Aerosol Science and Engineering最新文献

The rapid and massive deposition of particles on the vertical wall behind near-wall heat sources is a common and important phenomenon. However, the distribution pattern of such particle deposition has not been clarified. To evaluate the effect of the near-wall heat source on the particle deposition distribution on the vertical wall, an experimental study focused on 0.3 μm, 0.5 μm, 1.0 μm, and 3.0 μm particles under 12 cases with varying temperatures and rotation angles of near-wall heat sources was conducted. The results reveal that particle deposition at the vertical center axis of the rear wall initially exhibits a substantial increase, followed by a subsequent reduction as the distance from the upper surface of the heat source is enhanced. Additionally, in regions that are symmetrically positioned relative to the near-wall heat source, arranged horizontally, the particle deposition pattern of particles of identical size displays a remarkable degree of similarity. The effect of the near-wall heat source rotation angle on particle deposition on the rear wall is also intertwined with factors such as particle size and the position within the rear wall region.

Accurate estimation of Land Surface Reflectance (LSR) is the key to Aerosol Optical Depth (AOD) retrievals. However, the current band-specific LSRs retrieval using Look-Up Tables (LUTs) are typically pseudo-LSRs obtained by atmospheric corrections to the AOD predetermined in the LUTs that do not match the surface constraints established by the true LSRs, leading to an error in modeling reflectance at the top of atmosphere (TOA) using pseudo-LSRs calculation by linear interpolation. This study proposed a new LUT search method to improve the AOD retrievals from the Particle Observing Scanning Polarimetry (POSP) sensor onboard the China GaoFen-5 (02) satellite. Atmospherically corrected LSR using ERA5 reanalysis data and POSP AOD products for the year 2022 were adopted to create a new full-spectrum LSR self-consistent surface constraint. Results showed that the retrieved POSP AOD in January 2023 using the new method agrees with the ground-truth AOD values from AErosol RObotic NETwork (AERONET) site observations with the correlation coefficient (R) at 0.703 and the root mean square error (RMSE) at 0.068. 76.77% of the values fell into the expected error (EE) envelope of range ± (0.05 + 0.15 AOD_AERONET), and 67.35% met the accuracy requirements of the Global Climate Observing System (GCOS).

This study uses numerical methods and HYSPLIT trajectory cluster analysis to evaluate the influence of wind speed and mixing height on the dispersive potential of PM₁₀. The analysis reveals a correlation of 0.58 and 0.44 between PM₁₀ concentrations and wind speed and mixing height, respectively. Wind speed and mixing height are decisive parameters in modulating PM₁₀ levels in ambient air. The study highlights that PM₁₀ concentrations decreased by 41.28% in February with wind speeds over 2 m/s and mixing heights below 400 m. Conversely, in April, PM₁₀ concentrations increase by 52.65% due to wind-induced resuspension with wind speeds over 2 m/s and mixing heights above 450 m. The findings of this study underscore wind speed as a crucial factor in reducing PM₁₀ levels during winter, provided the mixing height is sufficiently high, and in increasing PM₁₀ levels during summer due to resuspension effects.

The pollutants in air are invisible but cause greater threat to the society. In recent times, the spread of the life-threatening disease was also spread through air. Outdoor and indoor air pollution is frequently cited as key contributors to environmental health issues. One of the areas in which the pollutants grow rapidly and the chance of mutating is slaughterhouse. Typically, hazardous gases, scents, and significant amounts of dust particles with biological and non-biological origin contaminate the air in slaughterhouses. However, there hasn’t been much research done on the exposure of air pollutants in slaughterhouses. So, this study focuses on the pollutants which are present in the slaughterhouse. In this research, the correlation results for weekend data showed highest positive relation between PM₁, PM_2.5, PM₁₀ and relative humidity. We identified highest bacterial load 3.9*10² CFU/m³ in chicken cutting area as compared to the lowest 8.5*10 CFU/m³ observed in area of live chicken. The isolated bacterial species identified as Macrococcus goetzii using 16s rRNA analysis and phylogenetic tree analysis showed 99.62% identity with Staphylococcus aureus. Hence, it may be responsible for pathogenesis and can be associated with health risk in workers.

In studying the several factors that can control the transition and settlement of aerosols, new descriptions are required to have a better understanding of the involved processes. For that matter, a new model was previously established to improve the theoretical description of the deposition of aerosols onto the internal vertical surfaces of small spaces. In this paper, the model’s description is extended to cover the deposition onto the other oriented surfaces, namely the horizontal ones with face up and down. Following that, an application is carried out to analyze the aerosols’ penetration through building cracks. An important new subject is considered, which is the penetration through vertical cracks in comparison to horizontal ones. Previous papers in the literature, never considered vertical cracks’ penetration. The ability of the current model to carry out such comparison comes from the way it is constructed, in which all the three dimensions of a crack are taken into consideration, not just the depth and thickness. The results of the model agree well with the experiments. This indicates the good ability of the developed deposition model in describing aerosols’ penetration through cracks. Penetrations through horizontal and vertical cracks are shown to be clearly different when aerosols of larger diameter than ~ 1 µm are considered.

To establish and complete the source profile of fine particulate matter (PM_2.5) in a Chinese megacity- Xi’an, the morphology, chemical characteristics and health risks of PM_2.5 emitted from different sources were explored. In this study, scanning electron microscope, inductively coupled plasma mass spectrometer, ion chromatograph and carbon analyzer were utilized to analyze and determine the source emission PM_2.5 samples. The results showed that PM_2.5 emitted from stationary source was mostly regular spherical, while the dust including soil wind dust and urban dust was practically irregular and with large size. PM_2.5 of mobile source was aggregated porous carbonaceous particles, and of biomass burning was floc or lamellar. Si was regarded as the marker of soil wind dust PM_2.5. Si and SO₄²⁻ accounted for a relatively high proportion in urban dust PM_2.5 (52.2% and 27.9%). Ca could be used as the tracer of construction cement dust due to its high mass fraction. Compared to other sources, mobile source showed higher NO₃⁻ proportion while biomass burning was dominated by Na and K. Attributed to relatively higher OC/EC in Xi’an than other cities, the secondary pollution was more serious. The health risk assessment results showed that the risk of Cr through inhalation route was 10^− 6~10^− 4 for a stationary source, which was over the threshold. In particular, the non-carcinogenic risk and carcinogenic risk of children were all higher than adults.

During a mega-event, the air pollution control measures for the key city and surrounding regions were within a certain distance was always implemented. The necessity of taking the similar or even same measures everywhere is suspect. The 7th Military World Games (MWG) was held in an inland city-Wuhan, and the air pollution control regions within a cycle of diameter as 400 km, which give a good opportunity to address this problem. Compared to the air pollution control period (10/08 − 10/28) in 2019 with those from 2015 to 2018, CO, NO₂, PM₁₀, PM_2.5, and SO₂ showed negative anomalies of 0.13 ± 0.09 mg m^− 3, 10.8 ± 3.34 µg m^− 3, 39.3 ± 5.98 µg m^− 3, 18.0 ± 3.17 µg m^− 3, and 4.30 ± 2.66 µg m^− 3, respectively, while O₃ showed positive anomalies (9.84 ± 4.06 µg m^− 3) in the core control area (Wuhan). Using the weather normalized technique, the contributions of emissions and meteorology to anomalies of air pollutants were quantified, i.e., emission variations contributed to 52.7% of PM_2.5 anomalies in Wuhan. The reduced mass concentrations of elemental carbon (0.49 µg m^− 3) and trace elements (0.88 µg m^− 3), as well as the reductions from biomass burning (4.15 µg m^− 3), vehicle emissions (2.75 µg m^− 3), and coal combustion (1.03 µg m^− 3) all verified the effectiveness and necessity of pollution control for local primary particles. While the elevated nitrate (6.14 µg m^− 3) and sulfate (2.23 µg m^− 3) concentrations during the MWG period highlighted the enhanced secondary formation when the air mass transported mainly from the north, northeastern and western regions of Wuhan, within a cycle of diameter of 300 km. The pollution control at the south regions of Wuhan is not necessary here. This study suggested that during a mega-event, the primary emission reduction of particles from local biomass burning, vehicle emission, fugitive dust as well as the NO₂ and NH₃ reduction from the unwind regions within a certain distance should be emphasized, which can save costs and human efforts effectively.

Particulate matter (PM) air pollution is one of India’s biggest issues due to the country’s rapid growth as a result of expanding urbanisation, growing industrialisation, and other related human activities. This means that the PM pollution levels that the Indian population is exposed to are among the highest in the world, increasing the risk of respiratory ailments, hospital admissions, and early deaths. Most of the research on PM conducted in India focused on large cities such as Delhi, Hyderabad, Mumbai, Bangalore, Kolkata, Chennai, etc. A comprehensive literature review reveals that there are relatively few studies on PM in and around western Indian industrial areas, especially in Gujarat’s Vapi and Ankleshwar. Therefore, in the current study, a comprehensive investigation of the chemical composition of PM containing Elemental Carbon-Organic carbon (EC-OC), Water soluble ions (WSIs), and marker elements is performed for the industrial area of Ankleshwar followed by a source apportionment study using Positive Matrix Factorization (PMF) receptor model. For each of the six locations, twenty samples were taken in February 2020. The PM₁₀ mass for the study area is found to be in the range of 100.98 to 225.47 µg/m³, which is higher than the National Ambient Air quality norm of 100 µg/m³ for 24 h. The contribution of EC & OC is between 44 and 48%, WSI’s is 21–26%, and elements are found to be between 29 and 31%. Source apportionment study performed by the PMF receptor model exhibited the influence from various sources as 27.73% from crustal or soil dust, 22.94% from fossil fuel combustion, 17.94% from vehicular emissions, 13.97% from secondary aerosols, 9.10% from biomass burning, and 8.32% from industrial emissions. This investigation shall further help to devise pollution abetment strategies and improve the ambient air quality for the study area. The source that is responsible for higher PM₁₀ or PM_2.5 concentrations shall be given higher priority while devising control strategies for air pollution control.

A total of 125 samples were collected to investigate the light absorption characteristics and formation mechanism of brown carbon (BrC) in Luoyang. The seasonal range of BrC light absorption was from 2.34 Mm^− 1 to 26.60 Mm^− 1, with extremely high in autumn and winter specifically. The seasonal water-soluble BrC light absorption (2*b_{abs, WS−BrC, 405 nm}/b_{abs, BrC, 405 nm}) varied from 13 to 73%. All the seasonal mean values of the Absorption Ångström Exponent (AAE_BrC) of brown carbon were greater than 3. Secondary organic carbon (SOC) had significantly positive correlation to b_{abs, BrC, 405 nm} when SOC to elemental carbon ratio (SOC/EC) > 1 (R = 0.45, p < 0.05) and water-soluble organic carbon to organic carbon (WSOC/OC) < 0.45 (R = 0.49, p < 0.05), indicating that water-insoluble SOC potentially contributed to BrC in autumn and winter. In autumn, secondary transformations are dominant when NO₃⁻/EC > 3 (R = 0.48, p < 0.01), and the secondary organic aerosols formed by the oxidation of organic gases are the main cause of BrC light absorption, therefore the formation of water-insoluble SOC is related to secondary transformations of nitrogen oxides (NO_x) and volatile organic compounds (VOCs). In winter, the correlation between BrC light absorption and SOC was higher than in autumn, this may be related to the lower winter temperatures, which benefit the condensation/coalescence of semi-volatile organic compounds into organic particulate matter, therefore more water-insoluble SOC is formed in winter. Overall, the results highlighted that it is crucial to alleviate BrC light absorption to keep eyes on water-insoluble SOC.

The effect of evaporation on relative trajectories of two spherical drops sedimenting due to gravity in air is investigated. Theoretical analysis and numerical simulation of the interactions are used to obtain results. Several assumptions are made in the model. The drops remain small enough that the Reynolds number, which is linear in the density of the surrounding fluid, is negligible. However, the Stokes number, which is proportional to droplet mass and is a measure of drop inertia, can be much larger than one. Another restriction is that evaporation is dominated by diffusion and that convection of mass is insignificant. In analyzing evaporation when two drops are present, it is noted that the loss of mass is not the same at each point on a droplet surface. That is, evaporation is non-uniform in a spatial sense. In order to maintain the required spherical drop shape, three approaches, involving the isolated droplet and bispherical coordinate solutions, were taken to determine the mass flux due to evaporation and subsequently the drop position at each time step. For a pair of water drops with radii between 2 and 30 (upmu)m, the following conclusions were obtained. In all three methods, evaporation leads to weaker inertial effects and stronger hydrodynamic effects. Most importantly, in comparing critical horizontal offsets, when both attractive molecular forces and Maxwell slip are considered, all three approaches to evaporation lead to similar results, making the choice of method nearly inconsequential.