Cloud condensation nucleus activity of organic compounds: a laboratory study

Critical or activation diameters of laboratory generated organic aerosols composed of succinic acid, adipic acid and glucose were determined. Measurements of sodium chloride and ammonium sulfate aerosols were performed for comparison. Our experimental approach involved producing single component aerosol particles of a known size, and measuring the fraction of aerosol number concentrations (CN) that act as CCN at several supersaturations. The particle diameter (D50) at which the CCN/CN ratio of 0.50 is reached is defined as the critical, or activation, diameter. These experimentally derived diameters are compared with the theoretical critical diameter (DC). The results indicate that highly water-soluble organic compounds exhibit critical diameters that approach that of ammonium sulfate.