Aerosol Particle Size Research Articles

An overlooked route of inhalation exposure to tap water constituents for children and adults: Aerosolized aqueous minerals from ultrasonic humidifiers

Fine particulates and aerosols emitted by commonly used, room-sized ultrasonic humidifiers may pose adverse health effects to children and adults. The literature documents adverse effects for children exposed to minerals emitted from humidifiers. This study performs novel and comprehensive characterization of bivariate particle size and element concentrations of emitted airborne aerosols and particles from ultrasonic humidifiers filled with tap water, including size distribution from 0.014 to 10 μm by scanning mobility particle sizer and AeroTrak; corresponding metal and elemental concentrations as a function of particle size by inductively coupled plasma mass spectrometer; and calculations of deposition fraction in human lungs for age-specific groups using the multi-path particle dosimetry model (MPPD). Deposition fraction is the ratio of mass deposited to total mass inhaled. When filled with tap water, water evaporated from emitted aerosols to form submicron particles that became essentially “dried tap water” with median size 146 nm and mean concentration of 211 μg-total elements/m3-air including 35 μg-calcium/m3-air in a room of 33.5 m3 and air exchange rate at ∼0.8 hr−1. Approximately 90% of emitted particles deposited in human lungs were <1 μm as shown by MPPD model. The smaller particles contained little water and higher concentration of minerals, while larger particles of >1 μm consisted of lower elemental concentrations and more water due to low evaporation. Deposition fraction in pulmonary region was ∼2-fold higher, and deposited particulate mass was 3.5-fold higher for children than adults, indicating greater inhalation exposure to children compared to adults. Modeled data of total particles mass per body weight (BW) that will deposit in adult and child lungs after 8-h humidifier exposure were respectively 2.8 μg/kg-BW and 9.8 μg/kg-BW, where calcium contributes 0.4 μg/kg-BW and 1.6 μg/kg-BW. This comprehensive study of bivariate inorganic chemical composition as a function of particle size expanded, quantified, and modeled exposure for children and adults to aerosolized calcium and other inorganic constituents in water.

A Method for Retrieving Stratospheric Aerosol Extinction and Particle Size from Ground-Based Rayleigh-Mie-Raman Lidar Observations

We report on the retrieval of stratospheric aerosol particle size and extinction coefficient profiles from multi-color backscatter measurements with the Rayleigh–Mie–Raman lidar operated at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) in northern Norway. The retrievals are based on a two-step approach. In a first step, the median radius of an assumed monomodal log-normal particle size distribution with fixed width is retrieved based on a color index formed from the measured backscatter ratios at the wavelengths of 1064 nm and 532 nm. An intrinsic ambiguity of the retrieved aerosol size information is discussed. In a second step, this particle size information is used to convert the measured lidar backscatter ratio to aerosol extinction coefficients. The retrieval is currently based on monthly-averaged lidar measurements and the results for March 2013 are discussed. A sensitivity study is presented that allows for establishing an error budget for the aerosol retrievals. Assuming a monomodal log-normal aerosol particle size distribution with a geometric width of S = 1.5, median radii on the order of below 100 nm are retrieved. The median radii are found to generally decrease with increasing altitude. The retrieved aerosol extinction profiles are compared to observations with the OSIRIS (Optical Spectrograph and InfraRed Imager System) and the OMPS-LP (Ozone Mapping Profiling Suite Limb Profiler) satellite instruments in the 60∘ N to 80∘ N latitude band. The extinction profiles that were retrieved from the lidar measurements show good agreement with the observations of the two satellite instruments when taking the different wavelengths of the instruments into account.

Continuous and comprehensive atmospheric observations in Beijing: a station to understand the complex urban atmospheric environment

ABSTRACT Due to profound impact on climate and human health, air quality has attracted attention from all levels of the civil society. The key step in the provision of required tools for the society to tackle the complex air quality problem is to characterize it in a comprehensive manner with a long-term perspective. Here, we describe a continuous and comprehensive observation station and its accompanying state-of-the-art instrumentation that was established to investigate the complex urban atmospheric environment in a rapidly developing Chinese Megacity. The station, located in downtown Beijing, aims to study air quality by identifying the major atmospheric pollutants and key processes determining their formation and loss mechanisms. A few hundreds of parameters are continuously measured with the state-of-the-art instruments, including trace gas concentrations, aerosol particle size distributions, and mass concentrations, covering aerosol particle chemical composition from molecules to micrometer-sized aerosol particles. This produced long-term, comprehensive big data with around bytes per year. In this paper, we provide an overview on the facilities of the station, the instrumentation used, the workflow of continuous observations and examples of results from 2018 to 2019 and a basis for establishing a modern long-term, comprehensive atmospheric urban observation station in other megacities.

Voltage and e-liquid composition affect nicotine deposition within the oral cavity and carbonyl formation

IntroductionThe diversity of e-liquids along with higher powered e-cigarette nicotine delivery devices are increasing. This study evaluated the effect of voltage and e-liquid composition on particle size, nicotine deposition in...

Aerosol diffusion battery: Analytical inversion from noisy penetration data

Abstract A new simple algorithm of analytical inversion is proposed for the determination of aerosol particle size spectrum from diffusion battery penetrations. It is simpler and more transparent than analytical approaches published previously. The idea of the analytical solution is based on the operation principle of diffusion battery, which separates particles by their diffusivity into several classes. The size spectrum of particles in each class is approximated by a single-mode distribution, and the total size distribution is the sum of spectra from these classes. For this purpose, simple analytical formulas are derived to calculate the mean diameter of particles in each class from the diffusion battery penetrations. The advantage of the analytical approach is that it gives a one-to-one correspondence between the penetrations and the resulting spectrum without the necessity of complex mathematical processing, in contrast to the traditionally used numerical methods of solution of the inverse solution. However, experimental errors from the fluctuations of aerosol concentration can make the measured penetrations incompatible with any spectrum. Therefore, a smoothing procedure is proposed, which transforms incompatible penetrations into compatible ones within corridor of experimental errors.

Prediction of Aerosol Particle Size Distribution Based on Neural Network

Aerosol plays a very important role in affecting the earth-atmosphere radiation budget, and particle size distribution is an important aerosol property parameter. Therefore, it is necessary to determine the particle size distribution. However, the particle size distribution determined by the particle extinction efficiency factor according to the Mie scattering theory is an ill-conditioned integral equation, namely, the Fredholm integral equation of the first kind, which is very difficult to solve. To avoid solving such an integral equation, the BP neural network prediction model was established. In the model, the aerosol optical depth obtained by sun photometer CE-318 and kernel functions obtained by Mie scattering theory were used as the inputs of the neural network, particle size distributions collected by the aerodynamic particle sizer APS 3321 were used as the output, and the Levenberg–Marquardt algorithm with the fastest descending speed was adopted to train the model. For verifying the feasibility of the prediction model, some experiments were carried out. The results show that BP neural network has a better prediction effect than that of the RBF neural network and is an effective method to obtain the aerosol particle size distribution of the whole atmosphere column using the data of CE-318 and APS 3321.

Particle‐Size Distributions and Solubility of Aerosol Iron Over the Antarctic Peninsula During Austral Summer

AbstractThis study provides new data on the properties of aerosol iron (Fe) over the Antarctic Peninsula, one of the fastest warming regions on Earth in recent decades. Atmospheric deposition delivers Fe, a limiting micronutrient, to the Southern Ocean, and aerosol particle size influences the air‐to‐sea deposition rate and fractional solubility of aerosol Fe. Size‐segregated aerosols were collected at Palmer Station on the West Antarctic Peninsula during austral summer 2016–2017. Results show single‐mode size distribution of aerosol Fe, peaking at 4.4 μm diameter. The average concentration of total aerosol Fe was 1.3 (±0.40) ng m−3 (range 0.74–1.8 ng m−3). High concentrations of total aerosol Fe occurred in January, implying increased Fe source strength then. Total labile Fe varied between 0.019 and 0.095 ng m−3, and labile Fe (II) accounted for ~90% of the total labile Fe. The average fractional solubility for total Fe was 3.8% (±1.5%) (range 2.5–7.3%). Estimated dry deposition fluxes for the study period were 3.2 μg m−2 year−1 for total labile Fe and 83 μg m−2 year−1 for total Fe in aerosols. We speculate that local and regional dust sources in Antarctica contributed to the observed aerosol Fe in austral summer and that warming on the Antarctic Peninsula during the past half century may have increased the formation of dust sources in this region. The potential biogeochemical impact of atmospheric Fe input to the West Antarctic Peninsula shelf waters and adjacent pelagic surface waters of the Southern Ocean may need to be re‐evaluated.

Issues related to the retrieval of stratospheric-aerosol particle size information based on optical measurements

Abstract. Stratospheric-sulfate aerosols play an important role in the physics and chemistry of the atmosphere. The radiative and chemical effects of stratospheric-sulfate aerosols depend critically on the aerosol particle size distribution and its variability. Despite extensive research spanning several decades, the scientific understanding of the particle size distribution of stratospheric aerosols is still incomplete. Particle size estimates (often represented by the median radius of an assumed monomodal log-normal distribution with a fixed width or by the effective radius) reported in different studies cover a wide range, even under background stratospheric conditions, and particle size estimates retrieved from satellite solar-occultation measurements in the optical spectral range show a tendency to be systematically larger than retrievals based on other optical methods. In this contribution we suggest a potential reason for these systematic differences. Differences between the actual aerosol particle size distribution and the size distribution function assumed for aerosol size retrievals may lead to systematic differences in retrieved aerosol size estimates. We demonstrate that these systematic differences may differ significantly for different measurement techniques, which is related to the different sensitivities of these measurement techniques to specific parts of the aerosol particle population. In particular, stratospheric-aerosol size retrievals based on solar-occultation observations may yield systematically larger particle size estimates (median or effective radii) compared to, e.g., lidar backscatter measurements. Aerosol concentration, on the other hand, may be systematically smaller in retrievals based on occultation measurements compared to lidar measurements. The results indicate that stratospheric-aerosol size retrievals based on occultation or lidar measurements have to be interpreted with caution, as long as the actual aerosol particle size distribution is not well known.

Influence of the dry aerosol particle size distribution and morphology on the cloud condensation nuclei activation. An experimental and theoretical investigation

Abstract. Combustion and other high-temperature processes frequently result in the emission of aerosols in the form of polydisperse fractal-like aggregates made of condensed-phase nanoparticles (soot for instance). If certain conditions are met, the emitted aerosol particles are known to evolve into important cloud condensation nuclei (CCN) in the atmosphere. In this work, the hygroscopic parameter κ of complex morphology aggregates is calculated from the supersaturation-dependent activated fraction Fa=Fa(SS) in the frame of κ-Köhler theory. The particle size distribution is approximated with the morphology-corrected volume equivalent diameter calculated from the electrical mobility diameter by taking into account the diameter of the primary particle and the fractal dimension of the aggregate experimentally obtained from transmission electron microscopy measurements. Activation experiments are performed in water supersaturation conditions using a commercial CCN-100 condensation nuclei counter. The model is tested in close-to-ideal conditions of size-selected, isolated spherical particles (ammonium sulfate nanoparticles dispersed in nitrogen), then with complex polydisperse fractal-like aggregates (soot particles activated by exposure to ozone with κ as low as 5×10-5) that represent realistic anthropogenic emissions in the atmosphere.

Aerosol characterization using satellite remote sensing of light pollution sources at night

ABSTRACT A demanding challenge in atmospheric research is the night-time characterization of aerosols using passive techniques, that is, by extracting information from scattered light that has not been emitted by the observer. Satellite observations of artificial night-time lights have been used to retrieve some basic integral parameters, like the aerosol optical depth. However, a thorough analysis of the scattering processes allows one to obtain substantially more detailed information on aerosol properties. In this letter, we demonstrate a practicable approach for determining the aerosol particle size number distribution function in the air column, based on the measurement of the angular radiance distribution of the scattered light emitted by night-time lights of cities and towns, recorded from low Earth orbit. The method is self-calibrating and does not require the knowledge of the absolute city emissions. The input radiance data are readily available from several spaceborne platforms, like the VIIRS-DNB radiometer onboard the Suomi-NPP satellite.

The Research Unit VolImpact: Revisiting the volcanic impact on atmosphere and climate – preparations for the next big volcanic eruption

This paper provides an overview of the scientific background and the research objectives of the Research Unit “VolImpact” (Revisiting the volcanic impact on atmosphere and climate – preparations for the next big volcanic eruption, FOR 2820). VolImpact was recently funded by the Deutsche Forschungsgemeinschaft (DFG) and started in spring 2019. The main goal of the research unit is to improve our understanding of how the climate system responds to volcanic eruptions. Such an ambitious program is well beyond the capabilities of a single research group, as it requires expertise from complementary disciplines including aerosol microphysical modelling, cloud physics, climate modelling, global observations of trace gas species, clouds and stratospheric aerosols. The research goals will be achieved by building on important recent advances in modelling and measurement capabilities. Examples of the advances in the observations include the now daily near-global observations of multi-spectral aerosol extinction from the limb-scatter instruments OSIRIS, SCIAMACHY and OMPS-LP. In addition, the recently launched SAGE III/ISS and upcoming satellite missions EarthCARE and ALTIUS will provide high resolution observations of aerosols and clouds. Recent improvements in modeling capabilities within the framework of the ICON model family now enable simulations at spatial resolutions fine enough to investigate details of the evolution and dynamics of the volcanic eruptive plume using the large-eddy resolving version, up to volcanic impacts on larger-scale circulation systems in the general circulation model version. When combined with state-of-the-art aerosol and cloud microphysical models, these approaches offer the opportunity to link eruptions directly to their climate forcing. These advances will be exploited in VolImpact to study the effects of volcanic eruptions consistently over the full range of spatial and temporal scales involved, addressing the initial development of explosive eruption plumes (project VolPlume), the variation of stratospheric aerosol particle size and radiative forcing caused by volcanic eruptions (VolARC), the response of clouds (VolCloud), the effects of volcanic eruptions on atmospheric dynamics (VolDyn), as well as their climate impact (VolClim).

Adapting the Aerogen Mesh Nebulizer for Dried Aerosol Exposures Using the PreciseInhale Platform.

Background: Many substances used in inhalation research are water soluble and can be administered as nebulized solutions. Typical examples are therapeutic, small-molecular agents, or macromolecules. Another category is a number of water-soluble agents used for airway diagnostics or disease modeling. Mesh nebulizers have facilitated well-controlled liquid aerosol exposures. Meanwhile, a benchtop inhalation platform, PreciseInhale, was developed for providing small-scale, well-controlled aerosol exposures in preclinical configurations. The purpose of the current research was to adapt the Aerogen mesh nebulizer to work within the PreciseInhale system for both cell culture and rodent exposures.Methods: The wet aerosols produced with the Aerogen Pro nebulizer were dried out in an aerosol holding chamber by supplying dry carrier air, which was provided by passing the incoming ambient air through a column with silica gel. The nebulizer was installed in an aerosol holding chamber between an upstream flow-rate pneumotach and a downstream aerosol monitor. By pulsing, the nebulizer output was reduced to 1%–10% of continuous operation to better match the exposure ventilation requirements. Additional drying was obtained by mantling the holding chamber with dried paper.Results and Conclusions: The nebulizer output was reduced to 3–30 μL/min and dried out before reaching the in vitro or in vivo exposure modules. Using solute concentrations in the range of 0.5%–2% (w/w), dried aerosols were produced with a mass median aerodynamic diameter of 1.5–2.0 μm, compared to the 4–5 μm droplets emitted by the nebulizer. Controlling the Aerogen nebulizer under a reduced output scheme within the PreciseInhale platform gave two major advantages: (i) by reducing aerosol output to better match exposure flow rates of single rodents, increased airway deposition yields were obtained in a range of 1%–10% relative to the nebulized amount of test substance and (ii) shrinking aerosol particle sizes through drying improved the peripheral lung deposition of test aerosols.

In Vitro Performance of an Investigational Vibrating-Membrane Nebulizer with Surfactant under Simulated, Non-Invasive Neonatal Ventilation Conditions: Influence of Continuous Positive Airway Pressure Interface and Nebulizer Positioning on the Lung Dose

Non-invasive delivery of nebulized surfactant has been a long-pursued goal in neonatology. Our aim was to evaluate the performance of an investigational vibrating-membrane nebulizer in a realistic non-invasive neonatal ventilation circuit with different configurations. Surfactant (aerosols were generated with a nebulizer in a set-up composed of a continuous positive airway pressure (CPAP) generator with a humidifier, a cast of the upper airway of a preterm infant (PrINT), and a breath simulator with a neonatal breathing pattern. The lung dose (LD), defined as the amount of surfactant collected in a filter placed at the distal end of the PrINT cast, was determined after placing the nebulizer at different locations of the circuit and using either infant nasal mask or nasal prongs as CPAP interfaces. The LD after delivering a range of nominal surfactant doses (100–600 mg/kg) was also investigated. Surfactant aerosol particle size distribution was determined by laser diffraction. Irrespective of the CPAP interface used, about 14% of the nominal dose (200 mg/kg) reached the LD filter. However, placing the nebulizer between the Y-piece and the CPAP interface significantly increased the LD compared with placing it 7 cm before the Y-piece, in the inspiratory limb. (14% ± 2.8 vs. 2.3% ± 0.8, nominal dose of 200 mg/kg). The customized eFlow Neos showed a constant aerosol generation rate and a mass median diameter of 2.7 μm after delivering high surfactant doses (600 mg/kg). The customized eFlow Neos nebulizer showed a constant performance even after nebulizing high doses of undiluted surfactant. Placing the nebulizer between the Y-piece and the CPAP interface achieves the highest LD under non-invasive ventilation conditions.

Hygroscopicity of Different Types of Aerosol Particles: Case Studies Using Multi-Instrument Data in Megacity Beijing, China

Water uptake by aerosol particles alters its light-scattering characteristics significantly. However, the hygroscopicities of different aerosol particles are not the same due to their different chemical and physical properties. Such differences are explored by making use of extensive measurements concerning aerosol optical and microphysical properties made during a field experiment from December 2018 to March 2019 in Beijing. The aerosol hygroscopic growth was captured by the aerosol optical characteristics obtained from micropulse lidar, aerosol chemical composition, and aerosol particle size distribution information from ground monitoring, together with conventional meteorological measurements. Aerosol hygroscopicity behaves rather distinctly for mineral dust coarse-mode aerosol (Case I) and non-dust fine-mode aerosol (Case II) in terms of the hygroscopic enhancement factor, f β ( R H , λ 532 ) , calculated for the same humidity range. The two types of aerosols were identified by applying the polarization lidar photometer networking method (POLIPHON). The hygroscopicity for non-dust aerosol was much higher than that for dust conditions with the f β ( R H , λ 532 ) being around 1.4 and 3.1, respectively, at the relative humidity of 86% for the two cases identified in this study. To study the effect of dust particles on the hygroscopicity of the overall atmospheric aerosol, the two types of aerosols were identified and separated by applying the polarization lidar photometer networking method in Case I. The hygroscopic enhancement factor of separated non-dust fine-mode particles in Case I had been significantly strengthened, getting closer to that of the total aerosol in Case II. These results were verified by the hygroscopicity parameter, κ (Case I non-dust particles: 0.357 ± 0.024; Case II total: 0.344 ± 0.026), based on the chemical components obtained by an aerosol chemical speciation instrument, both of which showed strong hygroscopicity. It was found that non-dust fine-mode aerosol contributes more during hygroscopic growth and that non-hygroscopic mineral dust aerosol may reduce the total hygroscopicity per unit volume in Beijing.

On the seasonal aerosol pollution levels and its sources in some primary schools in Vilnius, Lithuania.

Aerosol particle number (PNC) and mass concentrations (PMC) were studied in 11 primary schools during the 2017-2018 school years (from September to May) in Vilnius, Lithuania, with the aim to evaluate the main aerosol pollution sources and its levels. Expeditious information on the total aerosol particle concentration over the full range of sizes (from 0.01 to > 1μm) was estimated using a condensation particle counter (CPC). Particle number and mass concentrations in the size range of 0.3-10μm were measured and estimated using an optical particle sizer (OPS). The use of aerosol particle size spectra (OPS) in school lodgements facilitated the identification of the main sources of indoor air pollution. The main sources responsible for the elevated levels of indoor PN and PM aerosol concentrations were determined: local canteens in the absence of ventilation (particle concentrations up to 97,500 part/cm3 (CPC)), the school-grader activity during the lesson breaks (275-586μg/m3), soft furniture and carpets in the classrooms and corridors (~ 200μg/m3), and in some cases (city center) elevated outdoor aerosol pollution levels (16800-18,170 part/cm3). Elevated aerosol pollution levels were also due to the occasional sources: construction works during lessons (200-1000μg/m3), scraping the exterior walls of buildings near schools (up to 1600μg/m3), and the use of petrol-powered trimmers during cutting of green plantings (22500-66,400 part/cm3 (CPC)).

In Vitro Evaluation of Aerosol Performance and Delivery Efficiency During Mechanical Ventilation Between Soft Mist Inhaler and Pressurized Metered-Dose Inhaler

Soft mist inhalers (SMIs) generate aerosols with a smaller particle size than pressurized metered-dose inhalers (pMDIs). However, the whole-span particle size distribution (PSD) of SMIs and the optimal delivery method of SMIs during mechanical ventilation have not been fully investigated. This study aimed to measure the PSD of the SMI alone and the SMI coupled to an inhalation aid (eg, a spacer, a valved holding chamber), as well as the delivery efficiency of SMI in different actuation timings and circuit positions during mechanical ventilation. As a suitable comparison, the pMDI was chosen for the same measurement. SMIs (2.5 μg/actuation of tiotropium) were compared with pMDIs (100 μg/actuation of salbutamol). A microorifice uniform deposit impactor was utilized for the particle sizing of drug aerosols generated by inhalers alone, inhalers with a spacer, and inhalers with a valved holding chamber. To optimize the delivery efficiency of both inhalers during mechanical ventilation, the operating parameters included the circuit positions and actuation timings in the ventilator circuit. Particle sizes and inhaled doses were measured with an optical particle sizer and filters used to collect and quantify the drug, respectively. The SMI generated a smaller mass medium aerodynamic diameter (MMAD) than that from the pMDI. The extrafine-particle fraction (EFPF, < 1 μm) of the SMI was significantly higher than that of the pMDI. With the use of either inhalation aid, the MMAD of both inhalers decreased, and both inhalers with inhalation aid showed significant increases in EFPF. During mechanical ventilation, the optimum way to deliver the SMI and pMDI was at 15 cm from the Y-piece and actuated at the end of expiration and the onset of inspiration, respectively. The SMI with an inhalation aid showed marginal improvement on the PSD. The inhaler type, actuation timing, and position within the circuit also played important roles in delivery efficiency during mechanical ventilation.

Применение базы данных МКРЗ для расчета дозового коэффициента аэрозоля мультимодальной дисперсности

Purpose: Development of a method for calculating radioactive aerosol dose coefficient when the aerosol particle size measurements resulted in a multimodal radionuclide activity distribution by particle diameters. &#x0D; Material and methods: The physical prerequisite for the proposed method is that the multimodal distribution may be caused by the presence of several sources of aerosols with different particle sizes. In the ICRP database to each value of the aerosol dose coefficient there corresponds one of ten functions of log-normal (unimodal) distribution with specified parameters. In the developed method the result of the aerosol particle size measurement is approximated by the sum of said standard functions with weight factors of each of the functions defined such that the best least squares approximation is obtained. Then the dose coefficient of the aerosol under study is calculated based on the dose value additivity property, i.e. each weight factor is multiplied by a respective value of the dose coefficient from the ICRP database, and the obtained products are added up. &#x0D; Results: There was carried out a series of numerical experiments, in each of which “experimental” points were simply plotted on a graph of a certain cumulative distribution function. Coordinates of the points are used as input for the programme implementing the developed algorithm. The calculated dose coefficient value is compared with the true value and/or the value obtained with the linear interpolation method using the AMAD. &#x0D; Conclusion: Physical prerequisites and results of numerical experiments confirm the validity of the developed method.

Application of Multistep Inversion Method for Online Monitoring Aerosol Particle Size Distribution and Aerosol Concentration

Aerosol concentration in the flow is usually time varying, and aerosol particle size distribution (PSD) is considered to be unchanged, which increases the difficulty of the measurement of aerosol PSD and concentration online. To solve these problems, a kind of multistep inversion method based on the angular light-scattering (ALS) signals is proposed. First, the aerosol PSD is estimated using shuffled frog-leaping algorithms (SFLAs) from relative ALS signals. Then, with aerosol PSD as priori information, the aerosol concentration is obtained by the Kalman filter (KF) algorithm, widely used in the real-time control system of industrial facilities for its ability of fast predictions. The result reveals that the performance of the improved SFLA is better than that of the original SFLA in solving the aerosol PSD. Moreover, in studying the aerosol concentration, more accurate results can be obtained with larger standard deviation of process noise or smaller standard deviation of measurement noise, while decreasing sampling time interval can improve the accuracy of retrieval results and reduce time delay to a certain degree. So, to improve retrieval accuracy, the noise should be controlled, and appropriate sampling time interval should be selected. All the numerical simulations confirm that the methodology provides effective and reliable results in real-time estimating.

A Simple Method for Measuring Fine-to-Ultrafine Aerosols Using Bipolar Charge Equilibrium.

Low-cost methods for measuring airborne microparticles and nanoparticles (aerosols) have remained elusive despite the increasing concern of health impacts from ambient, urban, and indoor sources. While bipolar ion sources are common in smoke alarms, this work is the first to exploit the mean charge on an aerosol resulting from a bipolar charge equilibrium and establish experimentally its correlation to properties of the aerosol particle size distribution. The net current produced from this mean particle charge is demonstrated to be linearly proportional to the product of the mean particle diameter and total number concentration (i ∼ Nd̅) for two bipolar ion sources (85Kr and 241Am). This conclusion is supported by simple equations derived from well-established bipolar charging theory. The theory predicts that the mean charge on the aerosol particles reaches an equilibrium, which, importantly, is independent of the concentration of charging ions. Furthermore, in situ measurements of a roadside aerosol demonstrate that the sensing method yields results in good agreement (R2 = 0.979) with existing portable and laboratory-grade aerosol instruments. The simplicity, stability, and cost of the bipolar ion source overcome challenges of other portable sensors, increasing the feasibility of widespread sensor deployment to monitor ultrafine particle characteristics, which are relevant to lung deposition and by extension, human health.

Altitude Test Facility Humidity Control to Generate Defined Icing Conditions

Abstract In altitude test facility (ATF) operation, the requirements to control humidity to generate defined icing conditions are gaining more and more importance. In this context, the ability to predict humidity and condensation becomes a fundamental part of ATF control. For this purpose, classical nucleation theory has been applied in combination with in situ measurements to derive a model suitable to predict the onset of condensation during very low temperature ATF operation. The model parameters have been acquired inside the ATF of the University of Stuttgart downstream of its air coolers. This makes the application or assumption of generalized atmospheric aerosol data unnecessary. Polydisperse nano aerosol distributions were measured and statistically evaluated, showing that a constant distribution of nano aerosol particle size can be assumed. The composition of the ingested nanoparticles was analyzed and Arizona test dust was chosen as a valid substitute material for the application in the prediction model leading to a conservative prediction. The approach has been successfully verified using optical measurements during ATF testing. Its prediction accuracy fulfills the requirements of ATF control for a variety of icing conditions in component and engine altitude testing.