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Electronic waste stream grows day by day; printed circuit boards are a kind of solid waste that accounts for 6% of electronic waste. When these are discarded, they can cause soil, water, and air contamination; however, if recycled, these can be considered as a secondary source of metals. Physical comminution of printed circuit boards generates particles with sizes smaller than 250 µm, which are typically not included in the recycling process because they are considered as dust and unvaluable; nevertheless, precious and base metals can be found in these particles. The concentration of metals like silver, among others, from these particles can be achieved by reverse froth flotation in a flotation column followed by magnetic separation of the tails products. A mass balance of the flotation column feed, concentrate, and tails indicates that using a pulp modified with 5 ppm methyl isobutyl carbinol plus 5 g/ton oleic acid (both biodegradable reagents), the concentration of the products improved, resulting in recoveries of 86.13 and 13.87% in the concentrate and tails zones, respectively, with a grade of 74.4% in the tails flow. Magnetic separation of the tails product increases slightly the concentration of silver, reaching a silver grade of 74.5%, a recovery amount similar to those obtained employing complex and environmentally unfriendly processes. [ABSTRACT FROM AUTHOR]

This study investigated a new method for controlling the emission of fine particles through heterogeneous condensation. Specifically, the research focuses on the application of single-tower double-cycle desulfurization technology in the wet flue gas desulfurization process. The establishment of a supersaturation environment necessary for heterogeneous condensation was achieved by reducing the temperature of desulfurization slurry in the oxidation zone. Numerical simulations were used to study the distribution of the supersaturation degree and fluid dynamics characteristics in the desulfurization tower after the cooling of desulfurization slurry. Furthermore, the impact of single-tower double-cycle technology on the removal efficiency of fine particles was examined. The results of the numerical simulations indicate that cooling the desulfurization slurry in the absorption zone could establish a supersaturated vapor environment, with the supersaturation degree and region increasing as the slurry temperature decreases. Under typical operating conditions, a temperature drop of approximately 8~10 °C was found to be most suitable for the desulfurization slurry. Moreover, lowering the temperature of the desulfurization slurry in the absorption zone increases the supersaturation degree from 0.93 to 1.85. Additionally, the use of single-tower double-cycle desulfurization technology is shown to significantly enhance the removal efficiency of fine particles, particularly those within the particle size range of 0.1~1 μm. Ultimately, this method could increase the removal efficiency of fine particles from 39.9% to 57.9%. [ABSTRACT FROM AUTHOR]

Residential wood combustion (RWC) is a significant source of gaseous and particulate emissions causing adverse health and environmental effects. Several factors affect emissions, but the effects of the fuel wood species on emissions are currently not well understood. In this study, the Nordic wood species (named BirchA, BirchB, Spruce, SpruceDry, Pine and Alder) were combusted in a modern stove, and the emissions were studied. The lowest emissions were obtained from the combustion of BirchA and the highest from Spruce and Alder. The fine particle mass (PM2.5) was mainly composed of elemental carbon (50–70% of PM2.5), which is typical in modern appliances. The lowest PAH concentrations were measured from BirchA (total PAH 107 µg/m3) and Pine (250 µg/m3). In the ignition batch, the PAH concentration was about 4-fold (416 µg/m3). The PAHs did not correlate with other organic compounds, and thus, volatile organic compounds (VOCs) or organic carbon (OC) concentrations cannot be used as an indicator of PAH emissions. Two birch species from different origins with a similar chemical composition but different density produced partially different emission profiles. This study indicates that emission differences may be due more to the physical properties of the wood and the combustion conditions than to the wood species themselves. [ABSTRACT FROM AUTHOR]

Fine particles (PM2.5) have generally been reported as the major contributor to the adverse health effects of air pollution. Lebanon is characterized by a high density of transport, the production of electricity by generators, and a problem of uncontrolled incineration of household waste. For the purpose of this paper, the physico-chemical properties of fine (PM2.5-0.3) and quasi-ultrafine (PM0.3) particulate matter sampled in Southern Lebanon, were studied. Then, an evaluation and comparison of the toxicity of the different extracted fractions from PM (i.e., native PM2.5-0.3 vs. organic extractable matter fraction (OEM2.5-0.3), and non-extractable matter fraction (NEM2.5-0.3)) was performed. Also, an examination of the toxicity of PM0.3 was conducted indirectly through the evaluation of the OEM0.3 harmfulness. The physico-chemical analysis showed that PM0.3 was much more concentrated than PM2.5-0.3 in organic compounds such as polycyclic aromatic hydrocarbons (PAHs) (28-fold) and their nitrated (N-PAHs, 14-fold) and oxygenated (O-PAHs, 10-fold) derivatives. Normal human bronchial epithelial cells (BEAS-2B) were exposed to PM2.5-0.3, its derived fractions (i.e., OEM2.5-0.3 and NEM2.5-0.3), and OEM0.3 before evaluating the global cytotoxicity, metabolic activation of organic compounds, genotoxicity, and inflammatory response. Different responses were observed depending on the considered fraction of particles. The global cytotoxicity showed a pronounced response related to ATP and LDH activities after exposure to the quasi-ultrafine organic extractable matter fraction (OEM0.3). There was no significant induction of the AhR cell-signaling pathway by NEM2.5-0.3. Despite the apparent difference in the kinetics of induction of the toxicological endpoints under study, OEM0.3 provoked a higher overall cytotoxicity and genotoxicity than OEM2.5-0.3 and total PM2.5-0.3. Taken together, these results clearly showed that the finest particles are more damaging to BEAS-2B cells than PM2.5-0.3 because they are richer in organic compounds, thereby inducing more remarkable toxic effects. [ABSTRACT FROM AUTHOR]

Abstract Background Exposure to high levels of environmental air pollution causes several health outcomes and has been associated with increased mortality, premature mortality, and morbidity. Ambient exposure to PM2.5 is currently considered the leading environmental risk factor globally. A causal relationship between exposure to PM2.5 and the contribution of this exposure to cardiovascular morbidity and mortality was already demonstrated by the American Heart Association. Methods To estimate the burden of mortality attributable to environmental risk factors, a comparative risk assessment was performed, considering a “top-down” approach. This approach uses an existing estimate of mortality of the disease endpoint by all causes as a starting point. A population attributable fraction was calculated for the exposure to PM2.5the overall burden of IHD and stroke was multiplied by the PAF to determine the burden attributable to this risk factor. The avoidable burden was calculated using the potential impact fraction (PIF) and considering the WHO-AQG 2021 as an alternative scenario. Results Between 2011 and 2021, the ambient exposure to PM2.5 resulted in a total of 288,862.7 IHD YLL and a total of 420,432.3 stroke YLL in Portugal. This study found a decreasing trend in the mortality burden attributable to PM2.5 exposure, for both males and females and different age-groups. For different regions of Portugal, the same trend was observed in the last years. The mortality burden attributable to long-term exposure to PM2.5 was mainly concentrated in Lisbon Metropolitan Area, North and Centre. Changes in the exposure limits to the WHO recommended value of exposure (WHO-AQG 2021) have a reduction in the mortality burden due to IHD and stroke attributable to PM2.5 exposure, in Portugal. Conclusion Between 2011 and 2021, approximately 22% and 23% of IHD and stroke deaths were attributable to PM2.5 exposure. Nevertheless, the mortality burden attributable to cardiovascular diseases has been decreasing in last years in Portugal. Our findings provide evidence of the impact of air pollution on human health, which are crucial for decision-making, at the national and regional level.

In response to the issue of small particle size and difficult removal of suspended particles in the mine water of Baorixile open-pit coal mine, this study probed into the optimal parameters of the coagulation and precipitation process through single-factor and orthogonal experiments, and explored the mechanism behind the coagulation of fine particles in mine water.The optimal process parameters for coagulation and precipitation include: 50 mg/L of polyaluminum chloride (PAC), 5.0 mg/L of non-ionic polyacrylamide (NPAM) under 1 minute of rapid stirring (300 r/min), 8 minutes of slow stirring (50 r/min), and 5 minutes of settling.Under these optimum process conditions, the concentration of suspended solids (SS) is 5.0 mg/L with a removal efficiency of 99.1 %.Compared to the sole addition of PAC, the removal efficiency of fine particles below 10 μm increased by 25.9 %.Additionally, theζpotential of the mine water decreased from -40.9 mV to -16.3 mV, indicating that the coagulation mechanism of fine particles is mainly attributed to the adsorption and charge neutralization of PAC and the bridging effect of PAM.

The concentration of heavy metals in soil layers has increased due to the rapid development of the industry. Lead and zinc are two frequent heavy metal contaminants in soil. This paper aims to study the effect of these types of contaminants on different fines, including kaolinite, bentonite, and zeolite mixed with sand. First, mixtures of sand and kaolinite, bentonite, and zeolite were prepared, then they were contaminated by two contaminants of lead and zinc nitrates, separately. Consolidated undrained triaxial tests, Soil Conservation Service (SCS) double hydrometer tests, scanning electron microscope (SEM), Atterberg limits, and pH determination tests were conducted on the soil samples to investigate the changes in the strength and microstructure in the presence of heavy metals. In general, triaxial test results showed that various parameters influence the strength results of these heavy metal-contaminated sandy soil samples such as type, percentage, and structure of the fine portion, type, and concentration of contaminants, bonding mechanism of fine grains, and ion exchange capacity. For instance, in the presence of kaolinite (and kaolinite-zeolite mixtures), contamination with lead decreased the strength of soil samples, but in the soil mixtures containing bentonite (and bentonite-kaolinite mixtures), an opposite trend was seen. The plasticity index of mixtures containing kaolinite and zeolite increased in the presence of heavy metal contaminants, but it decreased when the fine portion of the soil was bentonite. Heavy metal contaminants decreased the pH of all soil mixtures and made them to be acidic. The results of the SCS double hydrometer test and SEM indicated that contaminated kaolinite and zeolite soil mixtures have a dispersed structure, while bentonite soil mixtures are not dispersive. [ABSTRACT FROM AUTHOR]

This paper is the first to examine the operation of the HawkEye satellite in the presence of dust aerosol. The study region is the Black Sea. Dust transport dates were identified using visual inspection of satellite imagery, back-kinematic HYSPLIT trajectory analysis, CALIPSO aerosol stratification and typing maps, and the global forecasting model SILAM. In a comparative analysis of in-situ and satellite measurements of the remote sensing reflectance, an error in the atmospheric correction of HawkEye measurements was found both for a clean atmosphere and in the presence of an absorbing aerosol. It is shown that, on average, the dependence of the atmospheric correction error on wavelength has the form of a power function of the form from λ−3 to λ−9. The largest errors are in the short-wavelength region of the spectrum (412–443 nm) for the dust and dusty marine aerosol domination dates. A comparative analysis of satellite and in situ measurements of the optical characteristics of the atmosphere, namely the AOD and the Ångström parameter, was carried out. It is shown that the aerosol model used by HawkEye underestimates the Angström parameter and, most likely, large errors and outliers in satellite measurements are associated with this. [ABSTRACT FROM AUTHOR]

Bubble columns are used in the mining industry for mineral recovery but are also widely utilized in the chemical and petrochemical industry. The hydrodynamic characteristics of their performance is a field of interest with a number of points, which are nonetheless poorly understood, and a considerable amount of methods have aimed to shed light on the flow regimes that prevail in the columns. The study of the hydrodynamic part of a flotation process should consider characteristics such as air flow, volumetric gas fraction, flow field, and bubble size, along with the mechanical and design factors and pulp properties. The present work aims to elucidate the characteristics of the gas phase of a hybrid flotation system. For this purpose, a hybrid flotation column was designed and constructed and the bubbles size distributions at different radial positions in the flotation column were computed by analyzing high resolution digital images. A patented electrical impedance technique was employed to instantaneously measure the local volumetric gas fraction. Flow dispersion in the column was studied by residence time distributions using conductivity tracers. The experimental results are discussed to comprehend the variation in the gas fraction in the column. In particular, the study showed that the size of the bubbles changed from the center to the walls of the column, and this was observed both radically and vertically. Moreover, the size of the bubbles affected the volume fractions, and no coalescence of the bubbles was observed. Finally, the dispersion of the tracer in the working solution was distributed uniformly in the volume of the column, with a time difference for the four positions of the column. [ABSTRACT FROM AUTHOR]

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Alterations in dopaminergic transmission are associated with neurological disorders, such as depression, autism, and Parkinson's disease. Exposure of rats to ambient fine (FP) or ultrafine (UFP) particles induces oxidative and inflammatory responses in the striatum, a neuronal nucleus with dense dopaminergic innervation and critically involved in the control of motor activity.Objectives: We used an ex vivo system to evaluate the effect of in vivo inhalation exposure to FP and UFP on motor activity and dopaminergic transmission.Materials and Methods: Male adult Wistar rats were exposed to FP, UFP, or filtered air for 8 weeks (subchronic exposure; 5 h/day, 5 days/week) in a particle concentrator. Motor activity was evaluated using the open-field test. Uptake and release of [3H]-dopamine were assessed in striatal synaptosomes, and dopamine D2 receptor (D2R) affinity for dopamine was evaluated by the displacement of [3H]-spiperone binding to striatal membranes.Results: Exposure to FP or UFP significantly reduced spontaneous motor activity (ambulatory distance: FP -25%, UFP -32%; ambulatory time: FP -24%, UFP -22%; ambulatory episodes: FP -22%, UFP -30%), decreased [3H]-dopamine uptake (FP -18%, UFP -24%), and increased, although not significantly, [3H]-dopamine release (113.3 ± 16.3 and 138.6 ± 17.3%). Neither FP nor UFP exposure affected D2R density or affinity for dopamine.Conclusions: These results indicate that exposure to ambient particulate matter reduces locomotion in rats, which could be related to altered striatal dopaminergic transmission: UFP was more potent than FP. Our results contribute to the evidence linking environmental factors to changes in brain function that could turn into neurological and psychiatric disorders.HIGHLIGHTSYoung adult rats were exposed to fine (FP) or ultrafine (UFP) particles for 40 days.Exposure to FP or UFP reduced motor activity.Exposure to FP or UFP reduced dopamine uptake by striatal synaptosomes.Neither D2R density or affinity for dopamine was affected by FP or UFP.UFP was more potent than FP to exert the effects reported.

This study evaluates low-cost sensors (LCSs) for measuring coarse and fine particulate matter (PM) to clarify and measure air pollution. LCSs monitored PM10, PM2.5 (fine particulates), and PM1.0 concentrations at four sites in Samutprakarn, Thailand from December 2021 to April 2022. Average daily PM10, PM2.5, and PM1.0 concentrations at the monitoring locations were 53–79, 34–45, and 31–43 μg/m3, respectively. In December 2021, the monitoring station had a daily PM2.5 value above 100 μg/m3, indicating haze occurrences. However, the monitoring site's daily PM10 and PM1.0 concentrations did not surpass Thailand's ambient air quality threshold. We also measured and calibrated comparative particulate matter concentrations from LCSs and a tapered element oscillating microbalance (TEOM) monitor (Pollution Control Department (PCD) standard analytical method). PM2.5 concentrations from the LCSs were lower than TEOM, but the difference was not statistically significant. The PM2.5 monitoring station provided near-real-time air quality data for health risk reduction, especially when PM levels were high. Based on this study, authorities and local agencies may consider improving air quality regulation in Samutprakan, focusing on suburban PM2.5 air pollution. [ABSTRACT FROM AUTHOR]

The adhesion of Martian surface dust to solar panels has been a longstanding challenge for Mars mission researchers. Anti-dust coatings have been developed to deter the adsorption of dust particles onto these solar panels. However, current ground testing methods struggle to accurately verify and assess the coating's ability to inhibit dust particle adsorption. Consequently, this paper introduces a computational model capable of calculating the contact force between fine particles and the coated surface. This model, grounded in the classical adhesive elastic interactions paradigm, establishes a normal force solution by approximating the pressure distribution on the contact area between the sphere and the coating, subsequently computing the composite force acting on the particle. Utilizing the API module of the EDEM simulation platform, we conducted simulations of the motion of fine particles on both smooth and coated plates. The results reveal that van der Waals forces are more prominent for light-mass particles, and the application of the coating can diminish the pull of these forces, facilitating easier detachment of dust particles from the plate surface. [ABSTRACT FROM AUTHOR]

In this paper, the CFD-DEM coupling method was utilized to study the water cleaning and regeneration process of fibrous filter material. The effects of cleaning flow rate, time and adhesion force on the particle removal process were simulated. The results showed that the particle removal rate had a diminishing marginal effect with the increasing of cleaning flow rate. More than 80% of the particles were removed in the initial period, and then tended to stabilize. The higher the flow rate, the shorter the time needed to achieve stability. For G4 filter material, the function between the particle removal rate and the cleaning flow rate and time was given, and the best cleaning flow rate was 1.2 m/s while the cleaning time was 30 seconds. The surface energy of the fibers plays a dominant role in the cleaning process, and the reduction 1/4 of the surface energy of the particles can effectively improve the cleaning and regeneration performance [ABSTRACT FROM AUTHOR]

This work is aimed at the analysis of the development of flotation technology by applying carrier minerals. Based on the concepts of continuum mechanics, a theoretical analysis of the influence of the carrier minerals (wall) on the motion of a single solid particle is provided, taking into account their hydrodynamic interaction (in the case of low Reynolds numbers). A correction was obtained in the form of a ratio of the particle size to its distance from the wall to take into account the influence of the wall on the hydrodynamic force acting on the particle. The influence of the wall is manifested through a rapid approximation of the liquid vortex flow in the gap between the solid wall and the particle to the steady-state mode, accompanied by the suppression of the transverse movement of particles. When the liquid slides along a wall-mounted gas–liquid layer with a reduced viscosity, the liquid flow increases in the interfacial gap, which can be analyzed by a dimensionless correction that includes values describing the properties of a continuous medium (dynamic viscosity) and a disperse phase (geometric particle size). The reason for the decrease in the induction time when gold grains adhere to each other is assumed to be due to the forces of hydrophobic attraction (when the grains have a mirror-smooth surface) and the sliding of the flow along the hydrophobic surface of the particles along the gas layer (when the grains have a rough surface). When polydisperse particles are aggregated, the threshold energy of the fast coagulation was established to be lower than that arising during the interaction of monodisperse particles, whose aggregation requires a large depth of the potential pit. Performing natural experiments on the ore using a rougher concentrate as a carrier material showed that the concentrate yield decreases by 20.52% rel. In the second case, the gold extraction was higher by 4.69% abs. While maintaining the achieved level of gold extraction, the double mixing of the rougher concentrate and the initial feed increased the gold content in the rougher concentrate from 4.97 to 6.29 g/t. [ABSTRACT FROM AUTHOR]

To accurately evaluate the size and distribution characteristics of the emission particles exhausted from in-use motor vehicle engines, we independently developed a condensation particle counter (CPC) known as BHCPC. It was calibrated by conducting the calibration procedures stated in the International Standard ISO 27981. After calibration, we conducted on-site measurements and offline sampling analysis of soot particles exhausted from different engines at a motor vehicle inspection center. The calibration results show that the detection efficiency is 90% when the particle diameter is 20.6 nm and the startup response time of the instrument is 3.53 s. The experiment results show that the self-developed BHCPC demonstrates good consistency in measuring particle-number concentration (PNC) in motor vehicle exhaust, with significant count fluctuations only occurring when PNC is higher than 25,000 P/cc. Under idle conditions, motor vehicles compliant with China VI emission regulations exhibit markedly lower exhaust emission PNC compared to those adhering to China IV emission regulations. Moreover, the results obtained from the offline electron microscope analysis show that fuel content in particle samples significantly decreases as engine speed increases, and a similar variation was also found in particle size. The micro-characteristics of the particle can give potential support to the combustion diagnostics. [ABSTRACT FROM AUTHOR]

Abstract Atmospheric particles have been significantly affecting urban air quality and urban-oriented living in an increasing share of the population in Bangladesh. This study assessed the concentration of PM1.0, PM2.5, and PM10 in Khulna, one of the largest cities in Bangladesh located near the Bay of Bengal. The maximum average concentrations were recorded 415 ± 184.01 µg/m3 for PM10, 302 ± 109.89 µg/m3 for PM2.5, and 143 ± 45.05 µg/m3 for PM1.0. These values are several times higher than the World Health Organization air quality standard and Bangladesh National Ambient Air Quality Standard. According to the size and fractional distribution of PM, most of the monitoring locations were dominated by fine particles. Carcinogenic and non-carcinogenic risks due to exposure to ambient PM1.0, PM2.5 and PM10 were also quantified to illustrate the relevant potential human health risks. The excess lifetime cancer risk (ELCR) values of PM1.0 ranged from 8.6E0–4 to 6.0E–07 and PM2.5 varied between 8.6E–04 and 6.0E–07 exceeded the allowable limit at every location indicating the potential cancer-developing risk to the urban population. The health quotient (HQ) values also crossed the least permissible value at most of the locations depicting strong non-carcinogenic risks. Average HQ values of PM2.5 varied from 1.07 to 20.13 while PM10 ranged from 0.44 to 8.3. This research revealed children and elderly people as the most vulnerable age groups with the highest carcinogenic risks through exposure to atmospheric PM in Khulna city. Therefore, air pollution reduction plans and risk mitigation strategies should be developed and implemented by the government authorities. Graphical Abstract

slime water generally contains a large number of highly dispersed suspended particles, making solid-liquid separation difficult. Strengthening fluid mixing and particle collision by regulating turbulence is an effective way to achieve solid-liquid separation. Particle collision flocculation mostly occurs in turbulent environments where the motion of fine particles is strongly influenced by the turbulent minimum vortex scale. In this study, turbulent vortices are modulated by impinging flows to enhance the mixing of two different density suspensions and the collision of fine particles in the suspension. Two different solution models were used to simulate the mixing condition of the suspension and the distribution of the particles in the mixing drum in three dimensions. The water phase entering the mixing drum was considered as a continuous phase and the solid particles were considered as a continuous phase (suspension) or a secondary discrete phase (particles). The effects of different inlet fluid velocity ratios at different feed densities on the turbulent characteristic parameters and particle distribution in the mixing drum were analyzed. The results of the study show that the impact flow formed by the jets colliding vertically with each other can induce turbulent macro-vortices such as hairpin vortices, spanwise vortices and axial vortices. The velocity of particles moving in the turbulent macro-vortex is in the following order: Large particle size and density > Large particle size and small density > Small particle size and high density > Small particle size and density. The interaction between vortex and vortex and between vortex and the main fluid significantly increases the turbulent kinetic energy and decreases the vortex scale, resulting in a minimum scale vortex that is conducive to particle coalescence and collision; the minimum vortex scale generated in the flow field in the mixing drum is mainly smaller than the average minimum vortex scale. The minimum vortex scale tends to increase when the inlet flow rate and flow rate ratio increase from 1.258:1.87 to 1.882:1.258, independent of the inlet density. When the flow rate ratio is similar, the minimum vortex scale decreases only when the flow rate increases. An appropriate increase in the ratio of the upper and side feed flow rates helps fluid mixing and particle aggregation and collision, and the mixing density, apparent viscosity and particle coalescence are all optimal when the ratio of the upper and side feed flow rates is between 1.40 and 1.50. In addition, at the same flow rate ratio, the mixing uniformity and mixing strength are better than the case where the upper inlet feed density is greater than the side inlet feed density, which is more conducive to fluid mixing and particle collision. The study promotes slime water mixing and fine particle coalescence in mixing drums through the regulation of fluid hydraulic conditions, providing a new way of thinking about how to enhance the liquid-liquid mixing and solid-liquid separation process.

Electronic waste stream grows day by day; printed circuit boards are a kind of solid waste that accounts for 6% of electronic waste. When these are discarded, they can cause soil, water, and air contamination; however, if recycled, these can be considered as a secondary source of metals. Physical comminution of printed circuit boards generates particles with sizes smaller than 250 µm, which are typically not included in the recycling process because they are considered as dust and unvaluable; nevertheless, precious and base metals can be found in these particles. The concentration of metals like silver, among others, from these particles can be achieved by reverse froth flotation in a flotation column followed by magnetic separation of the tails products. A mass balance of the flotation column feed, concentrate, and tails indicates that using a pulp modified with 5 ppm methyl isobutyl carbinol plus 5 g/ton oleic acid (both biodegradable reagents), the concentration of the products improved, resulting in recoveries of 86.13 and 13.87% in the concentrate and tails zones, respectively, with a grade of 74.4% in the tails flow. Magnetic separation of the tails product increases slightly the concentration of silver, reaching a silver grade of 74.5%, a recovery amount similar to those obtained employing complex and environmentally unfriendly processes.

Fine particles (PM2.5) have generally been reported as the major contributor to the adverse health effects of air pollution. Lebanon is characterized by a high density of transport, the production of electricity by generators, and a problem of uncontrolled incineration of household waste. For the purpose of this paper, the physico-chemical properties of fine (PM2.5-0.3) and quasi-ultrafine (PM0.3) particulate matter sampled in Southern Lebanon, were studied. Then, an evaluation and comparison of the toxicity of the different extracted fractions from PM (i.e., native PM2.5-0.3 vs. organic extractable matter fraction (OEM2.5-0.3), and non-extractable matter fraction (NEM2.5-0.3)) was performed. Also, an examination of the toxicity of PM0.3 was conducted indirectly through the evaluation of the OEM0.3 harmfulness. The physico-chemical analysis showed that PM0.3 was much more concentrated than PM2.5-0.3 in organic compounds such as polycyclic aromatic hydrocarbons (PAHs) (28-fold) and their nitrated (N-PAHs, 14-fold) and oxygenated (O-PAHs, 10-fold) derivatives. Normal human bronchial epithelial cells (BEAS-2B) were exposed to PM2.5-0.3, its derived fractions (i.e., OEM2.5-0.3 and NEM2.5-0.3), and OEM0.3 before evaluating the global cytotoxicity, metabolic activation of organic compounds, genotoxicity, and inflammatory response. Different responses were observed depending on the considered fraction of particles. The global cytotoxicity showed a pronounced response related to ATP and LDH activities after exposure to the quasi-ultrafine organic extractable matter fraction (OEM0.3). There was no significant induction of the AhR cell-signaling pathway by NEM2.5-0.3. Despite the apparent difference in the kinetics of induction of the toxicological endpoints under study, OEM0.3 provoked a higher overall cytotoxicity and genotoxicity than OEM2.5-0.3 and total PM2.5-0.3. Taken together, these results clearly showed that the finest particles are more damaging to BEAS-2B cells than PM2.5-0.3 because they are richer in organic compounds, thereby inducing more remarkable toxic effects.

Residential wood combustion (RWC) is a significant source of gaseous and particulate emissions causing adverse health and environmental effects. Several factors affect emissions, but the effects of the fuel wood species on emissions are currently not well understood. In this study, the Nordic wood species (named BirchA, BirchB, Spruce, SpruceDry, Pine and Alder) were combusted in a modern stove, and the emissions were studied. The lowest emissions were obtained from the combustion of BirchA and the highest from Spruce and Alder. The fine particle mass (PM2.5) was mainly composed of elemental carbon (50–70% of PM2.5), which is typical in modern appliances. The lowest PAH concentrations were measured from BirchA (total PAH 107 µg/m3) and Pine (250 µg/m3). In the ignition batch, the PAH concentration was about 4-fold (416 µg/m3). The PAHs did not correlate with other organic compounds, and thus, volatile organic compounds (VOCs) or organic carbon (OC) concentrations cannot be used as an indicator of PAH emissions. Two birch species from different origins with a similar chemical composition but different density produced partially different emission profiles. This study indicates that emission differences may be due more to the physical properties of the wood and the combustion conditions than to the wood species themselves.

Atmospheric particles have been significantly affecting urban air quality and urban-oriented living in an increasing share of the population in Bangladesh. This study assessed the concentration of PM1.0, PM2.5, and PM10 in Khulna, one of the largest cities in Bangladesh located near the Bay of Bengal. The maximum average concentrations were recorded 415 ± 184.01 µg/m3 for PM10, 302 ± 109.89 µg/m3 for PM2.5, and 143 ± 45.05 µg/m3 for PM1.0. These values are several times higher than the World Health Organization air quality standard and Bangladesh National Ambient Air Quality Standard. According to the size and fractional distribution of PM, most of the monitoring locations were dominated by fine particles. Carcinogenic and non-carcinogenic risks due to exposure to ambient PM1.0, PM2.5 and PM10 were also quantified to illustrate the relevant potential human health risks. The excess lifetime cancer risk (ELCR) values of PM1.0 ranged from 8.6E0–4 to 6.0E–07 and PM2.5 varied between 8.6E–04 and 6.0E–07 exceeded the allowable limit at every location indicating the potential cancer-developing risk to the urban population. The health quotient (HQ) values also crossed the least permissible value at most of the locations depicting strong non-carcinogenic risks. Average HQ values of PM2.5 varied from 1.07 to 20.13 while PM10 ranged from 0.44 to 8.3. This research revealed children and elderly people as the most vulnerable age groups with the highest carcinogenic risks through exposure to atmospheric PM in Khulna city. Therefore, air pollution reduction plans and risk mitigation strategies should be developed and implemented by the government authorities. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate atmospheric optical characteristics over the Gorky and Cheboksary Reservoirs and their multi-scale temporal variations to obtain the background characteristics and to identify events involving the transfer of absorbing aerosol to the studied region in 2022–2023. The region is located at a considerable distance (500 km) from the nearest AERONET station; therefore, previous atmospheric data were not available. As a solution, the in situ self-measured aerosol optical depth (AOD) and Angström exponent, as well as satellite products (MAIAC and CALIPSO) for MODIS data, were used. This allowed us to set background values of an AOD of 0.11 at a wavelength of 500 nm and an Angström exponent of 1.2, against their maximum values of 0.38 and 2.5, respectively. To explain these variations, the registered conditions and the microstructure of the dust aerosol over the studied region are presented. For days with background values, the analysis of the particle size distribution data did not show a predominance of any particle size. The optical properties of a smoke aerosol in an atmospheric column are described, and an analysis of the dynamics of particle size variability is presented. A comparative analysis of the optical characteristics of atmospheric aerosol over the Gorky and Cheboksary Reservoirs using in situ and MODIS products was carried out. [ABSTRACT FROM AUTHOR]

The impact of incense burning on ambient air quality was investigated by measuring the concentrations of fine particles (PM2.5), elemental carbon (EC), organic carbon (OC), and their oxidative potential (OP) at three temple premises in Kathmandu Valley, Nepal. These temples, namely, Bajrabarahi, Bagalamukhi, and Bhadrakali, are located in three distinct environments: forest, residential, and roadside, respectively. During the incense burning event days, the PM2.5 concentration at Bhadrakali (431.4 μgm−3) was significantly higher than that measured at the Bagalamukhi (135.2 μgm−3) and Bajrabarahi (84.7 μgm−3) temple premises. This observation is consistent with the fact that Bhadrakali Temple had the highest intensity of incense burning. Additionally, the temple premises were also influenced by vehicular emissions from transportation facilities. Carbonaceous aerosols significantly increased during incense burning events, indicating that incense burning contributes significantly to the formation of primary and secondary OC. Moreover, the OP of PM2.5 during the incense burning event days was higher compared to non-event days (p < 0.05), suggesting an elevated health risk due to the increased concentration and toxicity of fine particles. These findings highlight the substantial impact of incense burning on air quality in temple premises, emphasizing the need to implement effective strategies to mitigate the associated health risks. [ABSTRACT FROM AUTHOR]

Recent studies in the flotation of fine particles have necessitated new techniques and analyses for developing various strategies. Particularly, the improvements in flotation chemistry including the selection of the type of frother, collector, and other reagents have become very significant. In this study, the effect of different commercial polypropylene glycol frothers (PPG200, 400, and 600) in the presence of dodecylammonium hydrochloride (DAH) was investigated for their contribution to flotation recoveries and bubble–particle attachment time values of fine quartz minerals. Zeta potential measurements with DAH were also carried out as a function of pH and reagent concentration to justify the effect of collector usage alone on the charge of particles. A linear increase in flotation recoveries against collector concentration, e.g., 7.4% recovery at 1 × 10−5 mol/L DAH and 65.4% recovery at 1 × 10−3 mol/L DAH, was obtained. In this context, the contribution of frothers was particularly important in that a recovery of 15.91% in the absence of the frother and a modest increase to 19.70% was obtained upon the addition of PPG600 at its critical coalescence concentration (CCC) of 3 ppm. Finally, a strong correlation was found between the bubble–particle attachment time and flotation recovery as a function of collector concentration (lowest attachment time vs. highest flotation recovery). The latter correlation is very promising because bubble attachment time leads to various micro-mechanisms in flotation including bubble film thinning, bubble rupture, and induction time, and consequently, frother efficiency in the presence and absence of a collector. As a result, the experimental findings were gathered to achieve a consistent base for further fundamental studies on the application of the synergistic effect of frothers and collectors in the flotation of fine particles. [ABSTRACT FROM AUTHOR]

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Toxicological data and exposure levels of fine particulate matters (PM2.5) are necessary to better understand their health effects. Simultaneous measurements of PM2.5 oxidative potential (OP) and cell toxicity in urban areas (Beijing, China and Gwangju, Korea) reveal their dependence on chemical composition. Notably, acids (Polar), benzocarboxylic acids, and Pb were the chemical components that affected both OP and cell toxicity. OP varied more significantly among different locations and seasons (winter and summer) than cell toxicity. Using the measured OP, cell toxicity, and PM2.5 concentration, a health index was developed to better assess the potential health effects of PM2.5. The health index was related to the sources of PM2.5 derived from the measured chemical components. The contributions of secondary organic aerosols and dust to the proposed health index were more significant than their contributions to PM2.5 mass. The developed regression equation was used to predict the health effect of PM2.5 without further toxicity measurements. This new index could be a valuable health metric that provides information beyond just the PM2.5 concentration level.

Introduction: Fine particulate matter (PM2.5) pollution is a global public health concern, particularly in arid and semi-arid regions that experience dust events. Exposure to PM2.5 has been associated with various short- and long-term health effects, which can be attributed to the composition of the fine particles. This study aimed to assess the concentration of bacteria and fungi in PM2.5 in the air of Isfahan, Iran which experiences air pollution.Methods: A total of thirty-nine PM2.5 samples were collected over 1 year. Bacterial and fungal concentrations associated with PM2.5 were measured using both culture-based method and real-time polymerase chain reaction (PCR).Results: The average concentration of PM2.5 was found to be 56 μg m−3, with many samples exceeding the recommended limit of 15 μg m−3 set by the World Health Organization for PM2.5 in ambient air. The mean culturable bacterial and fungal concentrations were 39 and 4 CFU m−3, respectively which showed a significant difference compared to the results obtained through real-time PCR. No significant correlation was found between the levels of bacterial and fungal cells and PM2.5 concentrations. The dominant phyla found in PM2.5 were Firmicutes and Actinobacteria, while Proteobacteria as Gram-negative bacteria were rarely detected.Discussion: The findings suggest that the climate conditions in Isfahan, characterized by its semi-arid nature with low humidity content, influences the activity and viability of microbial populations, resulting in low concentrations of bioaerosols in PM2.5. Furthermore, it seems that desert dust events do not contribute to increasing the potential health risks associated with bacterial and fungal bioaerosols in PM2.5.

This study investigated a new method for controlling the emission of fine particles through heterogeneous condensation. Specifically, the research focuses on the application of single-tower double-cycle desulfurization technology in the wet flue gas desulfurization process. The establishment of a supersaturation environment necessary for heterogeneous condensation was achieved by reducing the temperature of desulfurization slurry in the oxidation zone. Numerical simulations were used to study the distribution of the supersaturation degree and fluid dynamics characteristics in the desulfurization tower after the cooling of desulfurization slurry. Furthermore, the impact of single-tower double-cycle technology on the removal efficiency of fine particles was examined. The results of the numerical simulations indicate that cooling the desulfurization slurry in the absorption zone could establish a supersaturated vapor environment, with the supersaturation degree and region increasing as the slurry temperature decreases. Under typical operating conditions, a temperature drop of approximately 8~10 °C was found to be most suitable for the desulfurization slurry. Moreover, lowering the temperature of the desulfurization slurry in the absorption zone increases the supersaturation degree from 0.93 to 1.85. Additionally, the use of single-tower double-cycle desulfurization technology is shown to significantly enhance the removal efficiency of fine particles, particularly those within the particle size range of 0.1~1 μm. Ultimately, this method could increase the removal efficiency of fine particles from 39.9% to 57.9%.

This paper is the first to examine the operation of the HawkEye satellite in the presence of dust aerosol. The study region is the Black Sea. Dust transport dates were identified using visual inspection of satellite imagery, back-kinematic HYSPLIT trajectory analysis, CALIPSO aerosol stratification and typing maps, and the global forecasting model SILAM. In a comparative analysis of in-situ and satellite measurements of the remote sensing reflectance, an error in the atmospheric correction of HawkEye measurements was found both for a clean atmosphere and in the presence of an absorbing aerosol. It is shown that, on average, the dependence of the atmospheric correction error on wavelength has the form of a power function of the form from λ−3 to λ−9. The largest errors are in the short-wavelength region of the spectrum (412–443 nm) for the dust and dusty marine aerosol domination dates. A comparative analysis of satellite and in situ measurements of the optical characteristics of the atmosphere, namely the AOD and the Ångström parameter, was carried out. It is shown that the aerosol model used by HawkEye underestimates the Angström parameter and, most likely, large errors and outliers in satellite measurements are associated with this.

Objective: To examine the distribution and the trend of airborne particles and bio-aerosol concentration in pediatric intensive care units (PICUs) in two tertiary care hospitals with different ventilation setting. Methods: Hospitals A but not B is provided with a central HEPA filter. PICUs in both hospitals were categorized into protective environment (PE) with room HEPA filter, semi-protective environment (SPE) with portable air-purifier, and non-protective environment (NPE) with neither system. Fine particles (≤ 2.5 µm) and coarse particles (≤ 10.0 µm) were obtained using optical particle counter (Lighthouse Handheld 3016) and total bacterial (TBC) and fungal (TFC) counts were obtained using Andersen air sampler. Results: Hospital B had significantly higher levels of fine and coarse particles (in all room), TBC (in PE), but not TFC compared with matched rooms in hospital A. In hospital B, the levels of fine particles, coarse particles, and TBC were lowest in SPE (p

Low-cost Particulate Matter (PM) sensors offer an excellent opportunity to improve our knowledge about this type of pollution. Their size and cost, which support multi-node network deployment, along with their temporal resolution, enable them to report fine spatio-temporal resolution for a given area. These sensors have known issues across performance metrics. Generally, the literature focuses on the PM mass concentration reported by these sensors, but some models of sensors also report Particle Number Concentrations (PNCs) segregated into different PM size ranges. In this study, eight units each of Alphasense OPC-R1, Plantower PMS5003 and Sensirion SPS30 have been exposed, under controlled conditions, to short-lived peaks of PM generated using two different combustion sources of PM, exposing the sensors' to different particle size distributions to quantify and better understand the low-cost sensors performance across a range of relevant environmental ranges. The PNCs reported by the sensors were analysed to characterise sensor-reported particle size distribution, to determine whether sensor-reported PNCs can follow the transient variations of PM observed by the reference instruments and to determine the relative impact of different variables on the performances of the sensors. This study shows that the Alphasense OPC-R1 reported at least five size ranges independently from each other, that the Sensirion SPS30 reported two size ranges independently from each other and that all the size ranges reported by the Plantower PMS5003 were not independent of each other. It demonstrates that all sensors tested here could track the fine temporal variation of PNCs, that the Alphasense OPC-R1 could closely follow the variations of size distribution between the two sources of PM, and it shows that particle size distribution and composition are more impactful on sensor measurements than relative humidity. [ABSTRACT FROM AUTHOR]

This paper analyses the basic obstacles preventing the fine particles from floating and suggests solutions for the wetting zone between the bubble and the particle during their collision. It has been shown in our recent paper that the basic problem of fine particle flotation is not the low frequency of collisions with the bubbles, but it consists of the efficiency of these collisions. Moreover, there exists a thermodynamic lower size limit for flotation of fine hydrophobized particles in the sub-micron range, and it is weakly dependent on the size of the bubbles. It was shown that fast flotation with high recovery of fine particles can be achieved by means of: (i) electrostatic attraction between particles and bubbles; (ii) a significant increase in the level of their hydrophobicity; (iii) existence of fine bubbles in the flotation cell. It was shown as well that the drainage of the wetting film between bubbles and particles is unimportant, but the deformation of the bubble by the particle during their clash plays a major role in its rupturing. Electrostatic attraction between bubbles and fine silica particles was achieved with hexylamine. It causes a moderate increase of their hydrophobicity from contact angle = 39.5° ± 2.5° to contact angle = 51.7° ± 7.5° and gave almost 90% recovery within 2 min. Unfortunately, the selectivity of this collector is unsatisfactory if the fine silica particles are mixed with fine magnesite particles. It was shown that even being hydrophilic, the recovery of fine particles can jump to almost 50% if strong electrostatic attraction with the bubbles exists. It was demonstrated as well with the collector hexamethyldisilazane causes significant increase of the hydrophobicity of the fine silica particles (contact angle ≈ 90°) results in skin flotation with 100% recovery when alone and 97% recovery when being mixed with fine magnesite particles (51/49). A new collector significantly increasing the hydrophobicity of magnesite fine particles was tested (disodium dodecyl phosphate) resulting in 89% recovery of fine magnesite particles alone and about 98% recovery in a mixture with fine silica particles. [ABSTRACT FROM AUTHOR]

Carrier flotation is a technique that can recover fine particles by using coarse carrier particles during the flotation process. In heterogeneous carrier flotation, coarse mineral particles of different minerals are used as carriers to recover fine mineral particles. By using Cu2+-treated pyrite particles as carriers, fine chalcopyrite particles recovery could be improved. However, a disadvantage of this heterogeneous carrier flotation is that it requires a post-flotation separation process to improve the grade of the final Cu concentrate. This study tested mechanical and chemical treatments to detach finely ground chalcopyrite (D50~3.5 µm) particles from Cu2+-treated coarse pyrite particles (−125 + 106 µm) after flotation. The results showed that the ultrasonic treatment was not effective to detach chalcopyrite fines from Cu2+-treated pyrite particles. However, acid treatment was effective to detach chalcopyrite fines from coarse pyrite particles. At pH 2, approximately 96% of chalcopyrite fines were detached from coarse Cu2+-treated pyrite particles. The acid treatment of flotation froth (mixture of chalcopyrite fines and Cu2+-treated pyrite particles) decomposed the collector KAX (potassium amyl xanthate) and dissolved the Cu precipitates adsorbed on the pyrite surface. This weakened the hydrophobic attraction force between the chalcopyrite fines and coarse pyrite particles, thus promoting the detachment of chalcopyrite fines from Cu2+-treated coarse pyrite particles. [ABSTRACT FROM AUTHOR]

The froth flotation technique can be considered one of the most efficient methods for the separation of minerals. Prior to utilizing any physicochemical separation method, the size of the mined ore must be decreased to facilitate the release of the valuable materials. This practice, along with the increased exploitation of ores that carry fine mineral particles caused the production of fine and ultrafine particles which are difficult to recover with classical enrichment methods, due to their different characteristics compared to coarser particles. It is established that fine and ultrafine particles are difficult to float, leading to losses of valuable minerals, mainly due to their low collision efficiency with bubbles. Moreover, fine particles require higher reagent consumption due to the fact that have a higher specific area, and finally, their flotation is limited by low kinetic energy. Flotation of fines can be enhanced by either decreasing bubble diameter or increasing their apparent size, or moreover, by enhancing the collector's adsorption (their hydrophobic behavior) using alternative reagents (non-ionic co-collectors). In the present research, flotation experiments on a hybrid electrolytic flotation column that can produce microbubbles (−50 μm), were carried out for recovering fine magnesite (−25 μm) particles. In addition, the synergistic effect of anionic/non-ionic collectors were studied for the enhancement of fines recovery. Experimental flotation results so far designate the enhancement of fine magnesite particle recovery by approximately 8% with the addition of microbubbles. Finally, the synergistic effect of anionic/non-anionic collectors led to the improvement of flotation recovery by almost 12%. [ABSTRACT FROM AUTHOR]

The chemical composition and size distribution of particulate matter produced at broiler poultry houses is not well understood, so this is a novel study to understand the particulate size distributions at a poultry house as well as the ionic composition of the particulate matter using real-time methods. Two optical particle counters provided particle size distributions inside and outside the house. An ambient ion monitor and a particle-in-liquid sampler analyzed the ionic chemical composition of the particulate matter in the house while a scanning mobility particle sizer provided size information in the nanoparticle range. Ammonia concentrations in the house were measured using a chemical sensor. Ammonia concentrations in the house were consistently in the lower part of the per million range 2–20 ppm. The optical particle counter and ion chromatography measurements both showed a strong diurnal variation of particulate matter concentration in the house throughout the study, associated with the lights being on and animal activity. Particulate mass concentration inside the house was dominated by coarse mode particles as opposed to the outdoor sampler which showed much smaller sizes. A few new particle formation and growth events were observed in the house. Ionic constituents detected by chromatography made up a small fraction of the overall mass concentration. The composition of the ionic constituents was similar for most of the study with typical ions being ammonium, sodium, potassium, chloride, sulfate, nitrate, nitrite, phosphate, and several carboxylates (formate, acetate, propionate, and butyrate.) At the end of the study, bromide was also detected during the last several days. Overall, we determined that the ionic components of the particulate matter formed through secondary particle formation was small, but also that some ionic constituents can be associated with management practices. [ABSTRACT FROM AUTHOR]

Bubble columns are used in the mining industry for mineral recovery but are also widely utilized in the chemical and petrochemical industry. The hydrodynamic characteristics of their performance is a field of interest with a number of points, which are nonetheless poorly understood, and a considerable amount of methods have aimed to shed light on the flow regimes that prevail in the columns. The study of the hydrodynamic part of a flotation process should consider characteristics such as air flow, volumetric gas fraction, flow field, and bubble size, along with the mechanical and design factors and pulp properties. The present work aims to elucidate the characteristics of the gas phase of a hybrid flotation system. For this purpose, a hybrid flotation column was designed and constructed and the bubbles size distributions at different radial positions in the flotation column were computed by analyzing high resolution digital images. A patented electrical impedance technique was employed to instantaneously measure the local volumetric gas fraction. Flow dispersion in the column was studied by residence time distributions using conductivity tracers. The experimental results are discussed to comprehend the variation in the gas fraction in the column. In particular, the study showed that the size of the bubbles changed from the center to the walls of the column, and this was observed both radically and vertically. Moreover, the size of the bubbles affected the volume fractions, and no coalescence of the bubbles was observed. Finally, the dispersion of the tracer in the working solution was distributed uniformly in the volume of the column, with a time difference for the four positions of the column.

This study evaluates low-cost sensors (LCSs) for measuring coarse and fine particulate matter (PM) to clarify and measure air pollution. LCSs monitored PM10, PM2.5 (fine particulates), and PM1.0 concentrations at four sites in Samutprakarn, Thailand from December 2021 to April 2022. Average daily PM10, PM2.5, and PM1.0 concentrations at the monitoring locations were 53–79, 34–45, and 31–43 μg/m3, respectively. In December 2021, the monitoring station had a daily PM2.5 value above 100 μg/m3, indicating haze occurrences. However, the monitoring site’s daily PM10 and PM1.0 concentrations did not surpass Thailand’s ambient air quality threshold. We also measured and calibrated comparative particulate matter concentrations from LCSs and a tapered element oscillating microbalance (TEOM) monitor (Pollution Control Department (PCD) standard analytical method). PM2.5 concentrations from the LCSs were lower than TEOM, but the difference was not statistically significant. The PM2.5 monitoring station provided near-real-time air quality data for health risk reduction, especially when PM levels were high. Based on this study, authorities and local agencies may consider improving air quality regulation in Samutprakan, focusing on suburban PM2.5 air pollution.

The adhesion of Martian surface dust to solar panels has been a longstanding challenge for Mars mission researchers. Anti-dust coatings have been developed to deter the adsorption of dust particles onto these solar panels. However, current ground testing methods struggle to accurately verify and assess the coating’s ability to inhibit dust particle adsorption. Consequently, this paper introduces a computational model capable of calculating the contact force between fine particles and the coated surface. This model, grounded in the classical adhesive elastic interactions paradigm, establishes a normal force solution by approximating the pressure distribution on the contact area between the sphere and the coating, subsequently computing the composite force acting on the particle. Utilizing the API module of the EDEM simulation platform, we conducted simulations of the motion of fine particles on both smooth and coated plates. The results reveal that van der Waals forces are more prominent for light-mass particles, and the application of the coating can diminish the pull of these forces, facilitating easier detachment of dust particles from the plate surface.

As the concentration of fine particles (PM _2.5 ) is declining, ozone (O _3 ) concentration has been increasing in China in recent years. To collaboratively control PM _2.5 and O _3 , it is critical to understand the relationship between the two and identify major controlling factors. We use a convergent cross-mapping method to detect the causal relationship between daily PM _2.5 and maximum daily 8 h average (MDA8) O _3 concentrations in Beijing, Taizhou, Shenzhen and Chengdu, China, in the four seasons in 2015–2021. In addition, we also examined causal effects of atmospheric oxidation capacity, precursors and meteorological elements on PM _2.5 and MDA8 O _3 in the four cities. PM _2.5 and MDA8 O _3 are strongly positively correlated and show bidirectional causal relationships during the Beijing and Taizhou summer and in the four seasons in Shenzhen, due mainly to the strong photochemical reactions in the daytime. During the Beijing winter, PM _2.5 and MDA8 O _3 show bidirectional causal relationships, but the two are significantly negatively correlated, driven by NO _2 and relative humidity. Weak bidirectional, unidirectional and no causal effects between PM _2.5 and MDA8 O _3 are detected in other seasons in the four cities. In these seasons and cities, the top three causal factors of PM _2.5 differ from those of MDA8 O _3 . Season-, city- and pollutant-specific control measures of PM _2.5 and MDA8 O _3 are required.

This work is aimed at the analysis of the development of flotation technology by applying carrier minerals. Based on the concepts of continuum mechanics, a theoretical analysis of the influence of the carrier minerals (wall) on the motion of a single solid particle is provided, taking into account their hydrodynamic interaction (in the case of low Reynolds numbers). A correction was obtained in the form of a ratio of the particle size to its distance from the wall to take into account the influence of the wall on the hydrodynamic force acting on the particle. The influence of the wall is manifested through a rapid approximation of the liquid vortex flow in the gap between the solid wall and the particle to the steady-state mode, accompanied by the suppression of the transverse movement of particles. When the liquid slides along a wall-mounted gas–liquid layer with a reduced viscosity, the liquid flow increases in the interfacial gap, which can be analyzed by a dimensionless correction that includes values describing the properties of a continuous medium (dynamic viscosity) and a disperse phase (geometric particle size). The reason for the decrease in the induction time when gold grains adhere to each other is assumed to be due to the forces of hydrophobic attraction (when the grains have a mirror-smooth surface) and the sliding of the flow along the hydrophobic surface of the particles along the gas layer (when the grains have a rough surface). When polydisperse particles are aggregated, the threshold energy of the fast coagulation was established to be lower than that arising during the interaction of monodisperse particles, whose aggregation requires a large depth of the potential pit. Performing natural experiments on the ore using a rougher concentrate as a carrier material showed that the concentrate yield decreases by 20.52% rel. In the second case, the gold extraction was higher by 4.69% abs. While maintaining the achieved level of gold extraction, the double mixing of the rougher concentrate and the initial feed increased the gold content in the rougher concentrate from 4.97 to 6.29 g/t.

Natural gas hydrate has gained significant attention in recent years. To safely and sustainably exploit the natural gas from gas hydrate-bearing sediments, it is crucial to understand the long-term mechanical characteristics of the hydrate reservoir. In this study, the influence of hydrate and fine particles on the strain rate dependence of hydrate-bearing sediments under plane strain conditions has been studied. The experimental results show that the strain rate dependency of the mechanical properties of hydrate-bearing sediments is positively correlated with hydrate saturation instead of the morphology of hydrate in sediments. The residual strength of hydrate-bearing sediments is primarily controlled by the hydrate saturation and is independent of the strain rate. Changes in hydrate saturation and fines content can affect the relationship between the strain rate and shear band angle. Finally, the local volumetric expansion effect of hydrate-bearing sediments without fines content is more significant and shows a strong strain rate dependence characteristic. Overall, this study provides valuable insights into the long-term mechanical characteristics of hydrate reservoirs. These insights can contribute to the development of a constitutive model of hydrate-bearing sediments with time dependence in the future, which is meaningful to the exploitation of natural gas hydrate. [ABSTRACT FROM AUTHOR]

Fine particle liquid–solid flow in porous media is involved in many industrial processes such as oil exploitation, geothermal reinjection, and filtration systems. It is of great significance to master the behaviours of the fine particle liquid–solid flow in porous media. At present, there are few studies on the influences of the migration of fine particles on the flow field in porous media, and the effects of the porosity of porous media and inlet fluid velocity on the migration behaviours of fine particles in porous media. In this paper, a liquid–solid flow model was established based on the lattice Boltzmann method (LBM)‐immersed boundary method (IBM)‐distinct element method (DEM) and verified by the classical Drag Kiss Tumble (DKT) phenomena and flow around a cylinder successfully. In this model, the interaction between solid particles is analyzed using the distinct element method, and the interaction between fine particles and flow field is handled by IBM. Then, the migration and blockage of fine particles in porous media was studied using this model. It is found that, in addition to the blockage, a large amount of blocked‐surface sliding‐separation occur in fine particles. At the same time, the decrease in porosity increases the damage degree of fine particles on the permeability. The porosity exerts great influence on the penetration rate and dispersion behaviour of fine particles. The inlet fluid velocity mainly affects the residence time of fine particles and the average velocity of motion in the direction perpendicular to the main flow direction. [ABSTRACT FROM AUTHOR]

A wet electrostatic precipitator (WESP) has much higher capture rate for fine particulate matter, PM2.5, than a traditional dry type electrostatic precipitator does. In order to make full use of existing dust removal equipment and reduce the emissions of smoke and dust to zero, a combination of chemical coagulation and humidification coagulation is proposed using a WESP. The results show that the addition of chemical coagulant can promote the coagulation of coal-fired dust particles. After the addition of pectin (PG), the median diameter of dust particles increases from 28.19 μm to 45.28 μm. Water vapor humidification can promote the coagulation of dust particles. When the water vapor injection rate increases from 0 kg/h to 3.2 kg/h, the median diameter of dust particles increases from 28.19 μm to 36.45 μm. The synergistic effect of the coagulant and water vapor can enhance the chemical coagulation effect; when 1.0 × 10−2 g/L PG and 3.2 kg/h water vapor synergize, the collection efficiency reaches 98.17%, and when 1.0 × 10−2 g/L polyacrylamide (PAM) and 3.2 kg/h water vapor synergize, the collection efficiency reaches 96.68%. Both chemical coagulation and water vapor humidification can promote the condensation of coal dust, which is beneficial to improve the efficient capture of fine particles using WESP. [ABSTRACT FROM AUTHOR]

Emissions of PAH, nitro-PAHs, and oxy-PAHs from a diesel engine fueled with diesel-biodiesel-ethanol blends need to be controlled and reduced, as they are unregulated emissions harmful to the environment and human health. The objective of this work was to investigate the effect of ethanol concentration on diesel engine emissions when fueled with diesel–biodiesel–ethanol blends. Ethanol was added with biodiesel–diesel blends. Diesel B7 and two ternary blends, B7E3 and B7E10, with 3% and 10% ethanol, were tested and studied in a diesel engine to determine engine performance characteristics and particulate matter emissions and to quantify polycyclic aromatic compounds (PACs) associated with PM1.0 and PM2.5. Under the same engine conditions, 18 PAHs, 27 nitro-PAHs, and 6 quinones (oxy-PAHs) were determined by GC–MS in real samples obtained from the engine. The mean concentrations of PACs found in the B7, B7E3, and B7E10 blends for PM1.0 ranged from 0.1 µg m−3 (coronene) to 118.1 µg m−3 (2-nitrofluorene). The concentrations for PM2.5 ranged from 0.1 µg m−3 (acenaphthylene) to 99.7 µg m−3 (2-nitrofluorene). Potent mutagens benzanthrone (BA) and 3-nitrobenzanthrone (3-NBA) were found at concentrations ranging from 0.10 µg m−3 to 1.9 µg m−3 and 0.3 µg m−3 to 1.6 µg m−3, respectively. Low molecular weight (LMW) PAHs were mainly PACs bounded to the PM1.0 and PM2.5 particles emitted by B7E10. Flow properties were improved by adding 3% and 10% ethanol to biodiesel. B7E3 and B7E10 blends presented low fuel consumption and a reduction in the emission factor (EF) by the engine. B7E10 blending showed a smaller total concentration of ∑PAH (26.8 µg m−3), ∑nitro-PAH (85.4 µg m−3), and ∑oxy-PAH (6.0 µg m−3) associated with PM2.5 particles compared PM1.0. [ABSTRACT FROM AUTHOR]

To examine the distribution and the trend of airborne particles and bio-aerosol concentration in pediatric intensive care units (PICUs) in two tertiary care hospitals with different ventilation setting. Hospitals A but not B is provided with a central HEPA filter. PICUs in both hospitals were categorized into protective environment (PE) with room HEPA filter, semi-protective environment (SPE) with portable air-purifier, and non-protective environment (NPE) with neither system. Fine particles (≤ 2.5 µm) and coarse particles (≤ 10.0 µm) were obtained using optical particle counter (Lighthouse Handheld 3016) and total bacterial (TBC) and fungal (TFC) counts were obtained using Andersen air sampler. Hospital B had significantly higher levels of fine and coarse particles (in all room), TBC (in PE), but not TFC compared with matched rooms in hospital A. In hospital B, the levels of fine particles, coarse particles, and TBC were lowest in SPE (p < 0.001, p = 0.004, and p = 0.006, respectively) while TFC was lowest in NPE (p = 0.014). Airborne particles, TBC, and TFC had variable trends with some of the indoor peaks follow outdoor peaks. Gram-positive bacteria (69 %) were the predominant bacteria in hospital A while bacterial flora (70 %) were the predominant bacteria in hospital B (p < 0.001 for each). The levels of airborne contaminants and microbial counts in PICUs are significantly affected by the ventilation system and to less extent by outdoor levels. The results indicated that advanced filtration system and central HEPA filters play a significant role in the reduction of indoor fine particulates and TBC. [ABSTRACT FROM AUTHOR]

Air quality monitors using low-cost optical PM2.5 sensors can track the dispersion of wildfire smoke; but quantitative hazard assessment requires a smoke-specific adjustment factor (AF). This study determined AFs for three professional-grade devices and four monitors with low-cost sensors based on measurements inside a well-ventilated lab impacted by the 2018 Camp Fire in California (USA). Using the Thermo TEOM-FDMS as reference, AFs of professional monitors were 0.85 for Grimm mini wide-range aerosol spectrometer, 0.25 for TSI DustTrak, and 0.53 for Thermo pDR1500; AFs for low-cost monitors were 0.59 for AirVisual Pro, 0.48 for PurpleAir Indoor, 0.46 for Air Quality Egg, and 0.60 for eLichens Indoor Air Quality Pro Station. We also compared public data from 53 PurpleAir PA-II monitors to 12 nearby regulatory monitoring stations impacted by Camp Fire smoke and devices near stations impacted by the Carr and Mendocino Complex Fires in California and the Pole Creek Fire in Utah. Camp Fire AFs varied by day and location, with median (interquartile) of 0.48 (0.44-0.53). Adjusted PA-II 4-h average data were generally within ±20% of PM2.5 reported by the monitoring stations. Adjustment improved the accuracy of Air Quality Index (AQI) hazard level reporting, e.g., from 14% to 84% correct in Sacramento during the Camp Fire.

Abstract A study on monitoring PM2.5 concentrations at an underground subway station using light scattering and beta attenuation methods was conducted. Six optical particle counters (OPCs), which were representative of the light scattering method and had 16 size channels, were installed at different sampling sites in the waiting room and platforms to compare PM2.5 concentrations, determine PM2.5 /PM10 ratios, and characterize the size distribution based on particle number. In terms of the beta attenuation method, a beta-ray attenuation monitor (BAM) was set up at the platform to compare it with OPCs for one month. It was found that 1h-average PM2.5 concentrations varied at different sampling sites depending on PM composition, while 24h-average PM2.5 concentrations were independent of the sampling sites. There was a significant difference between the means of 1h-average PM2.5 concentrations observed by the BAM and OPC when PM2.5 contributed to less than 50% or higher than 80% of PM10. In contrast, the 24h-average PM2.5 concentrations observed by the BAM and OPC showed the same patterns as each other with an insignificant difference. Therefore, an OPC can be used to monitor the 24h-average PM2.5 concentration in an underground subway station. However, the use of OPC to measure the 1h-average PM2.5 concentration should consider PM composition and other factors. In addition, more frequent calibration is needed on a regular basis.

This study was performed to investigate the improving effect of a mixture of Artemisia argyi and Saururus chinensis (AASC) on cognitive dysfunction in mice with long-term exposure to fine particles (particulate matter smaller than 2.5 µm: PM2.5). The main compounds of AASC were identified as dicaffeoylquinic acid isomers of A. argyi and a quercetin-3-glucoside of S. chinesis. As a result of behavioral tests for the evaluation of cognitive function, it was confirmed that cognitive dysfunction was induced in the PM2.5 exposure group, and a tendency to improve in the AASC group was confirmed. Increased oxidative stress and inflammatory response and mitochondrial dysfunction were observed in the brain and lung tissues of the PM group. Damage to the brain and lung affected the accumulation of amyloid beta (Aβ) in the brain. It increased Aβ and induced the cholinergic dysfunction, hyperphosphorylation of the tau protein, and activation of apoptosis, leading to cognitive impairment. However, AASC suppressed brain and lung oxidative stress and inflammation, thereby suppressing brain Aβ expression. Consequently, this study shows the potential that a steady intake of plant resources with antioxidant and anti-inflammatory activity could prevent cognitive impairment caused by PM2.5. [ABSTRACT FROM AUTHOR]