nucleation and condensation final -...
TRANSCRIPT
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Nucleation and condensationAdvanced Atmospheric Chemistry
CHEM‐5152
Dr. A. Franchin
Gas to particle conversion: condensation and nuclation
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Q: what is the smallest possible size for an aerosol particle?
•A: 30 nm•B: 10 nm•C: 3 nm•D: 1 nm
Nucleation: the classical description
∆ 44 ln
3
Vapor Aerosol
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Nucleation: the classical description
∆ 44 ln
3
Vapor Aerosol
∆ 44 ln
3 ; ‐2
;
Nucleation: the classical description
∆
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; J;
;
∆ 44 ln
3
Nucleation: the classical description
∆
∆ 44 ln
3
∆
Nucleation: the classical description
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What is the saturation ratio?
What is the saturation ratio?
• The saturation ratio is the maximum amount of vapor at a specific temperature that air can hold in the gas phase
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What is the saturation ratio?
1 1 1
Nucleation: the role of ions
∆ 44 ln
3 81
1 1 1
∆
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Nucleation: the role of ions
∆ 44 ln
3 81
1 1 1
∆
ATT!!! This is valid for an Homogeneous vapor. In the atmosphere is much more complicated!
What are the molecules that nucleate in the atmosphere?
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What are the molecules that nucleate in the atmosphere?
Sulfuric acid H2SO4
Ammonia NH3
Amines (dimethylamine shown)
ELVOCs (C10H14O12 shown)
How does nucleation look like?
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Nucleation: the experimental description
Nucleation: the experimental description
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Nucleation: the experimental description
Nucleation: the experimental description
Growth Rates Formation Rates
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1
10
100
1000
Diameter (nm)
08‐Apr‐201707‐Apr‐2017 09‐Apr‐2017 10‐Apr‐201706‐Apr‐201712:00 12:00 12:0012:0012:00
Data from: https://avaa.tdata.fi/web/smart
Nucleation: the experimental description
Where does atmospheric nucleation happen?
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Nucleation is not enough. Why do we need growth?
Nucleation is not enough. Why do we need growth?
If particles do not grow they will not able to 1‐ interact with light (direct effect of aerosol on climate)2‐ become cloud condensation nuclei (indirect effect of aerosol on climate)
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What are the phenomena that compete with nucleation?• A. Coagulation
• B. Condensation of condensing vapors on pre‐existing particles
• C. wall losses (in a chamber experiment)
• D. All of the above
The Kelvin effect
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exp4
The Kelvin effect
Remember this?
1 1 1
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Remember this?
1 1 ≫ 1
exp ≈1
The Kelvin effect
let sigma be equal to 0.023 N m‐2, as in Tröstl et al., 2016; density = 1400 kg m‐3; monomer molecule mass of 300 amuT = 300 K
It is ~800 times harder to condense molecules on a 10 nm particle than on a flat surfaceIt is ~ 20 times easier to condense molecules on a 200 nm particle than on a 100 nm particle
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Connection between Jc and GR
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22
4 3
4
34 33
4
22
2
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Extra slides
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Instruments: the condensation particle counter (CPC)
Instruments: the differential mobility analyzer (DMA)
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Instruments: DMA+CPC = DMPSthe differential mobility particle sizer
The chemical ionization mass spectrometerCI‐APiTOF
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Derivation of the link between GR and Jc
0
C = concentration of the diffusing vaporD = vapor diffusion coefficient; [D] = m2s‐1
Steady state
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0
0
0
0
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Boundary conditions:
→
Fick’s law:
4
4
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Connection between Jc and GR
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22
4 3
4
34 33
4
22
2