Journal of Atmospheric Chemistry最新文献

This study investigates the concentrations and spatial distribution of toxic heavy metals (Cd, Cu, Pb and Zn) through chemical analysis of rainwater samples collected in Tehran, Iran during winter and spring of 2022, characterized by different land use, emission sources, traffic conditions and population density. The average concentrations of the examined heavy metals at the five sampling sites were 52.9, 11.8, 14.6 and 0.93 μg l⁻¹ for Zn, Pb, Cu and Cd, respectively. The concentrations of all heavy metals were significantly higher (p < 0.05) at the sampling points in central and south Tehran compared to sites in the west and north, due to different urban characteristics, higher pollution emission rates from the traffic and domestic sectors, and local wind patterns developed within the city. High traffic load in the central part of Tehran also escalates the heavy metal concentrations in this region. The significant correlations between the examined heavy metals at the five sites indicate common, local anthropogenic sources. The heavy metal concentrations were higher for rain samples collected in spring than in winter, likely associated with dilution processes in winter and the restriction measures due to COVID-19 pandemic. During the lockdown period, a drastic decrease in traffic load was observed in Tehran, confirming that motor vehicles is the main regulatory factor for air pollution and potential toxic elements in the city.

This study investigates the sources and characteristics of PM₁₀ pollution in Tetouan city, Morocco, by employing a combination of chemical mass closure, source-receptor modelling (namely positive matrix factorization, PMF), and air mass trajectory statistical analyses (concentration weighted trajectory, CWT). It provides compelling evidence that using such a combination is a powerful approach for studying the composition and sources of PM₁₀ in the Tetouan region. The PMF analysis identifies four PM₁₀ sources, namely Vehicle Exhaust, Secondary Aerosols, Nitrate + Biomass Burning, and Fresh Sea Salt, with distinct seasonal contributions. CWT analysis reveals the Mediterranean Basin as the primary source region, with influences from populated areas in northern Morocco, southern Europe, and marine emissions. PM₁₀ mass closure highlights the abundance of Dust, Particulate Organic Matter (POM), and Water-Soluble Inorganic Ions (WSI), accounting for the majority of the mass. The low OC/EC ratio advocates that carbonaceous aerosols primarily originate from local traffic emissions. Diagnostic of WSI ratios shows that the [NH₄⁺]/[SO₄²⁻] ratio indicated an ammonium-poor environment and suggested an acidic nature of the PM₁₀ aerosols, while the [SO₄²⁻]/[NO₃⁻] ratio reflects the combined influence of stationary and mobile sources, with a partial contribution from industrial activities throughout the year. These findings are expected to shed light on the chemical composition, origin of emission sources, and transport pathways of PM₁₀ in the region, contributing to the understanding of air pollution in the south western Mediterranean.

This study addresses the spatio-temporal variability and plausible sources of criteria air pollutants in the Western Indian city-Ahmedabad. The air pollutants PM₁₀, PM_2.5, O₃, NO₂, SO_2, and CO have been analyzed at ten locations in Ahmedabad from 2017 to 2019. The seasonal variability indicates that the air pollutant concentration is highest during winter, followed by pre-monsoon, post-monsoon, and monsoon seasons. The concentration of PM_2.5 (59.52 ± 16.68–89.72 ± 20.68) and PM₁₀ (107.25 ± 30.43–176.04 ± 38.34) crosses the National Ambient Air Quality Standards (NAAQS) in all seasons. However, the seasonal difference from winter to pre-monsoon is not highly significant (p > 0.05), indicating that the pollution remains fairly similar during these two seasons. The spatial variability of air pollutants over Ahmedabad indicates that the concentration is highest in the south and central region of Ahmedabad and lowest at the east location. The Ventilation Coefficient (VC) has been used to understand the dispersion of air pollutants. The K-means clustering was performed to assess the locations within Ahmedabad with similar air pollutants sources followed by source identification using Principal Component Analysis-Multiple Linear Regression method (PCA-MLR) of 5 clusters. The different locations identified were industrial, residential, and traffic which mainly contribute to the air pollutants in Ahmedabad city. The health risk assessment indicates PMs are the leading pollutant and causing excess risk (ER > 1) at all the locations. With the help of the different statistical techniques, it helps in ascertaining the hotspots of air pollution in a region which will be beneficial in studying health exposure and for policymakers to adopt mitigation strategies.

Precipitation is one of the significant phenomena for deposition of nitrogen, carbon and metal fractions. In the current study, Total Nitrogen (TN), Dissolved Organic Carbon (DOC) and metal concentrations were measured at two sites having distinct land use patterns in Delhi National Capital Region during different seasons in 2018 and 2019 to find out their potential sources. The TN mean concentration was found to be 16.0 mg/l and 7.0 mg/l at DG and JN site respectively. Whereas the DOC mean concentration was found to be 3.8 mg/l and 2.5 mg/l at DG and JN site respectively. The sequence for the metal concentrations was recorded as Ca > Na > Mg >K> Al  > Cu > Fe > Mn > Zn > As for DG site whereas at JN site we recorded different sequence i.e., Ca > Al > Na > K > Mg > Fe > Mn > Zn > Cu > As. Different sources can be attributed to the influence of anthropogenic activities (agriculture, animal husbandry) on nitrogenous species, and biomass burning on dissolved organic carbon species. The wind rose plots indicated that the local and regional sources located in the south-eastern and north-western direction from the sites influenced the wet deposition of the species. Air-mass back trajectory analysis implied the influence of air masses originating from the Bay of Bengal during monsoon season while that of air masses originating from Haryana, Punjab and further north-west during winter season. Presently, very limited information is available on TN and DOC linking with heavy metals. The current study will be filling such gaps to further help nitrogen and carbon budgeting and linking nitrogen with climate change. The study has policy implications as well for north-central India especially for identifying and controlling local, trans-boundary and distance emission sources. The findings facilitate us to understand a holistic view of chemical composition of precipitation so that effective mitigation measures can be taken accordingly.

Lucknow is one of the most polluted metro-city in India with increasing vehicular density and fuel consumption in the last three decades. The study was conducted during years 2019–2021 for measurement of fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), respirable particulate matter (PM₁₀), and noise levels at nine selected sites; 4 residential, 4 commercial, and 1 industrial, encompassing prior-to-lockdown, during-lockdown, and after-lockdown periods. Values of PM₁₀ for prior-to-lockdown, during-lockdown, and after-lockdown period ranged from 133.2 to 197.4, 77.0 to 135.0, and 91.4 to 148.0 µg/m³, respectively while values of PM_2.5 were 66.5 to 93.6, 41.9 to 67.5 and 49.5 to 98.6 µg/m³, respectively. Corresponding values of SO₂ ranged from 8.7 to 12.8, 5.5 to 7.6, and 11.4 to 17.6 µg/m³, respectively while values of NO₂ were 24.6 to 57.0, 20.5 to 32.8, and 26.1 to 43.8 µg/m³, respectively. Order of the trace metals associated with PM_2.5 is Co < Cd < As < Cr < Ni < Cu < Pb < Mn < K < Zn, Co < Cd < As < Cr < Cu < Ni < Pb < Mn < Zn < K and Cd < Co < As < Cr < Cu < Ni < Pb < Mn < K < Zn in the same periods. Statistical data evidenced that the air quality of the city witnessed drastic improvement during the COVID-19 pandemic. WHO AIRQ + was utilized to calculate attributable health risk and post-neonatal disease burden; showing 1447 ± 768 estimated number of cases attributable to ambient PM₁₀ per lakh of population. Regulatory authorities need to establish new benchmarks for the prevention and management of public health risks for urban resilience and environmental management for episodic events in the near future.

Particulate-bound Polycyclic Aromatic Hydrocarbons (PAHs) have been identified as pollutants of serious concern due to their severe health impacts on human and animal life. In the present work, 16 USEPA (United States Environmental Protection Agency) identified PAHs present in PM_2.5 at Jorhat, India during the winter months (Jan-March, 2020) were analyzed. Apart from the temporal variability of these compounds, the impact of varying meteorological factors like temperature, wind speed, relative humidity, and planetary boundary layer height on PAHs concentration have also been studied. It has been observed that the effect of ambient air temperature and planetary boundary layer on PAHs concentration are significant compared to other meteorological parameters during the winter season. The average concentration of total PAHs during this period was 157.2 ± 127.7 ng/m³ with dominance of high molecular weight aromatics compared to the low molecular weight ones. Among all 16 PAHs studied, the contribution of benzo(b,j)fluoranthene (27.26%) to total PAHs concentration was found to be the highest followed by di-benzo(a,h)anthracene (10.37%). Source identification analysis using isomeric PAHs ratios indicated that crop residue burning, vehicular emission, coal, and wood combustion are the major emission sources of PAHs. A comparative study of PAHs emission at the present site with other northern cities of India has been performed and it is observed that vehicular emission contributing to PAHs is common to all cities but in Kolkata, wood and coal combustion were also responsible for PAHs emission. Biomass burning is also seen to be a contributor to Amritsar. Whereas in Jorhat, crop residue and coal/wood combustion are seen to be major contributors to PM_2.5 bound PAHs unlike other cities.

Graphical abstract

The data of 17 air quality monitoring stations of Greater Cairo are used to perform a statistical analysis aiming to detect any heterogeneous surface effects of mineral dust on the distribution of reactive trace gases (SO₂ NO₂, and ozone) in. After a thorough quality check, the methodology consisted of i) selecting representative stations by agglomerative hierarchical clustering, ii) identifying dust events based on PM₁₀ measurements, remote sensing observations, and meteorology, and iii) applying the non-parametric Kruskal Wallis (KW) hypothesis test to compare (at the 95% confidence level) trace gas concentrations during dust and non-dust events. The representative stations display either a background-like or a bimodal variability with concentrations (even that of the secondary product NO₂) peaking at traffic rush hours but during dust storms all stations capture the signal of mineral dust advection. Eight wintertime and springtime dust cases are retained for the study. After the role of the confounding factors (i.e., ventilation index, relative humidity, and photolysis) has been carefully discussed and taken into account, the KW test shows that there is no significant reduction of the SO₂, NO₂ and ozone concentrations attributable to dust during 7 of the 8 events. The drop of the concentrations coinciding with the advection of dry dust-laden Saharan air masses is rather an effect of the dilution resulting from the combination of large wind speed and mixing layer height than of the heterogeneous uptake of these gases on the mineral dust surface.