Dust Size Research Articles

Long-range transport of coarse mineral dust: an evaluation of the Met Office Unified Model against aircraft observations

Abstract. Coarse mineral dust particles have been observed much further from the Sahara than expected based on theory. They have impacts different to finer particles on Earth's radiative budget, as well as carbon and hydrological cycles, though they tend to be under-represented in climate models. We use measurements of the full dust size distribution from aircraft campaigns over the Sahara, Canaries, Cabo Verde and Caribbean. We assess the observed and modelled dust size distribution over long-range transport at high vertical resolution using the Met Office Unified Model, which represents dust up to 63.2 µm diameter, greater than most climate models. We show that the model generally replicates the vertical distribution of the total dust mass but transports larger dust particles too low in the atmosphere. Importantly, coarse particles in the model are deposited too quickly, resulting in an underestimation of dust mass that is exacerbated with westwards transport; the 20–63 µm dust mass contribution between 2 and 3.7 km altitude is underestimated by factors of up to 11 in the Sahara, 140 in the Canaries and 240 in Cabo Verde. In the Caribbean, there is negligible modelled contribution of d > 20 µm particles to total mass, compared to 10 % in the observations. This work adds to the growing body of research that demonstrates the need for a process-based evaluation of climate model dust simulations to identify where improvements could be implemented.

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.

Investigation of the Minimum Ignition Energy Required for Combustion of Coal Dust Blended with Fugitive Methane

Ventilation Air Methane (VAM) significantly contributes to global warming. Capturing and mitigating these emissions can help combat climate change. One effective method is the thermal decomposition of methane, but it requires careful control to prevent explosions from the high temperatures involved. This research investigates the influence of methane concentration and coal dust particle properties on the minimum ignition energy (MIE) required for fugitive methane thermal decomposition and flame propagation properties. This knowledge is crucial for the mining industry to effectively prevent and mitigate accidental fires and explosions in VAM abatement plants. Coal dust samples from three different sources were selected for this study. Experiments were conducted using a modified Hartmann glass tube and a Thermal Gravimetric Analyser (TGA). The chemical properties of coal dust were determined through ultimate and proximate analysis. The particle size distribution was determined using a Mastersizer 3000 apparatus (manufactured by Malvern Panalytical, Malvern, UK). The results showed that the MIE is significantly affected by coal dust particle size, with smaller particles (<74 µm) requiring less energy to ignite compared to coarser particles. Additionally, blending methane with coal dust further reduces the MIE. Introducing methane concentrations of 1% and 2.5% into the combustion space reduced the MIE by 25% and 74%, respectively, for the <74 µm coal dust size fraction. It was observed that coal dust concentration can either raise or lower the MIE. Larger coal dust concentrations, acting as a heat sink, reduce the likelihood of ignition and increase the MIE. This effect was noted at a methane concentration of 2.5% and coal dust levels above 3000 g/m3. In contrast, small amounts of coal dust had little impact on MIE variation. Moreover, the presence of methane during combustion increased the upward flame travel distance and propagation velocity. The flame’s vertical travel distance increased from 124 mm to 300 mm for a coal dust concentration of 300 g·m−3 blended with 1% and 2.5% methane, respectively.

Intercomparison of WRF-chem aerosol schemes during a dry Saharan dust outbreak in Southern Iberian Peninsula

The Iberian Peninsula (IP), where this study is conducted, has experienced an increase of the frequency and intensity of Saharan aerosol dust outbreaks over the latest decades, which may have an impact on its regional climate. The Weather Research and Forecasting model coupled with chemistry (WRF-chem) has been used worldwide to simulate dust outbreaks and can support the analysis of such potential impacts. However, it includes multiple alternative aerosol parameterization choices that have not been conveniently evaluated in the study region yet. Here, three of the most popular WRF-chem aerosol parameterization schemes, namely, the Goddard Chemistry Aerosol Radiation and Transport (GOCART), the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) and the Modal Aerosol Dynamics Model for Europe (MADE) schemes, are inter-compared during a strong and dry dust outbreak on July 2021 in southern IP. The results show that the three schemes predict qualitatively similar dust intrusion patterns that are consistent with ground observations and have inter-model dust loading differences smaller than 4%. However, their average dust size distributions differ notably. While GOCART is reasonably consistent with observations, MOSAIC underpredicts the amount of dust particles with sub-micron diameters and overpredicts that of large particles and MADE does the opposite. This is found to have a strong detrimental impact on the prediction performance of dust optical properties in MOSAIC and MADE, which is related, at least partially, with issues in the required inter-sectional redistribution of dust parameters during the dust emission and calculation of optical properties. Overall, GOCART generally appears a better choice for strong and dry dust outbreak events in southern IP. It remains to be evaluated during wet dust outbreaks, which is a work underway.

A new census of dust and polycyclic aromatic hydrocarbons at z = 0.7–2 with JWST MIRI

Aims. This paper utilises the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) to extend the observational studies of dust and polycyclic aromatic hydrocarbon (PAH) emission to a new mass and star formation rate (SFR) parameter space beyond our local Universe. The combination of fully sampled spectral energy distributions (SEDs) with multiple mid-infrared (mid-IR) bands and the unprecedented sensitivity of MIRI allows us to investigate dust obscuration and PAH behaviour from z = 0.7 up to z = 2 in typical main-sequence galaxies. Our focus is on constraining the evolution of PAH strength and the dust-obscured luminosity fraction before and during cosmic noon, the epoch of peak star formation activity in the Universe. Methods. In this study, we utilise MIRI multi-band imaging data from the SMILES survey (5 to 25 μm), complemented with NIRCam photometry from the JADES survey (1 to 5 μm), available HST photometry (0.4 to 0.9 μm), and spectroscopic redshifts from the FRESCO and JADES surveys in GOODS-S for 443 star-forming (without dominant active galactic nucleus (AGN)) galaxies at z = 0.7 − 2.0. This redshift range was chosen to ensure that the MIRI data cover mid-IR dust emission. Our methodology involved employing ultraviolet (UV) to IR energy balance SED fitting to robustly constrain the fraction of dust mass in PAHs and dust-obscured luminosity. Additionally, we inferred dust sizes from MIRI 15 μm imaging data, enhancing our understanding of the physical characteristics of dust within these galaxies. Results. We find a strong correlation between the fraction of dust in PAHs (PAH fraction, qPAH) with stellar mass. Moreover, the sub-sample with robust qPAH measurements (N = 216) shows a similar behaviour between qPAH and gas-phase metallicity to that at z ∼ 0, suggesting a universal relation: qPAH is constant (∼3.4%) above a metallicity of Z ∼ 0.5 Z⊙ and decreases to < 1% at metallicities ≲0.3 Z⊙. This indicates that metallicity is a good indicator of the interstellar medium properties that affect the balance between the formation and destruction of PAHs. The lack of a redshift evolution from z ∼ 0 − 2 also implies that above Z ∼ 0.5 Z⊙ the PAH emission effectively traces obscured luminosity and the previous locally calibrated PAH-SFR calibrations remain applicable in this metallicity regime. We observe a strong correlation between the obscured UV luminosity fraction (ratio of obscured to total luminosity) and stellar mass. Above the stellar mass of M* > 5 × 109 M⊙, on average, more than half of the emitted luminosity is obscured, while there exists a non-negligible population of lower-mass galaxies with > 50% obscured fractions. At a fixed mass, the obscured fraction correlates with SFR surface density. This is a result of higher dust covering fractions in galaxies with more compact star-forming regions. Similarly, galaxies with high IRX (IR to UV luminosity) at a given mass or UV continuum slope (β) tend to have higher ΣSFR and shallower attenuation curves, owing to their higher effective dust optical depths and more compact star-forming regions.

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.

The ALMA Legacy Survey of Class 0/I Disks in Corona australis, Aquila, chaMaeleon, oPhiuchus north, Ophiuchus, Serpens (CAMPOS). I. Evolution of Protostellar Disk Radii

We surveyed nearly all the embedded protostars in seven nearby clouds (Corona Australis, Aquila, Chamaeleon I and II, Ophiuchus North, Ophiuchus, Serpens) with the Atacama Large Millimeter/submillimeter Array at 1.3 mm observations with a resolution of 0.″1. This survey detected 184 protostellar disks, 90 of which were observed at a resolution of 14–18 au, making it one of the most comprehensive high-resolution disk samples across various protostellar evolutionary stages to date. Our key findings include the detection of new annular substructures in two Class I and two flat-spectrum sources, while 21 embedded protostars exhibit distinct asymmetries or substructures in their disks. We find that protostellar disks have a substantially large variability in their radii across all evolutionary classes. In particular, the fraction of large disks with sizes above 60 au decreases as the protostar evolves from Class 0 to Class I. Compiling the literature data, we discovered an increasing trend of the gas disk radii to dust disk radii ratio (R gas,Kep/R mm) with increasing bolometric temperature (T bol). Our results indicate that the dust and gas disk radii decouple during the early Class I stage. However, in the Class 0 stage, the dust and gas disk sizes are similar, which allows for a direct comparison between models and observational data at the earliest stages of protostellar evolution. We show that the distribution of radii in the 52 Class 0 disks in our sample is in high tension with various disk formation models, indicating that protostellar disk formation remains an unsolved question.

The Pre-perihelion Evolution of the Activity of Comet C/2017 K2 (Pan-STARRS) during the Water Ice-line Crossover

Comets, relics from the early solar system, consist of dust and ice. The ice sublimates as comets approach the Sun, ejecting dust from their nuclei seen as activity. Different volatiles sublimate at different Sun–comet distances and eject dust of unique sizes, structures, and compositions. In this study, we present new polarimetric observations of Oort cloud comet C/2017 K2 (Pan-STARRS) in R- and I-filter domains before, during, and after its crossover of the water-ice sublimation regime at phase angles of 15.°9, 10.°5, and 20.°0, respectively. Combining multiband optical imaging data covering a wide range of heliocentric distances (∼14−2.3 au), we aim to characterize the pre-perihelion evolution of cometary activity as well as the properties of its coma dust. Two discontinuous brightening events were observed: at ∼6 au presumably associated with changes in CO-like supervolatile ice activity, and at ∼2.9 au when water ice took over. Particularly, the latter activation is accompanied by changes in coma morphology and color whose trends differ between the inner (∼103 km) and outer (∼104 km) parts of the coma. No polarimetric discontinuities on the comet were observed over the inner coma region, all epochs showing phase-angle and wavelength dependencies compatible with those of active comets observed in similar observing geometry. During this period, the underlying dust continuum overwhelmed Hα emission at around 656.3 nm, suggesting less water ice on the comet’s surface than expected. We discuss K2's coma environment by combining numerical simulations of light scattered by dust and place the observations within the context of the comet’s evolution.

Sources and health risks of heavy metals in kindergarten dust: The role of particle size

Particle size effects significantly impact the concentration and toxicity of heavy metals (HMs) in dust. Nevertheless, the differences in concentrations, sources, and risks of HMs in dust with different particle sizes are unclear. Therefore, guided by the definition of atmospheric particulate matter, dust samples with particle sizes under 1000 μm (DT1000), 100 μm (DT100), and 63 μm (DT63) from Beijing kindergartens were collected. The concentrations of HMs (e.g., Cd, Pb, Zn, Ni, Cr, Ba, Cu, V, Mn, Co, and Ti) in dust samples with different particle sizes were measured. Besides, the differences in HM concentrations, contamination levels, sources, and source-oriented health risks in dust samples of different particle sizes were systematically explored. The results show that the concentrations of Mn, V, Zn, and Cd gradually increase with decreasing dust particle sizes, the concentrations of Ba and Pb show a decreasing trend, and the concentrations of Cr, Cu, Ni, and Co display an increasing and then decreasing trend. The degree of contamination of HMs in dust of different particle sizes varies, with Cd being the most dominant contaminant. Compared with DT1000 and DT63, DT100 is the most polluted. In addition, the sources of HMs in DT1000, DT100, and DT63 become more single with decreasing particle size, which may be mainly due to the particle-size effect inducing the redistribution of HMs in different sources. Notably, the potential health risk is higher in DT100 than in DT1000 and DT63. The highest contribution of industrial sources to the health risk is found in DT100, which is mainly caused by highly toxic chromium (Cr). This work emphasizes the importance of considering particle size in risk assessment and pollution control, which can provide a theoretical basis for precise management of HMs pollution in dust.

Experimental investigation on the impact of water immersion time and particle size on the ignition characteristics of coal dust

After drying, water-immersed coal is more prone to spontaneous combustion than raw coal. However, the influence mechanisms of particle size and water immersion duration on the physicochemical properties of coal dust, as well as the explosion and fire hazards of water-immersed coal dust, have not been sufficiently investigated. In this study, two particle sizes of coal dust were selected, and experiments were conducted using the Godbert-Greenwald furnace, Hartmann tube, Muffle furnace, and Fourier Transform Infrared Spectrometer. The study investigated the impact of different water immersion times, dust particle sizes, and dust concentrations on the sensitivity of coal dust fires and explosions, analyzed the process of functional group changes in coal dust particles in water and other mechanisms of transformation. The results indicated that the water immersion process increased the number of active functional groups on the surface of coal dust, significantly reducing the Minimum Ignition Temperature (MIT) and Minimum Ignition Energy (MIE) values for different samples, and also enhancing the ignition sensitivity and peak temperature of coal dust layer fires. This study contributes to a deeper understanding of the characteristics of coal dust and is of great significance for improving the prevention and control of coal dust fires and explosions.

Scattering properties of protoplanetary dust analogs with microwave analogy: Rough compact grains

Context. Scattering simulations of perfect spheres are not sufficient to explain the observations of scattered light from protoplanetary and debris disks, especially when the dust sizes are on the same order of magnitude as the wavelength used to perform the observations. Moreover, examples of grains collected from the Solar System have proved that the morphology of interstellar dust is irregular. These pieces of evidence lead us to consider that the morphologies of the dust that participates in these circumstellar disks are more complex than those of spheres. Aims. We aim to measure and simulate the scattering properties of six rough compact grains to identify how their morphology affects their scattering properties. These grains are intended to be dust analogs of protoplanetary and debris disks. Their convexity ranges from 75% to 99%. Methods. Grains were 3D printed using stereolithography, and their shape and refractive index were controlled. These analogs were measured with our microwave-scattering experiment (microwave analogy) at wavelengths ranging from 16.7 mm to 100 mm, leading to size parameters from X = 1.07 to X = 7.73. In parallel, their scattering properties were simulated with our finite-element method (FEM), which contained the same geometric file as the 3D printed grains. Results. We retrieved five scattering properties of these grains, that is, the phase function, the degree of linear polarization (DLP), and three other Mueller matrix elements 〈Sij〉. Two types of studies were performed. First, a study of the scattering properties averaged over several orientations of grains at different wavelengths. Second, a study of the same scattering properties, for which a power-law size distribution effect was applied. Conclusions. The very good correspondence between the measured and simulated Mueller matrix elements demonstrated the accuracy of our measurement setup and the efficiency of our FEM simulations. For the first study, DLP proved to be a good indicator of the grain morphology in terms of convexity and shape anisotropy. For the second study, backscattering enhancements of the phase function were related to the grain convexity. The maximum DLP and its negative polarization branches as well as the 〈S22〉/〈S11〉 levels were related to the shape anisotropy of our grains.

Numerical simulations of exocomet transits: Insights from β Pic and KIC 3542116

In recent years, the topic of existence and exploration of exocomets has been gaining increasing attention. The asymmetrical decrease in the star’s brightness due to the passage of a comet-like object in front of the star was successfully predicted. It was subsequently confirmed on the basis of the light curves of stars observed by Kepler and TESS orbital telescopes. Since then, there have been successful attempts to fit the asymmetrical dips observed in the stars’ light curves utilizing a simple 1D model of an exponentially decaying optically thin dust tail. In this work, we propose fitting the photometric profiles of some known exocomet transits based on a Monte Carlo approach to build up the distribution of dust particles in a cometary tail. As the exocomet prototypes, we used the physical properties of certain Solar System comets belonging to the different dynamical groups and moving at heliocentric distances of 0.6 au, 1.0 au, 5.0 au, and 5.5 au. We obtained a good agreement between the observed and modeled transit light curves. We also show that the physical characteristics of dust particles, such as the particle size range, the power index of dust size distribution, the particle terminal velocity, and distance to the host star affect the shape of the transit light curve, while the dust productivity of the comet nucleus and the impact parameter influence its depth and duration. The estimated dust production rates of the transiting exocomets are at the level of the most active Solar System comets.

The effect of the feed rate and revolutions of the cutting tool on the amounts of created chips in dust and respirable sizes from milling particleboards, and medium-density fibreboards

The CNC finish milling of wood-based materials creates chips in a wide size range, where considerable amounts were found even below <10.0μm. The presented article studied the effect of technological variables on determined amounts of chips in dust sizes and respirable range from medium-density fibreboards (MDF) and particleboards (PTCB). The materials were milled at a constant width of cut (ae) by 1mm, with the feed speed (vf) in the range of 6, 8, 10, and 12m·min-1, and with revolutions of the cutting tool (n) in the range of 16,000; 18,000; and 20,000revs·min-1. In dust size, we cover chips in the size range below <0.125mm, and respirable size below <10.0μm. The dust sizes from collected chip samples were determined by sieve analysis with pre-defined mesh sizes by weighting the retained mass on specific sieves and with the laser analysis we estimated the amounts of chips in sizes <10.0μm. The number of chips in the dust size ranged for MDF by 34.7-40.8w% and in PTCB by 38.1-54.7w%. Amount of chips in respirable size for MDF by 0.01-18% and for PTCB by 0.01-4.5% of the total mass volume. Increasing the (vf) from 6 to 12m/min significantly lowered amounts of Fine and chips in respirable size (p<0.05) in PTCB, no matter on adjusted cutting tool (n). In MDF such effect was observed only with (n) 20000revs/min for respirable sizes.

Tail Morphology of Near-Sun Comet C/2020 F3 (NEOWISE)

We study the morphological changes of bright near-Sun comet C/2020 F3 (NEOWISE) using a series of multi-color wide-field images obtained in 2020 July 8–30, as the comet receded from 0.3 to 0.8 au from the Sun. Syndyne–synchrone modeling shows that the dusts that makes up the visible tail were mostly produced at and after perihelion. The images show changes of dust size distribution throughout the observations, with a gradual depletion of micron-sized particles. We discuss caveats in using the syndyne–synchrone model to study tail dynamics of comets at small perihelion distances. The r-band images consistently show a straight, non-dust tail throughout our observations that is likely to be made by neutral sodium atoms and H2O+ molecules.

Numerical simulation of dust deposition characteristics of photovoltaic arrays taking into account the effect of the row spacing of photovoltaic modules

Dust deposition on the surfaces of Photovoltaic (PV) arrays during their operation markedly affects their power generation efficiency. Previous research has overlooked the impact of the row spacing of PV modules on the actual dust deposition on PV arrays. This study investigates the dust deposition process and its behavior on PV arrays considering variations in row spacings, inlet wind speeds, dust particle sizes, and dust particle counts. By employing commercial Computational Fluid Dynamics (CFD) software, incorporating the SST k-ω turbulence model and discrete particle model, numerical simulations were performed to analyze the airflow field, dust particle trajectories, dust deposition patterns, and deposition rates on the PV array through grid-independent verification and numerical validation. At the same time, we performed a comparative analysis of the deposition rate considering the rebound of dust particles on the PV module surface versus the case where rebound is not considered. Results revealed that the maximum dust deposition rates at different inlet wind speeds were 6.84 %, 8.84 %, 11.0 %, and 14.6 %, corresponding to dust sizes of 50 μm, 100 μm, 120 μm, and 300 μm, respectively. Smaller dust particles exhibited lower deposition rates, while larger particles were influenced more by mass inertia and gravity, leading to predominant deposition on the front row of PV modules. Larger dust particles are more likely to deposit primarily on the front row of PV modules in a PV array. The tilt angles of 30°, 45°, and 60° were chosen to study the effects of different tilt angles on the dust deposition of PV arrays, and the results show that the dust deposition rate decreases as the tilt angle increases, and it is worth noting that the larger the tilt angle, the larger the dust deposition rate is when the dust particles are especially small as 5 μm. When wind speeds are low and dust particles are small, the dust deposition rate gradually rises as the row spacing increases. However, at higher wind speeds with small dust particles, the row spacing has minimal impact on the dust deposition rate. Conversely, with larger dust particles, increasing the row spacing results in a lower dust deposition rate. These findings underscore the significance of optimizing PV array design for enhanced power generation efficiency.

Research on particle size distribution and composition of road deposit dust in Xi'an: From the perspective of non-exhaust emissions

Road dust, containing tire-road wear particles, atmospheric dust, or construction-related particles, contaminates road environments and poses a health hazard when inhaled by humans. To further explore the particle size and composition of road deposit dust, this study collects these particles in Xi'an, considering various road grades, materials, service conditions, sections, and locations. The collected particles undergo electron microscopy, laser particle size, thermal, mass spectrometry, infrared spectroscopy, and inductively coupled plasma analyses. Qualitative and quantitative analysis of the particles has been conducted, leading to the following conclusions: Asphalt & tire contribute 8.5% of the road deposit dust, while wear from calcium carbonate accounts for approximately 30%. The average particle size on urban roads (392 μm) is 1.25 times that of rural roads (312 μm). The smaller particles on rural roads are more easily resuspended and inhaled, posing health risks and requiring more attention. Brake zones, which often have 1.4 times the metal content compared to mid-sections, including potentially carcinogenic chromium (Cr), should receive focused watering and adsorption due to brake zone where is also at intersections and pedestrian crossing. New roads, which generate 3-6 times more organic matter than old roads, requires continuous cleaning after opening to traffic. Surface-blocked asphalt concrete (AC) pavements, as their lack of pores can lead to easy re-suspension of deposited particles due to tire-road interaction should also be attention. This study aims to contribute to the field of traffic-related dust pollution cleaning strategies and non-exhaust emissions mitigation measures in the future.

Isotopic variation of non-carbonaceous meteorites caused by dust leakage across the Jovian gap in the solar nebula

Abstract High-precision isotopic measurements of meteorites revealed that they are classified into non-carbonaceous (NC) and carbonaceous (CC) meteorites. One plausible scenario for achieving this grouping is the early formation of Jupiter, because massive planets can create gaps that suppress the mixing of dust across the gap in protoplanetary disks. However, the efficiency of this suppression by the gaps depends on dust size and the strength of turbulent diffusion, allowing some fraction of the dust particles to leak across the Jovian gap. In this study, we investigate how isotopic ratios of NC and CC meteorites are varied by the dust leaking across the Jovian gap in the solar nebula. To do this, we constructed a model to simulate the evolution of the dust size distribution and the $^{54}$Cr-isotopic anomaly $\varepsilon ^{54}$Cr in isotopically heterogeneous disks with Jupiter. Assuming that the parent bodies of NC and CC meteorites are formed in two dust-concentrated locations inside and outside Jupiter’s orbit, referred to as the NC reservoir and the CC reservoir, we derive the temporal variation of $\varepsilon ^{54}$Cr at the NC and CC reservoirs. Our results indicate that substantial contamination from CC materials occurs at the NC reservoir in the fiducial run. Nevertheless, the values of $\varepsilon ^{54}$Cr at the NC reservoir and the CC reservoir in the run are still consistent with those of NC and CC meteorites formed around $2\:$Myr after the formation of calcium–aluminum-rich inclusions (Sugiura & Fujiya 2014, Meteorit. Planet. Sci., 49, 772). Moreover, this dust leakage causes a positive correlation between the $\varepsilon ^{54}$Cr value of NC meteorites and the accretion ages of their parent bodies.

Observational signatures of the dust size evolution in isolated galaxy simulations

We aim to provide observational signatures of the dust size evolution in the interstellar medium (ISM). In particular, we explore indicators of the polycyclic aromatic hydrocarbon (PAH) mass fraction ($q_ PAH $), defined as the mass fraction of PAHs relative to the total dust grains. In addition, we validate our dust evolution model by comparing the observational signatures from our simulations to observations. We used the hydrodynamic simulation code, GADGET4-OSAKA to model the dust properties of Milky Way-like and NGC 628-like galaxies representing star-forming galaxies. This code incorporates the evolution of grain size distributions driven by dust production and interstellar processing. Furthermore, we performed post-processing dust radiative transfer calculations with SKIRT based on the hydrodynamic simulations to predict the observational properties of the simulations. We find that the intensity ratio between 8 um and 24 um ($I_ nu um )/I_ nu um )$) is correlated with $q_ PAH $ and can be used as an indicator of the PAH mass fraction. However, this ratio is influenced by the local radiation field. We suggest the 8 um -to-total infrared intensity ratio ($ I_ nu um )/ I_ TIR $) as another indicator of the PAH mass fraction, since it is tightly correlated with the PAH mass fraction. Furthermore, we explored the spatially resolved evolutionary properties of the PAH mass fraction in the simulated Milky Way-like galaxy using $ I_ nu um )/ I_ TIR $. We find that the spatially resolved PAH mass fraction increases with metallicity at $Z due to the interplay between accretion and shattering, whereas it decreases at $Z because of coagulation. Also, coagulation decreases the PAH mass fraction in regions with a high hydrogen surface density. Finally, we compared the above indicators in the NGC 628-like simulation with those observed in NGC 628 by Herschel Spitzer and JWST . Consequently, we find that our simulation underestimates the PAH mass fraction throughout the entire galaxy by a factor of $ 8$ on average. This could be due to the efficient loss of PAHs by coagulation in our model, suggesting that our treatment of PAHs in dense regions needs to be improved.

Flameless venting characteristics and design model of micro-nano PMMA dust explosion

The effects of Fe–Ni foam thickness and dust size on flame propagation, reduced overpressure, and venting efficiency in 30 μm and 150 nm polymethyl methacrylate (PMMA) dust explosions were investigated. The flame quenching mechanism was revealed by coupling the heat transfer and flow of the dust flame within the Fe–Ni foam. It is found that micron dust is more prone to quenching than nano dust, and the differences in the quenching process of micro-nano dust are explained by combining the dust combustion kinetics and the theory of inter-particle heat transfer. The pressure venting mechanism of micro-nano dust was analysed under different thicknesses of Fe–Ni foam, and the thermal expansion effect of the flame passing through the Fe–Ni foam and its flow resistance significantly increased the reduced explosion overpressure. The flow continuity of the micro-nano dust was classified by means of the Knudsen number (Kn), which elucidates the effect of dust size differences on the pressure evolution. A prediction model for the maximum reduced explosion overpressure is proposed based on the explosion pressure venting of micro-nano dust. Changes in vented pressure have a direct impact on the efficiency of flameless venting. Nano-dust has an efficiency of more than 20 % lower than that of micron dust.

Impact of Respiratory Dust on Health: A Comparison Based on the Toxicity of PM2.5, Silica, and Nanosilica.

Respiratory dust of different particle sizes in the environment causes diverse health effects when entering the human body and makes acute or chronic damage through multiple systems and organs. However, the precise toxic effects and potential mechanisms induced by dust of different particle sizes have not been systematically summarized. In this study, we described the sources and characteristics of three different particle sizes of dust: PM2.5 (<2.5 μm), silica (<5 μm), and nanosilica (<100 nm). Based on their respective characteristics, we further explored the main toxicity induced by silica, PM2.5, and nanosilica in vivo and in vitro. Furthermore, we evaluated the health implications of respiratory dust on the human body, and especially proposed potential synergistic effects, considering current studies. In summary, this review summarized the health hazards and toxic mechanisms associated with respiratory dust of different particle sizes. It could provide new insights for investigating the synergistic effects of co-exposure to respiratory dust of different particle sizes in mixed environments.