Structural Property Effect of Nanoparticle Agglomerates on Particle Penetration through Fibrous Filter

Most filtration studies have been conducted with spherical particles; however, many aerosol particles are agglomerates of small primary spheres. Filtration efficiency tests were conducted with silver NP agglomerates, with the agglomerate structure controlled by altering the temperature of a sintering furnace. The mobility diameter and mass of the silver NP agglomerates were measured using a differential mobility analyzer together with an aerosol particle mass analyzer. From these measurements, it was found that the fractal-like dimension, D _fm, varied from 2.07 to 2.95 as the sintering temperatures was increased from ambient to 600°C. The agglomerates were essentially fully coalesced at 600°C allowing direct comparison of the filtration behavior of the agglomerate to that of a sphere with the same mobility diameter. Other agglomerate properties measured include the primary diameter, the agglomerate length and aspect ratio, and the dynamic shape factor.

Agglomerate filtration modeling with no adjustable parameters has been investigated in terms of diffusion, impaction, and interception. The model results agree qualitatively with the experimental results in the particle size range of 50 to 300 nm. The results indicated that the larger interception length of agglomerates is responsible for the smaller penetration through a fibrous filter in comparison to spherical particles with the same mobility diameters.     

Observations of a Correlation Between Primary Particle and Aggregate Size for Soot Particles

For decades, soot has been modeled as fractal-like aggregates of nearly equiaxed spherules. Cluster–cluster aggregation simulations, starting from a population of primary particles, give rise to structures that closely match real aerosols of solid particles produced in flames. In such simulations, primary particle size is uncorrelated with aggregate size, as all aggregates contain primary particles drawn from the same population. Aerosol measurements have been interpreted with this geometric model. Examination of transmission electron micrographs of soot samples from various sources shows that primary particle sizes are not well mixed within an aerosol population. Larger aggregates tend to contain larger primary particles and the variation in size is much larger between aggregates than within aggregates. The soot sources considered here are all substantially not well-mixed (aircraft jet engine, inverted diffusion flame, gasoline direct injection engine, heavy-duty compression ignition engine). The observed variations in primary particle size can be explained if soot aggregates are formed and grew by coagulation in small zones of the combustion chamber, prior to dilution and transport (with minimal coagulation) to the sampling system.

Copyright 2014 American Association for Aerosol Research     

Air Entrainment During Flame Aerosol Synthesis of Nanoparticles

Enclosed flames typically produce substantially larger particles than open flames under identical reactant flows and composition. The enclosure hinders air entrainment to the flame and reduces heat losses by radiation and convection, facilitating particle coagulation and coalescence. Here the effect of natural air entrainment on flame aerosol synthesis is investigated by lifting off the enclosing tube from the burner surface and utilizing tracer gas (Ne) analysis after calibration with forced air entrainment. That way the effect of air entrainment on product primary particle diameter and mobility size distribution dynamics is investigated by microscopy, scanning mobility particle sizing, and N₂ adsorption, while temperature is measured by Fourier-transform infrared spectroscopy. So air entrainment during flame spray pyrolysis is examined here for its versatility in scalable manufacture of an array of material compositions, while copper oxide (CuO) is used for its electro-chemical applications (e.g., battery electrodes). It is shown that natural air entrainment facilitates rapid gas-to-particle conversion and high process yields by minimizing vortex recirculation and particle deposition on the enclosing tube walls and burner surface. For example, the average primary particle diameter of CuO can be controlled from 42 to 10 nm and the yield from 40 to 90% by gradually lifting off the enclosing tube, resulting in up to 250 L/min natural air entrainment at the present CuO synthesis conditions.

Copyright 2014 American Association for Aerosol Research     

Measurement of size-dependent dynamic shape factors of quartz particles in two flow regimes

Understanding and modeling the behavior of quartz dust particles, commonly found in the atmosphere, requires knowledge of many relevant particle properties, including particle shape. This study uses a single particle mass spectrometer, a differential mobility analyzer, and an aerosol particle mass analyzer to measure quartz aerosol particles mobility (d_m), vacuum aerodynamic, and volume equivalent diameters, mass, composition, effective density, and dynamic shape factor as a function of particle size, in both the free molecular and transition flow regimes. The results clearly demonstrate that dynamic shape factors can vary significantly as a function of particle size. For the quartz samples studied here, the dynamic shape factors increase with size, indicating that larger particles are significantly more aspherical than smaller particles. In addition, dynamic shape factors measured in the free-molecular (χ_v) and transition (χ_t) flow regimes can be significantly different, and these differences vary with the size of the quartz particles. For quartz, χ_v of small (d_m < 200 nm) particles is 1.25, while χ_v of larger particles (d_m ～ 440 nm) is 1.6, with a continuously increasing trend with particle size. In contrast, χ_t of small particles starts at 1.1 increasing slowly to 1.34 for 550 nm diameter particles. The multidimensional particle characterization approach used here goes beyond determination of average properties for each size, to provide additional information about how the particle dynamic shape factor may vary even for particles with the same mass and volume equivalent diameter.

© 2016 American Association for Aerosol Research     

Assessment of a Cylindrical and a Rectangular Plate Differential Mobility Analyzer for Size Fractionation of Nanoparticles at High-Aerosol Flow Rates

An existing differential mobility analyzer (DMA) of cylindrical electrodes and a novel DMA of rectangular plate electrodes are demonstrated for size fractionation of nanoparticles at high-aerosol flow rates in this work. The two DMAs are capable of delivering monodisperse size selected nanoparticles (SMPS σ_g < 1.1) at gas flow rates ranging from 200 slm to 500 slm. At an aerosol flow rate of 200 slm, the maximum attainable particle mean size is of about 20 nm for the cylindrical DMA and of nearly 50 nm for the rectangular plate DMA. The number concentration of the monodisperse nanoparticles delivered by the high-flow DMAs spans from 10⁴ cm^?3 to 10⁶ cm^?3 depending upon the particle mean size and particle size dispersion.

Copyright 2014 American Association for Aerosol Research     

Characterization of nanosized silica size standards

Nanosized silica size standards produced with a sol–gel synthesis process were evaluated for particle size, effective density, and refractive index in this study. Particle size and effective density measurements were conducted following protocol from the National Institute of Advanced Industrial Science and Technology (AIST) in Japan. Particle sizes were measured via electrical mobility analysis using a differential mobility analyzer (DMA) at sheath flow rates (Q_sh) of 3.0 and 6.0 L/min and a constant aerosol flow rate (Q_a) of 0.3 L/min. The measured mean and mode diameters agreed well with the labeled sizes in the size range 40–200 nm, with differences ranging from 0.03% to 0.8%, well within the labeled expanded uncertainties (95% confidence intervals) of 1.8%–2.2%. The coefficient of variation (CV) of the size distribution was 0.012–0.027 for 40–200 nm. Particle sizes measured for 20 nm and 30 nm standards showed size differences with respect to the certified sizes of 1.7% and 8.3% at Q_sh = 6.0 L/min, but the size distributions were narrow, with CV = 0.047–0.064. The average effective density for the range 40–200 nm measured with an aerosol particle mass analyzer (APM) was 1.9 g/cm³. The real component of the refractive index measured with an optical particle counter (OPC) was 1.41 at a wavelength of 633 nm. All properties (size, effective density, and refractive index) were stable and could be measured with good repeatability. From these evaluations, it was found that the nanosized silica size standards have good characteristics for use as size standards and constitute a feasible alternative to PSL particles.

© 2017 American Association for Aerosol Research     

Mobility Analysis of 2 nm to 11 nm Aerosol Particles with an Aspirating Drift Tube Ion Mobility Spectrometer

We describe the performance of a drift tube-ion mobility spectrometry (DT-IMS) instrument for the measurement of aerosol particles. In DT-IMS, the electrical mobility of a measured particle is inferred directly from the time required for the particle to traverse a drift region, with motion driven by an electrostatic field. Electrical mobility distributions are hence linked to arrival time distributions (ATDs) for particles reaching a detector downstream of the drift region. The developed instrument addresses two obstacles that have limited DT-IMS use for aerosol measurement previously: (1) conventional drift tubes cannot efficiently sample charged particles at ground potential and (2) the sensitivities of commonly used Faraday plate detectors are too low for most aerosols. Obstacle (1) is circumvented by creating a “sample volume” of aerosol for measurement, defined by the streamlines of fluid flow. Obstacle (2) is bypassed by interfacing the end of the drift region with a condensation particle counter. The DT-IMS prototype shows high linearity for arrival time versus inverse electrical mobility (R ² > 0.99) over the size range tested (2.2–11.1 nm), and measurements compare well with both analytical and numerical models of device performance. A dimensionless calibration curve linking drift time to inverse electrical mobility is developed. In less than 5 s, it is possible to measure 11.1 nm particles, while 2.2 nm particles are analyzable on a subsecond scale. The transmission efficiency is found to be dependent upon electrostatic deposition for short drift times and upon advective losses for long drift times.

Copyright 2014 American Association for Aerosol Research     

Calibration of a particle mass spectrometer using polydispersed aerosol particles

Routine calibrations of online aerosol chemical composition analyzers are important for assessing data quality during field measurements. The combination of a differential mobility analyzer (DMA) and condensation particle counter (CPC) is a reliable, conventional method for calibrations. However, some logistical issues arise, including the use of radioactive material, quality control, and deployment costs. Herein, we propose a new, simple calibration method for a particle mass spectrometer using polydispersed aerosol particles combined with an optical particle sizer. We used a laser-induced incandescence–mass spectrometric analyzer (LII-MS) to test the new method. Polydispersed aerosol particles of selected chemical compounds (ammonium sulfate and potassium nitrate) were generated by an aerosol atomizer. The LII section was used as an optical particle sizer for measuring number/volume size distributions of polydispersed aerosol particles. The calibration of the MS section was performed based on the mass concentrations of polydispersed aerosol particles estimated from the integration of the volume size distributions. The accuracy of the particle sizing for each compound is a key issue and was evaluated by measuring optical pulse height distributions for monodispersed ammonium sulfate and potassium nitrate particles as well as polystyrene latex particles. A comparison of the proposed method with the conventional DMA-CPC method and its potential uncertainties are discussed.

Copyright © 2018 American Association for Aerosol Research     

Modification and laboratory evaluation of a TSI ultrafine condensation particle counter (Model 3776) for airborne measurements

A butanol-type ultrafine condensation particle counter (UCPC, Model 3776, TSI, Inc., Shoreview, MN, USA), which can achieve a 50% detection efficiency diameter (d₅₀) of 2.5 nm using a capillary-sheath structure, was modified and tested in the laboratory for airborne measurements. The aerosol flow rate through the capillary is a key factor affecting the quantification of aerosol particle number concentrations. A pressure-dependent correction factor for the aerosol flow rate was determined using a newly added mass flow meter for the sheath flow and the external calibration system. The effect of particle coincidence in the optical sensing volume was evaluated using an aerosol electrometer (AE, Model 3068B, TSI, Inc.) as a reference. An additional correction factor for the coincidence effect was derived to improve the quantification accuracy at higher concentrations. The particle detection efficiency relative to the AE was measured for mobility diameters of 3.1–50 nm and inlet absolute pressures of 101–40 kPa. The pressure dependence of the d₅₀ value, asymptotic detection efficiency, and shape of the particle detection efficiency curve is discussed, along with simple theoretical calculations for the diffusion loss of particles and the butanol saturation ratio in the condenser.

© 2017 American Association for Aerosol Science     

Effects of size and shape on filtration of TiO2 nanoparticles

Titanium dioxide (TiO₂) is one of the most widely used nanoscale materials to date and could result in human exposures. The main objective of this study was to perform detailed characterization of TiO₂ agglomerate particles and how these properties influence particle penetration in a screen filter. Transmission electron microscope (TEM) photos showed compact agglomerates of nanoscale primary particles. The projected area diameter was close to the mobility diameter, where the length was about 25% larger than the mobility diameter. The mean aspect ratio of TiO₂ agglomerate was constant between 1.39 and 1.55. Using the tandem differential mobility analyzer-aerosol particles mass analyzer (DMA-APM) technique, we were able to measure aerodynamic diameter, mass, and fractal dimension. The value of fractal dimension based on mass and mobility diameter was 2.8. Penetration of classified TiO₂ particles through a screen filter was measured. Penetration increased with increasing mobility diameter and flow rate indicating that diffusion and interception were the main filtration mechanism. The measured physical dimensions, mobility diameter, and aerodynamic diameter were used in a single-fiber filtration theory for the fan model filter to predict the penetration of TiO₂ particles. The interception parameter was the key to estimate the penetration. Experimental penetration data were in best agreement with the model in which the maximum length was used to calculate the interception model. This result was consistent with the assumption that the rotation time of a non-spherical particle of small aspect ratio was much less than the transport time for the particle to pass through the filter fiber.

© 2017 American Association for Aerosol Research     

Real-time effective density monitor (DENSMO) for aerosol nanoparticle production

A new instrument, density monitor (DENSMO), for aerosol particle size distribution characterization and monitoring has been developed. DENSMO is operationally simple and capable of measuring the effective density as well as the aerodynamic and the mobility median diameters with a time resolution of 1 s, from unimodal particle size distributions. The characterization is performed with a zeroth order mobility analyzer in series with a low pressure impactor and a filter stage. The operation of DENSMO was investigated with sensitivity analysis and, based on the results, optimal operation parameters were determined. DENSMO was also compared, in lab test measurements, against a reference method with several particle materials with bulk densities from 0.92 to 10.5 g/cm³. The results show that the deviation from the reference method was less than 25% for suitable materials.

Copyright © 2016 American Association for Aerosol Research     

The initial stages of multicomponent particle formation during the gas phase combustion synthesis of mixed SiO2/TiO2

The ability to properly scale the synthesis of advanced materials through combustion synthesis routes is limited by our lack of knowledge regarding the initial stages of particle formation. In flame aerosol reactors, the high temperatures, fast reaction rates, and flame chemistry can all play a critical role in determining the properties of the resulting nanomaterials. In particular, multicomponent systems pose a unique challenge as most studies rely on empirical approaches toward designing advanced composite materials. The lack of predictive capabilities can be attributed to a lack of data on particle inception and growth below 2 nm. Measurements for the initial stages of particle formation during the combustion synthesis of SiO₂ and composite SiO₂/TiO₂ using an atmospheric pressure inlet time-of-flight mass spectrometer are presented. Both positively and negatively charged clusters can be measured and results show the presence of silicic acid species which grow through dehydration, hydrogen abstraction, and interactions with hydroxyl radicals. In the case of composite SiO₂/TiO₂ particle formation, new molecular species containing Ti atoms emerge. Tandem differential mobility analysis-mass spectrometry (DMA-MS) provided further insight into the size-resolved chemistry of particle formation to reveal that at each cluster size, further hydroxyl-driven reactions take place. From this we can conclude that previous assumptions on collisional growth from simple monomer species of SiO₂ and TiO₂ do not sufficiently describe the collisional growth mechanisms for particle growth below 2 nm.

Copyright © 2018 American Association for Aerosol Research     

Evaluation of a Portable Aerosol Collector and Spectrometer to measure particle concentration by composition and size

We evaluated a newly developed Portable Aerosol Collector and Spectrometer (PACS) in the laboratory. We developed an algorithm to estimate mass concentration by size and composition with a PACS. In laboratory experiments, we compared particle size distributions measured with the PACS to research instruments for multi-modal aerosols: two-mode generated by spark discharge, consisting of ultrafine (fresh Mn fume) and fine particles (aged Cu fume); and three-mode produced by adding coarse particles (Arizona road dust) to the two-mode. Near-real-time size distributions from the PACS compared favorably to those from a scanning mobility particle sizer and an aerodynamic particle sizer for the three-mode aerosol (number, bias?=?9.4% and R² = 0.96; surface area, bias?=?17.8%, R² = 0.77; mass, bias = ?2.2%, R² = 0.94), but less so for the two-mode aerosol (number, bias = ?17.7% and R² = 0.51; surface area, bias = ?45.5%, R² = 0; for mass, bias = ?81.75%, R² = 0.08). Elemental mass concentrations by size were similar to those measured with a nano micro-orifice uniform deposition impactor for coarse-mode particles, whereas agreement was considerably poorer for ultrafine- and fine-mode particles. The PACS has merit in estimating multi-metric concentrations by size and composition but requires further research to resolve discrepancies identified for two-mode aerosol.

Copyright © 2019 American Association for Aerosol Research     

Aerosol Process for the In Situ Coating of Nanoparticles with a Polymer Shell

This article presents a novel method to encapsulate gas-borne nanoparticles with a polymeric shell. This method implies heterogeneous condensation of monomer vapor around the surface of nanoparticles as nuclei and polymerization is then subsequently started by addition of NH₃ as aerosol initiator. Ag and SiO₂ nanoparticles were generated as inorganic core by spark discharge and nebulization, respectively, and glycidyl methacrylate (GMA) was used as organic monomer. The effect of several parameters, including vapor pressure of monomer and properties of inorganic core such as morphology, material, particle size, and production method on the thickness of polymeric shell and morphology of resulting nanocomposites has been investigated. The particle size distribution and morphology of the resulting core-shell nanoparticles have been studied via scanning mobility particle sizer (SMPS) and transmission electron microscope (TEM). Finally, the coating efficiency was determined by aerosol photoemission (APE) and the results show that monomer and polymer coating efficiency are 99% and 60%, respectively.

Copyright 2014 American Association for Aerosol Research     

A novel miniature inverted-flame burner for the generation of soot nanoparticles

Lab-scale soot nanoparticle generators are used by the aerosol research community to study the properties of soot over a broad range of particle size distributions, and number and mass concentrations. In this study, a novel miniature inverted-flame burner is presented and its emitted soot particles were characterized. The burner consisted of two co-annular tubes for fuel and co-flow air and the flame was enclosed by the latter. The fuel used was ethylene. A scanning mobility particle sizer (SMPS) and an aerodynamic aerosol classifier (AAC) were used to measure mobility and aerodynamic size distribution of soot particles, respectively. Particle morphology was studied using transmission electron microscopy (TEM). The elemental carbon (EC) and organic carbon (OC) content of the soot were measured using thermal-optical analysis (TOA). The burner produced soot particles with mobility diameter range of 66–270?nm, aerodynamic diameter range of 56–140?nm, and total concentration range of 2?×?10⁵–1?×?10⁷?cm^?3. TEM images showed that most soot particles were sub-micron soot aggregates. Some soot superaggregates, typically larger than 2?µm in length, were observed and their abundance increased with ethylene flow rate. TOA showed that the concentration of EC in the generated soot increased with ethylene flow rate, and the soot was observed to have high EC fraction at high ethylene flow rates. The miniature inverted-flame burner was demonstrated to produce soot nanoparticles over a range of concentrations and sizes with high EC content, making it a practical device to study soot nanoparticle properties in different applications.

Copyright © 2019 American Association for Aerosol Research     

Development and qualification of a VH-TDMA for the study of pure aerosols

We create and qualify a Volatility and Hygroscopicity Tandem Differential Mobility Analyzer (VH-TDMA) for the study of aerosols. This VH-TDMA measures size distributions, volatility, and hygroscopicity and includes an auxiliary conditioner that allows quick connection to other external aerosol conditioners. The differential mobility analyzers are not temperature controlled, allowing the surrounding environment to influence the measurement conditions, and this is fully accounted for when measuring aerosol volatility and hygroscopicity. For the volatility conditioner, the VH-TDMA uses a 15?m coil of tubing in an oven to evaporate aerosol samples at elevated temperatures. We measured several single component model aerosols to qualify the differential mobility particle sizer (DMPS) channel and each of the conditioners: hygroscopicity and volatility. Due to insufficient power supply calibration in this study, the TDMA channel is limited to particle sizes greater than 70?nm. The DMPS channel was able to reproduce ammonium sulfate size distributions when compared to common scanning mobility particle sizers. For hygroscopicity, the standard deviation in the measured ammonium sulfate growth factors was 0.03 over a 4-h experiment. From this data, the TDMA has an observed relative humidity error of ±0.6% with manufacturer reported error of ±1.2% relative humidity. The volatility channel reproduced the previously published saw tooth pattern of room temperature saturation vapor pressures from atomized C3-C9 diacids. The maximum percent difference in room temperature saturation vapor pressure was approximately 80%. The enthalpy of sublimation derived from the diacids increased monotonically (except for suberic acid) and resembled measurements from mass effusion techniques.

Copyright © 2019 American Association for Aerosol Research     

Effect of Aerosol Volatility on the Sizing Accuracy of Differential Mobility Analyzers

Differential mobility analyzers (DMAs) are widely used for calibrating other instruments and measuring aerosol size distributions. DMAs classify aerosol particles according to their electrical mobility, which is assumed to be constant during the classification process. However, particles containing semivolatile substances can change their size in the DMA, leading to sizing errors. In this article, the effect of particle size changes during the classification process on the sizing accuracy of DMAs is discussed. It is shown that DMAs select particles whose time-of-flight-averaged electrical mobility is equal to that of stable particles that are selected under given operating conditions. For evaporating particles, this implies that DMAs select particles that are originally larger than the reported size. At the exit of the DMA, selected particles are smaller than the reported size. Particle evaporation and growth inside DMAs was modeled to study the effect of particle size changes on the sizing accuracy and the transfer function of DMAs in constant- and scanning-voltage modes of operation. Modeling predictions were found to agree well with the results of experiments with ammonium nitrate aerosol. The model was used to estimate sizing errors when measuring hygroscopic and other volatile aerosols. Errors were found to be larger at smaller sizes and low sheath flow rates. Errors, however, are fairly small when saturation concentration is below 10 μg/m³, assuming an evaporation coefficient of 0.1. Particles size changes during classification lead to distortion of the DMA transfer function. In voltage scanning mode, errors are generally larger, especially at high scan rates.

Copyright 2014 American Association for Aerosol Research     

Aerosol Charge Fractions Downstream of Six Bipolar Chargers: Effects of Ion Source,Source Activity,and Flowrate

Bipolar diffusion charging is used routinely in aerosol electrical mobility size distribution measurements. In this study, aerosol charge fractions produced by six bipolar chargers (neutralizers) were measured using a tandem differential mobility analyzer system. Factors that were studied include the type of ion source (²¹⁰Po, ⁸⁵Kr, ²⁴¹Am, and soft X-ray), source activity, charger design, and aerosol flowrate. It was found that all six types of neutralizers achieve stationary state charge distributions when the source activity is sufficiently high. For ²¹⁰Po neutralizers with an initial radioactivity of 18.5 MBq (0.5 mCi), stationary state charge distributions are achieved when the source is less than 3.25 years old (residual activity no less than 0.0527 MBq). Stationary state was achieved for ⁸⁵Kr neutralizers having residual radioactivity greater than 70 MBq. Source activities of ²⁴¹Am and soft X-ray neutralizers are discussed. Aerosol charge fractions for six neutralizers remain reasonably invariant over a wide range of flowrates. The positive charge fractions achieved by the soft X-ray neutralizer are higher than those by the other five neutralizers using radioactive sources while negative charge fractions for all neutralizers studied are all in a similar range. This study also raises questions about bipolar charging fractions used for data inversion in some scanning mobility particle spectrometer (SMPS) systems, and underscores the need to better understand bipolar charging to achieve more accurate measurements of particle size distributions.

Copyright 2014 American Association for Aerosol Research     

Accuracy of recovered moments for narrow mobility distributions obtained with commonly used inversion algorithms for mobility size spectrometers

Aerosol mobility size spectrometers are commonly used to measure size distributions of submicrometer aerosol particles. Commonly used data inversion algorithms for these instruments assume that the measured mobility distribution is broad relative to the DMA transfer function. This article theoretically examines errors that are incurred for input distributions of any width with an emphasis on those with mobility widths comparable to that of the DMA's transfer function. Our analysis is valid in the limit of slow scan rates, and is applicable to the interpretation of measurements such as those obtained with tandem differential mobility analyzers as well as broader distributions. The analysis leads to expressions that show the relationship between the inverted number concentration, mean size, and standard deviation and true values of those parameters. For narrow distributions (e.g., for a mobility distribution produced by a DMA with a 1:10 aerosol:sheath air flow ratio) under typical operating conditions, number concentrations and mean mobility obtained with inversion algorithms are accurate to within 0.5% and 1.0%, respectively. This corresponds to mean diameter retrieval errors of 1.0% for large particles and 0.5% for small (kinetic regime) particles. The widths (i.e., relative mobility variance) of the inverted distributions, however, significantly exceed the true values.

Copyright © 2018 American Association for Aerosol Research     

Development of balloon-borne impactor payload for profiling free tropospheric aerosol

Size-segregated aerosol vertical profiles in the troposphere are critically important for source attribution, transformation processes, atmospheric stability, and radiative forcing. For the first time, the development of a 6-stage impactor for real-time balloon-borne measurements of size-segregated (cutoff diameter [D_ae]: 0.15–5?µm) aerosol mass concentrations in the free troposphere was tested during spring 2016 over Hyderabad, India, is presented. Total aerosol mass concentrations obtained with the 6-stage impactor (M_TI) and a co-located optical particle counter (M_TOPC) measurements at the surface under ambient conditions agreed to within 15%. The effect of aerosol particle growth on the M_TI data are assessed using an urban aerosol particle model by scaling mass concentration of water-soluble (hydrophilic) aerosol particles at ambient relative humidity (RH) to that at RH = 50%. An overall uncertainty of the measurement of the M_TI was estimated to be about 19%. The altitude variation of size-segregated mass concentrations of aerosol particles along with thermodynamic variables depicted convectively well-mixed layer extending up to about 4.5?km within which aerosol particles showed two distinct layers, one at ～2?km and another at about 4.5?km. The size-resolved air samples containing aerosol particles collected using the balloon-borne 6-stage impactor will be useful for their chemical characterization and also long-range transport studies.

Copyright © 2019 American Association for Aerosol Research