Cloud Condensation Nuclei properties of model and atmospheric HULIS E. Dinar1, I. Taraniuk1, E. R. Graber2, S. Katsman1, T. Moise1, T. Anttila3,*, T. F. Mentel3, and Y. Rudich1 1Department of Environmental Sciences, Weizmann Institute of Science, Rehovot 76100, Israel 2Institute of Soil, Water and Environmental Sciences, The Volcani Center, A.R.O., Bet Dagan 50250, Israel 3Institute for Tropospheric Chemistry, Research Center Jülich, Jülich Germany *current address: Research and Development, Finnish Meteorological Institute, 00101 Helsinki, Finland
Abstract. Humic like substances (HULIS) have been identified as a major fraction of
the organic component of atmospheric aerosols. These large multifunctional
compounds of both primary and secondary sources are surface active and water
soluble. Hence, it is expected that they could affect activation of organic
aerosols into cloud droplets. We have compared the activation of aerosols
containing atmospheric HULIS extracted from fresh, aged and pollution
particles to activation of size fractionated fulvic acid from an aquatic
source (Suwannee River Fulvic Acid), and correlated it to the estimated
molecular weight and measured surface tension. A correlation was found
between CCN-activation diameter of SRFA fractions and number average
molecular weight of the fraction. The lower molecular weight fractions
activated at lower critical diameters, which is explained by the greater
number of solute species in the droplet with decreasing molecular weight.
The three aerosol-extracted HULIS samples activated at lower diameters than
any of the size-fractionated or bulk SRFA. The Köhler model was found to
account for activation diameters, provided that accurate physico-chemical
parameters are known.
Citation: Dinar, E., Taraniuk, I., Graber, E. R., Katsman, S., Moise, T., Anttila, T., Mentel, T. F., and Rudich, Y.: Cloud Condensation Nuclei properties of model and atmospheric HULIS, Atmos. Chem. Phys., 6, 2465-2482, doi:10.5194/acp-6-2465-2006, 2006.