Size Spectrum Of Aerosol Particles Research Articles

Optimized method for simultaneous detection of fog/aerosol particle size distribution.

We propose forward/lateral scattering of dual-wavelength (ultraviolet and short-wave near-infrared bands) radiation to simultaneously detect aerosol particles and fog droplet size distribution in an open atmosphere. The size distributions were described using a gamma distribution. A light-scattering detection system was optimized and designed, and the final wavelengths and scattering angles of ∼ 350 nm and ∼ 1100 nm, and 1°, 2°, 12°, and 35°, respectively, were selected. Numerical simulation analyses and measurements were performed for the proposed detection scheme. The results confirmed that the proposed method is feasible and can rapidly acquire the fog droplet spectrum and aerosol particle size spectrum distribution in an open environment. The system structure of the method is simple and easy to implement, with high detection results and accuracy.

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.

Examining the physical and chemical contributions to size spectrum evolution during the development of hazes

China has experienced severe hazes with high concentrations of particulate matter in recent years. The understanding of the size spectrum evolution of submicron particulate matter is critical to making efficient remediation policies to minimize the regional and global environmental impacts from hazes. During a time period of about one month, we monitored five severe haze episodes in Xi’an and four severe haze episodes in Beijing, which were characterized by two distinct kinds of aerosol mass concentration growth processes: accumulative-rise and abrupt-rise. A new method was developed to quantitatively evaluate the physical and chemical contributions to growth processes by analysing the size spectrum evolution data. The results showed that the accumulative-rise processes are governed by primary emissions and the abrupt-rise processes are governed by secondary chemical reactions. The population balance equations (PBE) were used to describe the variation of size spectrum of fine particulate matter, and the respective contributions of the physical aggregation rate and the chemical growth rate. The PBE model is solved using the adjustable direct quadrature method of moments (ADQMOM) to simulate the abrupt-rise process of haze development and to calibrate the contribution of the physical and chemical effects on the size spectrum of aerosol particles.

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)).

Rapid measurement of sub-micrometer aerosol size distribution using a fast integrated mobility spectrometer

Rapid measurement of submicron particle size distributions enables the characterization of aerosols with fast changing properties, and is often necessary for measurements onboard mobile platforms (e.g., research aircraft). Aerosol mobility size distribution is commonly measured by a scanning mobility particle sizer (SMPS), which relies on voltage scanning or stepping to classify particles of different sizes, and may take about 1 minute or longer to obtain a complete size spectrum of aerosol particles. The recently developed fast integrated mobility spectrometer (FIMS) with enhanced dynamic size range separates and detects particles from 10 to ~600 nm simultaneously, allowing submicron aerosol mobility size distributions to be captured at a time resolution of 1 s.In this study, we present a detailed data inversion routine for deriving aerosol size distribution from FIMS measurements of aerosols with a wide size range. The inversion routine takes into consideration the FIMS transfer function, particle penetration efficiency in the FIMS, and multiple charging of aerosols. The accuracy of the FIMS measurement is demonstrated by comparing parallel FIMS and SMPS measurements of stable aerosols with a wide range of size spectrum shapes, including ambient aerosols and aerosols classified by a differential mobility analyzer (DMA). The FIMS and SMPS-derived size distributions show excellent agreements for all aerosols tested. In addition, total number concentrations of ambient aerosols were integrated from 1 Hz FIMS size distributions, and compared with those directly measured by a condensation particle counter (CPC) operated in parallel. The integrated and measured total particle concentrations agree well within 6.5%.

Influence of the nanoaerosol fraction of industrial coal dust on the combustion of methane–air mixtures

The mechanism of formation of nanosized aerosol particles during mechanical grinding of coal from Kuzbass mines is studied. The concentration and size spectrum of aerosol particles in a mine tunnel during cutter operation were measured using an aerosol spectrometer. It is found that 90% of the particles are less than 200 nm in size. In the nanometer range, there are two peaks corresponding to average diameters of 20 and 150 nm, the first of which is due to single particles, and the second to aggregates consisting of single particles. The formation of aerosol during mechanical coal grinding in a continuous flow mill was studied. The spectrum and morphology of the particles produced in the laboratory mill are in qualitative agreement with those for the nanoaerosol formed in the mine. The influence of the coal aerosol on the combustion of gas mixtures was studied. Laboratory experiments showed that the presence of the nanoaerosol in a lean methane–air mixture significantly increased its explosibility. This was manifested in an increase in the maximum pressure and a significant increase in the pressure rise rate during explosion. The study leads to the conclusion that the nanoaerosol is formed from the organic coal components released into the gas phase during local heating of coal on the cutter teeth.

An observational study of the atmospheric ultra-fine particle dynamics

This paper presents results derived from ultra-fine particle observations conducted in urban and semi-rural areas of the Athens basin in Greece. Aerosol particle size spectra were collected at 2.5-min time resolution with a Scanning Mobility Particle Sizer for approximately two months, along with standard meteorological, NO, NO2 and O3 measurements. The results obtained showed that a 10-fold less maximum number concentration of the mean spectrum was noticed at the semi-rural site compared with that at the urban site. The corresponding maximum for the median spectrum of urban site was only 20% less, indicating that extreme cases had little effect, at least in maximum mean concentration of 9.8 nm particles. The largest number concentration maximum in the mean size distribution spectrum for each area occurred at a modal diameter ≤9.8 nm. For particles ≥13.4 nm, the mean spectrum for Patision contained prominent accumulation particle populations at number median diameters of 13.4, 29.7, and 43.7 nm. In contrast, the major features of the accumulation region of the mean semi-rural spectrum were fit with 5 distribution functions of nearly the same amplitude. The most dominant feature occurred at a number median diameter of 70.1 nm, and thus substantially greater than the 43.7 nm most-dominant in the mean urban spectrum. High ultra-fine particle concentrations at the urban site generally coincided with periods of high NO concentrations and were well correlated with benzene, signifying emissions from motor vehicles.

Characteristics of atmospheric aerosol during the anomalous fall of 2005 in the Moscow region

Results are presented of measurements of total concentration and size spectrum of aerosol particles, of ice nuclei, and cloud condensation nuclei concentrations, as obtained during an anomalously arid period in September and October 2005 in the town of Dolgoprudny, Moscow oblast. It is shown that a two-month period of anticyclonic weather, associated with peat fires, caused a 1.5-time increase in the mean number concentration of aerosol at the site. Effects of accumulation of the industrial aerosol from Moscow and of peat bog burning products are different on fractions of particles of different sizes and on cloud-active nuclei. The smoke particles increased concentrations of almost all sizes from 0.042 to 10 μm; urban aerosol makes the greater part of concentration of particles in the middle subm-icron range and causes a significant increase in the concentration of cloud condensation nuclei.

Features of the multimodal aerosol size distribution depending on the air mass origin in the Baltic region

The purpose of this research is to study the dependence of the characteristics of the atmospheric aerosol size distribution (SD), especially its modal structure on the type and origin of the air mass using multivariate analysis. A large amount of the data of measurement campaigns of different duration, which were held all over Estonia from 1992 to 2001, was collected and systematized. The data were collected using the original electrical aerosol spectrometer, designed at the Institute of Environmental Physics of the University of Tartu. The dependence of aerosol particle size spectra on the air mass origin can be analyzed by means of air mass trajectories. The measurement data were classified according to the air mass origin taking into account of the starting point, climatic conditions and different kinds of pollution sources the air mass trajectory overpasses. The particle size mean spectra over all measurement campaigns were calculated for all selected air mass types. These mean spectra curves are quite smooth, so that their modal structure is visually not clearly seen. Therefore, their modal structure was identified by means of the factor analysis for most of the separated air masses. The retained factors were interpreted as the lognormally distributed components (modes) of the particle size spectrum. With the help of graphs that show the factor loadings as the functions of particle size, the modal diameter and the width of these modes were roughly assessed. Then, using the iterative least squares method, the parameters of the lognormal components were specified to obtain the best fit of the measured spectrum with the sum of lognormal components.

Atmospheric phase distribution of oxidized and reduced nitrogen at a forest ecosystem research site

Atmospheric concentrations of gaseous NH3 and HNO3 and of particulate NH4+ and NO3- were measured during various seasons at a forest ecosystem research site in the "Fichtelgebirge" mountains in Central Europe. Air masses arriving at this site were highly variable with respect to trace compound concentration levels and their concentration ratios. However, the distributions of NH4+ and NO3- within the aerosol particle size spectra exhibited some very consistent patterns, with the former dominating the fine particle concentrations, and the latter dominating the coarse particles range, respectively. Overall, the particulate phase (NH4+ + NO3-) dominated the atmospheric nitrogen budget (particulate and gas phase, NH4+ + NO3- + NH3 + HNO3) by more than 90% of the median total mixing ratio in winter, and by more than 60% in summer. The phase partitioning varied significantly between the winter and summer seasons, with higher relative importance of the gaseous species during summer, when air temperatures were higher and relative humidities lower as compared to the winter season. Reduced nitrogen dominated over oxidized nitrogen, indicating the prevailing influence of emissions from agricultural activity as compared to traffic emissions at this mountainous site. A model has been successfully applied in order to test the hypothesis of thermodynamic equilibrium between the particulate and gas phases.

Electrical aerosol spectrometer of Tartu University

The electrical aerosol spectrometer (EAS) of the parallel measuring principle at Tartu University is an efficient instrument for rapid measurement of the unstable size spectrum of aerosol particles. The measuring range from 10 nm to 10 μm is achieved by simultaneously using a pair of differential mobility analyzers with two different particle chargers. The particle spectrum is calculated and measurement errors are estimated in real time by using a least-squares method. Experimental calibration ensures reliability of measurement. The instrument is well suited for continuous monitoring of atmospheric aerosol.

Electrical aerosol spectrometer of Tartu University

The electrical aerosol spectrometer (EAS) of the parallel measuring principle at Tartu University is an efficient instrument for rapid measurement of the unstable size spectrum of aerosol particles. The measuring range from 10 nm to 10 μm is achieved by simultaneously using a pair of differential mobility analyzers with two different particle chargers. The particle spectrum is calculated and measurement errors are estimated in real time by using a least-squares method. Experimental calibration ensures reliability of measurement. The instrument is well suited for continuous monitoring of atmospheric aerosol.

Air ion measurements as a source of information about atmospheric aerosols

The mobility spectra of air ions recorded in the course of routine atmospheric electric measurements contain information about atmospheric aerosols. The mobility spectrum of air ions is correlated with the size spectrum of aerosol particles. Two procedures of conversion (and conversion errors) are considered in this paper assuming the steady state of charge distribution. The first procedure uses the fraction model of the aerosol particle size distribution and algebraic solution of the conversion problem. The second procedure uses the parametric KL model of the particle size distribution and the least square fitting of the mobility measurements. The procedures were tested using simultaneous side-by-side measurements of air ion mobilities and aerosol particle size distributions at a rural site during a monthly period. The comparison of results shows a promising agreement between the measured and calculated size spectra in the common size range. A supplementary information about nanometer particles was obtained from air ion measurements.

Method of calculation of the size spectrum of aerosol particles according to their mobility spectrum

Method of calculation of the size spectrum of aerosol particles according to their mobility spectrum

Information content of the spectral transmittance of the marine atmospheric boundary layer

We developed a procedure for using data for attenuation ς of the marine atmosphere at λ = 0.55 μm and Ångström parameter α in the visible range for the estimation of aerosol particle size spectrum. We evaluated the aerosol microstructure in the marine atmospheric boundary layer (MABL). To eliminate the effect of the upper troposphere and stratosphere, we assumed that the optical characteristics of the microstructure are average for the typical marine atmosphere. The sought-for MABL microstructure is parameterized by the sum of two fractions, each having a log-normal distribution (the fine and large components). The problem amounts to determining six unknown parameters from two characteristics. In accordance with experimental data as well as with theoretical aerosol models, the total particle concentration n and the fraction of the large component c(2) are assumed to be constant for the central regions of the world ocean. In this way, the problem can be reduced to the determination of the acceptable value area of the remaining four parameters. For all models situated in this area, values of ς and α fall within some intervals Δς and Δα, specific for each aerosol type. Since the problem is ambiguous, the number of models comprising an acceptable ensemble is great. So this number is equal to 5972 in the example that illustrates our procedure. It is noteworthy, however, that all the models entering the ensembles have a similar microstructure within the active radius interval of 0.02-3 μm, which is the main interval that governs the transmittance in the 0.3-1 μm spectral range. The average curve that can be plotted for the entire ensemble can be used as a solution to the problem, which is the main result of this study. We are also concerned with how aerosol transmittance measurements in one of the infrared channels could be used to diminish the ambiguity of the problem. The answer depends on the specific aerosol structure. In most cases, additional IR data in one channel barely decreases the ambiguity of the problem. However, such data might be useful for some other distributions. We consider the effect of six IR channels in our example.

Acceptable yearly precipitation and concentration of radioactive substances in atmospheric air

The acceptable concentration of radionuclides in atmospheric air for the general population, taking into account only internal irradiation via inhalation, is presented in the radiation safety standards NRC-76/87. For most radionuclides this path is not critical. For this reason different derivative standards, which adequately account for other possible irradiation paths and can be measured, must be developed. In so doing, the following two circumstances must be taken into consideration: the expected irradiation dose is not related uniquely to the volume activity of radionuclides in air because during transport of a cloud of emissions in the atmosphere the aerosol particle-size spectrum becomes deformed and the average rate of precipitation of the aerosol changes (large particles settle near the emission location and the finely dispersed aerosol can be transported over a large distance); the foods consumed and all types of agroclimatic conditions under which agricultural crops are grown and the regional phenological characteristics of the crops are extremely diverse. The authors consider some features of the irradiation dose to the population from gas-aerosol emissions of radioactive substances. The irradiation dose to local residents from radioactive gas-aerosol emissions can be represented as the sum of contributions from different sources. The main sources are:more » external irradiation by the gas-aerosol emission cloud (primarily radioactive inert gases); internal irradiation from inhaled radionuclides; external irradiation from the track of radionuclides precipitated from the emission cloud onto the soils, and internal irradiation due to the consumption of local food products contaminated by the fallout.« less

Distribution of natural radioactivity on the environmental submicronic aerosols

An electrial ion mobility analyzer has been built for the study of the environmental aerosol particle size spectrum and of the distribution of natural activity on this spectrum in the size range 10-5 cm r > 10-6 cm. The mobility analyzer was carefully tested by a new method to prove the laminarity of flow and the air velocity distribution inside the apparatus. The quantity of charged aerosol particles classified into discrete mobility (or size) groups was estimated by the ?-radioactivity of collected particles tagged before entering the analyzer by ThB ions. The electrical mobility analyzer was then completed by a sonic jet diffusion charger for unipolar aerosol charging by diffusion and the elctrical parameters of this device were tested to ensure reliable operation.The activity size spectra A(r) were transformed to relative particle size distribution curves N(r). The measurements were carried out in Stockholm, Sweden, under varying physical conditions (varying the activity, the residence time, the collector voltage or applying the diffusion charger for unipolar charging of particles). All experiments gave very similar results. The activity curves A(r) of positive and negative particles as a function of radius show a similar profile with a maximum in the region of radius r = 3–6 times 10-6 cm corresponding to Junge's model of aerosol particle distribution. The calculated relative particle size distribution curves N(r) are not always characterized by a peak as expected from Junge's model but are increasing below radii r < 10-6 cm, so that no peak is evident.