Distribution Of Aerosol Particles Research Articles

Conjugate analysis of the particle size distribution of aerosol matter in the surface air and snow cover: the effect of air masses on the distribution of aerosol particles

Conjugate analysis of the particle size distribution of aerosol matter in the surface air and snow cover: the effect of air masses on the distribution of aerosol particles

Droplet Size and Distribution of Nebulized 3% Sodium Chloride, Albuterol, and Epoprostenol by Phase Doppler Particle Analyzer

BackgroundAerosolized drug therapy administered to mechanically ventilated patients is a standard part of pulmonary critical care medicine. Aerosol particle size and distribution are important factors in the optimal delivery of aerosolized drugs to ventilated patients.ObjectiveThe objective of this study was to characterize aerosol droplet size and distribution with laser diffraction for nebulized 3% sodium chloride, albuterol, and epoprostenol sodium (containing glycine) delivered via Aeroneb Solo Mesh Nebulizers (Aerogen, Mountain View, California).MethodsA series of functional flow tests were run on each of 8 Solo mesh nebulizers before the study to verify accuracy of flow rates in milliliters per minute. Aerosolized droplets exiting the nebulizer heads were then measured using a phase Doppler particle analyzer. Data collected during delivery of 3% sodium chloride, albuterol, and epoprostenol sodium included aerosol droplet size distribution, mass median aerodynamic diameter (MMAD), and geometric standard deviation. For each Solo nebulizer, droplet size measurements were taken 2 cm away from the nebulizer head and 2 cm away from the wye of a heated, humidified adult ventilator circuit. For measurements taken at the wye, 4 distinct, continuous flow rates (2, 10, 20, and 40 L/min) were generated by an air pump to simulate inspiratory flows delivered with mechanical ventilation. The expiratory limb was capped, and the nebulizer head was inserted into the breathing circuit upstream of the humidifier.ResultsEach Solo nebulizer met Aerogen's recommended minimum flow rate of 0.2 mL/min, ranging from 0.23 to 0.31 mL/min. The MMAD of the 3 tested aerosols was several times smaller when measured at the wye outlet of the heated/humidified breathing circuit (0.82–2.73 µm) compared with droplets measured directly at the nebulizer outlet (MMAD, 4.6–7.3 µm). There was also significant variability across Solo heads with some ventilator flow rates. The mean MMAD at the wye for the 3% sodium chloride solution, albuterol, and epoprostenol test solutions was 1.62 µm, 1.09 µm, and 1.18 µm, respectively. The mean MMAD at the nebulizer for the 3% sodium chloride solution, albuterol, and epoprostenol test solutions was 5.37 µm, 5.73 µm, and 6.73 µm, respectively.ConclusionsResults from this study suggest that particle size of aerosolized drugs administered via a commonly used setup for delivery of in-line aerosols to mechanically ventilated patients may be several times smaller than expected and may result in less drug being delivered to the patient than previously realized.(Curr Ther Res Clin Exp. 2021; 82:XXX–XXX)© 2021 Elsevier HS Journals, Inc.

Mass Extinction Efficiency Approximation for Polydispersed Aerosol Using Harmonic Mean-Type Approximation

Among many parameters characterizing atmospheric aerosols, aerosol mass extinction efficiency (MEE) is important for understanding the optical properties of aerosols. MEE is expressed as a function of the refractive indices (i.e., composition) and size distributions of aerosol particles. Aerosol MEE is often considered as a size-independent constant that depends only on the chemical composition of aerosol particles. The famous Malm’s reconstruction equation and subsequent revised methods express the extinction coefficient as a function of aerosol mass concentration and MEE. However, the used constant MEE does not take into account the effect of the size distribution of polydispersed chemical composition. Thus, a simplified expression of size-dependent MEE is required for accurate and conventional calculations of the aerosol extinction coefficient and also other optical properties. In this study, a simple parameterization of MEE of polydispersed aerosol particles was developed. The geometric volume–mean diameters of up to 10 µm with lognormal size distributions and varying geometric standard deviations were used to represent the sizes of various aerosol particles (i.e., ammonium sulfate and nitrate, elemental carbon, and sea salt). Integrating representations of separate small mode and large mode particles using a harmonic mean-type approximation generated the flexible and convenient parameterizations of MEE that can be readily used to process in situ observations and adopted in large-scale numerical models. The calculated MEE and the simple forcing efficiency using the method developed in this study showed high correlations with those calculated using the Mie theory without losing accuracy.

Sensitivity of spatial aerosol particle distributions to the boundary conditions in the PALM model system 6.0

Abstract. High-resolution modelling is needed to understand urban air quality and pollutant dispersion in detail. Recently, the PALM model system 6.0, which is based on large-eddy simulation (LES), was extended with the detailed Sectional Aerosol module for Large Scale Applications (SALSA) v2.0 to enable studying the complex interactions between the turbulent flow field and aerosol dynamic processes. This study represents an extensive evaluation of the modelling system against the horizontal and vertical distributions of aerosol particles measured using a mobile laboratory and a drone in an urban neighbourhood in Helsinki, Finland. Specific emphasis is on the model sensitivity of aerosol particle concentrations, size distributions and chemical compositions to boundary conditions of meteorological variables and aerosol background concentrations. The meteorological boundary conditions are taken from both a numerical weather prediction model and observations, which occasionally differ strongly. Yet, the model shows good agreement with measurements (fractional bias <0.67, normalised mean squared error <6, fraction of the data within a factor of 2 >0.3, normalised mean bias factor <0.25 and normalised mean absolute error factor <0.35) with respect to both horizontal and vertical distribution of aerosol particles, their size distribution and chemical composition. The horizontal distribution is most sensitive to the wind speed and atmospheric stratification, and vertical distribution to the wind direction. The aerosol number size distribution is mainly governed by the flow field along the main street with high traffic rates and in its surroundings by the background concentrations. The results emphasise the importance of correct meteorological and aerosol background boundary conditions, in addition to accurate emission estimates and detailed model physics, in quantitative high-resolution air pollution modelling and future urban LES studies.

The evolution of cloud and aerosol microphysics at the summit of Mt. Tai, China

Abstract. The influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and the behaviours of clouds and their influence on climate. In an attempt to better understand the microphysical properties of cloud droplets, the simultaneous variations in aerosol microphysics and their potential interactions during cloud life cycles in the North China Plain, an intensive observation took place from 17 June to 30 July 2018 at the summit of Mt. Tai. Cloud microphysical parameters were monitored simultaneously with number concentrations of cloud condensation nuclei (NCCN) at different supersaturations, PM2.5 mass concentrations, particle size distributions and meteorological parameters. Number concentrations of cloud droplets (NC), liquid water content (LWC) and effective radius of cloud droplets (reff) show large variations among 40 cloud events observed during the campaign. The low values of reff and LWC observed at Mt. Tai are comparable with urban fog. Clouds on clean days are more susceptible to the change in concentrations of particle number (NP), while clouds formed on polluted days might be more sensitive to meteorological parameters, such as updraft velocity and cloud base height. Through studying the size distributions of aerosol particles and cloud droplets, we find that particles larger than 150 nm play important roles in forming cloud droplets with the size of 5–10 µm. In general, LWC consistently varies with reff. As NC increases, reff changes from a trimodal distribution to a unimodal distribution and shifts to smaller size mode. By assuming a constant cloud thickness and ignoring any lifetime effects, increase in NC and decrease in reff would increase cloud albedo, which may induce a cooling effect on the local climate system. Our results contribute valuable information to enhance the understanding of cloud and aerosol properties, along with their potential interactions on the North China plain.

Numerical investigation of aerosol transport in a classroom with relevance to COVID-19.

The present study investigates aerosol transport and surface deposition in a realistic classroom environment using computational fluid-particle dynamics simulations. Effects of particle size, aerosol source location, glass barriers, and windows are explored. While aerosol transport in air exhibits some stochasticity, it is found that a significant fraction (24%–50%) of particles smaller than 15 µm exit the system within 15 min through the air conditioning system. Particles larger than 20 µm almost entirely deposit on the ground, desks, and nearby surfaces in the room. Source location strongly influences the trajectory and deposition distribution of the exhaled aerosol particles and affects the effectiveness of mitigation measures such as glass barriers. Glass barriers are found to reduce the aerosol transmission of 1 µm particles from the source individual to others separated by at least 2.4 m by ∼92%. By opening windows, the particle exit fraction can be increased by ∼38% compared to the case with closed windows and reduces aerosol deposition on people in the room. On average, ∼69% of 1 µm particles exit the system when the windows are open.

Vertical distributions of boundary-layer ozone and fine aerosol particles during the emission control period of the G20 summit in Shanghai, China

Vertical observations of ozone (O3) and fine aerosol particles (PM2.5) below 3000 m above ground level were made by an O3 lidar and two hexacopter unmanned aerial system (UAS) platforms to investigate vertical distributions of the boundary-layer O3 and PM2.5 and their effects on surface air quality. Field observations were conducted in Shanghai, China before, during, and after the G20 Summit (Hangzhou) from 23 August to 13 September 2016, when stringent emission control measures were implemented over the Yangtze River Delta region. The results show that surface O3 and PM2.5 concentrations increased evidently during the emission control period due to the significant contribution of transport. Different transport types including regional transport, recirculation transport, and long-range transport were captured in the three stages of the emission control period. Regional transport mainly occurred in the middle and upper boundary layer, leading to positive altitude dependence of the boundary-layer O3 and PM2.5. Recirculation transport mainly occurred in the lower boundary layer, leading to negative altitude dependence of the boundary-layer O3 and PM2.5. Long-range transport of O3 mainly occurred in the lower free troposphere, leading to positive altitude dependence of the boundary-layer O3. Under the influence of northeasterly winds, Shanghai exhibited considerable transport potential of pollutants to Hangzhou during the emission control period. The findings in this study could help to understand complex interactions between different transport types and variations in surface air pollutant concentrations, as well as provide important implications in making regional emission control measures in the future.

Aerosol Measurements by Soot Particle Aerosol Mass Spectrometer: a Review

Atmospheric aerosol particles, being composed of various types of chemical mixtures, affect significantly on human health and climate. During the last decade, many studies were focused on characterization of chemical and physical properties as well as source apportionment of atmospheric aerosols, which have made substantial implications for aerosol-induced air pollution and climate mitigation. Instrumental measurement techniques provide one of the most direct and effective ways to determine aerosol physicochemical characterization and thereby to constrain aerosol modeling. The Aerodyne soot particle aerosol mass spectrometer (SP-AMS), a state-of-the-art instrument, combines the advantages of both high-resolution time-of-flight AMS (HR-ToF-AMS) and single particle soot photometer (SP2). It can measure high-resolution chemical composition, size distribution, and mixing state of both non-refractory and refractory aerosol particles. Specially, chemical-resolved coating materials of refractory black carbon-containing particles can be quantified by SP-AMS. Moreover, same as HR-ToF-AMS, highly time-resolved organic mass spectral data can be applied for further identification and quantification of organic aerosol sources with receptor models, such as positive matrix factorization (PMF). This review summarizes results and findings obtained by recent SP-AMS measurements in field observations and laboratory studies. These SP-AMS measurements mainly cover the topics of soot cluster ions, trace metals, chemical composition and sources of non-refractory bulk aerosols, mixing state, and light absorption properties of black carbon-containing particles. Finally, we propose some potential prospects for future studies by using the SP-AMS.

Observations of Aerosol, Cloud, Turbulence, and Radiation Properties at the Top of the Marine Boundary Layer over the Eastern North Atlantic Ocean: The ACORES Campaign

AbstractWe report on the Azores Stratocumulus Measurements of Radiation, Turbulence and Aerosols (ACORES) campaign, which took place around Graciosa and Pico Islands/Azores in July 2017. The main objective was to investigate the vertical distribution of aerosol particles, stratocumulus microphysical and radiative properties, and turbulence parameters in the eastern North Atlantic. The vertical exchange of mass, momentum, and energy between the free troposphere (FT) and the cloudy marine boundary layer (MBL) was explored over a range of scales from submeters to kilometers. To cover these spatial scales with appropriate measurements, helicopter-borne observations with unprecedented high resolution were realized using the Airborne Cloud Turbulence Observation System (ACTOS) and Spectral Modular Airborne Radiation Measurement System–Helicopter-Borne Observations (SMART-HELIOS) instrumental payloads. The helicopter-borne observations were combined with ground-based aerosol measurements collected at two continuously running field stations on Pico Mountain (2,225 m above sea level, in the FT), and at the Atmospheric Radiation Measurement (ARM) station on Graciosa (at sea level). First findings from the ACORES observations we are discussing in the paper are as follows: (i) we have observed a high variability of the turbulent cloud-top structure on horizontal scales below 100 m with local temperature gradients of up to 4 K over less than 1 m vertical distance, (ii) we have collected strictly collocated radiation measurements supporting the relevance of small-scale processes by revealing significant inhomogeneities in cloud-top brightness temperature to scales well below 100 m, and (iii) we have concluded that aerosol properties are completely different in the MBL and FT with often-complex stratification and frequently observed burst-like new particle formation.

The Giant Nucleus Impactor (GNI)—A System for the Impaction and Automated Optical Sizing of Giant Aerosol Particles with Emphasis on Sea Salt. Part I: Basic Instrument and Algorithms

AbstractSize distributions of giant aerosol particles (dry radius larger than 0.5μm, sometimes referred to as coarse-mode aerosol particles) are not well characterized in the atmosphere. Measurements are problematic for these particles because they (i) occur in low concentrations, (ii) have difficulty in passing through air inlets, (iii) may be dry or deliquesced particles, and (iv) if sampled by impaction, typically require labor-intensive methods. In this study, a simple, high-volume impaction system called the Giant Nucleus Impactor (GNI), based on free-stream exposure of polycarbonate slides from aircraft, is described along with an automated optical microscope–based system for analysis of the impacted particles. The impaction slides are analyzed in a humidity-controlled chamber (typically 90% relative humidity) that ensures deliquescence of soluble (typically sea salt) particles. A computer-controlled optical microscope with two digital cameras is used to acquire and analyze images of the aerosol particles. At relative humidities above deliquescence (74% RH for sea salt), such particles will form near-spherical cap solution drops on the polycarbonate slides. The sea-salt mass in each giant aerosol particle is then calculated using simple geometry and published water activity measurements. The system has a sample volume of about 10 L s−1at aircraft speeds of 105 m s−1. For salt particles, the measurement range is from about 0.7μm dry radius to at least 16μm dry radius, with a size-bin resolution of 0.2μm dry radius. The sizing accuracy was tested using polystyrene latex (PSL) beads of known size.

Carle Illinois College of Medicine.

Carle Illinois College of Medicine.

Numerical method development for oxidation particle formation during sodium spray fires in SFR containment

A new method was developed to predict particle generation during sodium spray fire by combining the spray combustion models and the classical nucleation theory. 224 data points calculated in the evaluation process show that the influence of oxygen concentration and temperature on the particle formation can be almost neglected when the sodium droplet mean diameter is less than 0.2 cm though observed data and the spray droplet diameter has the greatest effect on particle generation among them. Subsequently, the correlation between particle generation number and sodium burning rate can be obtained by fitting method as well as the conversion between the particle number and mass. The calculation results of the code with and without this method show that the predicted thermal-hydraulic responses, suspended aerosol concentration and particle distribution agree well with the experimental data in both cases, which shows the reliability of the particle generation method developed in this work.

Investigation of the distribution of particles of drugs with the help of cascade impactor

BACKGROUND. Successful nebulization is a result of joint usage of nebulizer and medication, which equally define availability and disposition of the active substance. Amount of the substance delivered by different nebulizer systems may differ in more than 10 times.
 OBJECTIVE. The aim of the study was to investigate the distribution of aerosol particles of drugs for inhalation manufactured by «Yuria-Pharm» under conditions of usage of Ulaizer Home.
 MATERIALS AND METHODS. We investigated Ulaizer Home nebulizer and medications for inhalation (Decasan, Lorde hyal, Nebufluson, Nebutamol) with the help of new generation impactor (“Copley Scientific Limited”, Great Britain).
 RESULTS AND DISCUSSION. Mass median aerodynamic diameter (MMAD) of Decasan particles was 4.878 µm, geometric standard deviation (GSD) – 1.72. MMAD of Lorde hyal particles was 3.194 µm, GSD – 1.556. Drop distribution for Nebutamol was alike the distribution for non-viscous aqueous solutions (MMAD – 5.363 µm, GSD – 1.924). For Nebufluson MMAD was 5.491 µm, GSD – 1.724.
 CONCLUSIONS. The delivery of the inhaled drug to the required area of the respiratory system is a key to successful nebulization. It directly depends on the parameters of the aerosol. The distribution of particles of drugs manufactured by «Yuria-Pharm» in case of nebulization using Ulaizer Home allows to deliver the required amount of drug to the predefined parts of the respiratory system.

Multi-wavelength radiometry of aerosols designed for more accurate night sky brightness predictions

Scattering by aerosols and gases cause a certain fraction of artificial light emitted upwards is redirected to the ground. Of all atmospheric constituents just the aerosols are most important modulators of night-sky brightness under cloudless conditions. Unlike most of the previous we highlight a crucial role of solar radiometry for determining the atmospheric optical depth before night-time observation is to be made. Aerosol optical depth at visible wavelengths extracted from the data measured provides then the information on size distribution or mean refractive index of aerosol particles that in turn are both necessary to make night sky brightness prediction more accurate. Therefore, combining daytime and night-time radiometry we can achieve accuracy much higher than ever before. This is due to significantly reduced uncertainty in aerosol properties.The aerosol data are retrieved from a new portable multi-wavelength optical analyzer that operates Ocean Optics spectrometer. The equipment provides the radiance data from 350 nm to 1000 nm with spectral resolution of 1 nm. Due to high sun radiance levels we use a system of mirrors each reducing the signal to about 4%, while keeping the integration time short. The minimum integration time of 3 ms allows for detection of direct sunlight. The system developed is sensitive to small changes in the aerosol system, while showing a good detection limit even under low turbidity conditions. The system performance is demonstrated in field experiment conducted shortly after front passage when most of aerosol particles is effectively removed by rain.

Overview of aerosol optical properties over southern West Africa from DACCIWA aircraft measurements

Abstract. Southern West Africa (SWA) is an African pollution hotspot but a relatively poorly sampled region of the world. We present an overview of in situ aerosol optical measurements collected over SWA in June and July 2016 as part as of the DACCIWA (Dynamics-Aerosol-Chemistry-Clouds Interactions in West Africa) airborne campaign. The aircraft sampled a wide range of air masses, including anthropogenic pollution plumes emitted from the coastal cities, long-range transported biomass burning plumes from central and southern Africa and dust plumes from the Sahara and Sahel region, as well as mixtures of these plumes. The specific objective of this work is to characterize the regional variability of the vertical distribution of aerosol particles and their spectral optical properties (single scattering albedo: SSA, asymmetry parameter, extinction mass efficiency, scattering Ångström exponent and absorption Ångström exponent: AAE). The first findings indicate that aerosol optical properties in the planetary boundary layer were dominated by a widespread and persistent biomass burning loading from the Southern Hemisphere. Despite a strong increase in aerosol number concentration in air masses downwind of urban conglomerations, spectral SSA were comparable to the background and showed signatures of the absorption characteristics of biomass burning aerosols. In the free troposphere, moderately to strongly absorbing aerosol layers, dominated by either dust or biomass burning particles, occurred occasionally. In aerosol layers dominated by mineral dust particles, SSA varied from 0.81 to 0.92 at 550 nm depending on the variable proportion of anthropogenic pollution particles externally mixed with the dust. For the layers dominated by biomass burning particles, aerosol particles were significantly more light absorbing than those previously measured in other areas (e.g. Amazonia, North America), with SSA ranging from 0.71 to 0.77 at 550 nm. The variability of SSA was mainly controlled by variations in aerosol composition rather than in aerosol size distribution. Correspondingly, values of AAE ranged from 0.9 to 1.1, suggesting that lens-coated black carbon particles were the dominant absorber in the visible range for these biomass burning aerosols. Comparison with the literature shows a consistent picture of increasing absorption enhancement of biomass burning aerosol from emission to remote location and underscores that the evolution of SSA occurred a long time after emission. The results presented here build a fundamental basis of knowledge about the aerosol optical properties observed over SWA during the monsoon season and can be used in climate modelling studies and satellite retrievals. In particular and regarding the very high absorbing properties of biomass burning aerosols over SWA, our findings suggest that considering the effect of internal mixing on absorption properties of black carbon particles in climate models should help better assess the direct and semi-direct radiative effects of biomass burning particles.

Characteristics of biological and non-biological aerosol particles in indoor environment and their inhalable fractions in the human lung

Air quality of public buildings is an important to assess human health. School and university buildings represent an important category of indoor environments. This study aimed to evaluate the concentration and size distribution of fungal and non-biological aerosol particles in classrooms of Minia university, Egypt. In addition, the inhalable fractions were determined and indoor exposure dose (IED) of fungi and aerosols were estimated for the students. A six-stage Andersen impactor was used for collecting the fungal particles and Berner cascade impactor was used for sampling the non-biological aerosol particles. indoor average concentration of fungi was 307±102 CFU/m3. The most frequently isolated genera were Aspergillus niger with concentration 175±85 CFU/m3 representing about 57% of the of the total collected fungi. Aspergillus flavus represents about 31% of the total fungi with concentration 96±32 CFU/m3. Low concentration 36 ±12 CFU/m3 of Penecillium was investigated representing only 12% of the total collected fungi. Mean concentration of non-biological aerosols was 442±99 µg/m3. The concentration of airborne fungal aerosol particles were lower than the World Health Organization guide line While the corresponding concentration of non-biological aerosols exceeds WHO limit. Most of the collected fungal particles were found in the inhalable size range (< 5µm) where inhalable fraction of fungi represents 84% of the total collected particles while inhalable fraction of non- biological aerosols represents 92% of the total collected particles. Size distributions of biological and non-biological aerosols were bimodal in nature. IED of fungi was 25.6 CFU/kg While the IED of non-biological aerosols was 37 CFU/kg.

Variation of size-segregated particle number concentrations in wintertime Beijing

Abstract. The spatial and temporal variability of the number size distribution of aerosol particles is an indicator of the dynamic behavior of Beijing's atmospheric pollution cocktail. This variation reflects the strength of different primary and secondary sources, such as traffic and new particle formation, as well as the main processes affecting the particle population. In this paper, we report size-segregated particle number concentrations observed at a newly developed Beijing station during the winter of 2018. Our measurements covered particle number size distributions over the diameter range of 1.5 nm–1 µm (cluster mode, nucleation mode, Aitken mode and accumulation mode), thus being descriptive of a major fraction of the processes taking place in the atmosphere of Beijing. Here we focus on explaining the concentration variations in the observed particle modes, by relating them to the potential aerosol sources and sinks, and on understanding the connections between these modes. We considered haze days and new particle formation event days separately. Our results show that during the new particle formation (NPF) event days increases in cluster mode particle number concentration were observed, whereas during the haze days high concentrations of accumulation mode particles were present. There was a tight connection between the cluster mode and nucleation mode on both NPF event and haze days. In addition, we correlated the particle number concentrations in different modes with concentrations of trace gases and other parameters measured at our station. Our results show that the particle number concentration in all the modes correlated with NOx, which reflects the contribution of traffic to the whole submicron size range. We also estimated the contribution of ion-induced nucleation in Beijing, and we found this contribution to be negligible.

Vertical distribution of aerosol mass concentration over Pearl River Delta observed by Lidar during autumn and winter

This study aims to analyze the vertical distribution of aerosol particles during autumn and winter by deriving the number density of aerosol particles from Mie Lidar return signals. Haze has always existed in regions with low humidity and stable weather. In such regions,particle vertical distribution characters are needed for transport mechanisms. As a widely used instrument, Mie Lidar surfer from the uncertainties caused by the Lidar ratio and boundary value assumption. However, Mie Lidar is the most powerful tool to observe the atmospheric vertical distribution because it performs well in day and night under all weather conditions in comparison with passive sensors.Moreover, Mie Lidar is easier to carry compared with Raman Lidar.Lidar radiation principles were studied to understand the Lidar equation and its solution. Several parameters were carefully chosen for the numerical solutions. Instead of using boundary value for approximation, the Lidar parameter k was directly calculated on the basis of Lidar-validated parameters to avoid uncertainties. Thus, aerosol particles backscatter and extinction coefficient were retrieved by solving the Lidar equation and integrated for Aerosol Optical Depth(AOD) results. A Cimel CE318 sun photometer and an ASD Field Spec3 were used to measure AOD as validation data. Lastly, the number density of aerosol particles was derived on the basis of Mie theory with the estimation of aerosol particle distribution, size, and refractive index of particles.According to the number density vertical profile, nearly no difference was observed between the number density vertical profile of aerosol particles during daytime and nighttime in one day at a low altitude. This result indicated that the sunlight effect is ignorable for aerosol particle distribution near ground. The retrieved AODs with the CE318 and ASD observations showed a root mean square error of approximately 0.0541 and 0.0100, demonstrating that the retrieved result is reliable. The comparison with traditional method showed that the proposed algorithm in this study improved the accuracy of the traditional Lidar equation solution. The near-real distribution results showed aerosol particle distribution characteristics near the ground. The number density of aerosol particles in Guangzhou was mainly distributed in low-altitude regions, and its relationship with height was approximately a negative exponential distribution. The retrieved results of the aerosol particle number density were similar to those from the previous years, indicating that the air pollution in Guangzhou has not worsened. However, potential environmental threats and air pollution problems still need to be governed.Several uncertainties, such as changes in air temperature and pressure, validation of Lidar instrument k, and overlap factor, that could cause deviation were identified. The overlap factor and molecular backscatter coefficient were carefully calculated using the theoretical method. Frequent updates on Lidar parameters will be requested from the Lidar company in the future. The theoretical and experimental methods were combined for the calculation of the overlap factor and molecular backscatter coefficient. Raman Lidar was used to measure the actual Lidar ratios and characteristics of molecular scatter.The aerosol particle number density-retrieved algorithm was based on Lidar radiation principles and revealed the particles’ spatial distribution characters. The vertical distribution characters remained unchanged for several days under stable weather in the autumn and winter seasons, and its relationship with height was approximately a negative exponential distribution;hence, air conditions can have huge effect on human health. Air pollution problem still needs to be governed.

Assessing the accuracy of low-cost optical particle sensors using a physics-based approach.

Low-cost sensors for measuring particulate matter (PM) offer the ability to understand human exposure to air pollution at spatiotemporal scales that have previously been impractical. However, such low-cost PM sensors tend to be poorly characterized, and their measurements of mass concentration can be subject to considerable error. Recent studies have investigated how individual factors can contribute to this error, but these studies are largely based on empirical comparisons and generally do not examine the role of multiple factors simultaneously. Here, we present a new physics-based framework and open-source software package (opcsim) for evaluating the ability of low-cost optical particle sensors (optical particle counters and nephelometers) to accurately characterize the size distribution and/or mass loading of aerosol particles. This framework, which uses Mie theory to calculate the response of a given sensor to a given particle population, is used to estimate the fractional error in mass loading for different sensor types given variations in relative humidity, aerosol optical properties, and the underlying particle size distribution. Results indicate that such error, which can be substantial, is dependent on the sensor technology (nephelometer vs. optical particle counter), the specific parameters of the individual sensor, and differences between the aerosol used to calibrate the sensor and the aerosol being measured. We conclude with a summary of likely sources of error for different sensor types, environmental conditions, and particle classes and offer general recommendations for the choice of calibrant under different measurement scenarios.

Ship borne studies of the distribution of PAHs and PM10 in the near-water atmospheric layer of Lake Baikal in the summer of 2016-2017

This work discusses the results of shipborne studies concerning the spatial distribution of PAHs and aerosol particles in the near-water atmospheric layer of Lake Baikal in July 2016-2017. We observed high concentrations of polluting components near the local sourceson the coast of the lake as well as in smoke plumes from wildfires. The low PAH concentrations recorded in 2017in the absence of wildfires were comparable with those of 2002 and 2008. Using the backward trajectory models, we traced air mass movements from the pollution sources to the lake.