Aerosol Science and Engineering最新文献

As studied by many authors, the behavior of particles in aerosol flow through bent tubes is relevant to a variety of technological developments for practical applications. The present work is no exception, motivated by the need of understanding ink droplet loss during mist transport in Aerosol Jet® printing. While the majority of works in the literature have considered particle deposition in tube bends with the tube-flow Reynolds number Re > 1000, the mist flow in transport channels of Aerosol Jet® printer often has Re < 100. Here, the effects of inertial impaction and gravitational settling with laminar flows in 90° bends are examined using an OpenFOAM® CFD package, for Re ~ 50 to 1000. The computational code is verified by comparing with the experimental result of Pui et al. for Re = 1000. Besides inertial impaction due to the centrifugal forces in bends, the effect of gravitational settling is shown to become increasingly significant with reduction of tube-flow velocity, which can also be quite sensitive to the bend orientation when the mist flow rate is low. For situations of downward bend or upward inlet, where the gravitational force and centrifugal force oppose each other, the effect of gravitational settling appears relatively insignificant. However, the particle deposition efficiency is generally enhanced in upward bends or bends with downward inlet, where the gravitational force and centrifugal force reinforce each other, exhibiting large deviations from the zero-g case, especially at lower flow velocities (i.e., smaller Froude number).

This study explores the quantification of PM_2.5 (particles with an aerodynamic diameter of less than or equal to 2.5 µm) and how it is impacted by meteorological parameters. The study was conducted in Benin City between January and December 2019. The city was divided into four zones, namely, North West (NW), North East (NE), South East (SE), and South West (SW). A total of 180 representative samples for PM_2.5 were collected from artisans’ workshops in both wet and dry seasons, using an Apex2IS Casella standard pump fitted with a conical inhalable sampling (CIS) head at a flow rate of 3.5 L/min for 8 h. Meteorological parameters were collected simultaneously with PM_2.5. The PM_2.5 levels range from 37.9 to 735.1 (µg/m³) and 60.6 to 313.9 (µg/m³) during the dry and wet seasons, respectively. The estimated PM_2.5 concentration exceeded the World Health Organization (WHO) and National Ambient Air Quality Standard (NAAQS) of 25 and 250 ug/m³, respectively. The meteorological parameters were estimated to be 27.9–33.4 (°C), 59.8–78.9 (%), 748.4–754.3 (mmHg), 2.8–6.9 (km/h), 154.9–205.4 (^o), 425.1–1,073.4 (W/m²), and 717.3–1,133.7 (µW/m²) for temperature, relative humidity, pressure, wind speed, wind direction, solar radiation, and ultra-violet radiation, respectively. A significant positive correlation was observed between PM_2.5, temperature, solar radiation, and ultra-violet radiation. However, a negative correlation was observed for pressure. This positive correlation may influence the poor dispersion of PM_2.5, particularly in the wet season when we experience low temperatures and low wind speeds, and consequently impact negatively on human health.

With the rapid development of the social economy and the frequent occurrence of haze, heavy metals in atmospheric particulates have been shown harmful to human health. In this paper, the samples of atmospheric particulate matter (PM₁₀ and PM_2.5) were collected in two typical sites of Tianjin in spring. The concentration of 6 heavy metals in PM₁₀ and PM_2.5 were analyzed by microwave digestion inductively coupled plasma mass spectrometry method. The enrichment factor (EF) method was used to identify the sources of heavy metals in particulate matter. The results showed that the daily average concentrations of PM₁₀ and PM_2.5 in Tianjin were notably influenced by building construction, traffic-related emission and meteorological condition. The heavy metals in the atmospheric particulate matter were as follows: ρ(Mn) > ρ(Pb) > ρ(Ni) > ρ(V) > ρ(Cd) > ρ(Co) and more easily enriched in fine particles PM_2.5. The result of EF analysis suggested that the V, Mn, Co and Ni were not enriched, and the source of them in the atmospheric particulate matter samples was mainly nature. Cd and Pb were typical pollution elements in spring of Tianjin, and predominantly derived from human activities. Health risk assessment demonstrated that the carcinogenic risk levels of heavy metals in the atmospheric particulate matter samples were generally followed the order of men > women > children. Cd and Pb in the atmospheric particulate matter had no carcinogenesis risk. The potential carcinogenic risk of Ni was evaluated as acceptable and tolerable. This study could provide a scientific reference for the prevention and control of atmospheric particulate pollution.

Nanotechnology (NT) refers to the generation and application of nanoparticles (NPs). Research in NT has been ongoing for several decades and has resulted in a wide range of materials at the nano-scale. Globally, NPs serve various domestic, pharmaceuticals, aviation, textiles, and other industrial purposes. These particles are currently used in kitchen utensils, medical applications, energy-related research, aircraft, etc. The future of our planet depends on NT. Numerous molecular indicators of genetic and autoimmune diseases, malignant tumors, and a wide range of other disorders can currently be diagnosed using NPs. Drug delivery to specific tissues and organs with controlled drug release and accumulation parameters is achieved through NPs. In addition, NPs have been used as active components in some cases. For example, photodynamic therapy’s incorporation and heating are photosensitizers and hyper-thermic tumor killing through NPs. Despite numerous beneficiary use and economic success of NPs, their toxic effects on terrestrial and aquatic ecosystems have also gained attention. Excessive exposure to NPs in sectors, such as agriculture, industry, etc. has generated negative health effects in humans. The review highlights about NPs in great detail. The paper discusses their sources, usage, toxicity and health effects, transportation, analysis, and treatment. It represents a summary of recent research developments and achievements in the field of NT and substantial gap areas that need to be addressed.

Continual research, development, and advancement in air filtration technology is important to abate the ever increasing health hazards of air pollution and global pandemics. The purpose of this review is to survey, categorize, and compare mechanical and thermal characteristics of fibers to assess their potential applicability in air filter media. The history of high-efficiency particulate air (HEPA) filter development explains how we arrived at the current state of the art nonwoven fibrous borosilicate glass filter paper. This review explores the history and practical uses of particular fiber types and explains fiber production methods in general terms. The thermal and mechanical properties of particular fibers are examined using the codes and standards produced by the American Society of Mechanical Engineers (ASME) to generalize the applicability of fiber categories for HEPA filter units within the nuclear air cleaning industry. This review discusses common measurements for specific strength and tenacity used by the textile and construction industries. Particular fibers are selectively compared for density, tensile strength, tensile stiffness, flexural rigidity, moisture regain, decomposition temperature, and thermal expansion. This review concludes with a subjective assessment of which types of fibers may be appropriate to study for HEPA filtration.

Aerosol optical depth (AOD) is a key parameter in atmospheric pollution and climate processes. In this paper, we compared the aerosol loading (550 nm) from 2000–2001 to 2017–2018 and total cloud cover using seasonal, latitudinal and solar activity cycle data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and determined the spectral optical range from the region of relatively clear air (Europe) to the region of more considerable biomass burning activity (Africa). To remove the large annual cycle influence, the data were deseasonalized, allowing exploration of inter-annual variability. Deseasonalization obtains the time series AOD monthly average anomaly over the years for each grid cell. We employ the solar flux index over the regions by correlating the absolute percentage mean difference of aerosol and cloud interactions and validate the result by modeling aerosol and cloud data from 2020 to 2021 using a neural network. AOD and solar flux for Africa show correlations of − 0.638 for 2000–2001 and − 0.218 for Europe, and at the same time, AOD with cloud cover for Africa shows correlations of − 0.129 and 0.360 for Europe. The analysis confirmed an inverse weak correlation of aerosols with cloud cover. This would help resolve the knowledge gap by demonstrating that aerosol and cloud interactions are not only dependent on region but also more dependent on the solar activity cycle and seasons. We observed dependence by the latitude of the aerosol load and solar flux index.

Several anthropogenic (like industries, vehicles, coal-based thermal power plants, etc.) and natural sources (like lightning, degradation of organic matter, etc.) emit a copious amount of primary gaseous pollutants like Sulphur dioxide (SO₂), Nitrogen dioxide (NO₂) and Ammonia (NH₃), which further contribute in the formation of particulate matters where they are present in the form of water-soluble inorganic ions (WSII) like SO₄²⁻, NO₃⁻, NH₄⁺, respectively. To assess the conversion of primary gaseous pollutants into dissolved ions in PM₁₀, real-time sampling (24 h average) of PM₁₀ and primary gaseous pollutants (SO₂, NO₂, NH₃) from September 2021 to March 2022 over 13 highly polluted places in Kolkata were performed. Then PM₁₀ was quantified using the gravimetric method, while NO₂ and NH₃ were estimated through chemiluminescence and SO₂ was estimated through the fluorescent spectrometric method. Analysis of WSII species in PM₁₀ was also performed through the spectrophotometric method and then to understand the conversion of the primary gaseous pollutants into WSIIs in PM₁₀, sulphur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) and ammonia conversion ratio (NHR) was calculated. The results showed that NO₂ is the most abundant primary gaseous pollutant in the ambient air of Kolkata [highest in Dumdum (73.6 μgm⁻³)] and NO₃^– is the most abundant WSII in PM₁₀ of Kolkata [highest in Bansdroni (3.74 μgm⁻³)] and the SOR and NOR values were significantly higher in Bansdroni and NHR was significantly higher in Santoshpur due to presence of optimum meteorological conditions. Lightning is one of the major natural sources of NO_x. So, due to lightning, atmospheric NOx level increases which then gets associated with particulate matter, increasing the concentration of NO₃⁻ ion in particulate matter due to gas-particle partitioning. This is indicated by strong linear correlation coefficients (R² = 0.746) between a number of flashes on the day of sampling and NO₃⁻ concentration in PM₁₀ aerosol.

Solid particle aerosol generation can be a costly technique that may have limited applications for a researcher. Herein, we discuss a low-cost method of solid aerosol generation for less than $1000 USD. The aerosol generation system was validated with acetaminophen and syloid 244 by studying the aerosolization into a chamber using this lab-built low-cost solid aerosol generator. This method used an inexpensive Venturi aspirator valve to pull the material from a hopper and disperse it into an 85 L chamber, creating a non-recirculating aerosol environment. The demonstrated system is a modification of a previously reported low-cost aerosol generator by the addition of electronic control valves automating the aerosolization process resulting in increased repeatability of air volume ejected into the chamber as well as decreasing the retrograde emission of materials. In each experiment, an initial spike of material was observed on the particle counter with exponential decay of total particles as they fell out of suspension or were consumed by the particle counter. In addition, the lab-built system was directly compared to a more expensive commercially available belt-fed Venturi aerosol generator and our experiments show that both methods produced similar results in regards to the particle distribution and time to create a stable aerosol environment. The addition of inexpensive electronic valves to this simple Venturi aspirator opens the area of solid particle aerosol generation to a larger audience without the high-cost burden normally associated with other commercially available technologies.

Household air pollution from use of solid biomass fuels (SBF) remains one of the primary causes of health and environmental issues in developing countries. Particulate emissions from SBF combustion exhibit variable physical and chemical properties in different phases of combustion which influences the way exposure to these emissions affects human health. The present study is an attempt to measure and compare cooking time concentrations of particulate matter (PM_2.5 and PM₁), carbon-monoxide (CO) and black carbon (BC) in the kitchen area of households dependent on three different types of biomass-based cookstoves. The variation in PM characteristics in addition to real time CO concentrations in different phases of cooking was also assessed. Observed mean concentrations of PM_2.5, CO and BC for forced draft cookstove (FDC) were 309.3 µg/m³, 4.8 ppm, 5.1 µg/m³ and forced draft mud cookstove (FDMC) was 355.2 µg/m³, 6.5 ppm and 5.3 µg/m³, respectively. Comparison with a traditional biomass cookstove showed that FDC resulted in higher reductions in PM mass concentrations (> 50%) compared to FDMC; however, BC the reduction was almost similar, i.e., 35% and 32% for FDC and FDMC, respectively. Temporal variation of PM, CO and BC were found to peak during the kindling phase (KP) for all the cookstoves followed by a decline during flaming phase (FP) and smoldering phase (SF). The total particle number concentration (PNC) for all combustion phases was 45.6 and 62.3% lower in FDC and FDMC, respectively, compared to TCS. However, fraction of PNC in total PM was higher in FDC and FDMC compared of TCS. Based on a ranking method which involved both technical and non-technical (such as ease of use) stove performance parameters showed user inclination more toward FDMC.