Dust Distribution Research Articles

Spatiotemporal evolution of dust over Tarim Basin under continuous clear-sky

The unique terrain and complex atmospheric boundary layer (ABL) processes result in a distinctive spatiotemporal distribution of dust in the Tarim Basin; however, this distribution remains unclear under continuous clear-sky conditions. In this study, 382 cases were selected to investigate the spatiotemporal evolution of dust and its potential mechanisms based on MERRA-2 and ERA5 reanalysis datasets combined with MODIS satellite observations during the warm seasons from 2000 to 2023. Taking the typical case of a completely cloudless on July 24–27, 2016, the dust aerosol optical depth (DAOD) at the margin of the Tarim Basin increased with time. The climatological characteristics showed a high DAOD in the northern, western, and southwestern regions and a relatively low DAOD in the central area. Nocturnal low-level jets dominated by northeasterly winds enhance the low-level westward airflow in weak anticyclonic systems, causing dust accumulation in the west and north of the basin. Vertical mixing within the ABL during the daytime increases dust loading in the residual layer, and these dust particles can ascend to high altitudes after breaking through the ABL by the vertical circulation. The dust loading at the lower level during the daytime was higher than that at night, whereas the opposite was true for the upper level. The downward airflow in the northwest slope of the Tibetan plateau weakens at night, leading to dust being uplifted to higher altitudes and transported outside the Tarim Basin by the westerlies. These results enhance our understanding of dust distribution and related mechanisms in Tarim Basin and support the development and utilization of climatic resources in this region.

Implications of scattering for CMB foreground emission modelling

Context. The extreme precision and accuracy of forthcoming observations of the cosmic microwave background (CMB) temperature and polarisation anisotropies, aiming to detect the tiny signatures of primordial gravitational waves or of light relic particles beyond the standard three light neutrinos, requires commensurate precision in the modelling of foreground Galactic emission that contaminates CMB observations. Aims. We evaluate the impact of second-order effects in Galactic foreground emission due to Thomson scattering off interstellar free electrons and to Rayleigh scattering off interstellar dust particles. Methods. We used existing sky survey data and models of the distribution of free electrons and dust within the Milky Way to estimate the amplitude and power spectra of the emission originating from radiation scattered either by free electrons or by dust grains at CMB frequencies. Results. Both processes generate corrections to the total emission that are small compared to direct emission and are small enough not to pose problems for current-generation observations. Conclusions. However, B modes generated by Thomson scattering of incoming radiation off interstellar free electrons at CMB frequencies are within an order of magnitude compared to the sensitivity of the most advanced forthcoming CMB telescopes, and might require more precise evaluation in the future.

Evaluation of 10‐m Wind Speed From ISD Meteorological Stations and the MERRA‐2 Reanalysis: Impacts on Dust Emission in the Arabian Peninsula

AbstractMineral dust is one of the most important aerosols when studying the radiative balance and climate of the planet. There are different dust emission schemes utilized by the atmospheric modeling communities, many of which disagree on basic output quantities such as mass of dust emitted and distribution of mass among size bins. In this work, we examined mineral dust emission from a leading model scheme, the Goddard Chemistry Aerosol Radiation and Transport (GOCART), as utilized in the Modern‐Era Retrospective analysis for Research and Applications, Version 2 (MERRA‐2) Reanalysis and compared it to dust emissions calculated using wind measurements from ground based weather stations located in the Arabian Peninsula that are included in the National Oceanic and Atmospheric Administration’s (NOAA) integrated surface database (ISD). An intercomparison of 10‐m wind speed is shown for the Arabian Peninsula region, differences of the observed and modeled wind field are quantified, and impacts of differences on dust emissions are calculated. This analysis shows 10‐m winds in the ISD were generally lower than MERRA‐2 winds, which propagated to dust emissions errors. Our estimate of one of the most significant mass impacts in dust emission is 0.178 Tg/year/grid box with a percent change of over 200% to the recalculated dust emissions from MERRA‐2. These differences in wind speed propagated to a difference in dust mass emitted by the use of a static source function which aids in scaling the mass emitted by the availability of dust in each grid. Additionally, the magnitude of these differences varies seasonally.

TriPoD: Tri-Population size distributions for Dust evolution

Context. Dust coagulation and fragmentation impact the structure and evolution of protoplanetary disks and set the initial conditions for planet formation. Dust grains dominate the opacities, they determine the cooling times of the gas via thermal accommodation in collisions, they influence the ionization state of the gas, and the available grain surface area is an important parameter for the chemistry in protoplanetary disks. Therefore, dust evolution is an effect that should not be ignored in numerical studies of protoplanetary disks. Available dust coagulation models are, however, too computationally expensive to be implemented in large-scale hydrodynamic simulations. This limits detailed numerical studies of protoplanetary disks, including these effects, mostly to one-dimensional models. Aims. We aim to develop a simple – yet accurate – dust coagulation model that can be easily implemented in hydrodynamic simulations of protoplanetary disks. Our model shall not significantly increase the computational cost of simulations and provide information about the local grain size distribution. Methods. The local dust size distributions are assumed to be truncated power laws. Such distributions can be fully characterized by only two dust fluids (large and small grains) and a maximum particle size, truncating the power law. We compare our model to state- of-the-art dust coagulation simulations and calibrate it to achieve a good fit with these sophisticated numerical methods. Results. Running various parameter studies, we achieved a good fit between our simplified three-parameter model and DustPy, a state-of-the-art dust coagulation software. Conclusions. We present TriPoD, a sub-grid dust coagulation model for the PLUTO code. With TriPoD, we can perform twodimensional, vertically integrated dust coagulation simulations on top of a hydrodynamic simulation. Studying the dust distributions in two-dimensional vortices and planet-disk systems is thus made possible.

Evaluating and comparison of WRF-chem model configurations for wind field impact on the April 2022 dust episode in western Iran

Accurate estimation of wind direction and speed is essential for enhancing the simulation and prediction of dust storms. Being highly susceptible to dust storms, Western Iran necessitates a detailed evaluation of dust concentration and wind fields. This study employs the WRF-Chem model to simulate these parameters over the period from April 7 to 26, 2022. Four different model configurations were tested, involving the Yonsei University (YSU) and Mellor-Yamada-Janjic (MYJ) boundary layer schemes, as well as the Lin and WRF Single-Moment 6-Class (WSM6) microphysics schemes. The results indicate that during the selected period, different synoptic systems led to the release of dust from Iraq and Saudi Arabia and its transport to western Iran. The mid-level southerly and southwesterly wind directions have a significant impact on dust transport to the northwestern regions of Iran by high and complex mountainous terrain. The horizontal and vertical distribution of simulated dust demonstrates good agreement with TERRA satellite imagery, MERRA-2 dust surface concentration, and CALIPSO, respectively. The daily dust concentration of the WRF-Chem model has a correlation of −0.32 to −0.96 with visibility and 0.68 to 0.86 with MERRA-2 data in Western Iran. The simulated dust concentration relation with visibility and AERONET AOD (Aerosol Optical Depth at 500 nm) was calculated at −0.78 and 0.29, respectively in Zanjan station. The horizontal and vertical distribution, temporal series, and statistical indices of the wind field show that the WRF-Chem model performs well in the Iran West boundary, especially in the west and northwest, where the 10-m wind speed increased to 14 m s−1. The boundary layer scheme in the WRF-Chem model has a more significant impact than the microphysics scheme in simulated 10-m wind speed and dust concentration. The final result shows that the combination of the YSU boundary layer and WSM6 microphysics schemes performs very well in simulating wind fields and dust in western Iran under various weather conditions.

The Correlation Between Dust and Gas Contents in Molecular Clouds

Molecular clouds are regions of dense gas and dust in space where new stars and planets are born. There is a strong correlation between the distribution of dust and molecular gas in molecular clouds. The present work focuses on the three-dimensional morphological comparisons between dust and gas in 567 molecular clouds identified in a previously published catalog. We confirm a sample of 112 molecular clouds, where the cloud morphology based on CO observations and dust observations displays good overall consistency. There are up to 334 molecular clouds whose dust distribution might be related to the distribution of gas. We are unable to find gas structures that correlate with the shape of the dust distribution in 24 molecular clouds. For the 112 molecular clouds where the dust distribution correlates very well with the distribution of gas, we use CO observational data to measure the physical properties of these molecular clouds and compare them with the results derived from dust, exploring the correlation between gas and dust in the molecular clouds. We found that the gas and dust in the molecular clouds have a fairly good linear relationship, with a gas-to-dust ratio of GDR=(2.80−0.34+0.37)×1021cm−2mag−1 . The ratio varies considerably among different molecular clouds. We measured the scale height of dust-CO clouds exhibiting strong correlations, finding hZ=43.3−3.5+4.0 pc.

Quantifying interstellar extinction at high galactic latitudes

Abstract A detailed map of the distribution of dust at high Galactic latitudes is essential for future cosmic microwave background (CMB) polarization experiments because the dust, while diffuse, remains a significant foreground in these regions. We develop a Bayesian model to identify a region of the Hertzsprung-Russell (HR) diagram suited to constrain the single-star extinction accurately at high Galactic latitudes. Using photometry from Gaia, 2MASS and ALLWISE, and parallax from Gaia, we employ nested sampling to fit the model to the data and analyse the posterior over stellar parameters for both synthetic and real data. Charting low variations in extinction is complex due to systematic errors and degeneracies between extinction and other stellar parameters. The systematic errors can be minimised by restricting our data to a region of the HR diagram where the stellar models are most accurate. Moreover, the degeneracies can be reduced by including astrophysical priors and spectroscopic constraints. We show that accounting for the measurement error of the data and the assumed inaccuracies of the stellar models are critical in accurately recovering small variations in extinction. We compare the posterior distribution for individual stars with spectroscopic stellar parameter estimates from LAMOST and Gaia ESO and illustrate the importance of estimating extinction and effective temperature as a joint solution.

Hazard and pollution characteristics of rock-containing dust in coal mine tunneling faces based on experimental and numerical study

The rock-containing dust poses a serious threat to the safe and efficient operation of coal mine tunneling faces (CMTFs). This study investigates the hazard and pollution characteristics of rock-containing dust in CMTFs by testing wettability, lithology surface functional groups, and particle size distribution of dusts with varying rock content. Furthermore, the spatial and temporal evolution of rock-containing dusts is explored through CFD simulation and the effects of rock-containing dust on the dedusting characteristics of water spray are analyzed. The results show that the crystallinity exhibits an exponential growth trend as the mudstone content increases, and the respirable dusts < 2.5μm and < 7μm increase by 15.04 % and 24.28 %, respectively. The rock-containing dust reaches the end of the simulated tunnel in just 50 seconds. On both the driver’s and pedestrian’s sides, the dust concentration shows an approximate S-shaped increase over time. Under the condition that only traditional water spraying measures are implemented, the concentration of respirable rock-containing dust will be approximately 1.2–1.5 times higher than the concentration of respirable coal dust. The results have provided valuable insights into the hazard and pollution characteristics of rock-containing dust in CMTFs, which are crucial for guiding dust disaster management in coal mines.

Using land use methodology to construct ring spatial variables for modeling and mapping spatial distribution of dust in snow cover

Using land use methodology to construct ring spatial variables for modeling and mapping spatial distribution of dust in snow cover

Using dust to constrain dark matter models

Abstract In this paper, we use hydrodynamic zoom-in simulations of Milky Way-type haloes to explore using dust as an observational tracer to discriminate between cold and warm dark matter universes. Comparing a cold and 3.5keV warm dark matter particle model, we tune the efficiency of galaxy formation in our simulations using a variable supernova rate to create Milky Way systems with similar satellite galaxy populations while keeping all other simulation parameters the same. Cold dark matter, having more substructure, requires a higher supernova efficiency than warm dark matter to achieve the same satellite galaxy number. These different supernova efficiencies create different dust distributions around their host galaxies, which we generate by post-processing the simulation output with the powderday codebase. Analysing the resulting dust in each simulation, we find ∼4.5 times more dust in our cold dark matter Milky Way halos compared with warm dark matter. The distribution of dust out to R200c is then explored, revealing that the warm dark matter simulations are noticeably less concentrated than their cold dark matter counterparts, although differences in substructure complicate the comparison. Our results indicate that dust is a possible unique probe to test theories of dark matter.

JWST’s PEARLS: Resolved study of the stellar and dust components in starburst galaxies at cosmic noon

Dusty star-forming galaxies (DSFGs) significantly contribute to the stellar buildup in galaxies during “cosmic noon,” the peak epoch of cosmic star formation. Major mergers and gas accretion are often invoked to explain DSFGs’ prodigious star formation rates (SFRs) and large stellar masses. We conducted a spatially resolved morphological analysis of the rest-frame ultraviolet/near-infrared (∼0.25–1.3 μm) emission in three DSFGs at z ≃ 2.5. Initially discovered as carbon monoxide (CO) emitters by NOrthern Extended Millimeter Array (NOEMA) observations of a bright (S350 μm = 111 ± 10 mJy) Herschel source, we observed them with the James Webb Space Telescope/NIRCam as part of the PEARLS program. The NIRCam data reveal the galaxies’ stellar populations and dust distributions on scales of 250 pc. Spatial variations in stellar mass, SFR, and dust extinction are determined in resolved maps obtained through pixel-based spectral energy distribution fitting. The CO emitters are massive (Mstar ≃ (3 − 30)×1010 M⊙), dusty starburst galaxies with SFRs ranging from 340 to 2500 M⊙ yr−1, positioning them among the most active star-forming galaxies at 2 &lt; z &lt; 3. Notably, they belong to the ∼1.5% of the entire JWST population with extremely red colors. Their morphologies are disk like (Sérsic index n ≃ 1), with effective radii of 2.0–4.4 kpc, and exhibit substructures such as clumps and spiral arms. The galaxies have dust extinctions up to AV = 5–7 mag extending over several kiloparsecs with asymmetric distributions that include off-center regions resembling bent spiral arms and clumps. The near-infrared dust-attenuation curve in these sources deviates from standard laws, possibly implying different dust–star geometries or dust grain properties than commonly assumed in starburst galaxies. The proximity (&lt; 5″) of galaxies with consistent redshifts, strong color gradients, an overall disturbed appearance, asymmetric dust obscuration, and widespread star formation collectively favor interactions (minor mergers and flybys) as the mechanism driving the CO galaxies’ exceptional SFRs. The galaxies’ large masses and rich environment hint at membership in two proto-structures, as initially inferred from their association with a Planck-selected high-z source.

Sub‐Milankovitch Signals in the Northern Polar Layered Deposits of Mars

AbstractOur understanding of the paleoclimate of Mars and the dominant forcing functions that drive large‐scale changes largely remains a mystery. However, the Martian Polar Layered Deposits (PLD) offer a promising avenue for unraveling the planet's recent paleoclimate history. Despite recent progress to detect a climate signal in the PLD, definitive evidence of a correlation between the stratigraphic record and Mars' recent orbital history remains elusive. We utilized new and updated techniques, including high‐resolution stratigraphic reconstruction from High Resolution Imagine Science Experiment stereo imagery and digital terrain models, combined with a technique of variable dip correction to account for three dimensional bedding orientations. Signal processing methods, such as wavelet and Fourier analysis, were applied to perform detailed time‐series analysis. These analyses revealed a quasi‐periodic signal indicative of fine bedding at a scale of approximately 2 m. Based on previously proposed deposition rates, these fine layers appear to correspond to timescales centering around 4,000 years. This suggests that the meter‐scale layers may not be the result of orbital forcing and hint at an unknown sub‐Milankovitch climate forcing mechanism. We discuss potential exogenic causal mechanisms, such as cyclic variations in solar activity, and endogenic factors, including large‐scale changes in dust distribution. Understanding the formation processes of these fine layers may significantly enhance our knowledge of Martian climate history and its driving forces.

Numerical Simulation Study of Gas–Liquid–Solid Triphase Coupling in Fully Mechanized Excavation Faces with Variation in Dust Source Points

In view of the current situation where research on the dust diffusion laws of different dust source points is limited and the gap with the actual field situation is too large; this study employs an innovative gas–liquid–solid triphase coupling method to investigate how dust moves and spreads in the fully mechanized excavation face 431305 at the Liangshuijing Mine; focusing on both the dust field and the dust–fog coupled field. The results indicate that using the long-pressure short-suction ventilation method; dust movement in the roadway is primarily influenced by the airflow; which can be classified into vortex; jet; and return flow regions. The analysis reveals that different dust source points affect dust distribution patterns. Dust source 1 generates the highest dust concentration; primarily accumulating on the duct side and return air side of the roadway. By contrast; dust source 2’s dust mainly gathers at the heading and the front of the cutting head. Dust sources 3 and 4 show lower dust concentrations near the top of the roadway. Dust source 5 achieves the most effective dust removal; aided by airflow and a suction fan; showcasing superior dust performance. A comprehensive comparison indicates that dust source 1 has the highest overall dust concentration. Therefore; further simulation of the distribution law of dust generated at dust source 1 under the action of water mist reveals that the dust concentration near the heading face is reduced from 2000 mg/m3 under the action of single air flow to about 1100 mg/m3. At t = 5 s; the spray droplets almost cover the entire tunneling face; leading to a significant decrease in dust concentration within 10–25 m from the tunneling face. Within 40 s; both coal dust and spray droplets are significantly reduced. The field measurement results verify the accuracy of the simulation results and provide certain guidance for promoting the sustainable development of the coal industry.

Linear polarization study of open clusters in the anticenter direction: Signature of the spiral arms

Aims. Our objective is to investigate the distribution of dust and associated large-scale structures of the Galaxy using optical linear polarization measurements of various open clusters located at different distances in the Galactic anticenter direction. Methods. We present R-band linear polarization observations of stars toward five open clusters: Kronberger 1, Berkeley 69, Berkeley 71, Berkeley 19, and King 8 in the anticenter direction. The polarization observations were carried out using the ARIES (Aryabhatta Research Institute of Observational Sciences) IMaging POLarimeter mounted on the 104 cm Sampurnanand telescope of ARIES, Nainital, making it the first study to target the polarization observations toward distant clusters (~6 kpc). We combined the observed polarization data with the distance information from the Gaia space telescope to infer the dust distribution along the line of sight. Results. The variation in the degree of polarization and extinction with distance reveals multiple dust layers in each cluster direction. In addition, common foreground-dust layers detected toward different cluster directions highlight global features such as spiral arms. Our results show that the dust clouds at 2 kpc toward Berkeley 69 and Berkeley 71 coincide with the Perseus arm, while the dust layer at ~4 kpc toward the distant clusters Berkeley 19 and King 8 indicates the presence of the Outer arm. The large-scale dust distribution obtained by combining our polarization results with previous polarization studies of nearby open clusters suggests that the anticenter direction is characterized by a low-extinction homogeneous dust distribution with a somewhat uniform orientation of the plane-of-sky component of the magnetic field along the line of sight. Conclusions. Our study demonstrates that polarization is useful as a tool for studying the large-scale dust distribution and structural features where kinematic distance methods are inadequate and cannot provide accurate distances to the dust clouds. The global dust distribution in the anticenter direction shows signatures of the intervening spiral arms.

Dust evolution during a protostellar collapse: Influence on the coupling between the neutral gas and magnetic field

Context. The extent of the coupling between the magnetic field and the gas during the collapsing phase of star-forming cores is strongly affected by the dust size distribution, which is expected to evolve by means of coagulation, fragmentation, and other collision outcomes. Aims. We aim to investigate the influence of key parameters on the evolution of the dust distribution, as well as on the magnetic resistivities during protostellar collapse. Methods. We performed a set of collapsing single-zone simulations with shark. The code computes the evolution of the dust distribution, accounting for different grain growth and destruction processes, with the grain collisions being driven by brownian motion, turbulence, and ambipolar drift. It also computes the charges carried by each grain species and the ion and electron densities, as well as the magnetic resistivities. Results. We find that the dust distribution significantly evolves during the protostellar collapse, shaping the magnetic resistivities. The peak size of the distribution, population of small grains, and, consequently, the magnetic resistivities are controlled by both coagulation and fragmentation rates. Under standard assumptions, the small grains coagulate very early as they collide by ambipolar drift, yielding magnetic resistivities that are many orders of magnitude apart from the non-evolving dust case. In particular, the ambipolar resistivity, ηAD, is very high prior to nH = 1010 cm−3. As a consequence, magnetic braking is expected to be ineffective. In this case, large size protoplanetary discs should result, which is inconsistent with recent observations. To alleviate this tension, we identified mechanisms that are capable of reducing the ambipolar resistivity during the ensuing protostellar collapse. Among them, electrostatic repulsion and grain-grain erosion feature as the most promising approaches. Conclusions. The evolution of the magnetic resistivities during the protostellar collapse and consequently the shape of the magnetic field in the early life of the protoplanetary disc strongly depends on the possibility to repopulate the small grains or to prevent their early coagulation. Therefore, it is crucial to better constrain the collision outcomes and the dust grain’s elastic properties, especially the grain’s surface energy based on both theoretical and experimental approaches.

Modelling the impact of host galaxy dust on type Ia supernova distance measurements

ABSTRACT Type Ia Supernovae (SNe Ia) are a critical tool in measuring the accelerating expansion of the universe. Recent efforts to improve these standard candles have focused on incorporating the effects of dust on distance measurements with SNe Ia. In this paper, we use the state-of-the-art Dark Energy Survey 5 year sample to evaluate two different families of dust models: empirical extinction models derived from SNe Ia data and physical attenuation models from the spectra of galaxies. In this work, we use realistic simulations of SNe Ia to forward-model different models of dust and compare summary statistics in order to test different assumptions and impacts on SNe Ia data. Among the SNe Ia-derived models, we find that a logistic function of the total-to-selective extinction $R_V$ best recreates the correlations between supernova distance measurements and host galaxy properties, though an additional 0.02 mag of grey scatter is needed to fully explain the scatter in SNIa brightness in all cases. These empirically derived extinction distributions are highly incompatible with the physical attenuation models from galactic spectral measurements. From these results, we conclude that SNe Ia must either preferentially select extreme ends of galactic dust distributions, or that the characterization of dust along the SNe Ia line-of-sight is incompatible with that of galactic dust distributions.

Dynamic diffusion characteristics of airflow and coal dust during the mining process based on MRF: A numerical simulation study

Turbulence generated by rotation of shearer has a great impact on the distribution of dust. The MRF method of multiple reference frame was employed to simulate airflow and dust distribution during mining process. The distribution of cutting dust under different airflow velocities, cutting speeds, and cutting direction (against or follow the direction of airflow) were compared and analyzed. Results show that the generated cutting dust using MRF method tends to move horizontally and vertically. As the speed of airflow increases, vertical characteristics diminish. Simultaneously, horizontal dissipation rises with the deviation of airflow speed. The increase of rotational speed augments the distance covered by cutting airflow, including vertical offset and windward motion. Moreover, the elevated drum speed amplifies airflow speed in the sidewalk and the primary influence range is approximately 80 m. When cutting in the downwind direction, the airflow exhibits a pronounced vertical and horizontal offset behind the drum. Conversely, when cutting in the upwind direction, these characteristics are less evident, resulting in a more uniform spatial distribution of cutting dust in the downwind direction. The majority of dust generated when cutting against the airflow tends to move in the low-altitude area, contributing to a more disordered pattern.

Analysis of the influence of dust particles in the peanut pickup harvester with a self-designed axial-flow dust-fall box on its dust suppression performance

The atmospheric particulate pollution poses a serious threat to human health and ecological environment. The dust particle pollution caused by the operation of agricultural machinery is becoming increasingly severe and the peanut pickup harvesters are widely used in agricultural operation. Therefore, it is necessary to reduce the concentration of dust particles in the work of peanut pickup harvesters. In this study, a self-designed dust-fall box composed of multipleaxial flow cyclone tubes in parallel was integrated with the peanut pickup harvester. Based on the CFD-DPM model, simulation analysis was conducted to explore the effects of different inlet velocities, different numbers of swirling blades, and two types of exhaust port on the dust removal performance of the cyclone. The Box-Behnken design was used to determine the optimal structural parameters of the axial flow cyclone. The influence of the pressure distribution and velocity variations of the internal flow field on the dust removal efficiency of the two schemes was simulated and analyzed. Thereafter, a reasonable parallel scheme of multiple axial flow cyclone tubes in the dust-fall box was determined. The drone was used to monitor dust in peanut harvesting operations, and dust particle concentrations at 8 detection points under varying working conditions were recorded. The distribution and diffusion rules of dust in harvesting operations were explored through cluster analysis, and the test data obtained were compared with numerical calculation results to verify the accuracy of numerical calculation. The results showed that for a single axial flow cyclone, when the inlet wind speed was 6 m/s to 8 m/s and the number of swirling blades was 4, the structural parameters of the cyclone separator had significant influence on the separation efficiency. The influencing factors ranking in descending order were cylinder diameter, cylinder length, and exhaust pipe insertion depth, respectively. To be more precisely, the separation efficiency was best when the cylinder diameter was 60 mm, the cylinder length was 150 mm, the insertion depth of the exhaust pipe was 50 mm and the cone angle was 20°. It was more reasonable to use 8 axial flow cyclone tubes in parallel, and the maximum separation efficiency can reach 84.21 %. Field operations showed that the numerical calculation results were similar to the actual harvesting process. The dust particle concentration in the peanut harvesting operation equipped with a dust-fall box was always lower than 10 mg/m3. The dust particle concentration was the highest at the rear of the whole machine and the lowest near the cab. Compared conventional harvesters, the harvester with a dust-fall box reduced its dust particle concentration by 64.37 %; the concentration of 30 μm dust particles was reduced by 69.31 %; the dust particle concentration at the rear of the whole machine also effectively reduced. This study can provide reference for controlling dust emissions during peanut harvesting operations and agricultural machinery harvesting operations.

Impact of anthropogenic and natural constituents on particulate matter in oasis cities on the southern margin of the Taklimakan Desert based on MERRA-2 and multi-site ground observation

Dust storms are associated with large amounts of particulate matter (PM) that can have adverse effects on health and the environment. The contribution of natural dust to atmospheric PM levels represents a scientific challenge, especially in areas with close proximity to dust sources. To improve our knowledge in this area, we collected 300 PM filter-samples across five oasis cities on the southern edge of the Taklimakan Desert in 2016, and applied the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) data to quantify the contribution of natural dust to PM on sand dust and non-sand dust days. Research has shown that the particle size distribution of mineral dust in Taklimakan dust aerosols was relatively uniform. On sand dust days, CaSO4 and Na2SO4 were directly emitted from the surface, leading to higher sulfate concentrations in PM. While the increase in the proportions of organic carbon - OC1 and OC2 was attributed to the mixed anthropogenic emissions. On non-sand dust days, SO42− concentration was significantly affected by emissions from anthropogenic sources. The automotive composite emissions and coal combustion were the main sources of elemental carbon - EC1. Based on the results of MERRA-2 reanalysis data, natural dust constituted 53 % and 70 % of the total PM2.5 and PM10, respectively. In this study, we have quantified the contribution of natural dust under different weather conditions and identifying potential sources of PM in oasis cities. This study provides support for the assessment of natural dust and PM prevention in oasis cities.

Consequence of Cattaneo-Christov heat and mass flux models on bioconvective flow of dusty hybrid nanofluid over a Riga plate in the presence of gyrotactic microorganisms and Stephan blowing impacts

This study investigates the impact of the Stephan blowing and Cattaneo-Christov flux model on bioconvective flow of dusty hybrid nanofluid over a Riga plate in the presence of gyrotactic microorganisms and variable dust particles volume friction. Mass and heat phenomena are explored in the context of Stefan blowing impacts. The hybrid nanofluid consists of nanoparticles of MgO and Ag base fluid water. The Cattaneo-Christov mass and heat flux model has a significant impact on the bioconvective flow. The model predicts a slower temperature distribution and a higher concentration gradient than the traditional Fick's law and Fourier's law, respectively. The occurrence of gyrotactic microorganisms enhance the flow characteristics. This model is important for optimizing mass and heat transfer in a variety of engineering systems, including heating and cooling technologies, where effective thermal control is essential. It can be used by employing the regulated migration of microbes. By maximizing the removal of impurities, it helps with the design of sophisticated water purification systems in environmental engineering. The amalgamation of gyrotactic microorganisms and Stefan blowing effects augments the comprehension of intricate fluid dynamics, maybe resulting in advancements in microfluidic apparatuses and bio-inspired technologies. In order to transform the controlling PDEs into nonlinear ODEs, a new set of non-dimensional variables is used. The MATLAB (RKF-45th) technique is then used to resolve the ODEs numerically. As the Stephan blowing parameter (0.1≤Sb≤1.9) increases, the outcomes show that the flow distributions upsurge for both the dust and fluid phases, but the dust and fluid phase thermal distributions drop.