Journal of Atmospheric Chemistry最新文献

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).

A novel coronavirus has affected almost all countries and impacted the economy, environment, and social life. The short-term impact on the environment and human health needs attention to correlate the Volatile organic compounds (VOCs) and health assessment for pre-, during, and post lockdowns. Therefore, the current study demonstrates VOC changes and their effect on air quality during the lockdown. The findings of result, the levels of the mean for total VOC concentrations were found to be 15.45 ± 21.07, 2.48 ± 1.61, 19.25 ± 28.91 µg/m³ for all monitoring stations for pre-, during, and post lockdown periods. The highest value of TVOCs was observed at Thane, considered an industrial region (petroleum refinery), and the lowest at Bandra, which was considered a residential region, respectively. The VOC levels drastically decreased by 52%, 89%, 80%, and 97% for benzene, toluene, ethylbenzene, and m-xylene, respectively, during the lockdown period compared to the previous year. In the present study, the T/B ratio was found lower in the lockdown period as compared to the pre-lockdown period. This can be attributed to the complete closure of non-traffic sources such as industries and factories during the lockdown. The Lifetime Cancer Risk values for all monitoring stations for benzene for pre-and-post lockdown periods were higher than the prescribed value, except during the lockdown period.

A detailed study on potential sources, variation, and environmental effects of the rainwater ions was carried out at Lothian Island, Sundarban mangrove forest, India, during the southwest monsoon (June–September) in 2019. On an event basis, the maximum rainwater precipitation was observed 17.65 mm Day ⁻¹ and a minimum of 1.02 mm Day ⁻¹. The maximum amount of total precipitation was recorded in the month of July (237 mm). The volume weighted mean (VWM) concentration shows that the total ionic composition was 93.7 μeq L⁻¹, whereas the percentage contribution of the total ionic concentration is found to be 45.97% to anions and 54.02% to the cations. Temporal variation was observed between early (June- July) and late monsoon (August—September), which shows a high concentration of major ions in early monsoon and low concentration in late monsoon due to the washout of atmospheric particles with the frequent and increasing precipitation. The pH values of the 78% samples show neutral pH and neutralization factors (NF) followed a sequence of NF_Ca ˃NF_Mg ˃ NF_NH4 with factors of 0.77, 0.34, and 0.14 indicating Ca²⁺ was the most potential species to balance the acidic ions (NO₃⁻, SO₄²⁻) over the study area. Source apportionment study indicates the significant influence of marine actions (long-range transport by monsoonal wind from marine origin, Sea spray, salty soil profile of mangrove) as the major source of ions over Sundarban. The rate of nutrient wet deposition in the form of rainwater was estimated and average monsoonal nitrogen flux was observed 0.87 kg ha⁻¹where NO₃ contributes the most (0.60 kg ha⁻¹). N and P deposition flux also showed a simultaneous pattern with the seasonal nutrient concentration of surrounding river water, which may be an indication of a possible contribution of atmospheric wet deposition in the spike of monsoonal nutrient concentration in river water.

The TROPOMI (TROPOspheric monitoring instrument) onboard Sentinel-5 Precursor (S5P) satellite provides high spatial resolution data of carbon monoxide (CO) while the MAIAC (Multiangle Implementation of Atmospheric Correction) is a newly developed algorithm applied to MODIS collection 6 observations to retrieve AOD (Aerosol Optical Depth) at a high spatial resolution of 1 km. The present study utilized the MAIAC AOD from MODIS Terra and Aqua polar-orbiting satellites between March 2000 to December 2021 and CO from Sentinel-5P during the available period July 2018-December 2021 over Pakistan. Moreover, we used three trend techniques (Linear regression, Mann–Kendall (MK), and Theil-Sen’s Slope) to examine the trends of AOD and CO over Pakistan. The results show that both AOD and CO have high values over central Punjab, western Balochistan, central Sindh, and Khyber Pakhtunkhwa. The mean annual high AOD of > 1.2 is observed in eastern Punjab because of an increase in urbanization, industrialization, and economical activities whereas the AOD of ~ 1.0 is observed over Balochistan, Sindh, and a few parts of Khyber Pakhtunkhwa. The highest mean annual CO of ˃0.03 mol/m^2 is seen over central Punjab, Sindh, and Khyber Pakhtunkhwa. The results show that seasonal mean MAIAC AOD ranging from 0.7 to > 0.9 was seen over Punjab and Sindh province during the monsoon season whereas the lowest AOD is detected in the winter season over few parts of Balochistan. In contrast, the highest mean seasonal CO ranging from 0.040 to > 0.055 mol/m^2 was seen in the winter season over Punjab. The lowest CO concentration is observed in the winter season over the northern region of Pakistan. Non-parametric analyses (MK and Theil-Sen’s slope) also show an increasing trend of CO over Pakistan from 2018 to 2021. Furthermore, we have also investigated the trends of AOD and CO over selected cities of Pakistan using linear regression, MK test, and Theil-Sen’s slope to reveal long-term air pollution trends.