Laboratory study of the collection efficiency of submicron aerosol particles by cloud droplets. Part I – Influence of relative humidity

Abstract. A new In-Cloud Aerosol Scavenging Experiment (In-CASE) has been conceived to measure the collection efficiency (CE) of submicron aerosol particles by cloud droplets. In this setup, droplets fall at their terminal velocity through a one-meter-high chamber in a laminar flow containing aerosol particles. At the bottom of the In-CASE's chamber, the droplet train is separated from the aerosol particle flow – droplets are collected in an impaction cup whereas aerosol particles are deposited on a High Efficiency Particulate Air (HEPA) filter. The collected droplets and the filter are then analysed by fluorescence spectrometry since the aerosol particles are atomised from a sodium fluorescein salt solution (C20H10Na2O5). In-CASE fully controls all the parameters which affect the CE – the droplets and aerosol particles size distributions are monodispersed, the electric charges of droplets and aerosol particles are controlled, while the relative humidity is indirectly set via the chamber's temperature. This novel In-CASE setup is presented here as well as the first measurements obtained to study the impact of relative humidity on CE. For this purpose, droplets and particles are electrically neutralised. A droplet radius of 49.6 ± 1.3 μm has been considered for six particle dry radii between 50 and 250 nm and three relative humidity levels of 71.1 ± 1.3, 82.4 ± 1.4 and 93.5 ± 0.9 %. These new CE measurements have been compared to the Wang et al. (1978) and the extended model of Dépée et al. (2019) where thermophoresis and diffusiophoresis are implemented. Both models adequately describe the relative humidity influence on the measured CE.

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Laboratory study of the collection efficiency of submicron aerosol particles by cloud droplets. Part II – Influence of electric charges

10.5194/acp-2020-832 ◽

2020 ◽

Cited By ~ 1

Author(s):

Alexis Dépée ◽

Pascal Lemaitre ◽

Thomas Gelain ◽

Marie Monier ◽

Andrea Flossmann

Keyword(s):

Relative Humidity ◽

High Efficiency ◽

Collection Efficiency ◽

Aerosol Particles ◽

Droplet Radius ◽

Sodium Fluorescein ◽

Extended Model ◽

Cloud Droplets ◽

Submicron Aerosol ◽

The Impact

Abstract. A new In-Cloud Aerosol Scavenging Experiment (In-CASE) has been developed to measure the collection efficiency (CE) of submicron aerosol particles by cloud droplets. Droplets fall at their terminal velocity through a one-meter-high chamber in a laminar flow containing aerosol particles. At the bottom of the In-CASE's chamber, the droplet train is separated from the aerosol particles flow and the droplets are collected in an impaction cup whereas aerosol particles are deposited on a High Efficiency Particulate Air (HEPA) filter. The collected droplets and the filter are then analysed by fluorescence spectrometry since the aerosol particles are atomised from a sodium fluorescein salt solution (C20H10Na2O5). In-CASE fully controls all the parameters which affect the CE – the droplets and aerosol particles size distributions are monodispersed, the electric charges of droplets and aerosol particles are known and set, while the relative humidity is indirectly controlled via the chamber's temperature. This paper details the In-CASE setup and the dataset of 70 measurements obtained to study the impact of the electric charges on CE. For this purpose, droplets and particles charges are controlled through two charging systems developed in this work – both chargers are detailed below. The droplet charge varies from −3.0 × 104 ± 1.4 × 103 to +9.6 × 104 ± 4.3 × 103 elementary charges while the particle charge ranges from the neutralisation to −90 ± 9 elementary charges depending on the particle radius. A droplet radius of 48.5 ± 1.1 μm has been considered for four particle dry radii between 100 and 250 nm. These new CE measurements have been compared to the correlation of Kraemer and Johnstone (1955) and the extended model of Dépée et al. (2019) where thermophoresis and diffusiophoresis are also considered since the measurements have been performed at a relative humidity level of 95.1 ± 0.2 %. As a result, both models adequately describe the electric charge influence on the measured CEs. Furthermore, the effect of the image charge (Jackson, 1999) in the electrostatic forces is measured.

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Contribution of Phoretic and Electrostatic Effects to the Collection Efficiency of Submicron Aerosol Particles by Raindrops

Atmosphere ◽

10.3390/atmos11101028 ◽

2020 ◽

Vol 11 (10) ◽

pp. 1028

Author(s):

Pascal Lemaitre ◽

Mamadou Sow ◽

Arnaud Quérel ◽

Alexis Dépée ◽

Marie Monier ◽

...

Keyword(s):

Relative Humidity ◽

Collection Efficiency ◽

Aerosol Particles ◽

Terminal Velocity ◽

Submicron Aerosol ◽

Percentage Decrease ◽

Relative Humidity Range ◽

The One

This article presents an experimental study, performed in the BERGAME setup, dedicated to studying the collection of submicron aerosol particles by raindrops. The initial aim was to focus on the influence of the electrical charges of raindrops on the efficiency with which they collect aerosol particles. However, in the relative humidity range considered in this article (26–36%), measurements highlight a first-order role of phoretic effect for submicron aerosol particles. Indeed, measurements highlight a 100% increase in the collection efficiency for each percentage decrease in the atmospheric relative humidity. Phoretic effects are known to play a role in collection by drops; however, none of the models found in the literature predicts the same magnitude as the one presently measured. Characterization of the aerosol trajectories around the drop, accelerated to terminal velocity, seems to show a coupling between phoretic effects and rear capture. This interaction, already suggested by Grover et al., is a line of explanation for such a sharp unpredicted increase of the collection efficiency with moisture decrease.

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A light-driven burst of hydroxyl radicals dominates oxidation chemistry in newly activated cloud droplets

Science Advances ◽

10.1126/sciadv.aav7689 ◽

2019 ◽

Vol 5 (5) ◽

pp. eaav7689 ◽

Cited By ~ 9

Author(s):

Suzanne E. Paulson ◽

Peter J. Gallimore ◽

Xiaobi M. Kuang ◽

Jie Rou Chen ◽

Markus Kalberer ◽

...

Keyword(s):

Hydroxyl Radicals ◽

Uv Light ◽

Aerosol Particles ◽

Cloud Droplet ◽

Radiative Properties ◽

Size Distributions ◽

Cloud Droplets ◽

New Process ◽

Oxidation Chemistry ◽

The Impact

Aerosol particles and their interactions with clouds are one of the most uncertain aspects of the climate system. Aerosol processing by clouds contributes to this uncertainty, altering size distributions, chemical composition, and radiative properties. Many changes are limited by the availability of hydroxyl radicals in the droplets. We suggest an unrecognized potentially substantial source of OH formation in cloud droplets. During the first few minutes following cloud droplet formation, the material in aerosols produces a near-UV light–dependent burst of hydroxyl radicals, resulting in concentrations of 0.1 to 3.5 micromolar aqueous OH ([OH]aq). The source of this burst is previously unrecognized chemistry between iron(II) and peracids. The contribution of the “OH burst” to total OH in droplets varies widely, but it ranges up to a factor of 5 larger than previously known sources. Thus, this new process will substantially enhance the impact of clouds on aerosol properties.

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Glyoxal's impact on dry ammonium salts: fast and reversible surface aerosol browning

10.5194/acp-2020-203 ◽

2020 ◽

Author(s):

David O. De Haan ◽

Lelia N. Hawkins ◽

Kevin Jansen ◽

Hannah G. Welsh ◽

Raunak Pednekar ◽

...

Keyword(s):

Relative Humidity ◽

Gas Phase ◽

Ammonium Sulfate ◽

Aerosol Particles ◽

Ammonium Salts ◽

Carbon Formation ◽

Cloud Droplets ◽

Brown Carbon ◽

Dicarbonyl Compounds ◽

Dry Conditions

Abstract. Alpha-dicarbonyl compounds are believed to form brown carbon in the atmosphere via reactions with ammonium sulfate (AS) in cloud droplets and aqueous aerosol particles. In this work, brown carbon formation in AS and other aerosol particles was quantified as a function of relative humidity (RH) during exposure to gas-phase glyoxal (GX) in chamber experiments. Under dry conditions (RH

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The impact of iron distribution among cloud droplets or aqueous aerosol particles on multiphase oxidant levels

10.5194/egusphere-egu21-2102 ◽

2021 ◽

Author(s):

Amina Khaled ◽

Minghui Zhang ◽

Barbara Ervens

Keyword(s):

Aerosol Particles ◽

Multiphase System ◽

Multiphase Model ◽

Aerosol Composition ◽

Cloud Droplets ◽

Iron Distribution ◽

Model Studies ◽

Oxidation Potentials ◽

The Impact ◽

Iron Concentrations

Reactive oxygen species (ROS), such as hydroxyl radical (OH&#8226;), hydroperoxy radicals (HO2&#8226;/O2-), and hydrogen peroxide (H2O2), are produced in cloud droplets and aqueous aerosol. Multiphase model studies suggest that the Fenton reaction, i.e. the oxidation of Fe(II) by H2O2 represents one of the main sources of the OH radical in the aqueous phase.Current cloud and aerosol multiphase chemistry models are usually initialized with equal iron concentrations in all droplets or particles as derived from bulk samples of cloud water or aerosol composition. However, analysis of single aerosol particles has revealed that only a small number fraction of particles and, thus, of cloud droplets contain iron.The aim of our study is to identify the impacts of the iron distribution in cloud droplets or aqueous aerosol particles on the total (gas + aqueous) budgets of OH, HO2, H2O2 and O3 in the multiphase system.By means of model studies, we compare predicted oxidant budgets based on the assumptions of iron distributed among all droplets or particles versus the same iron mass concentrated in a few droplets (or particles) in the total population only. Our results suggest that the traditional approach based on bulk iron concentrations may significantly underestimate total OH budgets, whereas the predicted levels of H2O2, HO2/O2- and ozone are less affected. The reasons for the different findings between (i) the various oxidants and (ii) cloud droplets vs aerosol particles will be discussed. In summary, our model studies suggest that oxidant levels and oxidation potentials of particulate matter in the atmosphere can only be accurately assessed if particle- and size-resolved aerosol composition is accounted for.

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Design and Demonstration of High-Efficiency Quantum Well Solar Cells Employing Thin Strained Superlattices

Scientific Reports ◽

10.1038/s41598-019-50321-x ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 6

Author(s):

Roger E. Welser ◽

Stephen J. Polly ◽

Mitsul Kacharia ◽

Anastasiia Fedorenko ◽

Ashok K. Sood ◽

...

Keyword(s):

Solar Cells ◽

Solar Cell ◽

Quantum Well ◽

High Efficiency ◽

Collection Efficiency ◽

Multiple Quantum ◽

Barrier Thickness ◽

Device Structure ◽

Single Junction ◽

The Impact

Abstract Nanostructured quantum well and quantum dot III–V solar cells provide a pathway to implement advanced single-junction photovoltaic device designs that can capture energy typically lost in traditional solar cells. To realize such high-efficiency single-junction devices, nanostructured device designs must be developed that maximize the open circuit voltage by minimizing both non-radiative and radiative components of the diode dark current. In this work, a study of the impact of barrier thickness in strained multiple quantum well solar cell structures suggests that apparent radiative efficiency is suppressed, and the collection efficiency is enhanced, at a quantum well barrier thickness of 4 nm or less. The observed changes in measured infrared external quantum efficiency and relative luminescence intensity in these thin barrier structures is attributed to increased wavefunction coupling and enhanced carrier transport across the quantum well region typically associated with the formation of a superlattice under a built-in field. In describing these effects, a high efficiency (>26% AM1.5) single-junction quantum well solar cell is demonstrated in a device structure employing both a strained superlattice and a heterojunction emitter.

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Laboratory studies of collection efficiency of sub-micrometer aerosol particles by cloud droplets on a single droplet basis

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-6207-2015 ◽

2015 ◽

Vol 15 (5) ◽

pp. 6207-6236 ◽

Cited By ~ 2

Author(s):

K. Ardon-Dryer ◽

Y.-W. Huang ◽

D. J. Cziczo

Keyword(s):

Collection Efficiency ◽

Aerosol Particles ◽

Sulfate Solution ◽

Polystyrene Latex ◽

Particle Analysis ◽

Chemical Compositions ◽

Laser Mass Spectrometry ◽

Single Droplet ◽

Cloud Droplets ◽

Experimental And Theoretical Studies

Abstract. An experimental setup has been constructed to measure the Collection Efficiency (CE) of sub-micrometer aerosol particles by cloud droplets. Water droplets of a dilute aqueous ammonium sulfate solution with a radius of ~20 μm fall freely into a chamber and collide with sub-micrometer Polystyrene Latex Sphere (PSL) particles of variable size and concentrations. Two RH conditions, ~15 and ~88%, hereafter termed "Low" and "High", respectively, were varied with different particles size and concentrations. After passing through the chamber, the droplets and aerosol particles were sent to the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument to determine chemical compositions on a single particle basis. Coagulated droplets had mass spectra that contain signatures from both an aerosol particle and a droplet residual. CE values range from 5.7 × 10−3 to 4.6 × 10−2 for the Low RH and from 6.4 × 10−3 to 2.2 × 10−2 for the High RH cases. CE values were, within experimental uncertainty, independent of the aerosol concentrations. CE values in this work were found to be in agreement with previous experimental and theoretical studies. To our knowledge, this is the first coagulation experiment performed on a single droplet basis.

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Diffusion characteristics of the industrial submicron particle under Brownian motion and turbulent diffusion

Indoor and Built Environment ◽

10.1177/1420326x21991055 ◽

2021 ◽

pp. 1420326X2199105

Author(s):

Chengjun Li ◽

Hanqing Wang ◽

Chuck Wah Yu ◽

Dong Xie

Keyword(s):

Heat Source ◽

Drag Force ◽

Lift Force ◽

Aerosol Particles ◽

Particle Model ◽

Thermal Plume ◽

Submicron Aerosol ◽

Brownian Force ◽

The Impact ◽

Saffman Lift Force

The industrial release of submicron aerosol particles at workplace could cause undue health effect on workers. To effectively capture and remove airborne particles, we need to study the characteristics of various interactive particle motion forces (drag force, Brownian force, Saffman lift force, etc.) and the dispersion of these aerosol particles in indoor air. In this study, the dominant force of submicron particles was determined by calculating the acting forces with different particle sizes. Then, a Discrete Particle Model (DPM) was used to calculate the trajectory of particle movement in turbulent thermal plume flow. Horizontal dispersity ( DH) was defined to evaluate the horizontal diffusion of the particulate matter. The impact of different particle diameters, heat source temperatures and initial relative velocities on DH was investigated. This study showed that the main acting forces for submicron aerosol particles were drag force, Brownian force, Saffman lift force and thermophoresis force. Brownian force cannot be ignored when the particle diameter was below 0.3 µm, which would promote the irregular movement of particles in space and enhance their diffusion ability. The smaller the particle size, the higher the heat source temperature and the lower the particles' initial velocity would lead to the increase of DH.

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Laboratory studies of collection efficiency of sub-micrometer aerosol particles by cloud droplets on a single-droplet basis

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-9159-2015 ◽

2015 ◽

Vol 15 (16) ◽

pp. 9159-9171 ◽

Cited By ~ 30

Author(s):

K. Ardon-Dryer ◽

Y.-W. Huang ◽

D. J. Cziczo

Keyword(s):

Collection Efficiency ◽

Aerosol Particles ◽

Sulfate Solution ◽

Polystyrene Latex ◽

Particle Analysis ◽

Chemical Compositions ◽

Laser Mass Spectrometry ◽

Single Droplet ◽

Cloud Droplets ◽

Droplet Sizes

Abstract. An experimental setup has been constructed to measure the collection efficiency (CE) of sub-micrometer aerosol particles by cloud droplets. Droplets of a dilute aqueous ammonium sulfate solution with an average radius of 21.6 μm fall freely into a chamber and collide with sub-micrometer polystyrene latex (PSL) sphere particles of known sizes and concentrations. Two relative humidity (RH) conditions, 15 ± 3 % and 88 ± 3 %, hereafter termed "low" and "high", respectively, were varied with different particles sizes and concentrations. After passing through the chamber, the droplets and aerosol particles were sent to the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument to determine chemical compositions on a single-droplet basis. "Coagulated droplets" (droplets that collected aerosols) had mass spectra that contained signatures from both an aerosol particle and a droplet residual. CE values range from 2.0 × 10−1 to 1.6 for the low-RH case and from 1.5 × 10−2 to 9.0 × 10−2 for the high-RH case. CE values were, within experimental uncertainty, independent of the aerosol concentrations. CE values in this study were found to be in agreement with previous experimental and theoretical studies. To our knowledge, this is the first collection experiment performed on a single-droplet basis with atmospherically relevant conditions such as droplet sizes, droplet charges and flow.

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Piezoelectric β-polymorph formation of new textiles by surface modification with coating process based on interfacial interaction on the conformational variation of poly (vinylidene fluoride) (PVDF) chains

The European Physical Journal Applied Physics ◽

10.1051/epjap/2020200158 ◽

2020 ◽

Vol 91 (3) ◽

pp. 31301

Author(s):

Nabil Chakhchaoui ◽

Rida Farhan ◽

Meriem Boutaldat ◽

Marwane Rouway ◽

Adil Eddiai ◽

...

Keyword(s):

High Efficiency ◽

Vinylidene Fluoride ◽

Research Work ◽

Research Area ◽

Interfacial Interaction ◽

Tetraethyl Orthosilicate ◽

Poly Vinylidene Fluoride ◽

Carbon Nanofillers ◽

The Impact ◽

Advanced Applications

Novel textiles have received a lot of attention from researchers in the last decade due to some of their unique features. The introduction of intelligent materials into textile structures offers an opportunity to develop multifunctional textiles, such as sensing, reacting, conducting electricity and performing energy conversion operations. In this research work nanocomposite-based highly piezoelectric and electroactive β-phase new textile has been developed using the pad-dry-cure method. The deposition of poly (vinylidene fluoride) (PVDF) − carbon nanofillers (CNF) − tetraethyl orthosilicate (TEOS), Si(OCH2CH3)4 was acquired on a treated textile substrate using coating technique followed by evaporation to transform the passive (non-functional) textile into a dynamic textile with an enhanced piezoelectric β-phase. The aim of the study is the investigation of the impact the coating of textile via piezoelectric nanocomposites based PVDF-CNF (by optimizing piezoelectric crystalline phase). The chemical composition of CT/PVDF-CNC-TEOS textile was detected by qualitative elemental analysis (SEM/EDX). The added of 0.5% of CNF during the process provides material textiles with a piezoelectric β-phase of up to 50% has been measured by FTIR experiments. These results indicated that CNF has high efficiency in transforming the phase α introduced in the unloaded PVDF, to the β-phase in the case of nanocomposites. Consequently, this fabricated new textile exhibits glorious piezoelectric β-phase even with relatively low coating content of PVDF-CNF-TEOS. The study demonstrates that the pad-dry-cure method can potentially be used for the development of piezoelectric nanocomposite-coated wearable new textiles for sensors and energy harvesting applications. We believe that our study may inspire the research area for future advanced applications.

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