Polydisperse Aerosol Research Articles

Characterisation and modification of the porous metal foams used for the EN 15051-2 dustiness rotating drum test.

Two approaches were used to evaluate the performance of the reticulated metal foams used to size select and collect dust generated in the dustiness rotating drum tester according to the EN 15051-2 standard "Workplace exposure-Measurement of the dustiness of bulk materials-Rotating drum test". Firstly, the detailed performance of the metal foams was measured in a calm air chamber using a polydisperse aerosol of glass particles and assessed against the respirable conventions described in the EN 481 standard "Workplace atmospheres-Size fraction definitions for measurement of airborne particles". Secondly, the performance of the EN 15051-2 metal foam size selection for the respirable fraction was compared using the rotating drum dustiness test, with that of a cyclone set-up, using 4 polydisperse glass powders of different size distribution and dustiness potential. The research discusses further improvements to the EN 15051-2 standard and an approach to more closely match the EN 481 convention. In general, for the respirable fraction, the tests in this study demonstrated a conservative oversampling by the current EN 15051-2 metal foam set-up in comparison with the EN 481 convention. Calculations and tests showed an improved fit was achieved by reducing the inner diameter of the flanges separating the metal foams and the filter. This study also showed the importance of sealing the circumference of the metal foams when testing highly dusty powders. A direct comparison of the respirable dustiness fraction, measured by the current EN 15051-2 metal foams set-up and by a cyclone set-up, showed broad agreement. However, for extremely dusty powders, the metal foams can clog, and dust can accumulate between the 20 and 80 pores per inch foams.

Characterization of pediatric extrathoracic aerosol deposition with air-jet dry powder inhalers

The use of air-jet dry powder inhalers (DPIs) offers a number of advantages for the administration of pharmaceutical aerosols, including the ability to achieve highly efficient and potentially targeted aerosol delivery to the lungs of children using the oral or trans-nasal routes of administration. To better plan targeted lung delivery of pharmaceutical aerosols with these inhalers, more information is needed on the extrathoracic (ET) depositional loss in pediatric subjects when using relatively small (e.g., 0.5–2 μm) particles and including oral or nasal device interfaces. The objective of this study was to implement validated computational fluid dynamics (CFD) models to characterize ET depositional loss during mouth-throat (MT) and nose-throat (NT) aerosol administration to pediatric subjects (2–10 years old) using an air-jet DPI platform across a range of initial small-particle aerosol sizes (0.41–13.65 μm) and inhalation flow rates (8–20 L/min).A new CFD model focused on small-particle aerosol depositional loss in existing pediatric airway models was developed and validated with existing in vitro data. The validated CFD model was then used to characterize depositional loss in the MT and NT regions of children using particle sizes, flow rates and interfaces consistent with air-jet DPIs.Successful validation of the CFD model for small-particle aerosol deposition was achieved through enhanced resolution of the near-wall transport conditions. Existing non-dimensional parameters were used to produce high quality single-curve deposition efficiency correlations with r2 values in the range of 0.95–0.97. A new method for predicting realistic polydisperse aerosol deposition using the developed correlations and an equivalent monodisperse particle diameter was also introduced. In conclusion, the newly developed correlations will be useful in planning the lung delivery of next-generation inhaled medications, where achieving both low ET loss and targeted airway deposition, perhaps with excipient enhanced growth technology, are critical factors.

Design and optimization of gradient fibrous media using the method of moments

The goal of this work is to optimize the deposition mass distribution of polydisperse particles inside the fibrous media by modifying the distribution of the fiber packing density across filter depth. Two types of gradient fibrous media with linear and exponential fiber packing density distribution along the flow direction were derived. The method of moments was employed to study the transport and deposition characteristics of polydisperse aerosol particles inside the fibrous media. The reliability of the calculated results by the method of moments was confirmed by the numerical simulations based on the discrete phase model (DPM). Results indicate that the gradient fibrous media allows more particles to transport and deposit into the interior of the fibrous media, which improves the uniformity of particle deposition distribution across filter depth. There exists an optimal fiber packing density distribution ratio for the gradient fibrous media where the non-uniformity of deposition mass distribution of polydisperse particles across filter depth is minimized. In this way, uniform deposition distribution along the flow direction can be generally achieved by optimizing the fiber packing density distribution, which will contribute to the optimal design of microstructures for the fibrous filter.

Velocity Map Imaging Photoelectron Spectroscopy of Silver Iodide Aerosol Particles.

The valence band electronic structure of isolated silver iodide nanoparticles (AgI NP) was investigated by vacuum-ultraviolet aerosol photoelectron spectroscopy using the velocity map imaging technique (VUV VMI-PES). The VUV VMI-PES results were obtained for polydisperse aerosol produced by aggregation of hydrocolloid of silver iodide particles 8-15 nm in size. The ionization energy of the AgI particles was found to be 6.0±0.1 eV with respect to the vacuum level. The DFT calculations showed that the main contribution to the density of AgI electronic states in the valence region originates from I 5p orbitals. The dependence of the asymmetry parameter on the electron energy showed that the value of the characteristic energy loss of excited photoelectrons was 2.7 eV, which coincided with the band gap of the nanomaterial.

Low-temperature ice nucleation of sea spray and secondary marine aerosols under cirrus cloud conditions

Abstract. Sea spray aerosols (SSAs) represent one of the most abundant aerosol types on a global scale and have been observed at all altitudes including the upper troposphere. SSA has been explored in recent years as a source of ice-nucleating particles (INPs) in cirrus clouds due to the ubiquity of cirrus clouds and the uncertainties in their radiative forcing. This study expands upon previous works on low-temperature ice nucleation of SSA by investigating the effects of atmospheric aging of SSA and the ice-nucleating activity of newly formed secondary marine aerosols (SMAs) using an oxidation flow reactor. Polydisperse aerosol distributions were generated from a marine aerosol reference tank (MART) filled with 120 L of real or artificial seawater and were dried to very low relative humidity to crystallize the salt constituents of SSA prior to their subsequent freezing, which was measured using a continuous flow diffusion chamber (CFDC). Results show that for primary SSA (pSSA), as well as aged SSA and SMA (aSSA+SMA) at temperatures >220 K, homogeneous conditions (92 %–97 % relative humidity with respect to water – RHw) were required to freeze 1 % of the particles. However, below 220 K, heterogeneous nucleation occurs for both pSSA and aSSA+SMA at much lower RHw, where up to 1 % of the aerosol population freezes between 75 % and 80 % RHw. Similarities between freezing behaviors of the pSSA and aSSA+SMA at all temperatures suggest that the contributions of condensed organics onto the pSSA or alteration of functional groups in pSSA via atmospheric aging did not hinder the major heterogeneous ice nucleation process at these cirrus temperatures, which have previously been shown to be dominated by the crystalline salts. Occurrence of a 1 % frozen fraction of SMA, generated in the absence of primary SSA, was observed at or near water saturation below 220 K, suggesting it is not an effective INP at cirrus temperatures, similar to findings in the literature on other organic aerosols. Thus, any SMA coatings on the pSSA would only decrease the ice nucleation behavior of pSSA if the organic components were able to significantly delay water uptake of the inorganic salts, and apparently this was not the case. Results from this study demonstrate the ability of lofted primary sea spray particles to remain an effective ice nucleator at cirrus temperatures, even after atmospheric aging has occurred over a period of days in the marine boundary layer prior to lofting. We were not able to address aging processes under upper-tropospheric conditions.

Fundamentals of low-cost aerosol sensor design and operation.

Most evaluations of low-cost aerosol sensors have focused on their measurement bias compared to regulatory monitors. Few evaluations have applied fundamental principles of aerosol science to increase our understanding of how such sensors work and could be improved. We examined the Plantower PMS5003 sensor's internal geometry, laser properties, photodiode responses, microprocessor output, flow rates, and response to mono- and poly-disperse aerosols. We developed a physics-based model of particle light scattering within the sensor, which we used to predict counting and sizing efficiency for 0.30 to 10 μm particles. We found that the PMS5003 counts single particle scattering events, acting like an imperfect optical particle counter, rather than a nephelometer. As particle flow is not focused into the core of the laser beam, >99% of particles that flow through the PMS5003 miss the laser, and those that intercept the laser usually miss the focal point and are subsequently undersized, resulting in erroneous size distribution data. Our model predictions of PMS5003 response to varying particle diameters, aerosol compositions, and relative humidity were consistent with laboratory data. Computational fluid dynamics simulations of the PurpleAir monitor housing showed that for wind-speeds less than 3 m s-1, fine and coarse particles were representatively aspired to the PMS5003 inlet. Our measurements and models explain why the PurpleAir overstates regulatory PM2.5 in some locations but not others; why the PurpleAir PM10 is unresponsive to windblown dust; and why it reports a similar particle size distribution for coarse particles as it does for smoke and ambient background aerosol.

Deposition of a Polydisperse Aerosol in a Narrow Closed Tube in Resonance Oscillation Mode

Deposition of a Polydisperse Aerosol in a Narrow Closed Tube in Resonance Oscillation Mode

Effect of polydisperse aerosol slit and classified aerosol outlet widths on the performance of a cylindrical differential mobility analyzer

The effects of polydisperse aerosol slit and classified aerosol outlet widths on the performance of a cylindrical differential mobility analyzer (DMA) were investigated using numerical simulations and measurements. The approach was verified by comparing the MF-DMA experimental voltages with numerical results. The study shows that the polydisperse aerosol slit width plays an important role in the performance of a cylindrical DMA and has an optimal value. When deviating from this optimal value, the DMA resolution decreases, specifically, increasing the radial ratio and aspect ratio while decreasing the optimal value. However, the enhanced classification length increases the resolution. It is also shown that the performance of DMA deteriorates as the classified aerosol outlet width increases.

Study of poly-disperse aerosols deposition in turbulent flow with different Reynolds numbers

The turbulent deposition mechanism is one of the main mechanisms of aerosol deposition in nuclear power plant tubes. An experimental study of poly-disperse aerosol deposition in a horizontal tube is conducted, where the nominal Reynolds number (Re) is in a range of 3600–200,000. The aerosol deposition velocity first increases and then decreases with the increase of Res, and at high Re, particle rebound occurs during aerosol deposition in the tube. When the Re is low, the aerosol deposition velocity increases with the increase of aerosol diameter. When the Re is greater than 60,000, the deposition velocity first increases and then decreases with the increase of aerosol diameter due to particle surface rebound. A new aerosol deposition model has been developed by establishing the energy conservation equation of the rebounded particles in the viscous sublayer. The calculated results of the new model are in good agreement with these experimental results, and the error between the aerosol deposition velocity calculated by the model and experimental results is between −60% and 150%.

Aerosol technology for edge treatment of a field for the destruction of weeds and pests

BACKGROUND: The subject of the study is the technological process of spraying weeds and pests in the edge area of the field with polydisperse drops from an air-dispersed system created by a fan with a nozzle and slotted liquid sprayers.
 AIMS: Justification of the technological process of spraying weeds and pests during the edge treatment of a field with a polydisperse aerosol.
 METHODS: There was a device for a mounted boom sprayer of plants used for edge treatment of a field by the main method of spraying weeds and pests with the required size and number of drops from an air-dispersed jet created by an axial fan with a hydraulic drive and a nozzle equipped with slotted sprayers of liquid located along its generatrix for supplying spray cones into the initial section of the jet. Based on the developed method, the results of tinted liquid spraying subject cards fixed in a certain position in compliance with the GOST 34630 on tablets and located perpendicular to the motion direction of the sprayer on soil and hills.
 RESEARCH NOVELTY: The aerosol technology for edge treatment of a field for the destruction of weeds and pests was proposed for the first time.
 RESULTS: Using eight LU-015. AD-015 (color code - green) slotted sprayers on the nozzle generatrix of the device, the number of drops deposited per 1 cm2 on the surface at a distance from the nozzle up to 15 m satisfies the agrotechnical requirements for the use of herbicides, as well as insecticides and fungicides. Throughout the height of the cards at a distance of 10 m from the nozzle, the number of drops per 1 cm2 decreases, and especially with an increase in the height of their location. Large drops of the polydisperse system settle on the soil earlier to kill weeds, while small ones move to the forest belt to kill pests at the base.
 CONCLUSIONS: With theoretical calculations and experimentally, the aerosol technology of combined edge treatment of a field and field-protective plantings with the environmentally friendly cold aerosol using slotted liquid sprayers was justificated. The performance of rational technology is ensured by: the technical unit motion velocity of 3 km/h, the spraying width of 10 m, the working fluid pressure of 4 bar, the productivity of 3 ha/h, the working solution flow rate of 108.8 l/ha.

Design, testing, and installation of a shrouded aerosol sampling probe at demonstration fast reactor fuel reprocessing plant

Abstract A shrouded air sampling probe was designed and fabricated to meet the effluent monitoring requirements of an upcoming reprocessing facility at IGCAR. Performance evaluation of the probe was carried out using standard polydisperse aerosols up to 2 μm at the high-efficiency particulate air filter test facility. Its performance was also verified for higher size particles till 10 μm using the “Deposition 2001a” code. Based on the results, the shrouded probe was found to qualify the air sampling requirements and the same was fixed at the sampling point in the exhaust duct. This paper describes the details of design, testing, and installation of the shrouded probe.

Parameterization of polydisperse aerosol optical properties during hygroscopic growth

Aerosol water uptake and the related influence on its optical properties owing to the hygroscopic growth of polydisperse aerosols have a significant effect on air quality and climate. This study develops an analytical parameterization for a single hygroscopic optical parameter and the scattering enhancement factor for polydisperse aerosol sizes. Polydisperse lognormal size distributions for geometric mean diameters of 0.05–1 μm and geometric standard deviations of 1.3–2.5 are considered with real refractive indices between 1.35-1.6. The analytical expression obtained for the optical parameter is compared to Mie theory and reasonable agreements within the size range investigated in this study are observed. Further, our results show that the analytical expression could express polydispersed aerosol optical properties as a function of geometric mean diameter and geometric standard deviation of a lognormal distribution and the refractive index. The obtained analytical expression can be efficiently used for 3D models with a reduced computational burden.

123 Characterisation and Modification of the Porous Metal Foams Used for the En 15051-2 Dustiness Rotating Drum Test

Abstract Handling of hazardous materials in occupational settings can lead to worker exposure by inhalation. Dustiness testing, such as the EN 15051-2 rotating drum tester, provides suppliers and users of bulk materials with information on the potential for dust emission from hazardous substances when handled or processed in the workplace. This tester agitates powder samples in a rotating drum and the resulting dust is collected and sized by drawing it through two reticulated metal foams. Two approaches were used to evaluate the performance of the metal foams. Firstly, the performance of the metal foams was measured in a calm air chamber using a polydisperse aerosol of glass particles and assessed against the EN 481 respirable convention. Secondly, the performance of the metal foam for the respirable fraction was compared using the rotating drum dustiness test, with that of a cyclone set-up, using four polydisperse glass powders of different size distribution and dustiness potential. In general, for the respirable fraction, the tests demonstrated a conservative oversampling by the current EN 15051-2 metal foam set-up in comparison with the EN 481 convention. This study also showed the importance of sealing the circumference of the metal foams when testing highly dusty powders. A direct comparison of the respirable dustiness fraction measured by the current EN 15051-2 metal foams set-up and by a cyclone set-up, showed broad agreement. However, the cyclone gave lower values except where foam clogging occurred. The research also highlighted suggested improvements to the EN 15051-2 standard. © Crown Copyright (2022)

NEW EXPERIMENTAL DATA OF CHILD DROPLETS IDENTIFICATION AFTER TWO-LIQUID DROPLET BREAKUP

New experimental data of child droplets characteristics (times to puffing/microexplosion, distribution of sizes, and ratio of the evaporation surface area before and after puffing/microexplosion) of heated two-liquid droplets in puffing and microexplosion modes are presented. Different droplet configuration effects (fuel liquid (rapeseed oil) - shell, water-core, vice versa) are discussed. The experiments were carried out with two-liquid droplets in which coal particles were added to meet nonpremixed spray technologies into the combustion chambers. Breakup conditions of water/fuel droplets in monodisperse and polydisperse aerosols are determined. The difference in secondary atomization effects of water and fuel is described. The effect of gas temperature in the range 720-1070 K on child droplets characteristics is discussed.

NOx reduction based on N2 dilution in a swirled-stabilized magnesium flame

New sources of clean energy with reduced greenhouse gas emissions must be considered because of global warming. Among these alternative sources, metal fuels such as aluminum or magnesium are promising. The present study focuses on the impacts of an air dilution by N2 and of the equivalence ratio on the amount of nitrogen oxides (NOx) produced by a swirled-stabilized magnesium flame. A polydispersed aerosol of pure magnesium in the size fraction 50–70 µm was injected in the combustion chamber. Different air–fuel ratios – from 0.14 to 1.0 – were obtained by changing the mass flowrate of the injected fuel. Thermocouples and a pyrometer were implemented to monitor the gas and flame temperatures. On-line paramagnetic analyzers were used to measure the oxygen (O2) and NOx concentrations. For each dilution condition (0, 30 and 50 %), the NOx mole fraction versus the equivalence ratio follows a parabolic shape. The amount of NOx first increases when increasing the air–fuel ratio as the power dissipated by the flame increases, leading to the rise of the gas temperature. For the highest air–fuel ratios, the NOx production is disfavored in the rich mixture. The maximal NOx emissions are shifted to higher equivalent ratios when increasing the dilution level and it decreases by a factor 2 with a dilution of 50 %, for a constant value of the air–fuel ratio. The gas temperature in the flame decreases due to the N2 dilution. The NOx emissions become negligible for an equivalence ratio of 1 at a 50 % dilution. Nevertheless, under the tested experimental conditions, the level of NOx never exceeded 7 gNOx/kWh, which is lower than the maximal value of NOx emissions from a gasoline engine.

Optical aerosol sizing method without prior refractive index

Existing light-based aerosol size analyzers suffer from measurement errors or even fail to measure particle size distribution (PSD) when the refractive index is unknown. To overcome this limitation, we introduced a new aerosol sizing method without the prior refractive index using the light scattering intensity field (LSIF) and deep learning. The LSIF is the intensity distribution of the light scattered in all directions around aerosol particles, which can be used to simultaneously characterize the PSD and the refractive index. A PSD retrieval approach based on deep learning was developed to efficiently retrieve (about 100 ms) the unconstrained PSD (141 independent channels). Our proof-of-concept prototype was tested on various aerosol samples with different particle sizes and refractive indices, where the relative standard deviation (RSD) of the particle size was 1.94% in the test of monodisperse aerosols and the Kullback-Leibler divergence of PSD was 0.13 in the test of polydisperse aerosols.

Behavior of child droplets during micro-explosion and puffing of suspension fuel droplets: The impact of the component mixing sequence

The article provides experimental research findings on the behavior of micro-explosion and puffing of two-liquid droplets in different droplet formation schemes: liquid combustible component (rapeseed oil) as the shell with liquid incombustible component (water) as the core and vice versa. The experiments were conducted on fuel compositions that had not been pre-mixed; no coal particles had been added into them. These conditions aimed to reflect industrial production conditions with separate injection and blow-in of components into combustion chambers. Shadow Photography and Planar Laser Induced Fluorescence techniques were used in the experiments. An alcohol burner was used for heating droplets. The temperature of the heating medium was varied in the range of 850–1050 K by adjusting the vertical distance of the droplet from the burner bottom to match the conditions typical for industrial applications, specifically, composite fuel creation technologies and thermal/flame purification of liquids. Conditions have been determined under which droplets of combustible and non-combustible components are atomized during fragmentation thus producing polydisperse and monodisperse aerosols. Effects have been discovered whereby the fragmentation of combustible and noncombustible liquid components produces droplets of different sizes. Correlations between the size and component composition of child droplets with the heating temperature and mixing sequence of the liquids in the parent droplet have been established.

Velocity map imaging VUV angle-resolved photoelectron spectroscopy of isolated silver sulfide nanoparticles

The angle-resolved photoelectron spectroscopy of isolated silver sulfide nanoparticles was carried out by using velocity map imaging technique at the DESIRS beamline of SOLEIL synchrotron facility. The reported spectroscopy results were obtained after interaction of the synchrotron radiation with a polydisperse aerosol produced from aqueous dispersion of silver sulfide particles, approximately 16 nm in diameter. The photoelectron and UV–Vis-NIR absorption spectra were used to estimate the maximum energy of the valance- and the minimum energy of the conduction-band of the nanoparticles. With respect to the vacuum level, the obtained values were found to be 5.5 ± 0.1 eV and 4.5 ± 0.1 eV for the valence band maximum and conduction band minimum, respectively. The dependence of the asymmetry parameter on the electron energy along the silver sulfide valence band showed an onset of inelastic scattering at ~ 1 eV electron kinetic energy.

Development and technical validation of an ultrasound nebulizer to deliver intraperitoneal pressurized aerosols in a rat colon cancer peritoneal metastases model

Background/aimTo develop and validate a nebulizer device for anti-cancer research on pressurized intraperitoneal aerosol supply in a preclinical peritoneal metastases (PM) rat model.Material and methodsFor aerosol generation, an ultrasonic nebulizer (USN) was modified. Aerosol analyses were performed ex-vivo by laser diffraction spectrometry (LDS). Intraperitoneal (IP) 99mtechnetium sodium pertechnetate (99mTc) aerosol distribution and deposition were quantified by in-vivo single photon emission computed tomography (SPECT/CT) and compared to liquid IP instillation of equivalent volume/doses of 99mTc with and without capnoperitoneum. PM was induced by IP injection of HCT116-Luc2 human colon cancer cells in immunosuppressed RNU rats. Tumor growth was monitored by bioluminescence imaging (BLI), 18F-FDG positron emission tomography (PET) and tissues examination at necropsy.ResultsThe USN was able to establish a stable and reproducible capnoperitoneum at a pressure of 8 to 10 mmHg. LDS showed that the USN provides a polydisperse and monomodal aerosol with a volume-weighted diameter of 2.6 μm. At a CO2 flow rate of 2 L/min with an IP residence time of 3.9 s, the highest drug deposition efficiency was found to be 15 wt.-%. In comparison to liquid instillation, nebulization showed the most homogeneous IP spatial drug deposition. Compared to BLI, 18F-FDG-PET was more sensitive to detect smaller PM nodules measuring only 1–2 mm in diameter. BLI, 18F-FDG PET and necropsy analyses showed relevant PM in all animals.ConclusionsThe USN together with the PM rat model are suitable for robust and species-specific preclinical pharmacological studies regarding intraperitoneal delivery of pressurized aerosolized drugs and cancer research.

Multi-mechanism theory of aerosol capture by fibrous filters, including fiber diameter/orientation dispersity and particle morphology effects. Preliminary tests vs. data for mobility-selected submicron particles

In Paper I (Sep. Purif. Technol. 257 (2021) 117676) we showed that a semi-analytic, multi-mechanism expression for the single-fiber capture fraction, ηcap,SF, (derived using asymptotically valid approximations: Ref<0.4, Pef≫1, R≪1, R⋅Pef1/3 arbitrary and Stkp≤Stkpcrit), facilitates a deterministic-, pseudo-continuum aerosol population-balance (PB-) approach to predicting fibrous filter performance. There we explicitly considered “deep” (Lf/df,g≫1), low solidity idealized fibrous filters (FFs) challenged by polydispersed aerosols—especially single-mode log-normal (LN) ASDs of modest spread captured by a spatially uniform array of fibers of a single diameter in crossflow. However, realistic fibrous filter media often possess a LN distribution of fiber diameters, as well as a near-Gaussian orientation distribution narrowly spread about normal incidence (θ=π/2). Moreover, even if this were not so, there would be meso-scale departures from a uniform average fiber solid fraction. We show here that our tractable aerosol PBE-approach to idealized FF performance (Paper I) can be generalized to incorporate these particular structural features of commercially available fibrous filter media. But, to clarify whether these generalizations are likely to be useful, if not fully sufficient, for practical circumstances, it is also necessary to compare such methods/predictions against selected sets of well-defined experimental results. We initiate this program here, having chosen the recent experiments of Kang et al. (2019) carried out using a commercially available fiberglass filter with Lf/df,g≃300, mean solid fraction of 0.039, and df,g=2.5μm, successively challenged by mobility-selected KCl(s) particles (with diameters between ca. 20 and 600nm) at the carrier gas velocities of 15 and 10 cm/s—capture conditions dominated by the transport mechanism of Brownian diffusion and convection, with “interception” (associated with non-negligible dp/df) becoming important above ca. dp=100nm. We conclude from these data that the effective interception diameter, dp,icpt,eff, of the particles studied is systematically larger than their stated mobility diameters—a situation which will deserve further attention in future studies. Encouraged by these preliminary but instructive comparisons, we expect that, for many current and future design purposes, our present class of semi-analytic/non-stochastic/multi-mechanism methods will provide a welcome complement, if not alternative, to much more computationally-intensive simulation methods for realistic fibrous media that have been described and implemented in the recent aerosol filtration literature. The consequences of including these structural features of fibrous filters in the presence of aerosol size- and shape polydispersity will be the subject of future studies, based on the generalized Population Balance Equation developed/proposed in Section 3.3.