Integrated Assessment of Affinity to Chemical Fractions and Environmental Pollution with Heavy Metals: A New Approach Based on Sequential Extraction Results

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.

Geochemical fractionation of iron in paper industry and municipal landfill soils: Ecological and health risks insights

Industrial processes and municipal wastes largely contribute to the fluctuations in iron (Fe) content in soils. Fe, when present in unfavorable amount, causes harmful effects on human, flora, and fauna. The present study is an attempt to evaluate the composition of Fe in surface soils from paper mill and municipal landfill sites and assess their potential ecological and human health risks. Geochemical fractionation was conducted to explore the chemical bonding of Fe across different fractions, i.e., water-soluble (F1) to residual (F6). Different contamination factors and pollution indices were evaluated to comprehend Fe contamination extent across the study area. Results indicated the preference for less mobile forms in the paper mill and landfill, with 26.66% and 43.46% of Fe associated with the Fe-Mn oxide bound fraction (F4), and 57.22% and 24.78% in the residual fraction (F6). Maximum mobility factor (MF) of 30.65% was observed in the paper mill, and 80.37% in the landfill. The enrichment factor (EF) varied within the range of 20 < EF < 40, signifying a high level of enrichment in the soil. The individual contamination factor (ICF) ranged from 0 to >6, highlighting low to high contamination. Adults were found to be more vulnerable towards Fe associated health risks compared to children. The Hazard Quotient (HQ) index showed the highest risk potential pathways as dermal contact > ingestion > inhalation. The study offers insights into potential Fe contamination risks in comparable environments, underscoring the crucial role of thorough soil assessments in shaping land use and waste management policies.

The role of chemical fractionation in risk assessment of toxic metals: a review

The identification of highly toxic metals like Cd, Ni, Pb, Cr, Co or Cu in ambient particulate matter (PM) has garnered a lot of interest recently. Exposure to toxic metals, including carcinogenic ones, at levels above recommended limits, can significantly affect human health. Prolonged exposure to even trace amounts of toxic or essential metals can also have negative health impacts. In order to assess significant risks, it is crucial to govern the concentrations of bioavailable/bio-accessible metals that are available in PM. Estimating the total metal concentrations in PM is only an approximation of metal toxicity. This review provides an overview of various procedures for extracting soluble toxic metals from PM and the importance of chemical fractionation in risk assessment. It is observed that the environmental risk indices such as bioavailability index (BI), contamination factor (CF) and risk assessment code (RAC) are specifically influenced by the concentration of these metals in a particular fraction. Additionally, there is compelling evidence that health risks assessed using total metal concentrations may be overestimated, therefore, the metal toxicity assessment is more accurate and more sensitive to the concentration of the bioavailable/bio-accessible fraction than the total metal concentrations. Hence, chemical fractionation of toxic metals can serve as an effective tool for developing environmental protection laws and improving air quality monitoring programs for public health.

Cadmium-resistant phosphate-solubilizing bacteria immobilized on phosphoric acid-ball milling modified biochar enhances soil cadmium passivation and phosphorus bioavailability

Cadmium (Cd) can accumulate in agriculture soil from the regular application of phosphorus (P) fertilizer. Microbiological method is considered as a potentially effective strategy that can not only remediate the Cd-contaminated soil but also provide the phosphorus needed for crop growth. However, the toxicity of Cd may affect the activity of microorganisms. To solve this problem, Klebsiella variicola with excellent phosphate solubilization ability (155.30 mg L^-1 at 48 h) and Cd adsorption rate (90.84 % with 10 mg L^-1 Cd initial concentration) was firstly isolated and identified in this study. Then, a phosphoric acid and ball milling co-modified biochar (PBC) was selected as the carrier to promote the activities of K. variicola under Cd pollution. Surface characterization revealed that the promotion of K. variicola by PBC was mainly attributed to the large specific surface area and diverse functional groups. Compared to contaminated soil, microbial PBC (MPBC) significantly increased the pakchoi biomass and phosphorus (P) content, while the Cd content in leave and root of pakchoi (Brassica chinensis L.) decreased by 25.90-43.46 % (P < 0.05). The combined application also favored the transformation of the resistant P fractions to bioavailable P, and facilitated the immobilization of 20.12 % exchangeable Cd to reducible, oxidizable, and residual Cd in the treated soil. High-throughput sequencing revealed that the response of the soil microbial community to the MPBC was more beneficial than K. variicola or PBC alone. Therefore, the application of MPBC has the potential to act as an efficient, stable, and environmentally friendly sustainable product for Cd remediation and enhanced P bioavailability in agricultural production.

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.

Road Dust in Urban and Industrial Environments: Sources, Pollutants, Impacts, and Management

Road dust (RD) is one of the most important sources of particles in the atmosphere, especially in industrial areas and cities. In this special issue, we collected 16 original articles that describe field, experimental, and modeling studies related to RD and its various size fractions as a key issue in understanding the relationships between several urban and industrial environments and in the identification of pollution sources. Articles in the special issue focus primarily on the following main topics: (1) study of the chemical composition and speciation of RD and its source attribution; (2) assessment of RD and aerosol pollution levels (including express technique), environmental hazards and public health risks; (3) distribution of stable and radioactive isotopes in RD; (4) determination of factors affecting the level of dust accumulation on roads and the intensity of its pollution; and (5) study of the effect of RD on the atmosphere and other environments. Based on the results presented in this special issue, but not limited to, some of the current challenges in studying RD are formulated, including the need for further geographically wider and analytically deeper work on various aspects of the formation, transport pathways, and accumulation of RD in urban, industrial and other areas.