skip to main content

Title: Enhanced growth rate of atmospheric particles from sulfuric acid
Abstract. In the present-day atmosphere, sulfuric acid is the mostimportant vapour for aerosol particle formation and initial growth. However,the growth rates of nanoparticles (<10 nm) from sulfuric acidremain poorly measured. Therefore, the effect of stabilizing bases, thecontribution of ions and the impact of attractive forces on molecularcollisions are under debate. Here, we present precise growth ratemeasurements of uncharged sulfuric acid particles from 1.8 to 10 nm, performedunder atmospheric conditions in the CERN (EuropeanOrganization for Nuclear Research) CLOUD chamber. Our results showthat the evaporation of sulfuric acid particles above 2 nm is negligible,and growth proceeds kinetically even at low ammonia concentrations. Theexperimental growth rates exceed the hard-sphere kinetic limit for thecondensation of sulfuric acid. We demonstrate that this results fromvan der Waals forces between the vapour molecules and particles anddisentangle it from charge–dipole interactions. The magnitude of theenhancement depends on the assumed particle hydration and collisionkinetics but is increasingly important at smaller sizes, resulting in asteep rise in the observed growth rates with decreasing size. Including theexperimental results in a global model, we find that the enhanced growth rate ofsulfuric acid particles increases the predicted particle number concentrationsin the upper free troposphere by more than 50 %.  more » « less
Award ID(s):
1801329 1801280 1649147 1801897 1801574
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; « less
Date Published:
Journal Name:
Atmospheric Chemistry and Physics
Page Range / eLocation ID:
7359 to 7372
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. null (Ed.)
    Iodic acid (HIO 3 ) is known to form aerosol particles in coastal marine regions, but predicted nucleation and growth rates are lacking. Using the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we find that the nucleation rates of HIO 3 particles are rapid, even exceeding sulfuric acid–ammonia rates under similar conditions. We also find that ion-induced nucleation involves IO 3 − and the sequential addition of HIO 3 and that it proceeds at the kinetic limit below +10°C. In contrast, neutral nucleation involves the repeated sequential addition of iodous acid (HIO 2 ) followed by HIO 3 , showing that HIO 2 plays a key stabilizing role. Freshly formed particles are composed almost entirely of HIO 3 , which drives rapid particle growth at the kinetic limit. Our measurements indicate that iodine oxoacid particle formation can compete with sulfuric acid in pristine regions of the atmosphere. 
    more » « less
  2. Abstract. Observations over the last decade have demonstrated that theatmosphere contains potentially hundreds of compounds that can react withsulfuric acid to nucleate stable aerosol particles. Consequently, modelingatmospheric nucleation requires detailed knowledge of nucleation reactionkinetics and spatially and temporally resolved measurements of numerousprecursor compounds. This study introduces the Nucleation Potential Model(NPM), a novel nucleation model that dramatically simplifies the diversereactions between sulfuric acid and any combination of precursor gases. The NPMpredicts 1 nm nucleation rates from only two measurable gas concentrations,regardless of whether all precursor gases are known. The NPM describes sulfuricacid nucleating with a parameterized base compound at an effective baseconcentration, [Beff]. [Beff] captures the ability of a compoundor mixture to form stable clusters with sulfuric acid and is estimated frommeasured 1 nm particle concentrations. The NPM is applied to experimental andfield observations of sulfuric acid nucleation to demonstrate how[Beff] varies for different stabilizing compounds, mixtures, andsampling locations. Analysis of previous field observations shows distinctdifferences in [Beff] between locations that follow the emissionsources and stabilizing compound concentrations for that region. Overall,the NPM allows researchers to easily model nucleation across diverseenvironments and estimate the concentration of non-sulfuric acid precursorsusing a condensation particle counter. 
    more » « less
  3. Abstract. New particle formation (NPF) consists of two steps: nucleation andsubsequent growth. At present, chemical and physical mechanisms that governthese two processes are not well understood. Here, we report initial resultsobtained from the TANGENT (Tandem Aerosol Nucleation and Growth EnvironmentTube) experiments. The TANGENT apparatus enables us to study these twoprocesses independently. The present study focuses on the effects oftemperature on sulfuric acid nucleation and further growth. Our results showthat lower temperatures enhance both the nucleation and growth rate.However, under temperatures below 268 K the effects of temperature on thenucleation rate become less significant and the nucleation rate becomes lessdependent on relative humidity, indicating that particle formation in the conditions of ourflow tube takes place via barrierless nucleation at lower temperatures. Wealso examined the growth of newly formed particles under differingtemperature conditions for nucleation and further growth. Our results showthat newly nucleated clusters formed at low temperatures can indeed surviveevaporation and grow in a warmer environment in the presence of SO2 andozone and potentially other contaminant vapors. These results implythat some heterogeneous reactions involving nanoparticles affect nucleationand growth of newly formed particles. 
    more » « less
  4. The energy landscape is changing worldwide, with a drastic reduction in sulfur dioxide (precursor to sulfuric acid, H2SO4) emitted from fossil fuel combustion. As a result, acid-base chemistry leading to new particle formation (NPF) from sulfuric acid is decreasing. At the same time, photooxidation of biogenic organosulfur compounds leading to the formation of H2SO4 and methanesulfonic acid (MSA) is expected to become more important. Aqueous solutions of alkanolamines have been proposed as carbon capture technology media to store carbon dioxide from stack plumes before release into the atmosphere. It is therefore expected that some of the alkanolamines will be released, making it critical to understand their atmospheric fates including their role in new particle formation and growth. We expanded our experimental studies of nucleation from the reaction of MSA with simple amines to the multifunctional alkanolamines, including mononethanolamine (HO(CH2)2NH2; MEA) and 4-aminobutanol (HO(CH2)4NH2; 4AB). Experiments were performed in a 1-m borosilicate flow reactor under dry conditions as well as in presence of water. These two systems were shown to produce sub-10 nm particles with MSA extremely efficiently. Surprisingly, the presence of water did not enhance NPF, in contrast to the drastic effect water had on small alkylamine reactions with MSA. This is likely due to the fact that MEA and 4AB have an -OH group that provides additional H-bond interactions within the cluster. Sampling of the chemical composition of these small nanoparticles with high resolution and high transmission was possible down to 3-4 nm using a novel high-flow differential mobility analyzer (half-mini DMA) interfaced to a thermal chemical ionization mass spectrometer (TDCIMS). There was no size dependence for the acid-to-base molar ratio (1:1) for either amine. Integration of these data with preliminary results obtained for a simple C4 alkylamine (butylamine) and a C4 diamine (putrescine) will be discussed in the context of developing a molecular structure-reactivity scheme for new particle formation from MSA and amines of varying structures. 
    more » « less
  5. null (Ed.)
    Abstract. Nucleation rates involving sulfuric acid and watermeasured in a photolytic flow reactor have decreased considerably over atime period of several years. Results show that the system – flow reactor,gas supplies and lines, flow meters, valves, H2SO4 photo-oxidantsources – has reached a baseline stability that yields nucleationinformation such as cluster free energies. The baseline nucleation rate ispunctuated by temporary bursts that in many instances are linked to cylinderchanges, delineating this source of potential contaminants. Diagnostics wereperformed to better understand the system, including growth studies to assessH2SO4 levels, chemiluminescent NO and NOx detection toassess the HONO source, and deployment of a second particle detector toassess the nanoparticle detection system. The growth of seed particles showstrends consistent with the sizes of nucleated particles and provides ananchor for calculated H2SO4 concentrations. The chemiluminescentdetector revealed that small amounts of NO are present in the HONO source,∼ 10 % of HONO. The second condensation-type particlecounter indicates that the nanoparticle mobility sizing system has a bias atlow sulfuric acid levels. The measured and modeled nucleation ratesrepresent upper limits to nucleation in the binary homogeneous system,H2SO4-H2O, as contaminants might act to enhance nucleationrates and ion-mediated nucleation may contribute. Nonetheless, theexperimental nucleation rates, which have decreased by an order of magnitudeor larger since our first publication, extrapolate to some of the lowest ratesreported in experiments with photolytic H2SO4. Results fromexperiments with varying water content and with ammonia addition are alsopresented and have also decreased by an order of magnitude from our previouswork; revised energetics of clusters in this three-component system arederived which differ from our previous energetics mainly in the five-acid andlarger clusters. 
    more » « less