Activation capability of water soluble organic substances as CCN

The activation capability of seven dicarboxylic acid compounds, ammonium oxalate, malonic acid, succinic acid, glutaric acid, adipic acid, malic acid and phthalic acid, was determined by laboratory experiments, and predictability by the Kohler theory was discussed. Experimental results showed that ammonium oxalate had the highest capability comparable to that of ammonium sulfate, and malic acid and phthalic acid followed, whereas adipic acid exhibited the lowest capability close to that of an insoluble particle. Malonic acid and glutaric acid were considered to evaporate under normal experimental operations at 8-9% RH but exhibited high and moderate capability, respectively, under supplementary humid operations. The activation capability of succinic acid tended to depend on the laboratory temperatures but was possibly high, comparable to that of malic acid. Particulate drying, associated solute vaporization, morphology and hydrophobicity of particles could be key factors in the theoretical prediction and the interpretation of the experimental results. (C) 2003 Elsevier Science Ltd. All rights reserved.