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.

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.

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, PM1-10, PM10-50, and PM50-1000 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 PM1-10 particles. In coarser fractions (PM10-50, PM50-1000), 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 PM1-10, 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 PM1-10 demonstrate the trend of rising pollution levels with the increase in road size, while in the eastern part of the city, only coarse particles PM50-1000 show the same trend. In the fractions PM1 and PM1-10 of road dust, a significant contribution was made by anthropogenic sources; however, its role decreased in the coarse fractions-PM10-50 and especially in PM50-1000- due to the influence of roadside soils and their parent material.

Main features and contamination of sealed soils in the east of Moscow city.

The aim of this paper is to characterize the main properties and level of pollution of sealed soils in different land use zones of the Eastern administrative district (EAD) of Moscow. In 2016-2017 overall, 47 samples were taken from 35 soil pits. The list of soil properties analyzed included actual acidity, organic carbon content, particle-size distribution, and degree of salinity. Pollution of sealed soils with petroleum products (PPs), benzo[a]pyrene (BaP) and heavy metals and metalloids (HMMs) was evaluated. Sealed soils are characterized by the medium organic matter content (2.24%), alkaline reaction (pH 8.0), sandy loamy texture, and the absence of soluble salts in the upper part of the profile. The pronounced technogenic anomalies of hydrocarbons are mainly formed in the sealed soils of the industrial and traffic land use zones. The mean content of BaP in the sealed soils is 56 times higher than that in the background soils, it exceeds MPC by 9.5 times. The concentrations of most HMMs in the sealed soils exceed the background level by two-four times. The most intense accumulation of As, Ba, Cr, Cu, Ni, Pb, Sb, and Sn takes place in the industrial zone with the high degree of sealing. The hygienic standards for BaP and PPs contents approved in the Russian Federation in the sealed soils of EAO are exceeded by almost ten times. Maximum permissible concentrations are also exceeded for a large group of HMMs. The high contamination of the sealed soils can create dangerous ecological situation in the EAD if road covering will be removed and pollutants begin to migrate.

Сontamination of urban soils with heavy metals in Moscow as affected by building development.

Building development in cities creates a geochemical heterogeneity via redistributing the atmospheric fluxes of pollutants and forming sedimentation zones in urban soils and other depositing media. However, the influence of buildings on the urban environment pollution is poorly understood. The aim of this study is to evaluate the barrier functions of urban development by means of a joint analysis of the contents of heavy metals and metalloids in the upper horizon of urban soils, their physicochemical properties, and the parameters of the buildings. The soil-geochemical survey was performed in the residential area of the Moscow's Eastern Administrative District (Russia). The parameters of the buildings near sampling points were determined via processing data from the OpenStreetMap database, 2GIS databases and GeoEye-1 satellite image. A high level of soil contamination with Cd, W, Bi, Zn, As, Cr, Sb, Pb, Cu was revealed, depending on building parameters. A protective function of the buildings for yards is manifested in the decreasing concentrations of As, Cd, Co, Cr, Mo, Ni, Pb, Sb, Sn, W by 1.2-3 times at distances of <23-36 m from the buildings with their total area ≥660 m2 and the height ≥7.5-21 m. An opposite effect which enhances concentrations of Bi, Cd, Co, Cr, Cu, Mo, Pb, Sb, Sn, W, Zn by 1.2-1.9 times is seen in "well-shaped" yards acting as traps under similar distances and heights, but at their average area ≥118-323 m2, and total area ≥323-1300 m2. The impact of these two building patterns on the soil contamination is only seen for certain directions of atmospheric flows. Buildings located in the northwestern sector relative to the sampling point protect the latter from the aerial pollution.

Geochemical disturbance of soil cover in the nonferrous mining centers of the Selenga River basin.

The anthropogenic geochemical transformation of soil cover in large nonferrous mining centers of the Selenga River basin was assessed. The results of the geochemical survey of 2010-2012 revealed the spatial distribution patterns and abundances of 18 hazardous heavy metals and metalloids in the soils of Erdenet (Mongolia) and Zakamensk (Buryat republic, Russian Federation). In both cities, mining activities disturbed soil cover which accumulates Mo, Cu, As, Sb, W in Erdenet and Bi, W, Cd, Be, Pb, Mo, Sb in Zakamensk. Maximum accumulation of elements in Erdenet is restricted to the industrial zone. In Zakamensk, it has spread on ½ of the territory with the degree of multielemental pollution exceeding the extremely dangerous level by 16 times. The effect of mining centers on the state of the river system is local and does not spread to the Selenga River. Downstream from Erdenet, an artificial pool intercepts heavy metal and metalloid flows of the Erdenetii-Gol River. By contrast, downstream from the tailing dumps of the Dzhida tungsten-molybdenum plant the concentrations of ore elements W and Mo and their accessories Bi and Cd in the Modonkul River exceed background values by 146, 20, 57, and 21 times, respectively, decreasing by an order of magnitude 30 km downstream.