Journal of Atmospheric Chemistry最新文献

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.

This paper investigates the chemical composition of Particulate Matter, Organic Carbon (OC), and Elemental Carbon (EC) in residential and traffic sites in Mumbai. The average PM_2.5 and PM₁₀ concentrations at the traffic site (Sakinaka) were 240 µg/m³ and 424 µg/m³, respectively. The observed levels of OC were 35 µg/m³, 22 µg/m³, and 15.5 µg/m³ at Sakinaka junction (high-density traffic), YP-Gate (low-density traffic), and Hostel Premise (Residential), respectively. The average OC/EC ratio value was high (4.5) at the residential site, indicating contributions from stationary combustion sources and secondary production of carbonaceous species to OC. The residential site has a higher percentage of low volatile OC fraction (57%) in total OC than the traffic sites. On the other hand, Sakinaka has a higher percentage of highly volatile OC fractions (36%) in total OC. The crustal-originated metals were dominating in all areas, but the concentration of metals from anthropogenic sources was highest at Sakinaka, i.e., As (381 ng/m³), Pb (352 ng/m³), Zn (679 ng/m³). The K/Al, Ca/Al, Mg/Al, and Fe/Al ratios were high in all the samples compared to the crustal ratio indicating biomass burning and traffic emission sources of these metals. PM originating from traffic was more enriched with heavy metals that are toxic to human health, increasing cancer risks (CR) through inhalation. The hazard quotient was above 1 at all the locations, and CR was above 1 × 10^− 4, causing health risks. According to the dosimetry model, more PM was deposited in the lungs of traffic location occupants through inhalation, increasing the cancerous risk.

This paper reports the chemistry of fine (PM_2.5) and coarse (PM₁₀) aerosols sampled over a period of three years during 2018–2021 at a semi -arid tropical location in the rain shadow region of the peninsular India. The data is classified in to dry (December to May) and wet (June to November) periods. Scavenging effect due to rains have culminated in to less concentrations of both fine and coarse aerosols and their ionic components in the wet period. Significantly high concentrations of the crustal components such as Ca, Na, K and Mg from the local dust resulted in the alkaline pH in both dry and wet periods with Ca and Mg emerging as major neutralizing components. Overall, < 20% samples of both fine and coarse aerosols depicted acidic pH. Concentration of SO₄ was comparatively more than NO₃ indicating towards more presence of stationary sources (industrial/domestic emissions) than mobile (vehicular emissions) sources. Combustion generated and highly absorbing black carbon aerosols showed high concentration during the dry period. Local activities comprising residential, agricultural, vehicular and industrial emissions were the major sources of aerosols at Solapur however, the contribution from the distant sources were also found to contribute as inferred from the cluster analysis and concentration weighted trajectories (CWT). The observed abundances of the alkaline dust aerosols that could act as cloud condensation nuclei or ice nuclei will have important implications on the studies related to cloud aerosol precipitation interaction over this region.

The atmospheric fate of 1,3-dioxolane is assessed by measuring the OH and Cl initiated gas-phase oxidation kinetics, and exploring their mechanistic pathways. Absolute OH reaction rate coefficient of 1,3-dioxolane using laser photolysis-laser induced fluorescence technique is found to be (1.27 ± 0.03) × 10^–11 cm³ molecule⁻¹ s⁻¹ at 298 ± 2 K and it is in good agreement with the measured relative value of (1.13 ± 0.12) × 10^–11 cm³ molecule⁻¹ s⁻¹, using gas-chromatography. Relative value of Cl reaction rate coefficient with 1,3-dioxolane is found to be (1.64 ± 0.60) × 10^–10 cm³ molecule⁻¹ s⁻¹. The tropospheric lifetime of 1,3-dioxolane is calculated to be about 22 h under ambient conditions. Interestingly, it reduces to about 8 h near marine boundary layer, where Cl reaction takes over the OH reaction. Such a short lifetime with respect to reaction with OH and Cl suggests the atmospheric impact of 1,3-dioxolane to be local. Formic acid, ethylene carbonate, and 1,2-ethanediol monoformate are observed as stable products in OH as well as Cl oxidation. 1,3-dioxolane may contribute as one of the sources of formic acid in the atmosphere. Theoretical calculations for the OH-initiated hydrogen abstraction of 1,3-dioxolane revealed that the reaction follows an indirect path through the formation of pre- and post-reaction complexes at entrance and exit channels, respectively with the lowest barrier height of 3.5 kcal/mol. Photochemical ozone creation potential of 1,3-dioxolane is calculated.

Investigation on organic particles was limited in the background regions of Yangtze River Delta (YRD) and little information has been obtained on organic particles of Lin’an (LA). In the present study, the morphology, composition, mixing state, and size of organic aerosols with diameter less than 1 µm were characterized at Lin’an from 20 March 2019 to 20 April 2019. In all samples, irregular types of organic matter (OM) particles were high fraction during morning (72.4%), afternoon (59.1%), and evening (52%), and most of them were internally mixed. In our study, we identified a higher fraction of internally mixed particles in evenings (85%), followed by afternoon (81%), and fewer mixed particles in mornings (68%), indicating particle growth during afternoon and evening. Further, the results show that fraction of organic coating particles was higher in evening (27.4%) and afternoon (12%) indicates strong photochemical processes and formation of secondary organic aerosol on the inorganic particles and new particles formation. Our study reveals that biomass burning in the morning and coal burning from heavy industries, power plants, and vehicles in surrounding urban regions in the afternoon and evenings significantly affected background air quality.

Aerosol affect the climate in number of ways. In order to investigate these effects, we need a deep insight into aerosols optical, physical and radiative properties. So, to understand aerosols climatology, we investigate the properties of aerosols such as aerosol optical depth (AOD) (500 nm), Angstrom exponent (AE) (440–870 nm), single scattering albedo (SSA), refractive index (RI) and aerosols radiative forcing (ARF). For this purpose, we select four different AErosol RObotic NETwork (AERONET) sites located in four different continents; Kanpur, (India) Asia, Sao-Paulo, (Brazil) Southern America, IIorin, (Nigeria) Africa and Canberra, Australia. High AOD and AE is found (AOD = 0.90, AE = 1.31) in November at Kanpur and in September (AOD = 0.39, AE = 1.48) at Sao-Paulo. High AOD (1.06 and 1.12) over IIorin in January and February is found because of fog and haze. SSA shows decreasing trend with increasing wavelengths having minimum value (0.88 and 0.78 at 1020 nm) during the months of DJF and SON over Sao-Paulo and Canberra respectively. The highest value of SSA (~ 0.96) is found during the months of MAM over IIorin because of presence of coarse aerosols. The low value of SSA over Kanpur during DJF months shows dominance of fine urban/ biomass burning aerosols. Based on the values of AOD, AE and SSA, Canberra is the most pristine site. The estimated ARF values indicate that Kanpur and Ilorin sites exhibit higher TOA and BOA values as compared to Sao-Paulo. ARF at ATM is observed to be 7.4 Wm⁻² higher during JJA months and 10.1 Wm⁻² during SON months than MAM months over Kanpur. We have also observed lowest ARF efficiency (F^eff_BOA) of − 181 Wm⁻² AOD⁻¹_550 nm during MAM months for Sao-Paulo while the highest value of − 297 Wm⁻² AOD⁻¹_550 nm is observed during DJF months for Kanpur.

Abstract

Abstract

Christian Junge (1912–1996) is considered by many to be the founder of the modern discipline of atmospheric chemistry. In studies from the 1950s through the 1970s, Junge was able to link chemical measurements in a few scattered locations around the earth and integrate them with meteorology to develop the first global view of the basic chemical and physical processes that control the sources, transport, transformations, and fate of particles and gases in the atmosphere. In this paper we summarize and comment upon a number of Junge’s seminal research contributions to atmospheric chemistry, including his discovery of the stratospheric sulfate layer (known as the Junge layer), his recognition of the relationship between the variability of the concentrations of trace gases and their atmospheric lifetimes, his studies of aerosol size and number distributions, his development of the first quantitative model of tropospheric ozone, and other significant scientific investigations. We also discuss Junge’s professional life, his many international leadership positions and honors, as well as some memories and reflections on his many abilities that led to his outstanding contributions to the science of atmospheric chemistry.

This study aimed to calculate size-fractionated PM-bound metals concentration (Co, V, Ni, Cu, Mn, As, Cd, Pb, Cr and Hg) in a European hot spot area in terms of PM air pollution (Zabrze, Poland) and to show their deposition ratios in human airways. Additionally, meteorological data was used to conclude the probable influence of atmospheric conditions on the variability of the PM mass concentrations in different periods of the year. Data regarding the elemental composition of size-fractionated PM in various regions of Poland was also presented. The determination of the selected metals in PM-fractionated samples (PM₁, PM_2.5, and PM₁₀) was performed in two periods – the heating and non-heating season. It was found that metals were primarily associated with particles less than 1 µm, however, the PM size distribution had shown bi-modal characteristics and the maxima of metal mass distribution occurred in both submicron and fine modes. High PM₁ mass loadings, observed especially in the non-heating season were probably due to an influx of fine and even smaller particles from traffic sources. Metals distributions as well as respiratory deposition ratios for PM-bound elements calculated using the MPPD V2.11 model favored nasal and head deposition. The overall mass deposition of metals in the respiratory tract of adults was: 0.39 (Head region, H); 0.07 (Tracheobronchial region, TB); 0.16 (Pulmonary region, P) respectively. No matter the season, the highest inhalable concentrations of metals were found for Cu, Mn, Cr and Pb. Only Cr and Pb are classified as carcinogenic and mutagenic (according to IARC classification).