Transport Of Dust Particles Research Articles

Enhanced mass scattering efficiencies of background dust aerosols over East Asia following the passage of dust plumes

The transported dust particles significantly impact global weather and climate. Previous studies focused primarily on the physical and chemical properties of dust plumes, but the interaction mechanism between these dust plumes and background dust aerosols remains unclear. We explored this issue using in-situ observation data of the East Asia dust from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) during January 2013. We identified a dust plume originating from the Gurbantunggut Desert, which triggered a four-day dust event with an average dust concentration of 67.2 μg m−3. Notably, this dust event led to a significant increase in mass scattering efficiencies of dust, shifting from an inverted U-shape to a continuously increasing pattern with wavelength. The enhanced dust mass scattering efficiency inhibited the development of the planetary boundary layer. These changes persisted for at least two weeks after the event, primarily due to the resuspension of deposited dust particles altering the size of background dust particle. Our findings highlight the ability of dust plumes to enhance the scattering efficiency of background dust aerosols and providing new insights into the complex interactions between dust and the atmosphere.

Effect of airflow velocity in vessel-pipelines on dust explosion during pneumatic conveying

In order to investigate the flame propagation and pressure characteristics of dust particles during airflow transportation, a dust explosion experimental apparatus simulating dust handling processes was designed. The system is supplied with a stable airflow by a high-pressure fan, capable of continuously transferring dust from the vessel to the pipeline at a controllable speed. Dust explosion experiments were meticulously executed by applying 1 kJ of ignition energy to the transported dust particles at airflow velocities of 5, 10, and 15 m/s. This study examines the effects of airflow velocity, pipe diameter, and ignition position on explosion characteristics and delves into the mechanisms of these effects through a detailed analysis of experimental results. For the maximum explosion pressure, an increase in airflow velocity causes the maximum explosion pressure to rise. As the pipe diameter increases, the maximum explosion pressure first rises and then falls. The maximum explosion pressure occurs in the case of bottom ignition. The range of maximum explosion pressure values is expected to provide a reference for explosion detection and explosion venting. For flame propagation, the flame undergoes five processes within the vessel, including ignition of dust particles, spherical flame development, flame stretching towards the mouth of the pipe, complete combustion of particles, and near exhaustion of particle combustion. The higher the airflow velocity and the larger the pipe diameter, the more pronounced the flame stretching and development towards the pipe opening become. Within the pipe, two distinct flame propagation behaviors were observed under conditions of high and low airflow velocities. Compared with the experimental results of high-pressure pneumatic powder spraying forming a dust cloud within a vessel-pipeline, this study measures the maximum explosion pressure at specific turbulence levels and establishes a quantitative relationship between airflow velocity and explosion characteristics. Utilizing this correlation can provide a reference for predicting industrial-grade dust explosion characteristics at different airflow velocity levels, thereby offering a more optimized design basis for the design and safety protection of industrial equipment.

Spatiotemporal of Particulate Matter (PM2.5) and Ozone (O3) in Eastern Northeast Brazil

ABSTRACT This research examines particulate matter with a diameter of 2.5 micrometers (PM2.5) and ozone (O3) variation across the climatic mesoregions of Alagoas. Mean PM2.5 and O3 concentrations across three mesoregions were as follows: East (5.91; 44.22 μg.m−3), Hinterland (6.90; 44.18 μg.m−3), and Arid (7.03; 44.23 μg.m−3). Spatial and temporal variations were observed, with PM2.5 concentrations highest in the northwest (NW) and O3 concentrations in the east (E), influenced by local sources, weather, and transportation. Differences between rainy and dry years were noted, attributed to biomass burning and dust particle transport. This study establishes a baseline for understanding air quality, lacking monitoring stations, aiding policymaking. It provides insights into PM2.5 and O3 dynamics, with PM2.5 concentrations highest in the NW and lower O3 concentrations in the E. Temporal variations emphasize the need for dynamic monitoring. Positive correlations between PM2.5 and O3 highlight complex relationships. Practical implications include proactive policymaking and the necessity for monitoring stations. Rigorous statistical methodologies inform model selection, enhancing environmental data understanding. Despite changes in land use, studies on extreme probability distributions are limited, emphasizing the need for robust methodologies for environmental data analysis to address air pollution challenges effectively in Alagoas.

A 2-year intercomparison of three methods for measuring black carbon concentration at a high-altitude research station in Europe

Abstract. Black carbon (BC) is one of the most important climate forcers with severe health effects. Large uncertainties in radiative forcing estimation and health impact assessment arise from the fact that there is no standardized method to measure BC mass concentration. This study presents a 2-year comparison of three state-of-the-art BC measurement techniques at the high-altitude research station Pic du Midi (PDM) located in the French Pyrenees at an altitude of 2877 m above sea level. A recently upgraded Aethalometer AE33, a thermal-optical analyser Sunset and a single-particle soot photometer SP2 were deployed to measure simultaneously the mass concentration of equivalent black carbon (MeBC), elemental carbon (MEC) and refractory black carbon (MrBC), respectively. Significant deviations in the response of the instruments were observed. All techniques responded to seasonal variations in the atmospheric changes in BC levels and exhibited good correlation during the whole study period. This indicates that the different instruments quantified the same particle type despite the fact that they are based on different physical principles. However the slopes and correlation coefficients varied between instrument pairs. The largest biases were observed for the AE33 with MeBC values that were around 2 times greater than MrBC and MEC values. The principal reasons of such large discrepancy were explained by the mass absorption cross section (MAC) that was too low and C values recommended by the AE33 manufacturer and applied to the absorption coefficients measured by the AE33. In addition, the long-range transport of dust particles at PDM in spring caused significant increases in the bias between AE33 and SP2 by up to a factor 8. The Sunset MEC measurements agreed within around 17 % with the SP2 MrBC values. The largest overestimations of MEC were observed when the total carbon concentrations were below 25 µg C cm−2, which is probably linked to the incorrect determination of the organic carbon (OC)–EC split point. Another cause of the discrepancy between instruments was found to be the limited detection range of the SP2, which did not allow for the total detection of fine rBC particles. The procedure used to estimate the missing mass fraction of rBC not covered by the measurement range of the SP2 was found to be critical. We found that a time-dependent correction based on fitting the observed rBC size distribution with a multimodal lognormal distribution is needed to accurately estimate MrBC over a larger size range.

Identification of dust sources inside and outside of Iran affecting air quality in the Tehran region

Introduction: Recent climate changes and droughts have exacerbated the impact of dust sources globally, necessitating a thorough understanding of their influence on air quality. In Tehran, the interaction between internal dust sources from Iran and external sources from neighboring countries significantly affects air quality. Materials and methods: This study spans a 20-year period (2003-2022), utilizing satellite data and advanced algorithms to analyze dust event trends and patterns. The material and methods section outlines the use of Aqua satellite MODIS sensor data alongside two algorithms to identify dust sources, focusing on Aerosol Optical Depth (AOD) data during peak dust event seasons. Statistical analysis of dust events in 2022 supplements the investigation. Results: The analysis reveals distinct patterns in dust particle origin and transport, highlighting the predominant contribution of internal dust sources from Iran's southern Semnan province and significant input from external sources in Iraq and northern Saudi Arabia. Examining meteorological conditions during severe dust events highlights the role of synoptic conditions, particularly the presence of a tropospheric trough, in facilitating dust transport. Increased convective motions and downburst occurrences in specific regions further exacerbate the spread of dust particles, particularly those originating from external countries and provinces. Conclusion: The conclusion emphasizes the complex interplay between internal and external dust sources and the necessity of understanding dust emission dynamics for effective mitigation strategies. It calls for proactive measures involving local and regional cooperation to mitigate dust pollution's adverse effects on air quality in Tehran and similar urban centers.

A numerical study on transport of dust particles accompanied by air gouging process and energy consumption in a circulating ventilation workshop

A modified circulating layered ventilation system is proposed to address the issue of particulate pollutants in the casting cleaning workshop, taking into account the characteristics of end treatment and production processes. By combining Reynolds Average Navier-Stokes (RANS) turbulence model and Discrete Phase Model (DPM), the particle transport law in the coupled flow process of thermal plumes generated by purified circulating airflow and heat source was explored, and ventilation energy consumption was evaluated from the perspective of particle removal energy efficiency ratio. Comparing three ventilation modes: mixed ventilation (MV), wall-based attachment ventilation (WAV), and wall-based attachment ventilation with deflector (WAV-D), it was found that the large vortex region formed by the change in airflow direction during WAV played a key role in particle transport. Placing deflector helped to reduce the impact of vortex recirculation zones generated by the intersection of airflow and plumes on particles. A higher fresh air rate will weaken the diffusion effect of particles in the horizontal air lake region. Continuously increasing the air supply volume to a certain level has little effect on the transportation of low-inertia particles, yet it still manages to effectively enhance the removal efficiency of medium-inertia particles. However, for high-inertia particles, an increase in air supply can easily lead to excessive particle concentration in local areas. When the particle removal efficiency reaches a certain level, higher supply air volume and fresh air rate may lead to a significant decrease in energy efficiency ratio.

Height-modulating horizontal transport of dust particles in a dusty plasma ratchet

Dust particles are often electrostatically trapped and levitated within the non-electroneutral region of a sheath. The fascinating transport phenomena of dust particles strongly depend on the plasma parameters surrounding them within the sheath, whereas, that are quite difficult to obtain, leading to an unclear understanding of particle transport mechanisms. Here, we demonstrate a tunable horizontal transport of micron-sized dust particles by precisely manipulating their vertically suspended heights in an asymmetric ratchet sheath by designing dusty plasma ratchet. A collection of dust particles serves as micro-probes to detect the height-dependent transport properties and the feature of the sheath. Two methods are employed to lift or reduce the suspended heights of dust particles while maintaining the sheath unchanged. As the suspended heights of dust particles vary, their directional transport changes accordingly, including a flow reversal. A two-dimensional model of the ratchet sheath depicts the nonlinear distributions of plasma parameters and reveals that these unexpected transport phenomena can be attributed to the dependence of the electric ratchet potential and the resulting non-equilibrium net ion drag force on the suspended heights of dust particles. Our combined experimental and theoretical study provides insights into the fundamental transport properties of dust particles in an asymmetrical sheath.

Aircraft observations of aerosol and BC during the East Asian dust storm event: Vertical profiles, size distribution and mixing state

The vertical structure of meteorological elements, black carbon (BC), and aerosols were in situ characterized by the King Air 350 aircraft measurements over the northeast of China during an East Asian dust storm event from April 10 to 13, 2023. The main causes of this dust storm event were the strong winds generated by the Mongolian cyclone, the cold front on the ground provided dynamic conditions, and the unstable atmospheric state provided thermal conditions and less precipitation in the dust source areas led to exposed the ground surface. The number concentrations of BC and aerosol had significant vertical distribution. The number concentration of aerosol in the dust storm (DS) layer increased rapidly with height, while the number and mass concentrations of BC were higher and varied slightly with height. The BC core mass median diameters (MMD) first increased with height, reaching a maximum value of 0.24 μm at 3000 m; and it rapidly decreased to 0.18 μm at 3200 m and then varied slightly with height above 3200 m. BC's bulk relative coating thickness (coated diameter divided by uncoated core diameter Dp/Dc) first decreased with height, reaching a minimum value of 1.16 at 3000 m, then increased with height, reaching a maximum of 1.38 (4250 m). A wind shear layer (7.9 m s−1 at 1850 m) with a sudden drop in temperature (the cooling rate can reach 7.4 °C·(100 m)−1) at 1900 m hinders the transportation of dust particles to the ground, allowing the dust particles to be transported at long-term distances. There were two stratifications in the dust storm layer: DS1 (1700–3000 m, the vertical wind speed was downward, the horizontal wind speed was small) and DS2 (3000–4500 m, the vertical wind speed was upward, the horizontal wind speed was large). The distinct atmospheric flow field conditions between DS1 and DS2 led to different BC and aerosol pollution characteristics. In DS2, the number concentrations of BC and aerosol were higher, the aging ratio of BC particles was higher, and the size of the core particle of BC was smaller. The concentrations of BC, aerosol, Dp/Dc, and MMD in DS2 were 1.1, 59.0, 1.02, and 0.84 times higher than those in DS1, respectively. Dust particles transported over long distances were primarily small. The number concentrations of aerosols at 0.1–0.12 μm and 0.1–0.24 μm were higher in DS1 and DS2, respectively. Still, the number concentration of aerosol at 0.12–0.28 μm in DS1 was lower than in the planetary boundary layer (PBL) and residual layer (RL).

Investigating the Role of the Low-Level Jet in Two Winters Severe Dust Rising in Southwest Iran

The dust storms with local and non-local dust sources mostly affect Khuzestan province in southwest (SW) Iran. In this study, the role of the low-level jet in the activation of the internal dust events in SW Iran during two severe dust cases was investigated. For this purpose, the fifth-generation ECMWF reanalysis for the global climate and weather (ERA5) data was used to identify the synoptic patterns and the low-level jet (LLJ) characteristics in the study area. Furthermore, the images of the moderate resolution imaging spectroradiometer (MODIS) sensor, the outputs of the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model, and a weather research and forecasting model coupled with chemistry (WRF-Chem) were used to investigate the propagation and transport of the dust particles. The results of the synoptic analysis in both dust cases show the simultaneous occurrence of the divergence zone associated with cyclonic curvature in the subtropical jet stream (STJ) at 300 hPa, causing convergence at 925 hPa, upward motion, and the development of low surface pressure in SW Iran. Examining the vertical wind profile shows the existence of the maximum horizontal wind speeds of 975 to 875 hPa, along with the positive and negative shear below and above it, respectively, which emphasizes the existence of the LLJ and its role in local dust emission. The results of the comparison between the satellite images, WRF-Chem, and HYSPLIT model outputs show the formation and transportation of dust particles from the inner regions of Khuzestan in SW Iran. The horizontal dust surface distribution, vertical raised dust mass, and kinetic energy transfers are well simulated by the WRF-Chem model when LLJ broke at 09:00 to 12:00 UTC. The most important finding of this research is that, for the first time, the role of low-level jet is investigated in the activation of internal dust events in SW Iran.

Investigations into the role of electrostatics in the transport of dust particles

Investigations into the role of electrostatics in the transport of dust particles

Simulation Analysis of Transport of Boron Dust Particles Injected by Impurity Powder Dropper in the Large Helical Device

Simulation Analysis of Transport of Boron Dust Particles Injected by Impurity Powder Dropper in the Large Helical Device

Observing a dust aerosol layer at a height of 3–4 km above the ground on the southern margin of the Tarim Basin

The vertical distribution and transport properties of dust aerosols play a key role in regional and even global climate and environmental changes. However, there are still gaps in understanding the optical properties, transport mechanisms, and topographic effects on dust in the dust-prone area-southern margin of the Tarim Basin. In this study, we use the Ground-Based Aerosol Lidar (GBQL-01) installed in Hotan and Minfeng in cooperation with the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) to synthesize and analyze the dust formation process at the southern margin of the basin once, and to test the reliability of the ground-based aerosol lidar. The variability characteristics of meteorological elements during this dust process will be discussed. Furthermore, the Weather Research and Forecasting Model with Chemistry (WRF-Chem) was used to reproduce this dust process. The results show that the vertical transport of dust particles reaches about 4 km and 3 km in Hotan and Minfeng, respectively, and the dust aerosol stratification intensity is obvious within 1 km height in both places, and there is a dust aerosol layer at 3 km height in both places. The high winds are blocked by the large topography of the Tianshan Mountains and the northern slopes of the Tibet Plateau, and they change to northeasterly winds, triggering dusty weather outbreaks at the southern margin of the Tarim Basin. When the dusty weather subsided, dust aerosols with concentrations of 300–400 μg m−3 were still present at an altitude of 4 km, and a clear suspended dust phenomenon was formed. Meanwhile, the increase of wind speed and relative humidity, as well as the decrease of temperature, easily contribute to the occurrence of dusty weather and the transport of particulate matter. This work provides a useful reference for the study of regional climate change, topographic effects and "suspended dust".

Effect of airflow velocity on flame propagation and pressure of starch dust explosion in a pneumatic conveying environment

To investigate the flame propagation and pressure characteristics of dust explosions during the airflow transportation of dust particles, a 2 m transparent pipeline, supplied with a constant airflow from a fan, was constructed as a dust explosion testing apparatus. The distribution patterns of airflow velocity were measured using an anemometer and subjected to statistical analysis. Dust explosion experiments were conducted with airflow velocities of 5, 10 and 15 m/s, and an ignition energy of 1 kJ was applied to the transported dust particles. The results revealed that the flame propagation of starch explosions undergoes distinct stages: ignition, slow propagation, accelerated propagation. The flame propagation speed and explosion pressure initially increased and subsequently decreased as the airflow velocity was raised. As the airflow velocity increased from 5 m/s to 10 m/s, the maximum flame propagation speed rose from 53.2 m/s to 67.7 m/s, and the maximum explosion pressure increased from 25.62 kPa to 31.96 kPa. At an airflow velocity of 15 m/s, both the maximum flame propagation speed and explosion pressure decreased, reaching 32.6 m/s and 19.67 kPa, respectively. In contrast to conventional closed container powder injections, chemical igniters in the pneumatic conveying environment exhibit elongated flames, with the airflow influencing the timing of dust deflagration flame appearance and accelerating flame propagation. Due to the connectivity of the airflow transport pipeline, the explosion pressure tends to be lower. Influenced by non-uniform airflow and temperature differentials, dust deflagration flames within the airflow transport pipeline manifest a spiral propagation structure.

Three distinct scales dominate the role of eolian electric fields in dust turbulent transport

Although previous studies have shown that eolian electric fields significantly alter the lifting and dynamics of dust particles, they are limited to mean fields. The effects of eolian electric fields on the dust turbulent transport have not been reported before. Here, by combing the observational data and wavelet-based spectral analysis, we find that eolian electric fields enhance the vertical turbulent transport of dust particles in the near-surface layer and exhibit three distinct crucial scales. Specifically, the eolian electric fields exhibit a dominant promoting effect at the kilometer-sized synoptic scale, a secondary suppressive effect at the hectometer-sized very-large-scale motion scale, and a negligible effect at the decameter-sized turbulent integral scale. Such scale-dependent electrical effects can be explained by the fact that the linear coupling between vertical eolian electric field and dust concentration is strongest at the synoptic scale, followed by the very-large-scale motion scale, and is weakest at the turbulent integral scale.

Computational investigation on transport of heat energy by flow of dusty Carreau fluid with nanoparticles using finite element method

Thermal performance of the working fluid depends on its thermal conductivity which can be enhanced by dispersion of nanoparticles. Therfore, the role of the simultaneous suspension of AA7072 and AA7072 and AA7072/AA7075 is analyzed in Carreau fluid, which has shear rate dependent viscosity and contains dust particles. The nanoparticles AA7072 is combination of aluminium, zinc and other alloys with ratio 98%:1%:1%, respectively. Whereas nanoparticles AA7075 is the combination of aluminium, zinc, magnesium, and copper in ratio 90%:6%:3%:1%, respectively. Further, the nanoparticle AA7072 in Carreau liquid form homogenized mixture which is mono nanofluid whereas nanoparticle AA7075 in Carreau liquid form homogenized mixture called hybrid nanofluid. Thermal radiation have significant impact on the temperature of AA7072 and AA7072/AA7075. The Carreau-constitutive model and correlations for thermo-physical properties are used with conservation laws for fluid and dust phases for modelling purposes. The governing equations are non-dimensionalized, and their numerical solutions are derived using the finite element method (FEM). These derived solutions are used to predict the behavior of physical quantities and flow fields for both AA7072/AA7075 and AA7072 nanoparticles. An increasing tendency in the temperature of dust particles in AA7072/AA7075 is greater than in AA7072. The simulations have exposed that AA7072/AA7075 is more radiative than AA7072. The velocity interaction parameter has an increasing tendency in affecting the transport of dust particles.

Changes in the Size Distributions of Oxalic Acid and Related Polar Compounds Over Northern Japan During Spring

AbstractSize distributions of chemical species provide evidence for their sources and formation mechanisms. Size‐segregated aerosols with 12 sizes were collected over Northern Japan (Sapporo: 43.07°N and 141.35°E) during the spring (9 April–21 May) of 2001 and analyzed for water‐soluble organic and inorganic species. The dominances of SO42– and NH4+ in submicron (Da < 1.1 μm) and Na+ and Ca2+ in supermicron (Da > 1.1 μm) aerosols suggest substantial contributions from anthropogenic sources, sea‐salt and dust particles via long‐range atmospheric transport. Oxalic acid (C2) is the dominant organic species followed by malonic (C3) and succinic (C4) acid. A supermicron mode enrichment of C2 is heavily involved with the long‐range transport of dust particles, whereas submicron mode C2 was influenced by anthropogenic sources from the East Asian continent. The size distributions of shorter‐chain diacids (C3–C6), phthalic (Ph) and glyoxylic acid are consistent with those of C2, whereas azelaic acid (C9) is enriched in submicron and supermicron modes by the influences of continental and marine air masses. The mass concentration ratios of C3/C4 in submicron (1.5–2.3) and supermicron (1.2–1.8) mode demonstrated that water‐soluble organic aerosols in Sapporo were photochemically processed during long‐range transport. The Ph/C9 ratios show that the influence of anthropogenic sources on 9–28 April samples was pronounced in supermicron (2.5–2.9) than the submicron (1.1–1.2) particles, and vice‐versa on 6–21 May samples. These contrast distributions suggest that the continental air masses from East Asia and marine air masses from the surrounding ocean likely control the chemical composition of aerosols over Northern Japan.

Dusty plasmas above the sunlit surface of Mercury

Above the sunlit surface of Mercury, the properties and formation of dusty plasmas are investigated. It is demonstrated that the dusty plasmas are formed for subsolar angles exceeding approximately 76° due to photoelectric and electrostatic processes. As a result, the dusty plasmas are present in the polar regions of Mercury, characterized by latitudes of about 70° and above. The formation of dusty plasmas is also possible for lower latitudes, but only where the surface profile allows it. Plasmas above the sunlit surface of Mercury consist, in particular, of photoelectrons, electrons, and ions of the solar wind, and also charged dust particles. The distribution functions of photoelectrons near the surface of Mercury, as well as the altitude dependences of the number densities of dust particles, their charges and sizes, as well as electric fields, are obtained. The calculations are carried out which correspond to the position of Mercury at aphelion and perihelion of its orbit for the situations of dusty plasma location in the vicinity of magnetic poles of Mercury and in other regions. It is shown that there are qualitative differences between the dusty plasma systems of Mercury and the Moon related to the fact that Mercury has a magnetosphere and Mercury's orbit is one of the most eccentric of all planetary orbits in the Solar System. The effects of magnetic fields can slightly influence the dust particle transport and, correspondingly, the expansion of the region of the existence of dusty plasmas above the surface of Mercury due to the effect of dust particle transport is not so significant as at the Moon. Furthermore, due to the presence of Mercury's magnetosphere, the solar wind is important for the formation of dusty plasmas at Mercury only in the vicinity of the regions of the magnetic poles. In other regions of Mercury, in contrast to the situation at the Moon, the solar wind does not influence significantly the dusty plasma properties. The dusty plasma parameters are different in the cases of aphelion and perihelion of the orbit of Mercury.

Classifying aerosol type using in situ and satellite observations over a semi-arid station, Anantapur, from southern peninsular India

The chemical composition of aerosols is crucial for understanding aerosol radiative characteristics, classifying aerosol sources, and improving atmospheric aerosol satellite retrieval algorithms. In this study, the absorption angström exponent (AAE) and scattering angström exponent (SAE) values are derived from an aethalometer and three wavelength integrating nephelometer. MERRA-2 (Modern-Era Retrospective Study for Research and Applications) speciated aerosol optical depths and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) aerosol subtypes are utilized for the identification of a possible aerosol type over a semi-arid station, Anantapur, in Southern peninsular India from March 2016 to February 2018. Analysis from MERRA-2 for different aerosols illustrates that sulphate aerosol optical depth (SO4 AOD) dominates (>0.16) during winter and post-monsoon, while dust aerosol optical depth (DU AOD), organic carbon optical depth (OCAOD), and sulphate aerosol optical depth (SO4 AOD) mainly contributed (>0.07) to the total AOD during summer. SO4 AOD accounted for over ∼ 50% of total AOD during winter and post-monsoon, whereas DU AOD accounted for<10% of total aerosol optical depth in the respective seasons. The seasonal mean values of SAE (AAE) were found to be 1.95 ± 0.37 (1.03 ± 0.08), 1.65 ± 0.55 (1.03 ± 0.08), 2.53 ± 0.20 (1.03 ± 0.08) and 2.66 ± 0.15 (1.03 ± 0.08) during summer, monsoon, post-monsoon, and winter, respectively. AAE and SAE classification schemes showed that during winter, summer, and post-monsoon, continental polluted aerosols dominated (>56%), while dust and marine pollution aerosols dominated (∼47%) to the total aerosols during the monsoon. Continental aerosols are predominant during all seasons except for monsoon, and result from local anthropogenic activities and the transport of mineral dust particles and smoke aerosols from the north and western India. The observed aerosol types are consistent with the air mass back-trajectory cluster analysis performed with the help of Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT). The various aerosol types (absorbing and non-absorbing) and their change over a region are essential for for reducing the uncertainty in the assessment of aerosol radiative effects.

Investigating the mechanism of dust transferring from Iraq to the north of Alborz mountains in Iran

Introduction: Recently, due to climate change, the number and intensity of dust sources are increasing, which leads to the occurrence of dust storms. Atmospheric patterns governing the region, topography and surface features are effective on transportation and dispersion of dust particles.&#x0D; Materials and methods: In this study, a severe dust phenomenon on the 3th and 4th March, 2022, was investigated. The dust was emitted from the east of Iraq and passed through the Zagros and Alborz mountain ranges toward the Caspian sea. Meteorological data of the country, satellite data, ERA5 reanalysis data and HYSPLIT and output from the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) were used.&#x0D; Results: Aerosol Optical Depth (AOD) anomaly compared to the long-term indicated that the intense transport of dust particles from eastern Iraq and reaching the Caspian Sea is not a common phenomenon. Synoptic analysis showed that the dust particles in the source area ascended to the mid-levels of the atmosphere and a large part of the particles passed through the Zagros Mountains. Then, the dust entered the Caspian Sea by passing through the Manjil valley. The vertical profile of WRF-Chem model output showed the ascent of dust particles up to 600 hPa near the dust source and its passage over mountainous areas.&#x0D; Conclusion: The main factors in the formation of this unusual dust phenomenon are: severe two-year drought in the Middle East, reduction of vegetation and cold front of the dynamic low-pressure located in the east of the Black Sea, east of Turkey and northern Iraq moving eastward to the Caspian sea in the following hours.

A 3D Monte Carlo Simulation for Aerosol Deposition onto Horizontal Surfaces by Combined Mechanisms of Brownian Diffusion and Gravity Sedimentation

A three-dimensional Monte Carlo model was developed to simulate the deposition of aerosol particles onto horizontal solid surfaces. The random walk method was employed to solve the particle transport equation, which allowed obtaining the trajectory of particle motion by a combined mechanism of Brownian diffusion and gravity sedimentation. The particle transport mechanism was described in terms of a Peclet number (Pe). The local structures of the dust layer, the relationship between the structure of the dust layer and particle transport mechanisms, and the number of the particles attached to the solid surface were investigated. The results showed that for a small Pe, when Brownian diffusion was a controlling mechanism for aerosol transport, the dust layer might exhibit a more open and looser structure, while for a large Pe, the dust layer was dense and tight. The differences of deposition morphologies under different transport mechanisms were caused by the different random intensities of particle motion. There was an upper limit of the maximum number of particles attached to the surface, and it strongly depended on particle transport mechanisms and size distributions. Additionally, the deposit morphologies obtained with the 3D Monte Carlo model were in good agreement with the experimental results found in the literature.