Cloud processing of soluble gases

• Published in: Atmospheric environment (1994) Vol. 31; no. 16; pp. 2589 - 2598
• Main Authors: Laj, P., Fuzzi, S., Facchini, M.C., Lind, J.A., Orsi, G., Preiss, M., Maser, R., Jaeschke, W., Seyffer, E., Helas, G., Acker, K., Wieprecht, W., Möller, D., Arends, B.G., Mols, J.J., Colvile, R.N., Gallagher, M.W., Beswick, K.M., Hargreaves, K.J., Storeton-West, R.L., Sutton, M.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.1997
• Subjects: Great Dun Fell, England; Henry's equilibrium; soluble gases; Cloud; in-cloud chemical reactions
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/S1352-2310(97)00040-X

Experimental data from the Great Dun Fell Cloud Experiment 1993 were used to investigate interactions between soluble gases and cloud droplets. Concentrations of H 2O 2, SO 2, CH 3COOOH, HCOOH, and HCHO were monitored at different sites within and downwind of a hill cap cloud and their temporal and spatial evolution during several cloud events was investigated. Significant differences were found between in-cloud and out-of-cloud concentrations, most of which could not be explained by simple dissolution into cloud droplets. Concentration patterns were analysed in relation to the chemistry of cloud droplets and the gas/liquid equilibrium. Soluble gases do not undergo similar behaviour: CH 3COOH simply dissolves in the aqueous phase and is outgassed upon cloud dissipation; instead, SO 2 is consumed by its reaction with H 2O 2. The behaviour of HCOOH is more complex because there is evidence for in-cloud chemical production. The formation of HCOOH interferes with the odd hydrogen cycle by enhancing the liquid-phase production of H 2O 2. The H 2O 2 concentration in cloud therefore results from the balance of consumption by oxidation of SO 2 in-cloud production, and the rate by which it is supplied to the system by entrainment of new air into the clouds.