Concentration Of Aerosol Particles Research Articles

Assessment of Atmospheric Particles Flux Variation on the Different Underlying Surfaces (Grasslands and Forest) in the Lake Baikal Region

In this study, the new data of experimental studies of the atmospheric particulate matter (PM) on the south-eastern coast of Lake Baikal (station Boyarsky) were analyzed in summer 2021. High-altitude measuring sites were arranged in the forest massif (mast, 16 m) and above the meadow vegetation (mast, 30 m). By the Giardina M. model and based on the measurements data the calculations of the deposition flux density of aerosol particles on forest and meadow vegetation were made. Our preliminary results of prediction obtained by Giardina M. model good agrees with measured dry deposition velocities across particle sizes. In the forest, the mass concentration of aerosol particles differs slightly from the mass concentrations in the grasslands and is equal on average 7.9 × 10−3 mg m−3 for the size particles below 200 nm (PM0.2) and 6.7 × 10−4 mg m−3 for particles in the size range from 0.2 to 10 μm (PM0.2–10). However, we found that mass flux density of aerosol particle is almost 4.8 times higher under forest canopy than in meadow vegetation. In addition, the leaf area index (LAI), which characterize the effective area of particle deposition, is also significantly higher in the tree canopy (5.6) compared to the grassland vegetation (2.4).

Quantitative evaluation of the impact of indoor relative humidity on deposition of aerosols generated during tooth grinding in a real-world clinical setting.

Exposure to aerosol particles generated from tooth grinding has a negative impact on the health of dental personnel. The aim of this study was to quantitatively analyze the impact of indoor relative humidity (IRH) on the deposition of these suspended particles in a well-controlled dental environment. In this study, a humidity control system was employed to effectively regulate and maintain indoor relative humidity (IRH). A novel computer-assisted numerical control system was developed to pre-treat the molar specimens, and accurately simulate clinical tooth grinding procedures. Each procedure was performed in triplicate, with an online real-time particle counter (ORPC; TR-8301, TongrenCo.) measuring aerosol production. All testing devices were controlled remotely. The data obtained were statistically analyzed using descriptive statistics and non-parametric tests (Kruskal-Wallis/ Dunn's post hoc test with Bonferroni correction, p < 0.05). The findings showed that with increasing IRH, the maximum peak concentration of aerosol particles decreased by 397% from 6.51 × 107 particles/m3 at 30% to 1.64 × 107 particles/m3 at 80%. The Kruskal-Wallis test results indicated a statistically significant effect of IRH on the aerosol increment (p < 0.05). Increasing the IRH level can effectively promote the deposition of aerosol particles, with a return to baseline within 15min after reaching 60% or above. Our study suggested that maintaining IRH above 70% during the cleaning process, allowing natural recovery to ambient humidity levels within 15min after cleaning, and taking basic precautions, may lead to an adequate reduction in the possible health risks of aerosol contamination.

The impact of aerosols and model grid spacing on a supercell storm from Swabian MOSES 2021

AbstractThe supercell storm that occurred in southwestern Germany on June 23, 2021, had an exceptionally long lifetime of 7.5 hr, travelled a distance of nearly 190 km, and produced large amounts of hail. During that summer, the Swabian MOSES field campaign was held in that area, and several hydro‐meteorological measurements are available, as the storm passed directly over the main observation site. We present hindcasts of this event with the Icosahedral Non‐hydrostatic model using two horizontal grid spacings (i.e., 2 km, 1 km) with a single‐moment and an advanced double‐moment microphysics scheme. Numerical results show that all 2 km model realizations do not simulate convective precipitation at the correct location and time. For the 1 km grid spacing, changes in aerosol concentration resulted in large changes in convective precipitation. Only the 1 km run assuming a low cloud condensation nuclei (CCNs) concentration is able to realistically capture the storm, whereas no supercell is simulated in the more polluted scenarios. Observed aerosol particle concentrations indicate that CCNs values were the lowest of the month, which suggests that the low aerosol concentration is a reasonable assumption. The thermodynamic structure of the pre‐convective environment, as well as other observations, showed the best agreement to this model run as well, indicating that the good representation of the supercell was obtained for the right reason. The automatic tracking of individual clouds revealed that more convective cells with longer lifetimes are simulated at finer resolution. We also find a negative aerosol–precipitation effect that is not only due to a reduced collision–coalescence process, but also to weaker cold‐rain processes. These findings demonstrate the benefits of using an aerosol‐aware double‐moment microphysics scheme for convective‐scale predictability and that the use of different CCNs concentrations can determine whether a supercell is successfully simulated or not.

Radon and Its Short-Lived Products in Indoor Air: Present Status and Perspectives

Initially, basic equations are given to express the activity concentrations and concentrations of potential α-energies of radon (222Rn) and thoron (220Tn) and their short-lived products in indoor air. The appearance of short-lived products as a radioactive aerosol is shown, and the fraction of the unattached products is particularly exposed, a key datum in radon dosimetry. This fundamental part is followed by giving the sources of radon and thoron indoors, and thus, their products, and displaying the dependence of their levels on the ground characteristics, building material and practice, and living–working habits of residents. Substantial hourly, daily, and seasonal changes in their activity concentrations are reviewed, as influenced by meteorological parameters (air temperature, pressure, humidity, and wind speed) and human activity (either by ventilation, air conditioning and air filtration, or by generating aerosol particles). The role of the aerosol particle concentration and their size distribution in the dynamics of radon products in indoor air has been elucidated, focusing on the fraction of unattached products. Intensifying combined monitoring of radon short-lived products and background aerosol would improve radon dosimetry approaches in field and laboratory experiments. A profound knowledge of the influence of meteorological parameters and human activities on the dynamics of the behaviour of radon and thoron accompanied by their products in the air is a prerequisite to managing sustainable indoor air quality and human health.

Low-Cost Sensor System for Air Purification Process Evaluation.

With the development of civilisation, the awareness of the impact of versatile aerosol particles on human health and the environment is growing. New advanced materials and techniques are needed to purify the air to reduce this impact. This brings the necessity of fast and low-cost devices to evaluate the air quality from particulate and gaseous impurities, especially in a place where gas chromatography (GC) techniques are unavailable. Small portable and low-cost systems may work separately or be incorporated into devices responsible for air-cleaning processes, such as filters, smoke adsorbers, or plasma air cleaners. Given the above, this study proposes utilising a self-assembled low-cost system to evaluate air quality, which can be used in many outdoor and indoor applications. ESP32 boards with the wireless communication protocol ESP-NOW were used as the framework of the system. The concentration of aerosol particles was measured using Alphasense sensors. The concentrations of the following gases were measured: NO2, SO2, O3, CO, CO2, and H2S. The system was used to evaluate the quality of air containing tobacco smoke after passing through an actual DBD plasma reactor where the purification occurred. A high amount of reduction in aerosol particles and a reduction in the SO2 concentration were detected. An increase in the NO2 concentration was seen as an undesirable effect. The aerosol particle measurements were compared with those using a professional device (GRIMM, Hamburg, Germany), which showed the same trends in aerosol particle behaviour. The obtained results are auspicious and are a step towards producing a low-cost, efficient system for evaluating air quality as well as indoor and outdoor conditions.

Variability of Concentration of Aerosol Particles, Polycyclic Aromatic Hydrocarbons, and Polychlorinated Biphenyls in the Atmosphere above the Surface of Lake Baikal

Variability of Concentration of Aerosol Particles, Polycyclic Aromatic Hydrocarbons, and Polychlorinated Biphenyls in the Atmosphere above the Surface of Lake Baikal

Identification of exhaust stack sampling location of a research reactor considering ANSI/HPS N13.1-2011 mixing criteria using computational fluid dynamics

ABSTRACT Research Reactors have exhaust stacks that emit filtered radioactive gaseous waste into the atmosphere. In this research work, to check whether the radioactive gaseous waste met the requirements of ANSI/HPS N13.1–2011 mixing criteria, computational fluid dynamics (CFD) analysis was performed. According to ANSI criteria, Coefficient of Variance (COV) of velocity uniformity, flow angle, tracer gas, and aerosol particles concentration should be less than 20%. Therefore, the COV of the four parameters at different sampling positions along the stack height, with eight tracer gas and eight particles injection cases, were analyzed. The COV of velocity at 6 m height is 17.5% and flow cyclone is 9.8 degree. The results indicated that the 6 m height of the stack is enough for cyclone angle and COV of velocity to fulfill the ANSI mixing criteria. The COV of tracer gas concentration in one to eight injection cases is 10%, 4.8%, 7.5%, 17%, 2.5%, 6%, 13%, and 5% at 14 m stack height so the tracer gas also satisfied the standard mixing criteria in a concise length of 14 m because of the minimal difference in densities of tracer gas and air. However, due to their much higher density, aerosol particles took much longer to mix into the air. At 60 m stack height, the COV of aerosol particle concentration in one to eight injection cases is 14.8%, 18%, 8%, 12%, 11%, 15%, 15.5%, and 2%, respectively. As a result, when the stack height is set to 60 m, the COV of velocity, cyclone flow angle, tracer gas concentration, and aerosol particle concentration are found to meet the ANSI mixing criteria. Therefore, the minimum recommended height of the stack is proposed to be 60 m for the case under consideration.

Mitigation of Aerosol and Microbial Concentration in a Weaning Piggery by Spraying Nanobubble Ozone Water with an Ultrasonic Sprayer.

Enhancing biosecurity measures in livestock is an essential prerequisite for producing animal products with the highest levels of safety and quality. In Japan, 70% of the mortalities post-weaning are attributed to respiratory pathogens. The research has shown that microorganisms, including both viruses and bacteria, do not merely float in the air independently. Instead, they spread by adhering to aerosols. Therefore, improving the control of aerosol dissemination becomes a critical strategy for reducing pathogenic loads and boosting the overall efficiency of livestock production. This study focused on reducing concentrations of aerosol particles, airborne microbial concentrations, and airborne mass concentrations by spraying ozone solution with an ultrasonic sprayer. The experiments were conducted at a farm in Fukushima Prefecture, Japan, known for its integrated management system, overseeing a herd of 200 sows. Nanobubble ozone water particles were dispersed using an ultrasonic sprayer, which allowed the particles to remain airborne significantly longer than those dispersed using a standard nozzle, at a rate of 30 mL per weaning pig 49 days old, for a 10 min period. This procedure was followed by a 10 min pause, and the cycle was repeated for 17 days. Measurements included concentrations of airborne bacteria, aerosol mass, and aerosol particles. The findings demonstrated a substantial reduction in airborne microbial concentrations of Escherichia coli and Staphylococcus aureus in the treated area compared to the control, with reductions reaching a peak of 85.7% for E. coli and 69.5% for S. aureus. Aerosol particle sizes ranging from 0.3-0.5 µm, 0.5-1.0 µm, 1.0-2.0 µm, 2.0-5.0 µm, to 5.0-10.0 µm were monitored, with a notable decrease in concentrations among larger particles. The average aerosol mass concentration in the test area was over 50% lower than in the control area.

Quantitative assessment of nano-plastic aerosol particles emitted during machining of carbon fiber reinforced plastic

Focusing on the relatively unexplored presence of micro- and nano-plastic aerosol particles, this study quantitatively assessed the emission of nano-plastic particles during the machining of carbon fiber reinforced plastic (CFRP) in the working environment. Measurements of aerosol particles smaller than 1 µm in size were performed by aerosol mass spectrometry. The findings revealed that concentrations of carbonous aerosol particles (organic aerosol and refractory black carbon (rBC)) were higher during working hours than during non-working hours. Positive matrix factorization identified CFRP particles as a significant source, contributing an average of approximately 30% of concentration of carbonous aerosol particles during working hours. This source apportionment was corroborated by the presence of bisphenol A and F fragments, principal components of the epoxy resins used in CFRP, and was corroborated by similarities to the carbon cluster ion distribution observed in rBC during CFRP pipe-cutting operations. Further, the particle size distribution suggested the existence of plastic aerosol particles smaller than 100 nm. This study established the method to quantitatively distinguish nano-plastic aerosol particles from other aerosol particles in high temporal resolution and these techniques are useful for accurately assessing exposure to nano-plastic aerosol particles in working environments.

Study of particulate emissions when using special wires for underwater welding

The article describes the study to evaluate the emissions to atmospheric air of airborne nano- and microparticles generated during underwater welding in seawater from Ajax Bay (Sea of Japan) using special wires and coated electrodes. The most commonly used underwater industrial production processes were selected: semi-automatic (mechanized) underwater welding with a welding wire, manual welding with electrodes, and semi-automatic (mechanized) underwater cutting with a welding wire for cutting. An aerosol particle counter was used to determine the mass concentration of fine aerosol particles in the air of the working area above the aquarium. The highest number of suspended particles in the atmospheric air was observed in the process of underwater welding with a welding electrode. Comparing the welding wire and the welding electrode for underwater welding, it can be concluded that the welding wire is less dangerous for people, which is confirmed by the lower amount of suspended particles emitted into the atmospheric air during its use.

Characteristics of aerosol at the research base “Ice Cape Baranova” in 2018–2023

Atmospheric aerosol plays an important role in the processes of radiative transfers and mass exchange by different substances in the “continent–atmosphere–ocean” system. In this paper we discuss the results of a five-year measurement cycle of the atmospheric aerosol characteristics at the polar station “Ice base Cape Baranov”, located on the Bolshevik Island (the Severnaya Zemlya Archipelago). The set of the characteristics analyzed includes: the aerosol optical depth (AOD) of the atmosphere; the ground concentration of aerosol particles in the radius range of 0.15–5 microns; the content of the absorbing substance (soot) in the aerosol in the equivalent of elemental black carbon. The average values of the aerosol characteristics for the general measurement period (from April 2018 to May 2023) were: volumes of submicron and coarse aerosol particles 0.43 and 0.46 μm3/cm3, respectively; mass concentration of black carbon — 45.8 ng/m3; AOT of the atmosphere at a wavelength of 0.5 µm — 0.08; Angstrom selectivity exponent — 1.67. The average annual variation of aerosol and black carbon concentrations is characterized by a maximum in winter (January–March) and a minimum in summer (June–August). A comparison is made against the data from analogous measurements of aerosol characteristics at the polar station in Barentsburg (the Spitsbergen Archipelago) and against the data from model calculations, i. e., MERRA-2 reanalysis. A distinctive feature of the data in the Cape Baranov area is the low content of coarse aerosol — 1.7 less than in Barentsburg. There is agreement with the annual variation of black carbon concentrations at other polar stations, but the opposite nature of the seasonal variability of model (MERRA-2) concentrations: low values in winter and high values in summer. It is shown that the average spectral AODs of the atmosphere at the “Cape Baranov” are intermediate values between the data from polar stations in NyÅlesund and Barentsburg.

Intra-event evolution of elemental and ionic concentrations in wet deposition in an urban environment

Abstract. A measurement campaign was conducted in the Paris region, focusing on the evolution of chemical composition of wet deposition during rainfall events from sequential sampling. A total of eight rain events were documented and characterized by varying meteorological conditions, atmospheric dynamics, and aerosol particle concentrations representative of urban conditions and influenced by long-range mineral dust transport. The intra-event evolution of the chemical composition of wet deposition revealed the predominant role of meteorological parameters and local sources in the observed mass concentration variability. From selected case studies, the washout ratios (WRs) and scavenging coefficients were quantified by conducting simultaneous measurements of aerosol particle composition and wet deposition. The results highlighted a variability of the WR and scavenging coefficients depending on the rainfall rate and on the chemical species. Scavenging coefficients estimated from WR ranged from 5.4×10-8 to 1.1×10-5 s−1 for chemical elements, and they are within the range of values reported in the literature for 0.2–2 µm particle diameters. Our results pointed out that the scavenging coefficient increases with rainfall rate according to a power law, as previously shown in the literature, indicating a stronger removal of particles from the atmosphere with greater precipitation intensity. Quantitative analysis of the data allowed us to estimate the relative contributions of in-cloud scavenging (ICS) for selected rain events. The ICS relative contributions ranged on average from 23 % to 62 % depending on the rain events, and they varied according to the chemical species within the same rain event. This highlights the variability and complexity of the wet deposition process and the influence of specific factors on the contribution of ICS, such as aerosol particle size and hygroscopicity. Overall, this study highlights the variability of wet deposition and its chemical composition and the need to consider the specificities of each event to fully understand the underlying mechanisms.

The Vertical Distribution of Ice-Nucleating Particles over the North China Plain: A Case of Cold Front Passage

Ice-nucleating particles (INPs) are crucial for cloud freezing processes in the atmosphere. Given the limited knowledge about the vertical distribution of INPs and its relation to aerosols in China, we present two aircraft observations of INPs over the North China Plain on 23 October 2019 and 25 October 2019, before and after a cold front passage. We used a well-established method to identify the INPs on a silicon wafer and then performed single-particle chemical composition analysis using an environmental scanning electron microscope-energy dispersive spectrometer (ESEM-EDS). The INP concentrations range from 0.1 to 9.2 L−1 within activation temperatures from −20 to −29 °C. INPs are mostly concentrated within the boundary layer, and their concentration shows a decreasing trend with height (0.5~6 km) before the cold front passage. However, the highest INP concentration always appears at higher altitudes (4~5 km) after the cold front passage. The cold front passage also significantly weakens the correlations between the concentrations of INPs and aerosol particles at different sizes. The activated fraction (AF) of total aerosols increases from 10−6 to 10−4 with height from near ground to 6 km, reflecting a better nucleating capacity of the aerosols at higher altitudes. There is no obvious variation in AF after the cold front passage. Chemical analysis reveals that the INPs containing mineral dust components comprise the majority of total INPs during both flights. The proportion of pure mineral dust declines from 52.2% to 43.5% after the cold front passage while the proportion of mixed mineral dust increases from 23.9% to 45.7%, suggesting that an increased probability of aging or coating of INPs is introduced by the cold front during their long-distance transport. In addition, 88% of INPs have a diameter larger than 1 μm. This indicates that larger aerosols (&gt;1 μm) are the major contributors to INPs at high altitudes despite their relatively low abundance. Our results demonstrate a significant impact of transport events on the sources and vertical distribution of INPs in the atmosphere.

The role of snow in scavenging aerosol particles: A physical-chemical characterization

The below cloud scavenging of aerosols by snow has been analysed in León (NW Spain). Six snow events were registered over the course of one year of study. Ultrafine and accumulation aerosol particles were measured using a scanning mobility particle sizer spectrometer, while hydrometeors were characterized using a disdrometer. Furthermore, the chemical composition of the melted snow-water samples (soluble and insoluble fractions) was analysed.The scavenging coefficient (λ) showed a great variability among events. An effective washing of particles was observed during the first 30 min of snowfall. The mean change in the scavenging efficiency (%ΔC) of particle number concentration (PNC) and λ coefficient during this time interval were: i) nucleation mode: 36.3 % and 3.02 · 10−4 s−1; ii) Aitken mode: 30.4 % and 2.37 · 10−4 s−1 and iii) accumulation mode: 22.4 % and 1.77 · 10−4 s−1. The range of particle sizes that is less efficiently scavenged by snowfall was observed between 400 and 600 nm. When analyzing the whole snow event, an increase of PNC was observed. Two possible explanations underlie this behaviour: it could be caused by changes in air masses or by the resuspension of aerosol particles scavenged by snowflakes upon reaching the ground. A clear relationship was observed between Ca2+, SO42− and NO3− concentrations of aerosol particles before the snow event and the concentrations registered in the melted snow-water.The largest and smallest changes in aerosol number concentrations were caused by snowflakes of 3 and 6 mm in diameter, respectively. The particle size distributions (PSD) were fitted to log-normal distributions and the parameters were compared before and after snowfall.

Effect of forceful suction and air disinfection machines on aerosol removal

BackgroundsDental procedures involving drilling and grinding can produce a significant amount of suspended aerosol particles (PM) and bioaerosols. This study aims to analyze the size and concentration of aerosol particles generated during drilling and to investigate the effectiveness of two air exchange systems, namely forceful suction (FS) and air disinfection machines (DM), in removing PM.MethodsFor this study, 100 extracted permanent teeth were collected and divided into three groups: without suction (n = 50), suction with forceful suction (n = 25), and suction with air disinfection machines (n = 25). The removal rate of suspended aerosol particles was analyzed using particle counters and air data multimeter.ResultsWhen drilling and grinding were performed without vacuum, 0.75% of the aerosol particles generated were PM2.5-10, 78.25% of total suspended aerosol particles (TSP) were PM2.5, and 98.68% of TSP were PM1. The nanoanalyzer measurements revealed that the aerodynamic diameter of most aerosol particles was below 60 nm, with an average particle diameter of 52.61 nm and an average concentration of 2.6*1011 ultrafine aerosol particles. The air change per hour (ACH) was significantly lower in the air disinfection machines group compared to the forceful suction group. Additionally, the number of aerosol particles and mass concentration was significantly lower in the air disinfection machines group compared to the forceful suction group in terms of PM2.5 levels. However, the forceful suction group also reduced the mass concentration in PM10 level than the air disinfection machines group.ConclusionIn conclusion, the air exchange system can reduce the aerosol particles generated during drilling and grinding. Comparing the two air exchange systems, it was found that the air disinfection machines group reduces the number of aerosol particles and mass concentration in PM2.5 levels, while the forceful suction group reduces the mass concentration in PM10 level.

Aerosol Pollution over St. Petersburg in Different Seasons Based on the Results of Lidar Measurements from 2014 to 2022

The results of long-term (during the 8-year period) observations of aerosol optical depth in the center of St. Petersburg are presented, which are performed using the stationary lidar complex of the Resource Center "Observatory of environmental safety", Research Park, St. Petersburg University. It has been established that the content of aerosol particles over the city prevails in the summer and spring seasons, while the minimum content of aerosols is observed in winter.

Classroom scale measurements of the efficacy of ventilation, filtration, and electronic air cleaners for the removal of aerosol particles

Exposure to aerosol particles in the indoor environment is of particular importance due to the confinement of particles in poorly ventilated spaces. Reduction in the number concentration of aerosol particles can be achieved by increasing supply air flow rates and installation of in-room particle filtration devices. Electronic air cleaning technology has been proposed as a low-cost mitigation strategy, although the efficacy and unintended consequences on indoor air quality are not well characterized. We determined the efficacy of ventilation, in-room filtration, and air ionizers for the reduction of aerosol number concentrations in an unoccupied classroom. We focus on particles larger than 500 nm to assess the efficacy of this technology for reducing the number concentration of virus containing particles. We show that increases in supply air flow and in-room HEPA filtration result in reductions in particle number concentrations at clean air delivery rates that match those measured at the supply air register or specified by the filtration unit. We find no evidence for a reduction in particle number concentrations, or enhanced deposition, for the air ionizers tested. For two of the air ionizer units tested rapid new particle formation and growth (10 nm h−1) was observed. We directly measured the speciation of air ions from both tube-based and needlepoint bipolar ionizer (BPI) devices. We do not observe highly reactive ions such as O2− in the immediate vicinity of the BPI device. In contrast, we observe stable ions, such as NO3−, that have limited disinfecting power when exhausted to the room.

Effect of radiation interaction and aerosol processes on ventilation and aerosol concentrations in a real urban neighbourhood in Helsinki

Abstract. Large-eddy simulation (LES) is an optimal tool to examine aerosol particle concentrations in detail within urban neighbourhoods. The concentrations are a complex result of local emissions, meteorology, aerosol processes and local mixing conditions due to thermal and mechanical effects. Despite this, most studies have focused on simplification of the affecting processes such as examining the impact of local mixing in idealised street canyons or treating aerosols as passive scalars. The aim of this study is to include all these processes into LES using the PALM model system and to examine the importance of radiative heating and aerosol processes in simulating local aerosol particle concentrations and different aerosol metrics within a realistic urban neighbourhood in Helsinki under morning rush hour with calm wind conditions. The model outputs are evaluated against mobile laboratory measurements of air temperature and total particle number concentration (Ntot) as well as drone measurements of lung-deposited surface area (LDSA). The inclusion of radiation interaction in LES has a significant impact on simulated near-surface temperatures in our study domain, increasing them on average from 8.6 to 12.4 ∘C. The resulting enhanced ventilation reduces the pedestrian-level (4 m) Ntot by 53 %. The reduction in Ntot due to aerosol processes is smaller, only 18 %. Aerosol processes particularly impact the smallest particle range, whereas radiation interaction is more important in the larger particle range. The inclusion of radiation interaction reduces the bias between the modelled and mobile-laboratory-measured air temperatures from −3.9 to +0.2 ∘C and Ntot from +98 % to −13 %. With both aerosol and radiation interaction on, the underestimation is 16 %, which might be due to overestimation of the ventilation. The results show how inclusion of radiative interaction is particularly important in simulating PM2.5, whereas aerosol processes are more important in simulating LDSA in this calm wind situation.

Mathematical Model of Propagation of an Aerosol Created by an Impulse Method in Space.

When developing neutralization systems for harmful agents, it is necessary to understand the mechanisms of the formation and evolution of an aerosol cloud in a closed or open space. Effective decontamination with aerosol clouds is provided by a rather high particle concentration and dispersion in an open space or on contaminated surfaces. This paper considers neutralization systems based on pulsed powder aerosol generators. It is shown that an aerosol cloud consisting of micron- and submicron-sized particles appears for several seconds after spraying. A further evolution of the aerosol cloud in a room is associated with the gravitational settling, diffusion, and coagulation of particles and their settling on the walls and ceiling. In the case of an open space or a ventilation system in a room, the evolution of the aerosol cloud is affected by the airflow. The main purpose of this paper is to determine the most important parameters and critical conditions of pulsed aerosol generation. A mathematical model is, thus, proposed for pulsed aerosol generation, and its parametric study is conducted in the most typical conditions. The purpose performance predicted by the model is the mass concentration of aerosol particles in the air and on surfaces, depending on the time of particle spraying and dispersion.

Quantitative Microbial Risk Assessment of Contracting COVID-19 Derived from Measured and Simulated Aerosol Particle Transmission in Aircraft Cabins.

SARS-CoV-2 can be effectively transmitted between individuals located in close proximity to each other for extended durations. Aircraft provide such conditions. Although high attack rates during flights were reported, little was known about the risk levels of aerosol transmission of SARS-CoV-2 in aircraft cabins. The major objective was to estimate the risk of contracting COVID-19 from transmission of aerosol particles in aircraft cabins. In two single-aisle and one twin-aisle aircraft, dispersion of generated aerosol particles over a seven-row economy class cabin section was measured under cruise and taxi conditions and simulated with a computational fluid dynamic model under cruise conditions. Using the aerosol particle dispersion data, a quantitative microbial risk assessment was conducted for scenarios with an asymptomatic infectious person expelling aerosol particles by breathing and speaking. Effects of flight conditions were evaluated using generalized additive mixed models. Aerosol particle concentration decreased with increasing distance from the infectious person, and this decrease varied with direction. On a typical flight with an average shedder, estimated mean risk of contracting COVID-19 ranged from to . Risk increased to with a super shedder ( of cases) on a long flight. Risks increased with increasing flight duration: 2-23 cruise flights of typical duration and 2-10 flights of longer duration resulted in at least 1 case of COVID-19 due to onboard aerosol transmission by one average shedder, and in the case of one super shedder, at least 1 case in 1-3 flights of typical duration cruise and 1 flight of longer duration. Our findings indicate that the risk of contracting COVID-19 by aerosol transmission in an aircraft cabin is low, but it will not be zero. Testing before boarding may help reduce the chance of a (super)shedder boarding an aircraft and mask use further reduces aerosol transmission in the aircraft cabin. https://doi.org/10.1289/EHP11495.