Aerosol Science and Engineering最新文献

The urbanisation and its detrimental impact on climate is a well-documented phenomenon in today’s world, but research documenting the Urban Pollution Island (UPI) especially over South Asia is seldom found. With the advancement of the satellite datasets, the quantification of UPI has become possible only in recent years. When measured using satellite data, the UPI is the spatial anomaly of Aerosol Optical Depth (AOD) over an urban area with reference to a nearby non-urban zone. UPI may influence energy budget, precipitation patterns and human health over the city. In the present research, it has been attempted to analyse the climatology and characteristics of UPI and its association with the Surface Urban Heat Island (SUHI) over six cities (Patna, Gaya, Ranchi, Jamshedpur, Bardhaman and Siliguri) from eastern India, which is a highly populated region and infamous for climatic concerns. Alongside, a Surface PM2.5 data is also investigated further, to find heat and pollution island links. The UPI–SUHI interactions have been evaluated and found to be very distinct for each city. It is found that high urban AOD value can be noticed irrespective of the UPI magnitude over Patna. Bardhaman has exhibited very high AOD (> 3.0) even in very low UPI conditions. Jamshedpur’s urban loadings found to be contributing somewhere to UPI formations. UPII has also shown a clear sign of a seasonal cycle across the cities. In Patna, increase in PM2.5 may be linked to SUHII in medium loading cases and very high PM2.5 loadings (> 200 μg/m³) result in low average SUHII. It may be summarised that Patna, Gaya and Bardhaman are exhibiting high surface PM2.5 loads over urban zones, whilst Ranchi, Siliguri and Jamshedpur have much cleaner urban air. The Mann–Kendall test and Pettitt’s test also detected significant increasing trend and change point in recent times for UPI intensity. The well-developed UPI system shows an exigency of more in-depth studies to mitigate the detrimental effects of UPI–SUHI in upcoming times.

Size-resolved aerosols collected at Tianjin, North China in winter were studied for inorganic ions, carbonaceous components, dicarboxylic acids, benzoic acid, oxocarboxylic acids and α-dicarbonyls. Na⁺ found to be the dominant ions, while sum of SO₄²⁻, NO₃⁻ and NH₄⁺ was almost more than half of the total ionic mass in all size fractions. Both inorganic anions and carbonaceous components showed a bimodal distribution. Water-soluble organic carbon (WSOC) accounted for 53.9% to total OC, with 36.0% in fine- and 17.9% in coarse-mode fractions (≤ 2.1 and ≥ 2.1 μm particles, respectively) of aerosols. Most of dicarboxylic acids and related compounds peaked at 0.43–0.65 μm size bin followed by a gradual decrease, except for few species. Average concentrations of total dicarboxylic acids were 1223 and 516 ng m⁻³ in fine and coarse mode fractions, respectively. Oxalic acid found to be the most abundant species followed by phthalic and azelaic acids in fine- and coarse-mode fractions, except the third most abundance of glyoxylic acid in the coarse mode fraction. Based on size-resolved distributions, correlations and mass ratios of selected marker species, we found that inorganic aerosols were mainly derived from sea salt and vehicular exhaust and coal combustion emissions rather than biomass burning and soil dust in winter over the Tianjin region, North China. While dicarboxylic acids and related compounds were mainly originated from fossil fuel including coal combustion and their contributions from biomass burning and marine and terrestrial biogenic emissions were minor. Their in situ secondary formation and transformations were intensive at local and regional scales.

The black carbon (BC) aerosol is the organic remanence of the incomplete burning of various fuels. The study attempts to analyse the temporal variability of BC over Ranchi, Jharkhand, India using ground based measurements of aethalometer. The diurnal variation reveals two prominent sharp peaks throughout the year, one in the morning hours (0130-0330 UTC) and other in the evening hours (1330-1530 UTC). The results show a marked seasonal variation in BC concentration, with highest value during the pre-monsoon (7.24 µg/m³) and least in the monsoon (2.01 µg/m³) season. The relationship of meteorological variables such as temperature, precipitation, aerosol optical depth (AOD), organic carbon and vegetation represented via Normalized Difference Vegetation Index (NDVI) with BC is also computed using satellite-based measurements. A significant correlation is in the spatial pattern of organic carbon (r = 0.927), AOD (r = 0.86) and temperature (r = 0.748) with BC, whereas precipitation (r = − 0.146) and NDVI (r = − 0.203) shows insignificant correlation with BC. Significantly higher level of BC concentration (11.95 µg/m³) in response to the fog event is observed throughout the day against lower (6.5 µg/m³) BC in winter. The morning peak is increased by 4.71 µg/m³ and delayed by two hours on foggy day than the winter mean. During the thunder squall event, mean BC is reduced to 3.84 µg/m³ from 7.24 µg/m³ in  pre-monsoon. Similar reduction is also observed in mean BC (1.2 µg/m³) in response to a rainy day during monsoon. The variability in BC is key to the changes in AOD that impacts the air quality, energy balance, cloud-precipitation processes, global warming and climate change.

Combustion of fossil fuel produces emissions and is one of the major environmental problems leading to climate change. Diesel engines are highly efficient but produce particulate emissions. These particulate emissions are considered dangerous to human health because inhaling particulates may cause respiratory and heart disease. Substituting fossil diesel fuel with renewable diesel fuel and using diesel particulate filters is one possibility to meet stringent legislative requirements. With this motivation, the present experimental investigation aimed to evaluate the particle size distribution (PSD), optical properties of particulate matter (PM) emitted, and the outcome of using an after-treatment system comprising of a diesel particle filter (DPF). This investigation aimed to make a comparative analysis of particulate emission upstream and downstream of the DPF with and without ultraviolet (UV) light (405 nm and 781 nm wavelength) turned on/off. Experiments were performed at (a) engine idle with a torque of 6 Nm at 750 rpm, IMEP of 1.35 bar and power of 0.5 kW, (b) engine at part load with a torque of 32 Nm at 1200 rpm, IMEP of 8.5 bar and power of 4.5 kW. Diesel engine was operated on two fuels (a) Diesel and (b) EHR7. Results showed that as and when UV light was turned on, a distinct nucleation mode that dominated the number concentration for both test fuels were observed. Downstream of the filter had relatively higher AAE values which show the contribution to climate change. Present experimental research is important for renewable fuel industries, industrial innovation's future, and the exhaust gas after-treatment system (EATS) community. The results contribute to knowledge for occupational exposure, human health, and the environment.

Air quality improved due to a sudden reduction in the mass concentration of criteria pollutants (PM_2.5, PM₁₀, NO_x, CO, SO₂) except ozone (O₃) over cities of the world during the novel coronavirus diseases (COVID-19) lockdown. Such reduction in pollutants concentration during the lockdown period is an indicator of pollutants contributed from human-induced sources. The elevated ozone level during the lockdown period is explained by shifted NOx-mediated reaction towards volatile organic carbon (VOCs) mediated reaction. The reduction in pollutants concentration and improved air quality is not uniform for outdoor and indoor environments. The indoor air quality is quite poor compared to outdoor throughout the lockdown period. The degradation in indoor air quality is associated with increased human activities and the degree of ventilation inside the home. The number of active COVID-19 cases is associated with air quality over a region. The improved air quality helped in a reduction in COVID-19 virus transmission among the people. Present review articles provide detailed insight into current research progress, the impact of lockdowns on outdoor and indoor air quality in different cities of the world. Further, this review articles provide a detailed overview of an elevated O₃ level during the lockdown period and the mechanism of formation.

Globally, the transportation sector is expanding at a fast pace in tandem with urban and socioeconomic development, contributing significantly to severe air pollution. Due to concerns about air quality, human exposure, public health, and climate change, air pollution has garnered considerable attention. Most people in the country are unaware of the policy and legislation on vehicular exhaust emissions, so vehicular air pollution and its consequences have received little attention. Although the majority of rich countries have implemented automobile emission control measures, developing countries such as Ghana continue to use extremely crude methods. Based on available research, this study summarizes global policies and regulations that have been used to regulate vehicular exhaust emissions from high-emitting automobiles. The purpose of this research is to assist a broader audience in comprehending Ghana's overall system for preventing and controlling motor vehicle-related air pollution by providing an overview of pertinent legislation, policies, and enforcement, as no such review has been presented in the country. Policymakers will benefit from the insights and lessons offered in this study to develop robust air quality control legislative packages in Ghana.

In this work, we are interested in the characterization, identification of the sources and seasonal variation of airborne particles in suspension and their chemical compositions as well as their human health risk assessment in Meknes city in Morocco. For this, samples were taken with Gent sampler, making it possible to separate the coarse fractions (PM₁₀) from the fine fractions (PM_2.5). The particles were collected, for a year in the city center in Meknes–Morocco, near the highways with very important automobile traffic and not far from the rail traffic. The concentrations of eight elements (Ca, Cr, Cu, Fe, K, Mn, Pb and Zn) were analyzed using Total Reflection X Rays Fluorescence (TXRF). Some filters were analyzed by Scanning Electron Microscopy coupled to the Energy-Dispersive Spectrometer (SEM–EDS). The statistical approach to pollution sources is carried out by the application of Positive Matrix Factorization (PMF). The results obtained for particulate matter show the importance of terrigenous inputs and soil resuspension, especially in July and August when the coarse fraction reaches the highest levels (increased wind erosion of the soil). European quality standards and WHO recommendations have also been exceeded. While for the chemical composition, the seasonal variations are not significant. It is also noted that the Pb contents are higher than the quality standards. Regarding the sources of pollution, the application of PMF and SEM–EDS show the influence of three major sources: mineral emissions (cement industry), mix of re-suspended soil particles and road traffic and rail traffic. Health risk assessments revealed that non-cancerous hazards were lower than the acceptable level (< 1), hence no significant risk is expected, while, the cancer risk was higher than the acceptable level (10^–6) particularly for Cr. In addition, mortality risk for PM_2.5 and PM₁₀ were higher due to higher ambient concentrations measured in Meknes city.

Vehicles are one of the main contributors to outdoor air pollution in urban areas of developing nations. Addis Ababa is experiencing the fastest rate of urbanization with increasing heavy traffic across the city. Megenagna is one of the city’s busiest transportation hubs, connecting traffic to most of Addis Ababa’s lower town via major highways and railways. The ever-increasing air pollution from heavy traffic in the area is an alarming environmental problem for the city. This research aimed to assess and evaluate traffic-related particulate and gaseous pollutants in Megenagna. There were 41 sampling points, 16 of which were near the root of the Megenagna bus station, and the rest 25 were taken on the six main road lines. The samples were collected for the 2-month variations of January and February during the rush hour. Sampling was done using the hand-held portable air test equipment (Model-CW-HAT2005) and Aeroqual Series 500 (2016). Geo-statistical analysis and descriptive and inferential statistical analysis were used. The mean values of PM_2.5, PM₁₀, SO₂, and NO₂ in the Megenagna area were 30.3 ± 2.2 µg/m³_, 58.6 ± 3.1 µg/m³, 777.5 ± 151.2 µg/m³, and 58.6 ± 3.04 µg/m³_, respectively. The difference between sampling locations was statistically significant (p < 0.05), suggesting that there is significant spatial variation between different parts of the study site. Individual comparisons, however, revealed that they are not significantly different from one another on some sites. The hotspot analysis also confirmed that there are hot and cold spots in the distribution of pollution over space and time.

The purpose of the study is to investigate the dispersion of droplet nuclei/aerosol which are produced during coughing and continuous talking to quantify the risk of infection due to airborne disease transmission. A three-dimensional modelling of aerosol transport due to human respiratory activities such as coughing and talking within a room environment has been simulated using CFD technique. An inert scalar transport equation was used to represent aerosol cloud, while turbulence was modelled with the (k-epsilon ) turbulence model. A modified Wells–Riley equation was used to calculate the risk of infection based on quanta emission concept. The spatial and temporal distribution of aerosol cloud within the room is initially driven by the upward flowing thermal plume surrounding the human, but later driven by the flow field constrained by the walls and cooler air movement. While the cough generated aerosols are concentrated in a smaller space within the room, the continuous talk generated aerosols are distributed throughout the room. Within an indoor environment, 2 m distancing will not be enough to protect healthy people from aerosols coming from an infected person due to continuous talking with prolonged exposure.