Title: Atmospheric Nanoparticle Survivability Reduction Due to Charge‐Induced Coagulation Scavenging Enhancement
Abstract
New‐particle formation is important to aerosol–cloud interactions and thus climate, but for newly formed particles to become cloud condensation nuclei, they must grow and avoid scavenging by larger background particles. Whereas ion‐induced new‐particle formation and growth have received attention recently, here we study an opposing effect, blunting the enhancement due to ions, that has received less attention: Small charged particles are scavenged more efficiently due to their charge, and thus their survival probability is lower than that of their neutral counterparts. Through simulations, we show that particle survival is reduced, in some cases dramatically, matching updated theoretical predictions. We also show that the survival of charged particles is enhanced if particles lose their charge via neutralization; therefore, for ion‐induced nucleation to be important, the resulting charged particles must become neutral as soon as possible. Overall, the coagulation scavenging enhancement due to charge ought to lessen the influence of ions in new‐particle formation and growth.
Mahfouz, Naser G.; Donahue, Neil M.(
, Atmospheric Chemistry and Physics)
null
(Ed.)
Abstract. We show that the limit of the enhancement of coagulation scavenging of charged particles is 2, that is, doubled compared to the neutral case.Because the particle survival probability decreases exponentially as the coagulation sink increases, everything else being equal, the doubling of the coagulation sink can amount to a dramatic drop in survival probability – squaring the survival probability, p2, where p≤1 is the survival probability in the neutral case.Thus, it is imperative to consider this counterbalancing effect when studying ion-induced new-particle formation and ion-enhanced new-particle growth in the atmosphere.
Kong, Weimeng; Amanatidis, Stavros; Mai, Huajun; Kim, Changhyuk; Schulze, Benjamin C.; Huang, Yuanlong; Lewis, Gregory S.; Hering, Susanne V.; Seinfeld, John H.; Flagan, Richard C.(
, Atmospheric Measurement Techniques)
Abstract. Particle size measurement in the low nanometer regime is of great importance to the study of cloud condensation nuclei formation and to better understand aerosol–cloud interactions. Here we present the design, modeling, and experimental characterization of the nano-scanning electrical mobility spectrometer (nSEMS), a recently developed instrument that probes particle physical properties in the 1.5–25 nm range. The nSEMS consists of a novel differential mobility analyzer and a two-stage condensation particle counter (CPC). The mobility analyzer, a radial opposed-migration ion and aerosol classifier (ROMIAC), can classify nanometer-sized particles with minimal degradation of its resolution and diffusional losses. The ROMIAC operates on a dual high-voltage supply with fast polarity-switching capability to minimize sensitivity to variations in the chemical nature of the ions used to charge the aerosol. Particles transmitted through the mobility analyzer are measured using a two-stage CPC. They are first activated in a fast-mixing diethylene glycol (DEG) stage before being counted by a second detection stage, an ADI MAGIC™ water-based CPC. The transfer function of the integrated instrument is derived from both finite-element modeling and experimental characterization. The nSEMS performance has been evaluated during measurement of transient nucleation and growth events in the CLOUD atmospheric chamber at CERN. We show that the nSEMS can provide high-time- and size-resolution measurement of nanoparticles and can capture the critical aerosol dynamics of newly formed atmospheric particles. Using a soft x-ray bipolar ion source in a compact housing designed to optimize both nanoparticle charging and transmission efficiency as a charge conditioner, the nSEMS has enabled measurement of the contributions of both neutral and ion-mediated nucleation to new particle formation.
Simon, Mario; Dada, Lubna; Heinritzi, Martin; Scholz, Wiebke; Stolzenburg, Dominik; Fischer, Lukas; Wagner, Andrea C.; Kürten, Andreas; Rörup, Birte; He, Xu-Cheng; et al(
, Atmospheric Chemistry and Physics)
null
(Ed.)
Abstract. Highly oxygenated organic molecules (HOMs) contributesubstantially to the formation and growth of atmospheric aerosol particles,which affect air quality, human health and Earth's climate. HOMs are formedby rapid, gas-phase autoxidation of volatile organic compounds (VOCs) suchas α-pinene, the most abundant monoterpene in the atmosphere. Due totheir abundance and low volatility, HOMs can play an important role innew-particle formation (NPF) and the early growth of atmospheric aerosols,even without any further assistance of other low-volatility compounds suchas sulfuric acid. Both the autoxidation reaction forming HOMs and theirNPF rates are expected to be strongly dependent ontemperature. However, experimental data on both effects are limited.Dedicated experiments were performed at the CLOUD (Cosmics Leaving OUtdoorDroplets) chamber at CERN to address this question. In this study, we showthat a decrease in temperature (from +25 to −50 ∘C) results ina reduced HOM yield and reduced oxidation state of the products, whereas theNPF rates (J1.7 nm) increase substantially.Measurements with two different chemical ionization mass spectrometers(using nitrate and protonated water as reagent ion, respectively) providethe molecular composition of the gaseous oxidation products, and atwo-dimensional volatility basis set (2D VBS) model provides their volatilitydistribution. The HOM yield decreases with temperature from 6.2 % at 25 ∘C to 0.7 % at −50 ∘C. However, there is a strongreduction of the saturation vapor pressure of each oxidation state as thetemperature is reduced. Overall, the reduction in volatility withtemperature leads to an increase in the nucleation rates by up to 3orders of magnitude at −50 ∘C compared with 25 ∘C. Inaddition, the enhancement of the nucleation rates by ions decreases withdecreasing temperature, since the neutral molecular clusters have increasedstability against evaporation. The resulting data quantify how the interplaybetween the temperature-dependent oxidation pathways and the associatedvapor pressures affect biogenic NPF at the molecularlevel. Our measurements, therefore, improve our understanding of purebiogenic NPF for a wide range of tropospherictemperatures and precursor concentrations.
Pfeifer, Joschka; Mahfouz, Naser G.; Schulze, Benjamin C.; Mathot, Serge; Stolzenburg, Dominik; Baalbaki, Rima; Brasseur, Zoé; Caudillo, Lucia; Dada, Lubna; Granzin, Manuel; et al(
, Atmospheric Chemistry and Physics)
Abstract. Aerosol particles have an important role in Earth'sradiation balance and climate, both directly and indirectly throughaerosol–cloud interactions. Most aerosol particles in the atmosphere areweakly charged, affecting both their collision rates with ions and neutralmolecules, as well as the rates by which they are scavenged by other aerosolparticles and cloud droplets. The rate coefficients between ions and aerosolparticles are important since they determine the growth rates and lifetimesof ions and charged aerosol particles, and so they may influence cloudmicrophysics, dynamics, and aerosol processing. However, despite theirimportance, very few experimental measurements exist of charged aerosolcollision rates under atmospheric conditions, where galactic cosmic rays inthe lower troposphere give rise to ion pair concentrations of around 1000 cm−3. Here we present measurements in the CERN CLOUD chamber of therate coefficients between ions and small (<10 nm) aerosol particlescontaining up to 9 elementary charges, e. We find the rate coefficient of asingly charged ion with an oppositely charged particle increases from 2.0(0.4–4.4) × 10−6 cm3 s−1 to 30.6 (24.9–45.1) × 10−6 cm3 s−1 for particles with charges of 1 to9 e, respectively, where the parentheses indicate the ±1σuncertainty interval. Our measurements are compatible with theoreticalpredictions and show excellent agreement with the model ofGatti and Kortshagen (2008).
Organic nucleation has been identified as an important way to form secondary organic aerosol (SOA) and change the number concentration of aerosol and thus its climate effect. A global atmospheric chemistry model is developed to include a comprehensive organic nucleation scheme that includes heteromolecular nucleation of sulfuric acid and organics, neutral pure organic nucleation, and ion‐induced pure organic nucleation. Our model simulation shows reasonable agreement with the seasonal as well as spatial pattern of organic carbon concentration in America, while it fails to predict the seasonal pattern of organic carbon in Europe due to the lack of sharp increases in primary organic aerosol emissions in the winter. Including organic nucleation decreases the bias of the annual average particle number concentration at 54% of the available observation sites and increases the temporal correlation coefficients at 58% of the sites. Ion‐induced pure organic nucleation contributes the most to the total organic nucleation rate, which peaks around 400 hPa in the tropics. Heteromolecular nucleation of sulfuric acid and organics dominates the total organic nucleation rate in the summer and mostly occurs in the lower troposphere. The number concentration of particles formed from organic nucleation (newSOA) in the nucleation and Aitken modes is highest in the tropics, while accumulation mode newSOA is highest in the Northern Hemisphere due to growth as a result of the condensation of sulfate. Three sensitivity experiments suggest that more studies are needed to investigate the formation mechanism of newSOA, so that a more accurate simulation of the spatial and size distribution of newSOA can be developed.
Mahfouz, Naser G. A., and Donahue, Neil M. Atmospheric Nanoparticle Survivability Reduction Due to Charge‐Induced Coagulation Scavenging Enhancement. Geophysical Research Letters 48.8 Web. doi:10.1029/2021GL092758.
Mahfouz, Naser G. A., & Donahue, Neil M. Atmospheric Nanoparticle Survivability Reduction Due to Charge‐Induced Coagulation Scavenging Enhancement. Geophysical Research Letters, 48 (8). https://doi.org/10.1029/2021GL092758
Mahfouz, Naser G. A., and Donahue, Neil M.
"Atmospheric Nanoparticle Survivability Reduction Due to Charge‐Induced Coagulation Scavenging Enhancement". Geophysical Research Letters 48 (8). Country unknown/Code not available: DOI PREFIX: 10.1029. https://doi.org/10.1029/2021GL092758.https://par.nsf.gov/biblio/10373154.
@article{osti_10373154,
place = {Country unknown/Code not available},
title = {Atmospheric Nanoparticle Survivability Reduction Due to Charge‐Induced Coagulation Scavenging Enhancement},
url = {https://par.nsf.gov/biblio/10373154},
DOI = {10.1029/2021GL092758},
abstractNote = {Abstract New‐particle formation is important to aerosol–cloud interactions and thus climate, but for newly formed particles to become cloud condensation nuclei, they must grow and avoid scavenging by larger background particles. Whereas ion‐induced new‐particle formation and growth have received attention recently, here we study an opposing effect, blunting the enhancement due to ions, that has received less attention: Small charged particles are scavenged more efficiently due to their charge, and thus their survival probability is lower than that of their neutral counterparts. Through simulations, we show that particle survival is reduced, in some cases dramatically, matching updated theoretical predictions. We also show that the survival of charged particles is enhanced if particles lose their charge via neutralization; therefore, for ion‐induced nucleation to be important, the resulting charged particles must become neutral as soon as possible. Overall, the coagulation scavenging enhancement due to charge ought to lessen the influence of ions in new‐particle formation and growth.},
journal = {Geophysical Research Letters},
volume = {48},
number = {8},
publisher = {DOI PREFIX: 10.1029},
author = {Mahfouz, Naser G. A. and Donahue, Neil M.},
}
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