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This study aimed to assess the effects of rock dust on Meloidogyne javanica in soybean grown in autoclaved and non-autoclaved soil and investigate the impacts on plant foliar nutrition. The nematode reproduction experiment was conducted in two periods (Trials 1 and 2) in a 5 × 2 factorial design (rock dust rates of 0, 1000, 2000, 3000, and 4000 kg ha−1 × autoclaved and non-autoclaved soil). Soybean were inoculated with 2000 eggs + second-stage juveniles (J2) of M. javanica, and nematode and vegetative variables were evaluated at 60 days after inoculation (DAI). The penetration experiment followed a 2 × 2 factorial design (rock dust rates of 0 and 2500 kg ha−1 × autoclaved and non-autoclaved soil). Soybean were inoculated with 2000 eggs + J2 of M. javanica and evaluated at 5, 10, 15, 20, and 25 DAI. The shoot dry biomass from the reproduction experiment (Trial 1) was analyzed for macro- and micronutrients. In Trial 1, nematode reproduction decreased proportionally to the increase in rock dust rate in non-autoclaved soil. In Trial 2, the lowest nematode numbers were predicted to be achieved with rates of 2213 to 2309 kg ha−1, and nematode numbers were lower in autoclaved than in non-autoclaved soil. Rock dust reduced J2 penetration at 10 and 15 DAI, and there was no formation of females in treated plants. Rock dust application increased foliar levels of Fe, B, and Cu. Rock dust reduced M. javanica reproduction, penetration, and development in soybean and promoted gains in Fe, Cu, and B foliar contents. [ABSTRACT FROM AUTHOR]

Mineral dust from the Sahara desert can travel long distances at high altitudes, perturbing the energy budget of the atmosphere. Charging of dust has been observed to occur near the surface through triboelectric charging during dust lofting, potentially affecting particle coagulation, fall speeds, and the lofting process itself. Apart from near-surface studies, measurements at elevated dust layers, where charge may play a role in particle long-range transport, are rare. This study presents new observations from an uncrewed aircraft system (UAS) of type MASC-3, through an elevated Saharan dust layer over Cyprus on 6 April 2022. The dust layer ranged from 1500 to 2500 meters above sea level (a.s.l), with maximum particle number concentrations (PNC) of 80–100 cm − 3 , primarily consisting of particles up to 2.5 µm in size. Measurements showed elevated charge within the dust layer, with magnitude proportional to PNC. It was concluded that there was a small influence of aircraft charge on the measurements, which was handled by developing a PNC-based correction factor. Corrected charge within the dust layer ranged from 0.2 to 3 pC m − 3 , with most of the charge at the upper and lower dust layer boundaries. The magnitude and location of the charge was consistent with predictions of ion-particle attachment. This suggests that most of the measured charge did not originate from the lofting process, but dust particles were charged on site through ion-particle attachment processes. [ABSTRACT FROM AUTHOR]

Dust resuspension from four typical fabrics (cotton, linen, silk, and polyester) exposed to airflow with common velocities within 0–10 m/s, including a moving fabric case and a fixed fabric case, was experimentally studied in this article. A set of empirical correlations, involving air velocity, fabric motion mode, fabric type, and airflow duration was developed to describe and predict the moving fabric case. It was found that a stronger-than-expected resuspension was triggered by short-term accelerating airflow. The resuspension enhancement of over 90% was reported for the moving fabrics compared with the fixed ones. Fabric motion induced by airflow was proposed to account for these resuspension findings. Fabric acceleration was then demonstrated to be a key factor in evaluating the resuspension for such a scenario. This article not only reveals an inconspicuous phenomenon of dust resuspension from fabrics under the impact of airflow and consequent fabric motion, but also provides a theoretical basis for particulate matter assessment and regulation. Copyright © 2024 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

The Empire State mine in Balmat, New York, is known for its fine mineral specimens, including sphalerites, calcites, pyrite, pyrrhotite, halite, and quartz. The article acknowledges the lack of detailed documentation on mineral discoveries in the area but provides a list of 116 known minerals from the Balmat mines. The Empire State mine, owned by Titan Mining Corporation, is one of six zinc mines in the region. The rocks in the mines have undergone metamorphism, and the formation of mineral pockets occurred due to fluid movements. Recent discoveries of minerals in the mine have attracted attention from collectors and researchers, and it is hoped that future documentation will provide more information about these finds. [Extracted from the article]

The use of rock dust in agriculture has increased worldwide and particularly in Brazil since its regulation by Law 12.890 (2013). However, some inconsistent results in standard chemical analysis of soils amended with rock dust have drawn attention, and among them, cation exchange capacity (CEC). This paper evaluates the increase in sum of bases (SB) and CEC of two soils amended with commercial rock dust (magnesium silicate), measured by four methods: ion exchange resin, potassium chloride (KCl), compulsive exchange and cesium adsorption. The maximum possible increase of SB in the soil was estimated based on the total chemical analysis of the rock dust and compared to the measured CEC results. We concluded the resin method inflated the results, due to the dissolution of rock dust particles by the acid extraction used to recover the adsorbed cations in resin beads. These extra cations caused overestimation of the sum of bases and consequently, of the estimated CEC. Among the methods used, direct CEC methods were more appropriate, as well as the KCl, since it does not employ acid extractions at any step. In addition, calculations based on the total chemical analysis of the rock dust can help to identify some of the cases in which the routine analysis is inflated by the dissolution of rock dust. [ABSTRACT FROM AUTHOR]

Soil-free sodic salt pans with local pH >10 have formed on loess and schist-derived clay surfaces in the semi-arid climate of Central Otago. This study identifies evaporative mineral distributions and associated variations in surface geochemistry, and these results are relevant to survival of rare halophytic plants on some of the pans. Evaporative salts on pan surfaces are dominated by NaCl from marine aerosols, and Na-sulphates and Na-carbonates. Some of the Na in evaporites was derived from alteration of schist-derived albite and Na-bearing smectite formed from albite. The high pH pan surfaces result from a combination of long-term (decades to millennia) albite alteration and short-term (minutes to months) Na-carbonate dissolution and recrystallisation. This muscovite is variably cemented by evaporative salts, and some crusts have abundant salt-dissolution voids. High pH has facilitated dissolution of aluminium and silica from albite and smectite, with evaporative precipitation of Al-oxyhydroxide contributing to crust cementation. Different dissolution rates of evaporative minerals during rain events and damp seasons results in differential mobility of salt components downslope. The salt pans are physically and chemically dynamic features that have formed on time scales of decades to centuries. [ABSTRACT FROM AUTHOR]

The oxidation of sulfur dioxide (SO2) to sulfate in the atmosphere is an important concern in regional air quality, global climate change, and human health. While gas-phase and liquid-phase oxidation of SO2 are widely regarded as important sources of sulfate, the contribution of the heterogeneous oxidation process on particle surfaces is controversial. Recently, this heterogeneous chemistry has been considered to be an important mechanism that is missing in current models to explain sulfate concentrations observed in haze episodes in East Asia. Therefore, the heterogeneous oxidation of SO2 on particles under the conditions of complex air pollution needs to be reassessed. This review summarizes the fundamental understanding of the heterogeneous reactions of SO2 on solid particles such as mineral dust, black carbon, sea salts, organic aerosol, and so on. The factors affecting the mechanism and kinetics of the heterogeneous reactions of SO2, including coexisting components (O3, NO2, H2O2, NH3, and VOCs), reactive sites, surface properties, relative humidity, and illumination, are reviewed. Reactive oxygen species involved in the heterogeneous oxidation of SO2 on particles are discussed. To our knowledge, while previous reviews have appeared on the oxidation of SO2 in the aqueous-phase, this is the first review on the atmospheric heterogeneous reactions of SO2 on the surface of solid particles, which can be of help in understanding the sulfur cycle in the atmosphere and its environmental impacts. A number of recommendations for future research are also presented. [ABSTRACT FROM AUTHOR]

Water-insoluble aerosol particles (WIAPs), such as black carbon (BC), mineral dust, and primary biological aerosol particles (PBAPs), affect climate through their interaction with radiation and clouds. However, with the exception of BC, methods to identify WIAP types and quantify their number concentrations are limited. Here, we evaluated a method that has been recently developed to measure the number concentrations of submicron WIAPs based on atmospheric aerosol measurements at an urban site in Nagoya, Japan. In this method, atmospheric aerosol particles are collected on a filter and dispersed in water. Then, the complex forward-scattering amplitudes of individual particles are measured. This complex parameter reflects the complex refractive index, volume, and shape of each measured particle, enabling the characterization of these physical properties from the signals. The WIAPs were classified as BC-like, dust-like, and PBAP-like particles based on their complex amplitude data. The number concentrations of BC-like particles were strongly correlated with those of refractory BC particles measured by a Single Particle Soot Photometer. BC-like and dust-like particles dominated the population of the submicron WIAPs, which was also confirmed using electron microscopy and Wideband Integrated Bioaerosol Sensor observations. Under the observed atmospheric conditions, the number concentrations of WIAPs were measured with their dispersion efficiency from a filter to water of approximately 50%. These results indicate that our method based on filter sampling and complex forward-scattering amplitude measurements has the potential to become a new technique for quantifying the spatio-temporal distributions of WIAPs. [ABSTRACT FROM AUTHOR]

Aerosol water uptake and the related influence on its optical properties owing to the hygroscopic growth of polydisperse aerosols have a significant effect on air quality and climate. This study develops an analytical parameterization for a single hygroscopic optical parameter and the scattering enhancement factor for polydisperse aerosol sizes. Polydisperse lognormal size distributions for geometric mean diameters of 0.05–1 mm and geometric standard deviations of 1.3–2.5 are considered with real refractive indices between 1.35 and 1.6. The analytical expression obtained for the optical parameter is compared to Mie theory and reasonable agreements within the size range investigated in this study are observed. Further, our results show that the analytical expression could express polydispersed aerosol optical properties as a function of geometric mean diameter and geometric standard deviation of a lognormal distribution and the refractive index. The obtained analytical expression can be efficiently used for 3D models with a reduced computational burden. [ABSTRACT FROM AUTHOR]

NASA is currently planning return missions to the Moon for further exploration and research. The Moon is covered by a layer of potentially reactive fine dust, which could pose a toxicological risk of exposure to explorers. To assess this risk, we exposed rats to lunar dust (LD) that was collected during the Apollo14 mission. Rats were exposed to respirable sizes of LD at concentrations of 0, 2.1, 6.8, 20.8, or 60.6 mg/m3 for 4 weeks. At thirteen weeks after exposure, we assessed 44,000 gene transcripts and found the expression of 614 genes with known functions were significantly altered in the rats exposed to the 2 higher concentrations of LD, whereas few changes in gene expression were detected in the group exposed to the lowest concentration of LD. Many of the significant changes in gene expression involved genes known to be associated with inflammation or fibrosis. Four genes encoding pro-inflammatory chemokines were analyzed further for all the sampling points at 1 day, and 1, 4, and 13 weeks after the 4-week dust exposure, using real-time polymerase chain reaction. The expression of these genes was altered in a dose- and time-dependent manner and persistently changed in the lungs of the rats exposed to the two higher concentrations of LD. Their expressions are consistent with changes we detected in pulmonary toxicity biomarkers and pathology in these animals during a previous study. Because Apollo-14 LD contains common mineral oxides similar to an Arizona volcanic ash, besides revealing the toxicity of LD, our findings could help elucidate the genomic and molecular mechanisms involved in pulmonary toxicity induced by terrestrial mineral dusts. [ABSTRACT FROM AUTHOR]

Crystalline quartz is an important element of many materials and one of the major compounds of mineral dust. Thus, knowledge of its optical properties is essential for many applications, in particular for remote sensing techniques. However, despite the fact that crystalline quartz has been an object of study for many years using various experimental approaches, its optical properties and in particular its complex refractive indices (CRI) remain uncertain. The focus of this investigation is the determination of a new set of CRI of crystalline quartz particles retrieved from a methodology which has already demonstrated its efficiency on pure amorphous materials and volcanic ashes. The experimental set-up allows recording simultaneously size distribution (from 15 nm to 20 µm) of airborne particles and extinction spectra over a wide continuous spectral range from thermal infrared (650 cm−1) to UV (40,000 cm−1) with high spectral resolution (up to 0.5 cm−1). By associating these measurements and a numerical procedure coupling scattering theories, the single subtractive Kramers-Kronig relation, and an optimal estimation method in an iterative process, we precisely determine the real and imaginary parts of the CRI of crystalline SiO2 with mean values of the uncertainties of 2.5% and 1.7%, respectively. Moreover, the use of these CRIs allows to simulate an extinction spectrum of another quartz sample very well, which shows their suitability as well as the good reproducibility of the whole process. [ABSTRACT FROM AUTHOR]

Aluminium metal matrix composites (AMMCs) are attractive and effective materials due to their tailored properties for outstanding applications, like high specific strength, lightweight, high specific stiffness, excellent wear resistance, corrosion resistance and high elastic modulus than the base metal matrix. These materials are widely used in aerospace, automobile, marine, mining and mechanical structural applications. In the present study, rock dust was considered as reinforcement particles in various wt % (2, 4, 6, 8 and 10) in aluminium material. Rock dust is a by-product of the crushing processes of rocks in the production of gravel aggregates. The purpose of this investigation is to identify the influence of rock dust reinforcements on mechanical and wear properties of aluminium-based surface composites fabricated through the Friction Stir Processing (FSP). Traverse speed, rotational speed and tool tilt angle are fixed input parameters. From the experimental results it was observed that in the fabricated composite, rock dust addition to Al material gives better wear-resistant characteristics. Enhanced trends occurred in Impact strength and micro-hardness values due to the addition of reinforcements to the aluminium material. [ABSTRACT FROM AUTHOR]

Increase in industrial and construction activities has led to an enormous rise in waste generation and its hazardous impacts on the environment. Quarrying of rocks and manufacturing of artificial sands for civil engineering projects leads to the dumping of rock waste dust, which is a source of landfill problems. Further, excessive energy requirements for cement manufacturing, higher greenhouse gas emissions and rapid depletion of natural resources have focused the research towards the development of environment friendly and sustainable materials such as geopolymers. In this paper, a novel geopolymer has been developed from industrial wastes such as basalt rock fines considering partial replacement with ground granulated blast furnace slag up to 30%. After a detailed mix-design investigation, the optimum molarity (M) of the sodium hydroxide solution was found to be 8 M whereas the optimum ratio (R) of sodium silicate to sodium hydroxide solution as 0.75. Unconfined compressive strength evaluation showed 7-day strengths up to 34 MPa, comparable to geopolymers based on conventional precursor materials. The scanning electron microscopy imaging of the specimens revealed a dense geopolymer gel formation resulting in a homogeneous microstructure. As a result, this innovative material produced can be used as an alternative, sustainable and cost-effective construction material. [ABSTRACT FROM AUTHOR]

Atmospheric aerosol over the Arabian Sea is significantly impacted by the long-range transported mineral dust from the surrounding continents. This transported mineral dust is hypothesized and tested during several studies to see the impacts on the surface ocean biogeochemical processes and subsequently to the Carbon cycle. It is, thus important to quantify dust contributions and their fluxes to the Arabian Sea. Here we assess temporal variability of dust concentration, their elemental characteristics as well as quantify their dry and wet deposition fluxes over the North-eastern Arabian Sea. The dust concentrations were found to vary from 59 to 132 µg m−3 which accounts for 50% to 90% of total mass during dusty days. However, its contribution during pre and post dust storms ranges between 6% and 60%. Relatively higher dust dry deposition flux of 28 ± 7 mg m−2 day−1 (range: 20–44) is estimated for dusty days compared to pre and post dusty days (range: 0.4–22 mg m−2 day−1). In contrast to dry deposition fluxes, significantly higher fluxes are estimated from wet deposition, averaging around 240 ± 220 mg m−2 day−1. These values are five times higher than those reported from cruise samples collected over the Arabian Sea. The contribution of dust to aerosol mass is further ascertained using elemental composition, wherein a significant correlation was observed between Fe and Al (r2 = 0.77) for samples collected during the dusty period, highlighting their similar crustal sources. Our estimation of dust flux over this region has implications for the supply of nutrients associated with natural dust to the surface water of the Arabian Sea. Implications: The Arabian Sea, one of the productive oceanic regions among the global oceans, has been identified as a perennial source of atmospheric CO2. This basin is heavily impacted by atmospheric dust deposition/inputs owing to its geographical location being surrounded by arid and semi-arid regions. It has been hypothesized that aeolian dust plays a significant role in modulating surface water biogeochemical processes including primary productivity, in the Arabian Sea. Furthermore, modelling studies have highlighted on the role of dust (containing Fe) in fueling and enhancing primary productivity in the Arabian Sea. However, quantification of dust deposition fluxes (wet and dry) on seasonal time scale is missing in the literature. This paper aims to partially fulfil this research gap by providing a long-term data of wet and dry deposition fluxes over the northeastern Arabian Sea. We have also discussed their seasonal variability and factors affecting this flux. Thus, this study will be valuable contribution to the aeolian research community and have significant implication toward the role of aeolian deposition to the surface water biogeochemical processes in the Arabian Sea. [ABSTRACT FROM AUTHOR]

We conducted surveillance for work-related asthma (WRA) in Washington State to identify the industry sectors and asthma exposures most commonly affecting injured workers and in need of prevention activities. Using workers' compensation data as the primary data source, valid cases were classified as work-aggravated asthma (WAA) or new onset asthma that includes occupational asthma (OA) and reactive airways dysfunction syndrome (RADS). The source of exposure that caused the worker's asthma, their industry and occupation were determined. There were 784 valid work-related asthma cases identified for the period 2009–2016, WAA (n = 529) was most common followed by occupational asthma (n = 127) and RADS (n = 12). The Health Care and Social Assistance industry had the highest number of cases (n = 170) with 82% classified as WAA. The highest overall proportions of new onset asthma are occurring in Agriculture, Forestry, Fishing and Hunting (33% of work related asthma cases), Manufacturing (31%) and Construction (30%). The leading substances associated with new onset asthma across all industries include hop plant dust, wood and cedar dust, mineral and inorganic dust, mold, and cleaning materials. We describe ten cases of cannabis-associated asthma including seven from workers in the legalized cannabis industry, four of whom had OA. State-based work-related asthma surveillance is critical in identifying the workers and exposures associated with this occupational disease, including the detection of a case-series in the cannabis industry. [ABSTRACT FROM AUTHOR]

Glacial Lake Outburst Floods (GLOFs) are a recurring hazard in the Himalayas, posing significant threat to downstream communities. The North Sikkim district of India, comprising the upper reaches of the Teesta River in the Eastern Himalayas, has experienced past GLOF events. The identification of lakes susceptible to this phenomenon is therefore paramount. Using multi-temporal satellite images, this study tracks lake growth in the region, revealing that 203 new lakes had developed herein during the observation period (2000–2018). Of these, 82 lakes had formed during 2011–2018 alone; indicating marked glacial retreat and consequent lake area growth, alongside a rising temperature trend. Using various weighted geometric and geomorphic parameters, the 36 most hazardous lakes were identified, from which the 10 lakes posing the greatest GLOF threat were discerned. These lakes are mostly situated along the main snowline and Great Himalayan water-divide in the north-eastern part of Sikkim and should be monitored continuously. [ABSTRACT FROM AUTHOR]

An accurate observational dataset of the size-resolved concentration of mineral dust particles in the atmosphere, hydrosphere, and cryosphere is needed for investigating the effect of mineral dust on the climate with earth system models. However, automated measurements of dust particles remain challenging due to the complexities of the physicochemical properties (e.g., shape and mineralogy) of individual dust particles and the difficulties in discriminating dust from other particulate components (e.g., black carbon). Here, we suggest the use of complex forward-scattering amplitude data obtained by the single particle extinction and scattering (SPES) method as a low-cost optical approach for identification and quantification of silicate (aluminosilicates + quartz) particles, the major particulate component of desert dust. We focus here on the submicron particle-size range to challenge the robust identification of wavelength or smaller scale dust solely according to the principle of elastic light scattering. The two-dimensional nature of the complex scattering amplitude data allows us to identify silicate-dominant particles in waterborne dust samples and discriminate them from light-absorbing particulate components (e.g., hematite). We demonstrate that the two-dimensional dataspace of the complex amplitude allows an accurate retrieval of the particle-size distribution of silicate particles thanks to the simultaneous retrieval of the particle's effective refractive index. We discuss some notable differences in our results from those retrieved from conventional elastic light scattering approaches. Copyright © 2022 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Ice nucleating particles (INPs) impact cloud properties and precipitation processes through their ability to trigger cloud glaciation. Dust and bioparticles are two important sources of INPs that have markedly different atmospheric loadings and ice nucleating efficiencies. In-situ identification of the sources of INPs in clouds has been accomplished using single particle mass spectrometry (SPMS). However, external mixtures of dust and bioparticles present a unique challenge as they have overlapping mass spectral ion signatures, complicating their unambiguous identification. This study presents a detailed discussion of dust and bioparticle SPMS signatures, uniting data from a broad array of studies. As emphasized, the ion signals from both dust and bioparticles are highly sensitive to ionization conditions. To understand the observed variations, we characterize the mass spectral dependence of distinct dust and bioparticle samples using total positive ion intensity (TPII) as an indicator of the laser pulse energy each particle encountered. Through this analysis, a broad range of characteristic biogenic low intensity ion peaks that may be useful to distinguish bioparticles from dust became apparent and are highlighted. Insights informed by this analysis were utilized to identify bioparticles in ambient SPMS data. Ambient particles exhibiting both dust and characteristic biogenic spectral fingerprints were excluded from the bioparticle classification. Although bioparticles only made up 0.2% of all sampled particles, their abundance was moderately correlated with INP concentrations measured at −15 °C. Copyright © 2022 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Surgical masks are one of the most widely used personal protective equipment to keep pandemics under control. Medical face masks help slow the spread of the coronavirus (SARS-CoV-2) that causes COVID-19. Due to their lower cost and comfort, surgical masks are mostly preferred for the prevention of the epidemic. There are dozens of different face masks in the market. However, users do not have the opportunity to scientifically evaluate masks and analyze their performance against viruses. Surgical masks are classified according to EN 14683 standard but, the testing standards has been standardized considering bacterial permeability. In this study, a simple surgical mask testing approach has been demonstrated based on Quartz Crystal Microbalance (QCM) technique and variety of commonly available surgical masks' aerosol filtration performances were compared using the proposed approach. Then, SEM images of some masks were taken, and the results obtained from SEM analysis were compared with the results that was taken by proposed mask testing approach. In short, a simple direct mask test method taking into account the entire human aerosol distribution is proposed. Copyright © 2022 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Humans will set foot on the Moon again soon. The lunar dust (LD) is potentially reactive and could pose an inhalation hazard to lunar explorers. We elucidated LD toxicity and investigated the toxicological impact of particle surface reactivity (SR) using three LDs, quartz, and TiO2. We first isolated the respirable-size-fraction of an Apollo-14 regolith and ground two coarser samples to produce fine LDs with increased SR. SR measurements of these five respirable-sized dusts, determined by their in-vitro ability to generate hydroxyl radicals (•OH), showed that ground LDs > unground LD ≥ TiO2 ≥ quartz. Rats were each intratracheally instilled with 0, 1, 2.5, or 7.5 mg of a test dust. Toxicity biomarkers and histopathology were assessed up to 13 weeks after the bolus instillation. All dusts caused dose-dependent-increases in pulmonary lesions and toxicity biomarkers. The three LDs, which possessed mineral compositions/properties similar to Arizona volcanic ash, were moderately toxic. Despite a 14-fold •OH difference among these three LDs, their toxicities were indistinguishable. Quartz produced the lowest •OH amount but showed the greatest toxicity. Our results showed no correlation between the toxicity of mineral dusts and their ability to generate free radicals. We also showed that the amounts of oxidants per neutrophil increased with doses, time and the cytotoxicity of the dusts in the lung, which supports our postulation that dust-elicited neutrophilia is the major persistent source of oxidative stress. These results and the discussion of the crucial roles of the short-lived, continuously replenished neutrophils in dust-induced pathogenesis are presented. [ABSTRACT FROM AUTHOR]

Gold-bearing dust generated during the roasting process of refractory gold concentrates is valuable as secondary gold resources. In this study, the characterization of gold-bearing dust from carbon-bearing gold concentrates was determined by direct cyanidation and mineralogy research. Moreover, identification of refractoriness in the dust was determined by selective removal of minerals. Results showed that the dust belonged to refractory ores. Gold was observed to be presented as native and electrum which main associated with iron oxides. After preleaching with a 6 mol/L NaOH solution, arsenic, and carbon removal rates were 99.66% and 60.63%, respectively, and gold extraction was 58.90%, only 4.60% higher than that of direct cyanidation. After preleaching with a 15 wt.% H2SO4 solution, iron, arsenic, and carbon removal rates were 33.65%, 80.38%, and 12.60%, respectively, and gold extraction achieved 80.40%. After roasting, carbon and arsenic removal rates were 95.00% and 54.65%, respectively, and gold extraction achieved 84.52% under the optimum condition. Removal of carbonaceous matter and iron oxides could efficiently improve gold extraction, and the adverse effects of carbonaceous matter and iron oxides were the main reasons for refractoriness. Based on these results, a proper process for gold extraction from the dust was developed, and gold extraction achieved 95.50%. [ABSTRACT FROM AUTHOR]

The total and individual aerosol direct radiative effects (ADREs) were estimated for clear-sky conditions using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) observations and radiative transfer model. In this study, a parametric sensitivity analysis was performed for the Santa Barbara DISORT Atmospheric Radiative Transfer model using a global sensitivity analysis method. Uncertainties in the ADREs due to aerosol optical properties and surface albedo errors were evaluated. The single-scattering albedo and asymmetry factor for marine, dust, pollution, and smoke aerosols required for the model calculations were obtained from the classified AErosol RObotic NETwork observations. The estimated average global ADREs and errors at the top-of-atmosphere (TOA) and the surface were −2.36 ± 0.54 and −4.78 ± 2.2 Wm−2, respectively. In regions with higher dust, pollution, and smoke aerosol loading, the ADREs exhibited significant seasonal variability. In the Sahara and Arabian deserts, during the June-July-August season with higher dust aerosol loading, the seasonal average ADREs in the region were −3.23 and −21.37 Wm−2 at the TOA and surface, respectively. In the Indian region, during the March–April–May season with higher pollution aerosol loading, the ADREs were −10.33 and −28.04 Wm−2 at the TOA and surface, respectively. In Southern Africa, the smoke aerosol with a single-scattering albedo of 0.87 caused negative radiative effects at the TOA, and during the September-October-November season with higher smoke aerosol loading, the seasonal average ADREs were −2.34 and −6.36 Wm−2 at the TOA and surface, respectively. [ABSTRACT FROM AUTHOR]

Respiratory particles produced by breathing, coughing, and speaking or generated during medical procedures serve as important routes for disease transmission. Characterizing the number of particles generated as well as their size distribution is fundamental for guiding policy on infection control. However, sampling such particles carries inherent challenges. Respiratory particles are polydisperse in size, temporally and spatially variable, and emitted in very low concentrations, usually lower than the preexisting aerosol concentration in indoor environments. In addition, they are typically emitted in a highly dynamic, warm and humid jet, leading to further rapid processes, such as dispersion and evaporation. Here, we discuss important considerations for sampling respiratory aerosol, focusing on sampling particles <20 μm in diameter. Instruments capable of counting single-particles within this size range are commercially available. We provide recommendations for experimental protocols and demonstrate the limitations behind such approaches. We highlight the importance of a measurement space with as low a background aerosol concentration as possible, and of sampling for as long as possible to enable accurate quantitation of the size distribution of an aerosol plume. This is particularly important for the larger particles (>5 μm diameter) that are so low in concentration that they may require hours of sampling time to be accurately quantified. We explore the relationship between the flow rates of the exhalation and the sampling instrument and the consequent quantification of particle flux. We also discuss the transport and evaporation dynamics of liquid particles within respiratory jets, and their impacts on conducting aerosol sampling studies. [ABSTRACT FROM AUTHOR]

In order to solve the serious dust pollution problem in mining and loading process of burnt rock open-pit coal mines, a dust suppression technology was proposed to investigate the compound dust suppressant with four functions of wetting, coagulation, moisture absorption, and moisture retention, and improve the hydrophilicity and dust suppression efficiency of burnt rock. Through single-factor experiments, four functional reagents were selected. Determined the best mass concentration ratio by orthogonal test, and the optimum dilution ratio was determined through the contact angle verification test. Fourier infrared spectroscopy (FTIR) analysis of the functional group of the compound dust suppressant showed that the hydrophilic functional group was increased. The scanning electron microscopy (SEM) revealed that the dust surface formed a dense film after spraying the dust suppressant, and the effect of fine dust coagulation was obvious. The results of the wind tunnel simulation test revealed that the inhibitory efficiency of the compound dust suppressant on total dust and respirable dust could reach up to 81.90% and 87.06%, respectively, under a wind speed of 4.00 m/s. The field test data for mining and loading spray dust suppression in open-pit coal mines revealed that the dust suppression efficiency of whole dust and respirable dust was greater than 85.70%, which indicates that the compound dust suppressant can effectively suppress the dust of burnt rock, and effectively improve the working environment quality of mining and loading in open-pit coal mines. Implications: Open-pit coal mines located in arid areas will produce a large amount of dust during the mining and loading process, which will cause serious air pollution. In particular, the burnt rock is highly hydrophobic, and it is difficult to achieve effective removal by water spraying. The open-pit coal mine face advances faster and has strong mobility, There are few researches on dust reduction in this link. Therefore, in this study, in order to improve the dust suppression efficiency in the mining and loading process, a compound dust suppressant to improve the hydrophilicity of the burnt rock was developed through single-factor experiments and orthogonal experiments. Microscopic analysis using FTIR and SEM confirmed the wetting and coagulation effect of the dust suppressant. Then designed a spray dust suppression program for the mining and loading process and achieved good results. [ABSTRACT FROM AUTHOR]

Gaseous pollutants serve as precursors of ionic particles in the atmospheric environment, thus their control is necessitated along with the particulate with special reference to soluble ions. The present study was undertaken to assess the effect of Particulate Matter (PM10) associated Water-Soluble Ions (WSI) on the ambient air concentration. In total 134 airborne particulate matter (PM10) samples were collected from 11 stations from January to December in and around Gandhidham, Gujarat, India. Monthly sampling was carried out by the Respirable Dust Sampler (RDS) on 24 hr basis. The samples were subjected to chemical analyses for estimating water-soluble ions. The PM10 concentration in the analyzed samples ranged from 29 to 401 µg/m3. The amount of Na+, Ca2+ and K+ varied from 0.04 to 8.43 µg/m3, Below Detection Level (BDL) to 12.25 µg/m3, and 0.09 to 3.49 µg/m3, respectively following flame photometer method. The anions SO 2-, NO - and Cl- ranged from 0.31 to 3.68 µg/m3, 0.39 to 32.47 µg/m3, and 4.03 to 54.08 µg/m3, respectively. Higher concentrations were reported for all the ions during winter. From the results, it is evident that secondary anthropogenic aerosols, natural mineral aerosols and mixed sea salt contributed to higher ionic concentrations in the air. [ABSTRACT FROM AUTHOR]

Atmospheric dust samples were collected using PM10 (particulate matter less than 10 µm) and PM2.5 (particulate matter less than 2.5 µm) filters in 2019 from Southeast Anatolia, Turkey. The direction and source of the dust were determined using the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite view and Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. X-ray diffraction (XRD) has shown the presence of calcite and quartz as major components of the aerosol dust. The albedo parameters of atmospheric dust were experimentally determined for 59.54 keV photons emitted from an Am-241 source. Compton and coherent scattered peaks were acquired with a high purity germanium detector. The sample collected in May has a higher density than in June. The sample density at PM10 is larger than PM2.5 and the density of 23 June 2019 is smaller than for the other dates. The albedo parameters of the filter in June and May for PM10 are greater than those of PM2.5. The dust of larger particles is more reflected by the high-energy photons. [ABSTRACT FROM AUTHOR]

The objective of this study was to develop mathematically described characteristic tracheobronchial bifurcations that are representative of aerosol transport and deposition in the intermediate airways of children with cystic fibrosis (CF), where bronchiectasis is a major contributor to changes in lung anatomy. Realistic airway models in the region of bifurcations B4-B7 were extracted from CT scans of children that were scored as having either low (CT-Low) or moderate (CT-Mod) CF lung disease and served as a basis for comparison with characteristic models. Aerosol deposition characteristics in these CT-extracted models were compared with a previously developed baseline stochastic individual path model (Baseline SIP), based on mathematically defined physiologically realistic bifurcations (PRBs), and new characteristic PRB geometries with modifications made to account for the CF disease state. The Baseline SIP models provided a poor approximation of aerosol deposition in the scan-extracted geometries, as expected. In contrast, the new characteristic (modified) PRB geometries adequately captured deposition consistent with the scan-extracted geometries across the two disease states considered for multiple particle sizes and inhalation flow rates. This was surprising considering that the modified PRB geometries, which can be mathematically specified, only captured an expanded bifurcation region and extended carinal curvature, both representative of bronchiectasis, and neglected asymmetry, surface roughness and non-circular branch cross-sections. In conclusion, the new characteristic PRB geometries adequately captured the deposition characteristics of scan-extracted airway models and can be implemented to represent airway structures in the intermediate and likely deeper lung regions of children with CF for future complete-airway modeling studies. Copyright © 2021 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Long-term (2000–2020) trend in aerosol optical depth (AOD) and the associated radiative effect over Indian Ocean region (Arabian Sea and Bay of Bengal) during winter time south Asian outflow is investigated using multi-satellite data. Analysis revealed a statistically significant increasing trend of ~0.01 year−1 over the study regions. This study revealed that aerosols are confined within 2 km from ocean surface, and the trend in columnar AOD is significantly modulated by aerosol loading at higher altitudes. Although there has been no significant change in aerosol direct radiative forcing efficiency, the significant enhancement in AOD over the study region has induced an increase in cooling at the top of the atmosphere by ~0.1 to 0.2 W m−2 year−1. [ABSTRACT FROM AUTHOR]

Ahmedabad is an urban site in western region of India. Dust loading and its variability are very high over this semi-arid location. A state-of-the-art ground-based Raman lidar has been used for the study of day-to-day variability in vertical distribution of aerosol loading over Ahmedabad (23.02° N, 72.57° E) from 8 to 11 May 2018. We have done a comprehensive study about vertical profiles of aerosols across two wavelengths recorded simultaneously, namely, 355 nm and 532 nm, over this location. An interesting hump feature has been noted on 9 May at around 18 h (Local Time), with an additional peak at 19 h on 10 May. The loading over this region has more fine-mode aerosols than coarse-mode particles. Further, findings from ground-based lidar have been compared with MACC-II model simulations and Cloud-Aerosol Lidar with Orthogonal Polarization on-board Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observational. Back-trajectory analysis showed majority of the influx came from middle-east, carrying mineral dust and traces of marine aerosols from Arabian Sea, except for 11 May, where low-level dust carrying trajectories and also coarser dust particles were not seen. This type of manifestation has also been observed while classifying aerosols over Ahmedabad using Lidar Depolarization Ratio and Lidar Ratio obtained from Raman Lidar. Fine mode aerosols have been characterized as industrial, vehicular and marine, while coarser as mineral dust and biomass burning. This study focuses on local variation and classification of aerosols based on size and type, which will further help in better estimation of radiative budget and other impacts of aerosols. [ABSTRACT FROM AUTHOR]

This study examined the effect of compost fortified with rock dust on the soil properties, soil microbial activity, and yield and fruit quality in a mature apple orchard from the Jiangsu province of China. The incorporation of rock dust significantly improved the microelement contents of Ca, Mg, Fe, Mn, Zn, B, and Al, but without increasing phytotoxicity of the compost. The fortified compost had higher metabolic activity and functional diversity of microorganisms as determined by the community-level physiological profiling with Biolog EcoPlates. The two-year incorporation of the rock dust compost into a poor-quality soil led to a significant increase in the yield with the increase of 120% and 187% compared to untreated control in 2013 and 2014, respectively. Application of the rock dust compost obviously promoted superoxide dismutase (SOD) activity and concentration of vitamin C in mature apple trees. The beneficial effects coincided with higher microbial activity and shifts in the composition of the soil microbiome. Our results demonstrate that the practice of combining the rock dust-fortified compost with NPK fertilizers provides a cost-effective way of supplying crops with macro-and micronutrients ensuring better vegetative growth and higher yields. [ABSTRACT FROM AUTHOR]

To realize the environmental impacts of mineral dust from different sources, it is necessary to develop aerosol generation systems that can mimic the processes of aerosolization of sediments into dusts under controlled laboratory settings. Current laboratory dust generation systems would benefit from a critical evaluation of the mechanisms by which they generate dust beyond mere resuspension to include natural eolian processes such as saltation/sandblasting. Without realistically generated aerosols, laboratory-measured dust properties may not capture properties relevant to the natural environment. We describe the development of a benchtop system, the Constant Output Dust Generator (CODG), whose design takes into account the dominant natural physical processes of wind erosion and mineral dust production. The CODG's major components include a wrist-action shaker, custom-built flask, dilution drum, cyclone, and neutralizer. A carrier gas provides flow through the system resulting in dust entrainment. We achieved constant output, typically <10% variation in aerosol surface area concentration, for both a commercial standard as well as environmental samples (saline crusts and loose sediments). We find that the composition of aerosols generated from the CODG is consistent with the composition of the parent source material. We further show that our system is suitable for determination of reaction rates on suspended dust aerosols. At similar mechanical energy inputs, it generates sufficient material (particle surface area concentrations between 10−5 − 10−3 cm2 cm−3) for many applications from both loose sandy sediment and cohesive evaporite crusts. The CODG represents a system potentially applicable for numerous applications of dust aerosol research. Copyright © 2021 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Mars atmospheric in-situ resource utilization processes will require dust filtration of large gaseous volumes. An electrostatic precipitator capable of operating in the Martian environment is under development to meet this need. We performed experimentation to aerosolize and inject Martian simulant particles with a representative dust density and size range into the precipitator intake and to measure removal efficiency. The experimental set up added to the existing electrostatic precipitator system included two customized dust particle analyzers, a laser, and optical sensors to measure particle size distribution, particle morphology, and collection efficiency. In this paper, we describe the methods used to determine particle density and collection efficiency using the fine particle analyzers along with the laser extinction method. We also describe the method used to introduce and aerosolize simulant dust particles with the desired size and particle concentration into the precipitator at the required gas flow rates. Results of precipitator dust removal efficiency obtained from the fine particle analyzers and from the laser extinction method are shown along with a description of the assumptions made and the limitations of each method. [ABSTRACT FROM AUTHOR]

The characteristics of dust acoustic solitary waves (DASWs), described by the Zakharov-Kuznetsov equation, have been studied in a five component cometary plasma. Negatively charged dust, positively charged lighter and heavier ions (described by Maxwellian distributions) and two components of electrons (modelled by kappa distributions with different temperatures and spectral indices) constitute the plasma. The system supports rarefactive solitary waves whose amplitude increases when charge variation on the dust particles is considered. We find that the second, superthermal component of electrons has a strong influence on the characteristics of the DASWs: it's amplitude and width decreases with decreasing temperatures and spectral indices, respectively, of the second component of electrons. The amplitude of the DASW, however, increases with increasing heavier ion densities. Correlation of our results with observations at comet Halley is also indicated. [ABSTRACT FROM AUTHOR]

This study used fine and coarse PM concentrator technology in a Mobile Particle Concentrator Platform (MPCP) designed and built to allow the collection of large amounts of ambient PM, enabling time-resolved speciation analysis, which would not be feasible using conventional methods. One hour of sampling yielded sufficient sample loading for trace elemental analysis using X-Ray Fluorescence (XRF). In addition, we developed a novel Road Dust Aerosolizer (RDA) sampler in order to collect PM2.5 and PM10 surface road dust in situ. This sampler aerosolizes dust from the road surface, simulating ambient road dust resuspension, resulting in measured PM composition and size more appropriately (and less labor-intensive) than those obtained from studies using bulk road dust sieved and re-suspended in the laboratory. Overall, our modified fine and coarse particle concentrators yielded good reproducibility between co-located samples and sufficient loading for trace elemental analysis. For particle mass concentration, we observed a relative error of 3% and 4% among pairs of filters for fine and coarse concentrators, respectively; confirming that the mass collected on an unweighted quartz filter in parallel with a Teflon filter will have the same PM mass as the weighed Teflon filter. For samples with elements that are well above the LOD, relative uncertainty values were between 5% and 10% for the fine and 3% and 10% for the coarse. Our results show that the RDA system has an excellent precision for mass and elements as well. The relative error for mass is 7% for PM10 and 3% for PM2.5 within pairs and ranged from 2 to10% for elements. In conclusion, we developed a method for collecting PM10 and PM2.5 near-road air and surface road dust for short durations, which allows investigation of the composition of direct (airborne) and indirect (re-suspended road dust) non-tailpipe vehicular emissions. Implications: The methods we developed in this study allow the collection of one-hour PM10-2.5 and PM2.5–0.2 samples from near-road ambient air at several distances from the same roadway in 1 day, and collection of road dust directly from the road surface, with sufficient loading for trace elemental analysis. This will allow investigation of the composition of direct (airborne) and indirect (re-suspended road dust) vehicular emissions. [ABSTRACT FROM AUTHOR]

Ions enhance the formation rate of atmospheric aerosol particles, which play an important role in Earth's radiative balance. Ion-induced nucleation involves the stepwise accretion of neutral monomers onto a molecular cluster containing an ion, which helps to stabilize the cluster against evaporation. Although theoretical frameworks exist to calculate the collision rate coefficients between neutral molecules and ions, they need to be experimentally confirmed, ideally under atmospherically relevant conditions of around 1000 ion pairs cm−3. Here, in experiments performed under atmospheric conditions in the CERN CLOUD chamber, we have measured the collision rate coefficients between neutral iodic acid (HIO3) monomers and charged iodic acid molecular clusters containing up to 11 iodine atoms. Three methods were analytically derived to calculate ion-polar molecule collision rate coefficients. After evaluation with a kinetic model, the 50% appearance time method is found to be the most robust. The measured collision rate coefficient, averaged over all iodine clusters, is (2.4 ± 0.8)×10−9 cm3 s−1, which is close to the expectation from the surface charge capture theory. [ABSTRACT FROM AUTHOR]

Air filtration to remove viruses is considered for use in the swine industry to reduce epidemic episodes in Canada. The capture efficiencies of commercially available air filters against biological particles (bioaerosols) such as viruses needs to be determined in standardized and controlled conditions such as the ones required by the ASHRAE Standard 52.2. Artificially nebulized viruses may not accurately represent the bioaerosols present in swine buildings as associated viruses are likely to be transported on dust particles. The present study seeks to develop an infectious phages - carrying dust characterized by a similar particle size distribution of bioaerosols in swine buildings. A test duct was used to challenge MERV-16 and antimicrobial filters against the aerosolized infectious phages – dust mixtures (artificial viral aerosols). ISO 12103-1 A3 medium test dust, phages, and sucrose were lyophilized to form dried infectious phages – dust preparations. Observations of TEM imaging and results from Electrical Low Pressure Impactor (ELPI) samplings support MS2 phages were aggregated with dust particles. MS2 genomes were detectable on particles sized from 0.017 to 10 µm. The reduction efficiency of the MERV-16 filter challenged against the artificial viral aerosols was 99.4% for infectious MS2 phages (culture), 99.4% for total MS2 phages (qPCR), and 96.4% for dust. The antimicrobial filters had efficacies of 97.9% (culture), 83.4% (qPCR), and 48.5% (dust). The present study supports the possibility of making an infectious phages - bearing dust for use in environmentally controlled experiments evaluating reduction efficiency of air filters against viruses. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

This paper demonstrates the use of Quantitative Evaluation of Minerals by SCANning electron microscopy (QEMSCAN®), an automated scanning microscopy technique, which combines scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), providing ultra-fast analysis of particle grains at a micron-scale resolution. We evaluate its application in aerosol studies by comparing surface and airborne samples from the Makgadikgadi Pan in Botswana. The playa is a major global dust emitter and its aerosols have a widespread effect on atmospheric, biological and terrestrial processes. Sampling was conducted at a carefully selected surface location and associated BSNE dust trap stack at 0.25, 0.5, 0.85 1.65 meters. The dominant minerals identified here are quartz, halite, thernadite, mica, calcite and feldspar. Surface sample results from QEMSCAN are in line with other forms of elemental and mineralogical analyses. When comparing surface samples with elevated trap samples, we noted a fining and fractionation during grain entrainment, resulting in a compositional shift with height. We also observed some ultra-fine fraction losses from the BSNE traps. Overall, the single location here establishes the link between fluvial playa basin inputs, sediment storage, evaporation products and aeolian losses and outputs from a dry lake surface, not unlike semi-arid evaporative dust sources elsewhere. [ABSTRACT FROM AUTHOR]

Atmospheric dust can play a very important role in the polluted atmosphere. This has a direct impact on human health, global warming, climate change, visibility, precipitation, cloud formation, and so on. To evaluate the atmospheric dustfall rate and their mineralogical aspects, three separate sites were selected, namely mining, suburban, and control for dust sampling. Dustfall samples were collected at monthly intervals from copper and iron mining areas, in Singhbhum, India. The average atmospheric dustfall rate varied from 7.51 to 28.58 g/m2/month, and 7.40 to 26.37 g/m2/month during the summer and winter seasons, respectively, in the copper mining areas. At the same time, an average atmospheric dustfall rate varied from 7.23 to 76.99 g/m2/month during summer season and 6.48 to73.92 g/m2/month during the winter season in the iron mining area. The major minerals identified by X-ray diffraction (XRD) analysis of dustfall samples from copper mining area were quartz, kaolinite, pyrite, albite, and magnesio hornblende. However, in the case of iron mining area, the major minerals found were quartz, cristobalite, hematite, magnetite, biotite, albite, ilmenete, pyrite, rutile, and dolomite. Overall, the intensity of dust pollution is greater in the vicinity of mining and industrial sites of the copper and iron mining areas. Implications: The study has been conducted in the copper and iron mining areas of East and West Singhbhum districts of Jharkhand state, respectively. The aim of the present study was twofold, namely, (i) to evaluate the dustfall rates (ii) and to characterize the mineralogy of atmospheric dust. East and West Singhbhum are the significantly industrialized areas of India known for the mining of copper and iron ores, steel production, power generation, and other related activities. In order to improve local people's living conditions, there is an urgent need for baseline data of dust pollution and its general characteristics based on scientific disclosures to allow policy recommendations and their implementation. Therefore, the study falls within the scope of the journal. The atmospheric dustfall rates were found to be higher during the summer season due to increased dispersion caused by the high wind speed during the summer season. During the winter season, lower rates were observed due to monsoonal rainfall washout and higher relative humidity, which reduces dust resuspension. However, the present study considered the extent of dustfall rates and their mineral characteristics. An immediate need arises to regularly monitor the dust pollution and to implement suitable dust control system like wet dust suppression and airborne dusts capture for dust abatement. [ABSTRACT FROM AUTHOR]

This study describes a significant upgrade to the particulate matter (PM) size disaggregation profile library used for preparing emissions files for the GEM-MACH (Global Environmental Multiscale-Modelling Air-quality and CHemistry) chemical transport model (CTM). This model uses a sectional (bin) approach to represent the PM size distribution, where one configuration employs 12 size bins to disaggregate PM2.5 and PM10 inventory emissions into the first 10 bins ranging from 0.01 to 10.24 μm in diameter. For the size disaggregation step, a small library of three generic PM size disaggregation profiles is currently applied for three broad source categories (area, mobile, and point). However, as might be expected, these generic profiles are not always representative: for example, emissions from two very different area sources ‒ paved road dust and residential wood combustion ‒ are disaggregated using the same generic size distribution profile. In order to improve the current small PM size disaggregation profile library, a comprehensive literature review was conducted: over 100 relevant publications were identified and PM size distribution profiles for 36 different emission source types were selected and compiled. These 36 source-type-specific PM size distribution profiles were then combined based on process type with corresponding PM speciation profiles to create a library of chemically speciated and size-resolved PM disaggregation profiles. This library can now be used by the SMOKE (Sparse Matrix Operator Kernel Emissions) emissions processing system for the 12-bin version of GEM-MACH to perform PM chemical speciation and size allocation in one step. The size-profile data collected and compiled in this study may also be used for emissions processing for other CTMs with a size-resolved representation of PM. Details of the compilation of the 36 PM size disaggregation profiles are discussed, and the differences in processed PM emissions based on the current and updated PM size disaggregation profile libraries are shown. Implications: A new and expanded particulate matter (PM) size disaggregation profile library covering 36 emission source types has been developed based on an extensive literature review. Its use can produce significant changes in the size allocation of bulk PM inventory emissions processed for input to size-resolved PM chemical transport models. Such models are used to predict atmospheric visibility and to simulate the interactions of aerosol particles with atmospheric radiation and with clouds. The use of more accurate, size-resolved primary PM emissions by these models should improve their predictive skill for atmospheric PM processes affecting air quality, meteorology, and climate. [ABSTRACT FROM AUTHOR]

Mineral dust aerosol is present throughout the atmosphere, though the climate impact of this aerosol type is still not well known. One of many factors that contributes to this uncertainty is how water uptake alters the physical and optical character of the aerosol. A sensitive optical technique, cavity ring down spectroscopy, was used to quantify changes in the extinction cross-section with increasing relative humidity for montmorillonite, Na-rich montmorillonite, and illite aerosol. An iterative approach for converting the measured optical extinction enhancement to physical growth factor over increasing relative humidity was employed to quantify the effect of changing both size and refractive index. The method demonstrates an important application of previously retrieved effective refractive indices allowing for the determination of average particle size for the non-spherical particles from simple Mie theory calculations. The changed refractive index and particle size were used to show how these properties combine and interact to alter the distribution between scattering and absorption for the aerosol. The water uptake shifted the calculated single scattering albedo of the aerosol species more toward scattering when both optical and size changes were accounted for, as opposed to just size; limitations on these calculations are discussed. These findings demonstrate the necessity of understanding the effect of optical properties and size together, especially as many climate models do not account for water uptake properties of clay aerosol. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

The analysis of dust collected on the filters installed in the heating, ventilation, and air-conditioning (HVAC) systems, filter forensics, is a useful approach to explore concentration, size distribution, and composition of indoor particles. The extraction of dust from filters represents one of the biggest challenges to obtain accurate results from filter forensics. Although vacuuming is one of the most common dust extraction techniques, it is unclear how efficient it is and whether it provides a representative sample in terms of particle size. In this article, we used a high-capacity vacuum sampler to extract dust from 20 filters artificially loaded with well-characterized test dust as well as from 41 filters naturally loaded in residential HVAC systems. After all extractions, we recovered 0.1–5.5 g and 0.02–11.4 g of dust from the artificially and naturally loaded filters, respectively. These ranges were equivalent to 11.3–52.2% and 1.8–72.9% recovery efficiency, the ratio of dust recovered to the dust loaded in the filters. Multiple extractions were found to be an effective strategy to add to the recovery to enable filter forensics for the detection of multiple analytes. The recovered samples were slightly over-representative of particles greater than 10 µm. Therefore, caution should be taken when applying filter forensics for studying contaminants associated with smaller particles. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Monitoring of airborne PM associated with Saharan dust storms has been implemented in Ile-Ife, Nigeria during characteristic Harmattan weather conditions over southern West Africa. Collected at low flow rates on quartz fiber filters, all samples were equilibrated and gravimetrically analyzed. Particle size was determined through Scanning Electron Microscopy (SEM) coupled with an ISIS X-ray detector. Concentrated organic extracts from the dust-laden filters were analyzed by Gas chromatography/Mass Spectrometry (GC/MS) for the purpose of characterizing polycyclic- and aromatic-hydrocarbon content. Obtained mass concentrations (predominantly in the range 280–450 µg m−3 with the exception of 780 µgm3 recorded on a certain day) were well above the daily limits of the WHO standard. Particles sizes were mostly between 10 and 20 µm with a few below 5 µm on the filters analyzed by SEM, indicating the possibility of Saharan dust with adsorbed fractions being capable of penetrating to the lower lungs. The results from the organic analysis carried out in this study indicated that a number of both aromatic and aliphatic hydrocarbons were adsorbed to the airborne PM collected at Ile-Ife. The most occurring aromatic hydrocarbon was quinoline (MEiQ); a heterocyclic aromatic amine and a member of a family of hydrocarbons known to be mutagenic and carcinogenic. [ABSTRACT FROM AUTHOR]

Potentially toxic elements and particulate matter (PM) in the ecosystem are regarded as extremely hazardous because of their persistence, toxicity and bioaccumulative characteristics. Therefore, present study was conducted to estimate the ecological and human health risks of potentially toxic elements (Cu, Mn, Pb, Cd and Ni) and particle pollution (TSP, PM10 and PM2.5) at 2 and 60 m roadside distance from 15 different sites at dust polluted megacity of Pakistan. The AQI assessments suggested that the majority of sites were found unhealthy for sensitive at 2 and 60 m roadside distance, which reveals that that quality of road pavement and streets are far below than the required standards resulting huge quantity of dust particles suspended in air by natural and anthropogenic activities. The maximum geo-accumulation index (Igeo) values (1.47 and 0.52) and pollution index (PI) values (4.18 and 2.15) were observed for Ni at 2 and 60 m distance away from the muddy edge of the roads. Similarly, maximum contamination factor (CF) values (24.5 and 94.5) and ecological risk index (ERI) values (4.11 and 3.15) were found for Cd at 2 and 60 m. The Igeo and PI indicated that the road dust at a distance of 2 m was relatively more contaminated as compared to 60 m roadside distance. Highest cancer risk (CR) values (2.33 adult and 10.9 for children) were observed for Pb at 2 m, while highest CR values (1.21 for adult and 5.67 for children) at 60 m distance. No probable health risk was observed as the total hazard index (HIexp) of all potentially toxic elements was <1. However, children were appeared to be more susceptible to potentially toxic elements. Based on the results, we believe that the exponential increase in traffic load and industries have aggravated the pollution level and it is expected to be increased in the future. [ABSTRACT FROM AUTHOR]

This paper describes the development of a method that can be used to simulate in a laboratory the effects of air side fouling of condensers from split system air conditioners. The method includes a synthetic fouling agent that realistically mimics field fouling. The fouling agent was developed by considering the fouling materials and effects on heat transfer and air side pressure drop that were measured on a set of condenser coils that had been fouled in situ. The proposed fouling agent matches these effects by combining a fiber component with a particulate component. The particulate component is made from quartz dust that has a particle size distribution based on averages of size distributions in samples collected from condensers in Omaha, NE and Las Vegas, NV. The fouling agent is applied to coils with several different designs, including a range of fin pitches, and plate fin, spine fin, and microchannel configurations. The rates of fouling deposition, as well as the effects of fouling on coil performance, are shown and compared for these coils. [ABSTRACT FROM AUTHOR]

An open source software (Aerosol and Air Quality Research Lab-Aerosol Dynamics Model, AAQRL-ADM) used for aerosol dynamics simulations is developed by including four models: discrete, discrete-sectional, method of moments, and modal. First, the mathematical description of these models as well as the effects of aerosol dynamics available in the software are reviewed, and a modal model is developed to use multiple modes to represent particle size spectrum. Second, the design of a working principle and user graphical interface (GUI) of AAQRL-ADM is described. Third, the models in AAQRL-ADM are validated by investigating the evolution of particle size distribution (PSD) in considering the effects of coagulation, condensation, and nucleation. Next, the trade-off between simulation accuracy and numerical efficiency is discussed for all of the four models, and a guide to choosing the appropriate aerosol dynamic model in practical simulation is presented. Finally, discrete-sectional, moment, and modal models are used to investigate the particle size distribution in a furnace aerosol reactor along a streamline, coupled with the velocity and temperature profiles. AAQRL-ADM is provided free of charge for the use of public researchers. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Snow algae growth and mineral dust deposition are both known to strongly decrease snow albedo. Previous work has shown snow algae growth is enhanced in the presence of trace nutrient-containing minerals. Increased dust deposition with aridification due to climate change may therefore additionally enhance snow algae growth. Here we performed batch growth experiments with a snow alga (Chloromonas brevispina) and bacteria co-culture and the minerals andradite (Ca3.0(Fe0.6,Al0.43)2(SiO4)3), olivine (Mg1.8Fe0.2SiO4), and quartz (SiO2), to observe differences in snow algae attachment to mineral surfaces with differing iron (Fe) contents. In the presence of olivine, which has a low Fe content (∼9%), the number of snow algae on the surface of the olivine decreased with decreasing concentrations of snow algae in the medium. In contrast, in the presence of andradite, which has a higher Fe content (∼16%), the number of snow algae on the surface of andradite remained high even when concentrations of snow algae in the medium were greatly decreased. Additionally, µX-ray Fluorescence (µXRF) measurements indicate greater formation of Fe-containing precipitates on the mineral surfaces in the presence of the snow algae cells than in abiotic controls. These results show that the snow alga both preferentially grows on Fe-rich surfaces and forms Fe-containing precipitates, indicating the presence of a potential positive feedback system that could amplify the effect of dust deposition on snow albedo and therefore climate change. [ABSTRACT FROM AUTHOR]

Particulate Matter (PM) pollution is an alarming environmental problem and one of the most used PM control devices in industry is fabric filter, with a pulse-jet cleaning system. A better understanding of the flow behavior of such pulse-jets is essential to improve cleaning efficiency and diminish dust emissions. Therefore, the present study aims to analyze the flow patterns of the cleaning pulse of an industrial-scale bag filter, with high-pressure and low-pressure systems, using transient three-dimensional CFD simulations. The results show that the center bags in a row take slightly higher shares of air volume and the larger part of it is due to secondary flow. The simulations also give insights into the degree of centralization of the jets: misalignment is progressively reduced along the purge tube, being less pronounced in the high-pressure than in the low-pressure system. Although the mass flow is higher in the high-pressure system, the distribution of the flow among the bags is relatively uniform and similar for both systems. Implications: This work shows, through simulations, that the behaviour of the air pulse during the cleaning is not uniform. There is a variation of the pulse along the duct, due to the movement of the wave that is formed. Besides wave intensity and pressure, the position and shape of the cleaning nozzle also affects the air pulse. [ABSTRACT FROM AUTHOR]

In order to solve the problem of insufficient durability and long-term performance of concrete, the compressive and splitting properties of nano-silicon dioxide modified concrete are analyzed in this study, which provides strong evidence for the synergistic interaction between nano-silicon dioxide modified concrete, fly ash and mineral powder and the improvement of durability. Firstly, ordinary concrete and high-performance concrete are modified and mixed. Then, they are separately mixed with nano-silicon dioxide. Nano-silicon dioxide is mixed with fly ash, and nano-silicon dioxide is mixed with mineral dust. Compressive strength and splitting tensile strength of modified concrete are tested and compared, and mechanical properties of modified concrete are analyzed. The results show that the synergistic effect of nano-silicon dioxide, fly ash and mineral powder on the strength of concrete is remarkable. The maximum increment of compressive strength of modified ordinary concrete is 10Mpa, and that of synergistic modified high-strength concrete is 20 MPa. In addition, a small amount of nano-silicon dioxide can improve the splitting tensile strength of ordinary concrete, but it has no obvious effect on the splitting tensile strength of high-strength concrete. Therefore, the problem of insufficient durability and long-term performance of concrete can be solved to some extent by adding nano-silicon dioxide in concrete according to reasonable proportion. [ABSTRACT FROM AUTHOR]