1. Equilibrium Composition of Aerosol Particles
Equilibrium: What are xX, xY, and xZ?
Some time scale Z X
New particle Y

2. Ideal and Non-Ideal Behavoir of SolutionsxA 1 pA pB xA 1 pA pB

3. Question
Consider an air parcel at T = 300 K and 30% RH with 20 ppb HNO3 and 20 ppb NH3 in the gas-phase. Will NH4NO3 particles form? If so, what is the NH4NO3 aerosol mass concentration if no other particulate matter exists? Assume only solid particles (no aqueous solutions).

4. Deliquescence – Efflorescence of a Single Component System (NaCl)
Tang, JGR-D 1997

5. Free Energy of Deliquescence - Efflorescence
Gsolution
Solid favored
Gsolid
Gibbs Free Energy
DRH
Solution favored RH

6. Evolution of Water Activity in Atmospheric Particle
Often requires knowledge of RH-histroy
RH>80%
RH<40%
RH=70%
RH=80%
Ocean
Land

7. Deliquesence-Efflorescence of Complex Compositions
Lightstone, et al. JPC 2000
Schlenker, et al. JPC 2005

8. Kelvin Effect: Physical Cartoon
Equilibrium vapor pressure is higher over a curved surface than a flat one.
Important for nucleation of new particles, lifetime of small droplets.