Critical supersaturations for aerosol particles of succinic acid and its salts
Abstract
Dicarboxylic acids, like succinic acid, have been identified as important water soluble organic compounds in the atmosphere. Salts of carboxylic acids can be formed in the atmosphere in reactions between the acid and an inorganic salt. In this work we have studied the cloud droplet nucleating ability for succinic acid and some of its salts: disodium succinate, diammonium succinate and calcium succinate. A monodisperse aerosol was generated by atomizing a water solution of the compound of interest, drying the particles in diffusion driers and selecting a narrow size range using a differential mobility analyzer. The aerosol was then analyzed using a static thermal gradient cloud condensation nucleus spectrometer (CCNC-100B from the University of Wyoming). A CPC was used to count the number of particles as a reference. For a fixed particle diameter, the supersaturation was scanned to find a steep increase in the fraction of particles that were activated to cloud droplets. This critical supersaturation is compared with theoretical calculations using Köhler theory. Experimental critical supersaturations for succinic acid agree with Köhler theory with a van't Hoff factor of 1, i.e. it activates as if it does not dissociate. For the sodium salt, a van't Hoff factor of 2 fits laboratory data and theoretical calculations.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....8536S