HR: 09:25h
AN: A41E-06    [Abstracts]
TI: Black Carbon Activation
AU: * Henson, B F
EM: henson@lanl.gov
AF: Los Alamos National Laboratory, C-PCS, J567 , Los Alamos, NM 87545 United States
AU: Smilowitz, L
EM: smilo@lanl.gov
AF: Los Alamos National Laboratory, C-PCS, J567 , Los Alamos, NM 87545 United States
AB: We present the results of recent modeling and experimental studies on the activation of black carbon (BC) aerosol to form cloud condensation nuclei (CCN). The modeling studies address the mechanism of activation of dry BC by interaction of ambient water vapor through adsorption. We have constructed a model of BC activation using a modification of the K”hler equation in which we introduce a term based on the activity of water adsorbed on the particle surface. We parameterize the model using the free energy of adsorption, a parameter directly comparable to laboratory measurements of water adsorption on carbon. Several features of a suite of measured carbon activation data are captured by the model. In particular, upper and lower bounding curves are predicted for activation supersaturation as a function of diameter and a large body of recent activation data fall within these bounds. The model also predicts that activation of BC aerosol leads to activation diameters from 3 to 10 times smaller than activation of soluble particles of identical dry diameter. The experimental studies address the activation of wet BC, or a BC aerosol in contact with a liquid drop. We present contact angle aging studies of graphite in contact with water and salt solutions which show increasing hydrophilicity over the time scale of days to weeks.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 0321 Cloud/radiation interaction
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3311 Clouds and aerosols
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005