Abstract
Accurate models of water and solute activities in aqueous atmospheric aerosols are central to predicting aerosol size, optical properties and cloud formation. A powerful method has been recently developed (Dutcher et al. JPC 2011, 2012, 2013) for representing the thermodynamic properties of multicomponent aerosols at low and intermediate levels of RH (< 90%RH) by applying the principles of multilayer sorption to ion hydration in solutions. In that work, statistical mechanics was used to model sorption of a solvent (water), onto each solute or ion in solution as n energetically distinct layers. This corresponds to n hydration layers surrounding each solute molecule. Here, we extend the model to the 100% RH limit and reduce the number of adjustable model parameters, allowing for a unified thermodynamic treatment for a wider range of atmospheric systems. The long-range interactions due to electrostatic screening of ions in solution are included as a mole fraction based Pitzer-Debye-Hückel (PDH) term. Equations for the Gibbs free energy, solvent and solute activity, and solute concentration are derived, yielding remarkable agreement between measured and fitted solute concentration and osmotic coefficients for solutions over the entire 0 to 100% RH range. By relating the values of the energy of sorption in each hydration layer to known short-range Coulombic electrostatic relationships governed by the size and dipole moment of the solute and solvent molecules, it may be possible to reduce the number of parameters for each solute. Modified equations for mixtures that take into account the long range PDH term will also be presented; these equations include no additional parameters.
| Original language | English (US) |
|---|---|
| Title of host publication | AIP Conference Proceedings |
| Pages | 441-444 |
| Number of pages | 4 |
| Volume | 1527 |
| DOIs | |
| State | Published - 2013 |
| Event | 19th International Conference on Nucleation and Atmospheric Aerosols, ICNAA 2013 - Fort Collins, CO, United States Duration: Jun 23 2013 → Jun 28 2013 |
Other
| Other | 19th International Conference on Nucleation and Atmospheric Aerosols, ICNAA 2013 |
|---|---|
| Country | United States |
| City | Fort Collins, CO |
| Period | 6/23/13 → 6/28/13 |
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Keywords
- Activity coefficients
- adsorption isotherms
- Debye-Hückel
- electrolyte solutions
- McKay-Perring
- Zdanovskii-Stokes-Robinson
ASJC Scopus subject areas
- Physics and Astronomy(all)
Cite this
Thermodynamic modeling of atmospheric aerosols : 0-100% relative humidity. / Dutcher, Cari S.; Ge, Xinlei; Asato, Caitlin; Wexler, Anthony S.; Clegg, Simon L.
AIP Conference Proceedings. Vol. 1527 2013. p. 441-444.Research output: Chapter in Book/Report/Conference proceeding › Conference contribution
}
TY - GEN
T1 - Thermodynamic modeling of atmospheric aerosols
T2 - 0-100% relative humidity
AU - Dutcher, Cari S.
AU - Ge, Xinlei
AU - Asato, Caitlin
AU - Wexler, Anthony S.
AU - Clegg, Simon L.
PY - 2013
Y1 - 2013
N2 - Accurate models of water and solute activities in aqueous atmospheric aerosols are central to predicting aerosol size, optical properties and cloud formation. A powerful method has been recently developed (Dutcher et al. JPC 2011, 2012, 2013) for representing the thermodynamic properties of multicomponent aerosols at low and intermediate levels of RH (< 90%RH) by applying the principles of multilayer sorption to ion hydration in solutions. In that work, statistical mechanics was used to model sorption of a solvent (water), onto each solute or ion in solution as n energetically distinct layers. This corresponds to n hydration layers surrounding each solute molecule. Here, we extend the model to the 100% RH limit and reduce the number of adjustable model parameters, allowing for a unified thermodynamic treatment for a wider range of atmospheric systems. The long-range interactions due to electrostatic screening of ions in solution are included as a mole fraction based Pitzer-Debye-Hückel (PDH) term. Equations for the Gibbs free energy, solvent and solute activity, and solute concentration are derived, yielding remarkable agreement between measured and fitted solute concentration and osmotic coefficients for solutions over the entire 0 to 100% RH range. By relating the values of the energy of sorption in each hydration layer to known short-range Coulombic electrostatic relationships governed by the size and dipole moment of the solute and solvent molecules, it may be possible to reduce the number of parameters for each solute. Modified equations for mixtures that take into account the long range PDH term will also be presented; these equations include no additional parameters.
AB - Accurate models of water and solute activities in aqueous atmospheric aerosols are central to predicting aerosol size, optical properties and cloud formation. A powerful method has been recently developed (Dutcher et al. JPC 2011, 2012, 2013) for representing the thermodynamic properties of multicomponent aerosols at low and intermediate levels of RH (< 90%RH) by applying the principles of multilayer sorption to ion hydration in solutions. In that work, statistical mechanics was used to model sorption of a solvent (water), onto each solute or ion in solution as n energetically distinct layers. This corresponds to n hydration layers surrounding each solute molecule. Here, we extend the model to the 100% RH limit and reduce the number of adjustable model parameters, allowing for a unified thermodynamic treatment for a wider range of atmospheric systems. The long-range interactions due to electrostatic screening of ions in solution are included as a mole fraction based Pitzer-Debye-Hückel (PDH) term. Equations for the Gibbs free energy, solvent and solute activity, and solute concentration are derived, yielding remarkable agreement between measured and fitted solute concentration and osmotic coefficients for solutions over the entire 0 to 100% RH range. By relating the values of the energy of sorption in each hydration layer to known short-range Coulombic electrostatic relationships governed by the size and dipole moment of the solute and solvent molecules, it may be possible to reduce the number of parameters for each solute. Modified equations for mixtures that take into account the long range PDH term will also be presented; these equations include no additional parameters.
KW - Activity coefficients
KW - adsorption isotherms
KW - Debye-Hückel
KW - electrolyte solutions
KW - McKay-Perring
KW - Zdanovskii-Stokes-Robinson
UR - http://www.scopus.com/inward/record.url?scp=84877348540&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84877348540&partnerID=8YFLogxK
U2 - 10.1063/1.4803299
DO - 10.1063/1.4803299
M3 - Conference contribution
AN - SCOPUS:84877348540
SN - 9780735411524
VL - 1527
SP - 441
EP - 444
BT - AIP Conference Proceedings
ER -