Atmospheric aerosol models for systems including the ions H+, NH4+, Na+, SO42−, NO3−, Cl−, Br−, and H2O

Wexler, Anthony S.; Clegg, Simon L.

doi:10.1029/2001jd000451

Cited by 624 publications

(488 citation statements)

References 40 publications

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“…E-AIM is usually considered as an accurate benchmark model (Zaveri et al, 2008;Seinfeld and Pandis, 2016), whereas ISORROPIA 5 employs a number of simplifications to make it computationally efficient for application in large-scale atmospheric models (Fountoukis and Nenes, 2007;Pye et al, 2009). E-AIM uses the Pitzer, Simonson, and Clegg equations to calculate activity coefficients for water and ions (Wexler and Clegg, 2002;Clegg et al, 1992;Pitzer and Simonson, 1986). With ISORROPIA, γ H + and γ OH − are assumed equal to unity, whereas the activity coefficients for the other ionic pairs (e.g., H + -Cl − ) are calculated (Fountoukis and Nenes, 2007).…”

Section: Ph Prediction By Thermodynamic Modelsmentioning

confidence: 99%

Fine particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Song¹,

Gao²,

Xu³

et al. 2018

Preprint

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Abstract. pH is an important property of aerosol particles but is difficult to measure directly. Several studies have estimated the pH values for fine particles in North China winter haze using thermodynamic models (i.e., E-AIM and ISORROPIA) and ambient measurements. The reported pH values differ widely, ranging from close to 0 (highly acidic) to as high as 7 (neutral).In order to understand the reason for this discrepancy, we calculated pH values using these models with different assumptions 25 with regard to model inputs and particle phase states. We find that the large discrepancy is due primarily to differences in the model assumptions adopted in previous studies. Calculations using only aerosol phase composition as inputs (i.e., reverse mode) are sensitive to the measurement errors of ionic species and inferred pH values exhibit a bimodal distribution with peaks between −2 and 2 and between 7 and 10. Calculations using total (gas plus aerosol phase) measurements as inputs (i.e., forward mode) are affected much less by the measurement errors, and results are thus superior to those obtained from the reverse mode 30 calculations. Forward mode calculations in this and previous studies collectively indicate a moderately acidic condition (pH from about 4 to about 5) for fine particles in North China winter haze, indicating further that ammonia plays an important role in determining this property. The differences in pH predicted by the forward mode E-AIM and ISORROPIA calculations may be attributed mainly to differences in estimates of activity coefficients for hydrogen ions. The phase state assumed, which can be either stable (solid plus liquid) or metastable (only liquid), does not significantly impact pH predictions of ISORROPIA. 35Atmos. Chem. Phys. Discuss., https://doi

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Section: Ph Prediction By Thermodynamic Modelsmentioning

confidence: 99%

Fine particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Song¹,

Gao²,

Xu³

et al. 2018

Preprint

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“…To do this, the thermodynamic Extended Aerosol Inorganics Model (E-AIM) 5,6,47 (http://www.aim.env.uea.ac.uk/) is used to calculate how water activity and density change with the solution composition during evaporation and to predict the equilibrated radius of the droplet after water evaporation has ended at a given RH. For the relationship between water activity and NaCl concentration, the model is based upon the critical review of Archer, 48 and electrodynamic balance measurements of several authors (see Table 1 of Clegg et al 49 ).…”

Section: Aerosol Hygroscopic Growth From Comparativementioning

confidence: 99%

“…4 Rigorous thermodynamic models for calculating the hygroscopic response of mixed component aerosol have been developed on the basis of bulk phase and aerosol phase measurements of the equilibrium response of binary solutions of a single solute and water. 5,6 When combined with treatments of solution density and surface tension, accurate predictions of the variation in equilibrium particle size with relative humidity are possible. 7,8 To represent the equilibrium properties of solutions containing the myriad of potential organic compounds found in the atmosphere, it is often necessary to resort to functional group activity models that require consideration of the interactions between electrolytes and organic species.…”

Section: Introductionmentioning

confidence: 99%

Accurate Measurements of Aerosol Hygroscopic Growth over a Wide Range in Relative Humidity

et al. 2016

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Using a comparative evaporation kinetics approach, we describe a new and accurate method for determining the equilibrium hygroscopic growth of aerosol droplets. The time-evolving size of an aqueous droplet, as it evaporates to a steady size and composition that is in equilibrium with the gas phase relative humidity, is used to determine the time-dependent mass flux of water, yielding information on the vapor pressure of water above the droplet surface at every instant in time. Accurate characterization of the gas phase relative humidity is provided from a control measurement of the evaporation profile of a droplet of know equilibrium properties, either a pure water droplet or a sodium chloride droplet. In combination, and by comparison with simulations that account for both the heat and mass transport governing the droplet evaporation kinetics, these measurements allow accurate retrieval of the equilibrium properties of the solution droplet (i.e., the variations with water activity in the mass fraction of solute, diameter growth factor, osmotic coefficient or number of water molecules per solute molecule). Hygroscopicity measurements can be made over a wide range in water activity (from >0.99 to, in principle, <0.05) on time scales of <10 s for droplets containing involatile or volatile solutes. The approach is benchmarked for binary and ternary inorganic solution aerosols with typical uncertainties in water activity of <±0.2% at water activities >0.9 and ∼±1% below 80% RH, and maximum uncertainties in diameter growth factor of ±0.7%. For all of the inorganic systems examined, the time-dependent data are consistent with large values of the mass accommodation (or evaporation) coefficient (>0.1).

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“…The pH and liquid water content (LWC) of the aerosol phase were calculated using the Extended Aerosol Inorganics Model (E-AIM model II, http://www.aim.env.uea.ac.uk/aim/aim.php) 53,54 constrained by measurements of temperature, relative humidity, particle phase nitrate, sulfate, and ammonium. All solid formation was suppressed in the model and no organic compounds were included.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Observational Insights into Aerosol Formation from Isoprene

Worton

Surratt

LaFranchi

et al. 2013

Environ. Sci. Technol.

120

161

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Atmospheric aerosol models for systems including the ions H⁺, NH₄⁺, Na⁺, SO₄²⁻, NO₃⁻, Cl⁻, Br⁻, and H₂O

Cited by 624 publications

References 40 publications

Fine particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Fine particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Accurate Measurements of Aerosol Hygroscopic Growth over a Wide Range in Relative Humidity

Observational Insights into Aerosol Formation from Isoprene

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