Laboratory study of the uptake of acetic acid by cloud droplets

M. L. ASAR; AVILA E. E.; R. A. TACCONE; S. I. LANE.

Leipzig

Conferencia; 16th International Conference on Clouds and Precipitation; 2012

Field experiments have shown that fogs, clouds and precipitation play a significant role in the chemical composition of the atmosphere. The clouds redistribute trace compounds emitted at the Earth?s surface vertically from the boundary layer to the free troposphere and, in some cases, to the stratosphere, through many processes, such as scavenging, chemical reactions, precipitation, etc. Laboratory experiments have been carried out to investigate the uptake of acetic acid (CH3COOH) by water droplets under controlled temperature and liquid water content conditions. The measurements were performed with a continuous-flow cloud chamber. A special device has been developed to collect the cloud droplets in sufficient quantity for chemical analysis by means of gas chromatography. The scavenging ratios were determined by measuring the concentration of CH3COOH in the cloud droplet and in air. The experiments were performed under warm cloud conditions and the results show that the scavenging ratio is roughly independent of T and LWC for temperatures between 278 and 285 K and LWC between 0.1 and 3 g m-3. The average scavenging ratio obtained in this work is Ŵ=1200 m3 L-1. The experimental results are compared with field measurements because, to the best of our knowledge, there are no other laboratory measurements of this parameter, reported in the literature, for direct comparison with our results.