in windowsill dusts from an area affected by long-term Pb smelting

Non-ferrous metal smelting results in heterogenous spatial distribution of potentially toxic metals (PTM) near smelters. In this work, windowsill dusts were collected from smelting (SA) and urban (UJ) sub-areas of Jiyuan (a city affected by >70 years of Pb smelting) to investigate PTM source and bioaccessibility. The <10 μm fraction of dusts were analyzed for total and bioaccessible Pb, Cd, Cu and Zn concentrations; bioaccessibility was analyzed by a three-stage assay (i.e., lung phase, gastric phase and gastrointestinal phase) using artificial lysosomal fluid (ALF, L phase) followed by simulated gastric and gastrointestinal fluids (G and GI phases). This assay mimicked the movement of particles phagocytosed by alveolar macrophages in the respiratory system, then transported up the oropharynx and subsequently swallowed and transported into the digestive system. Zinc had greater bioaccessible concentrations in L and GI phases than other metals, and the mean L phase bioaccessible PTM concentrations in SA were greater than in UJ. The mean L + GI phase bioaccessible concentrations of Pb, Cd, Cu and Zn in SA were 280, 79, 124 and 1458 mg kg^-1, while those in UJ were 215, 54, 116 and 598 mg kg^-1, respectively. The L phase extracted 87.7 to 98.8 % of PTM within the L + GI assay. Lead had a lower L + GI bioaccessibility than Cd, Cu and Zn (70-76 % vs. 82-92 %). Higher tolerable Cd carcinogenic risks based on bioaccessibility were found in SA sub-area than in UJ while no carcinogenic or non-carcinogenic risk was found for other metals. Lead isotopic ratios indicated that both Pb ore and smelting bottom ash contributed to dust Pb accumulation in SA, while coal burning, lead ore, Pb smelting bottom ash and diesel engine exhaust contributed to dust Pb accumulation in UJ. Overall, results indicated heterogenous distribution of PTM source and bioaccessibility in the vicinity of Pb smelters.

Pollution Characteristics, Source Apportionment, and Health Risk Assessment of Potentially Toxic Elements (PTEs) in Road Dust Samples in Jiayuguan, Hexi Corridor, China

The sources of potentially toxic elements (PTEs) in road dust are complex and potentially harmful to humans, especially in industrial cities. Jiayuguan is the largest steel-producing city in Northwest China, and this study was the first to conduct a related study on PTEs in road dust in this city, including the pollution characteristics, source apportionment, and health risk assessment of PTEs in road dust. The results showed that the highest concentration of PTEs in the local road dust samples were Mn, Ba, Zn, and Cr. The enrichment factor (EF) of Se was the highest, and it was "Very high enrichment" in areas other than the background area, indicating that the local Se was more affected by human activities. The geoaccumulation index (I_geo) of Se was also the highest, and the pollution level was 5 in all areas except the background area, indicating that the local Se was more polluted and related to coal combustion. The sources of PTEs in local road dust samples mainly included geogenic-industrial sources, coal combustion, traffic sources, and oil combustion. For the non-carcinogenic risk, the hazard index (HI) of each element of children was higher than that of adults, and the sum of the HI of each element was greater than 1, indicating that there was a non-carcinogenic risk under the combined influence of multiple elements, which was especially obvious in industrial areas. For the carcinogenic risk, the cancer risk (CR) of Cr at a certain point in the industrial area exceeded 10^-4, which was a carcinogenic risk, and the Cr in this area may be related to the topsoil of the local abandoned chromate plant.

Contamination, sources and health risks of toxic elements in soils of karstic urban parks based on Monte Carlo simulation combined with a receptor model

Understanding the health risks of toxic elements (TEs) in urban park soils and determining their priority control factors are crucial for public health and pollution management. Soil samples were collected from 33 urban parks in Guiyang, a typical karstic city. For each park, 15-45 topsoil samples were collected according to the area and then thoroughly mixed to obtain a representative sample. The results showed that the mean concentrations of TEs in park soils (22.5, 0.37, 88.6, 43.7, 0.26, 39.9, 44.7, and 101.0 mg/kg for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, respectively) were higher than their background values. Approximately 54.5% and 33.3% of enrichment factor (EF) values reached moderately enriched to significantly enriched levels for Cd and Hg, respectively. Moreover, 54.5% and 42.4% of monomial potential ecological index (EI) values were at considerable to high risk levels for Cd and Hg, respectively. These results illustrate that Cd and Hg pose high ecological risks. According to the potential ecological risk index (RI) values, 21.2% of the parks were exposed to considerable ecological risk and 48.5% were at moderate risk. Based on the positive matrix factorization (PMF) model, four sources governing TE contamination (including coal combustion, natural sources, traffic emissions, and industrial activities) were identified, with contribution rates of 32.3%, 31.0%, 19.6%, and 17.1%, respectively. A probabilistic health risk assessment showed acceptable non-carcinogenic risks and high levels of carcinogenic risk in all populations. Based on the source-specific health risk assessment, arsenic from coal combustion was determined to be a major contributor to human health risks. Although several efforts have been made by the local government to eliminate coal-borne arsenicosis, our results revealed that the accumulation of arsenic in the soil due to coal combustion poses a potential threat to human health.

Receptor model-oriented sources and risks evaluation of metals in sediments of an industrial affected riverine system in Bangladesh

Toxic metals in river sediments may represent significant ecological concerns, although there has been limited research on the source-oriented ecological hazards of metals in sediments. Surface sediments from an industrial affected Rupsa River were utilized in this study to conduct a complete investigation of toxic metals with source-specific ecological risk assessment. The findings indicated that the average concentration of Ni, Cr, Cd, Zn, As, Cu, Mn and Pb were 50.60 ± 10.97, 53.41 ± 7.76, 3.25 ± 1.73, 147.76 ± 36.78, 6.41 ± 1.85, 59.78 ± 17.77, 832.43 ± 71.56 and 25.64 ± 7.98 mg/kg, respectively and Cd, Ni, Cu, Pb and Zn concentration were higher than average shale value. Based on sediment quality guidelines, the mean effective range median (ERM) quotient (1.29) and Mean probable effect level (PEL) quotient (2.18) showed medium-high contamination in sediment. Ecological indexes like toxic risk index (20.73), Nemerow integrated risk index (427.59) and potential ecological risk index (610.66) posed very high sediment pollution. The absolute principle component score-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) model indicated that Zn (64.21%), Cd (51.58%), Cu (67.32%) and Ni (58.49%) in APCS-MLR model whereas Zn (49.5%), Cd (52.7%), Cu (57.4%) and Ni (44.6%) in PMF model were derived from traffic emission, agricultural activities, industrial source and mixed sources. PMF model-based Nemerow integrated risk index (NIRI) reported that industrial emission posed considerable and high risks for 87.27% and 12.72% of sediment samples. This work will provide a model-based guidelines for identifying and assessing metal sources which would be suitable for mitigating future pollution hazards in Riverine sediments in Bangladesh.

Seasonal variation of dissolved bioaccessibility for potentially toxic elements in size-resolved PM: Impacts of bioaccessibility on inhalable risk and uncertainty

The health effects of potentially toxic elements (PTEs) in airborne particulate matter (PM) are strongly dependent on their size distribution and dissolution. This study examined PTEs within nine distinct sizes of PM in a Chinese megacity, with a focus on their deposited and dissolved bioaccessibility in the human pulmonary region. A Multiple Path Particle Dosimetry (MPPD) model was used to estimate the deposited bioaccessibility, and an in-vitro experiment with simulated lung fluid was conducted for dissolved bioaccessibility. During the non-heating season, the dissolved bioaccessible fraction (DBF) of As, Cd, Co, Cr, Mn, Pb and V were greater in fine PM (aerodynamics less than 2.1 μm) than in coarse PM (aerodynamics between 2.1 and 10 μm), and vice versa for Ni. With the increased demand of heating, the DBF of Pb and As decreased in fine particle sizes, probably due to the presence of oxide/silicate compounds from coal combustion. Inhalation health risks based on the bioaccessible concentrations of PTEs displayed the peaks in <0.43 μm and 2.1-3.3 μm particulate sizes. The non-cancer risk was at an acceptable level (95th percentiles of hazard index (HI) was 0.49), but the cancer risk exceeded the threshold value (95th percentiles of total incremental lifetime cancer risk (TCR) was 8.91 × 10^-5). Based on the results of uncertainty analysis, except for the exposure frequency, the total concentrations and DBF of As and Cr in <0.43 μm particle size segment have a greater influence on the uncertainty of probabilistic risk.

Sources and uncertainties of health risks for PM2.5-bound heavy metals based on synchronous online and offline filter-based measurements in a Chinese megacity

Accurate measurements of PM_2.5 related heavy metals (HMs) and some components are critical to better understanding the sources and health risks of PM_2.5. HMs and other components in PM_2.5 were simultaneously measured using online and offline filter-based methods in a Chinese megacity. Online Mn, Pb, Cu, and Zn concentrations exhibited good correspondence with offline results (R² ≥ 0.7, relative biases = -3%-22%). Some differences were observed for Cr, As, Co, and V. The assessment of online and offline probabilistic health risks indicated that non-cancer and total cancer risks were higher than the acceptable limits. Different analytical methods of As may result in different uncertainties in risk analysis. The positive matrix factorization model (PMF) was used to perform online and offline source apportionment. Five sources (coal combustion, vehicle source, industrial source, secondary source, and resuspended dust) were identified. Lower online percentage contribution of resuspended dust (8%) might relate to the lack of Si and Al measurements. The different rate contributions of vehicle source were potentially linked to the different time resolutions of the online and offline data. The assessment of online and offline source-specific health risks revealed that industrial source and coal combustion were the most important sources. Online and offline source-specific risks were not significantly different (P > 0.05). This contrastive study not only helps decision makers to manage health risk more effectively, but also provides insights into the applicability of online and offline measurements for quantifying source-specific risks.

Source-specific ecological risk assessment and quantitative source apportionment of heavy metals in surface sediments of Pearl River Estuary, China

In this study, surface sediments of the Pearl River Estuary were collected from 29 stations and investigated the spatial distribution, pollution level, quantitative source apportionment, and source-specific ecological risk of 10 heavy metals. The mean concentrations followed the order of Mn > Zn > Cr > Cu > Ni > Pb > As > Co > Cd > Hg. In terms of spatial distribution, it showed that the heavy metals were enriched in the inner Pearl River Estuary with 'extremely high' level of Hg, whereas, Cd and Zn posed 'moderate to high' contamination potential. We apportioned four main sources using positive matrix factorization model, in which natural geogenic and industrial manufacturing sources accounted for 36.84% and 27.11% of the total, respectively. However, the source-specific risk assessment suggested that mixed anthropogenic sources were the main contributors, and ecological risks were strongly affected by anthropogenic imports from the surrounding cities.

Seasonal changes of heavy metals and health risk assessment based on Monte Carlo simulation in alternate water sources of the Xinbian River in Suzhou City, Huaibei Plain, China

The urban alternate water source (AWS) is of great significance to the sustainable development of the city, the pollution degree, and source of heavy metals (HMs) in AWS, and whether it will adversely affect human health has received widespread attention. In this study, the urban AWS of Xinbian River in Suzhou City, Huaibei Plain, China, was used as the research object to study the seasonal changes of HMs (As, Cr, Cu, Cd, Pb, and Zn), quantitative identification of pollution sources, and human health risks (HHR). Research results show that the contents of those HMs, except As, are less than the drinking standards limit set by the World Health Organization (WHO), and the contents of As, Cr, and Zn are the largest in summer. The multivariate statistical analysis combined with positive matrix factorization (PMF) model analysis revealed that industrial sources accounted for 44.83%, and agricultural sources accounted for 55.17%. HHR assessment based on Monte Carlo simulation shows that the noncarcinogenic risks of adults and children are in the acceptable range (hazardous ingestion (HI) < 1), and the probability of carcinogenic risk values of children and adults are 95.03% and 38.96%, respectively, which are exceed the acceptable range (1 × 10^-4) recommended by the United States Environment Protection Agency (USEPA). Approximately 30.75% of the carcinogenic risk value of agricultural source HMs to children exceeds the acceptable range (1 × 10^-4). The above research results indicate that the effect of agricultural non-point source pollution on AWS should be prevented.

A four-way model (FEST) for source apportionment: Development, verification, and application

In studying the spatial, temporal, and particle size variations heavy metal sources, a source apportionment model for a four-way array of data is required. In this study, referencing two-way and three-way models, a four-way (particle fractions, elements, sites, and time) source apportionment model (FEST) was developed. Errors in the three-way models solving four-way problems verified the necessity of developing the FEST model. The results showed that the FEST model had a higher accuracy than the existing models, which was probably because of more constraints and input data in the FEST model. Based on the sampled data in Beijing, sources were apportioned for the four-way array of data using the FEST model, and the spatial, temporal, and particle size variations of sources were evaluated. The main sources of heavy metals were similar to those in our prior studies, whereas the contributions of sources to specific heavy metals differed. Traffic exhaust and fuel combustion contributed more to fine particles than coarse particles, indicating that the two should be controlled preferentially among all sources. The management of traffic exhaust should be focused on the central and northern areas in each season, and the control of fuel combustion should be strengthened in the southern area in winter.

Determination of priority control factors for the management of soil trace metal(loid)s based on source-oriented health risk assessment

Trace metal(loid)s (TMs) in soils can seriously threaten the ecological environment and human health. With the limitation of resources and costs, determining priority control factor is critical for managing soil TM pollution. To explore the pollution characteristics, source apportionment, and human health risk of TMs, a total of 209 surface soil samples were collected from Anqing City, China. Results showed that all the average values of TM concentration, except for Cr, were higher than their corresponding background value. Using a Positive matrix factorization model coupled with Correlation analysis, four sources (including agricultural sources, atmospheric deposition sources, industrial sources, and natural sources) were identified as the determinants for the accumulation of soil TMs, with the contribution rates of 12.4%, 8.1%, 64.1%, and 15.4%, respectively. The assessment of probabilistic health risks revealed that Non- carcinogenic risks of all populations were acceptable (HI < 1), while Carcinogenic risks were all at a high level (TCR > 10E-04). Agricultural pollution and As were identified as priority control factors, according to the analysis results of the relationship among TMs, pollution sources and health risks. Our findings provide scientific support for decision-makers to formulate target control policies and reduce management costs of soil pollution.

Metal(Loids) Bioaccessibility in Road Dust from the Surrounding Villages of an Active Mine

Human activities, in general, cause a significant impact on the environment and human health. The present study aims to characterize the road dust of villages located near an active mine and to assess metal(loids) bioaccessible fractions. From the collected road dust samples (<250 µm fraction), the pseudo total, gastric (G) and gastrointestinal (GI) phase (UBM assay) concentrations, mineralogical composition, enrichment factor (EF), and risk for humans were determined. The obtained results revealed that arsenic represents the highest risk to humans, with mean pseudototal values higher than the maximum reference value range. The enrichment factor pointed to As as having significant to very high enrichment in all of the villages. In addition, Cd presented the maximum EF values in all of the villages, and was thus classified as having a very high enrichment. Particles enriched in As, Ca, Fe, Cu, Al, and Ti were identified by SEM-EDS in weathered agglomerates, and were linked to mine wastes and long-distance transport through both wind and/or traffic. The arsenic bioaccessibility fraction (%BAF) presented low values in the studied samples, possibly because of the low complex solubility of Fe with adsorbed As, limiting the release of arsenic and reducing its bioaccessibility. The concentrations of bioaccessible Cd for the G and GI phases were within the reference range, while for Cu, they were above and for Pb they were lower than the reference value range. The results show that the pseudototal fraction risk is overestimated when compared with BAF%; nevertheless, the total G and GI risks were above the carcinogenic target risk (1 × 10−6) in most of the samples. The carcinogenic risk of the bioaccessible contaminants showed that As represented the higher risk for developing cancer over a lifetime, with ingestion being the main risk route.