Sources and Chemistry of Organic Aerosol Material V. Faye McNeill, Department of Chemical Engineering, Columbia University Atmospheric aerosol particles nucleate cloud droplets, thereby influencing the radiative properties, amount and lifetime of clouds, also known as the aerosol “indirect effects” on climate. Organic aerosol material is typically hydrophobic, however surface-active organics can lower aerosol surface tension, thus enhancing cloud droplet formation (CCN activity).
Exposing (NH4)2SO4 particles to acetaldehyde leads to increased cloud droplet nucleation 1
5 hr AC 250 ppb
7 6 5 4 3
Oxidizing NaCl particles coated in oleic acid films leads to decreased CCN activity. 1
1
e Critical SS [%]
Critical supersaturation [%]
Surface tension depression by acetaldehyde-methylglyoxal mixtures in aqueous aerosol mimic solutions
9 8
9
7
8
6
7
5 6
4 5
25
3
2 2
3
4
5
6
7
8 9
3
Critical dry diameter [nm]
4
5
6
7
8
9
100
100
30
35
40
0.05 M NaCl 0.001 M OA-NaCl 0.001 M OA-NaCl-1 ppm O3 0.01 M OA-NaCl 0.01 M OA-NaCl-1 ppm O3
Critical Dry Diameter [nm] B
Sareen et al., Atmos. Chem. Phys. , 10, 997‐1016 (2010) Schwier et al., Environ. Sci. Technol. , 44(16) 6174‐6182 (2010) Schwier et al., J. Geophys. Res.‐Atmos., 116, D16202 (2011) Li et al., Atmos. Chem. Phys. Discuss., 11, 19477‐19506 (2011)
Sources and Chemistry of Organic Aerosol Material V. Faye McNeill Columbia University
