10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

Abstract View


A New Chamber for Studying Aerosol Formation and Aging in Clouds

DON COLLINS, Cassandra Milan, Geoffrey Roest, Jacob Escobedo, Ariana Castillo, Kate Godfrey, Texas A&M University

     Abstract Number: 890
     Working Group: Instrumentation

Abstract
Aqueous phase chemical reactions inside clouds can produce low volatility species that remain in the aerosol phase after the droplets evaporate. In recent years there has been considerable interest in identifying precursor species responsible for in-cloud production of secondary organic aerosol and in quantifying the rates and products of the reactions. Whereas most studies have used homogeneous solutions containing the soluble organic precursors and oxidants, it is likely that large gradients exist in actual cloud droplets because the hydroxyl radical responsible for most oxidation will not penetrate far before reacting. The Multiphase Aging and Production of Particles (MAPP) chamber was developed primarily to study aqueous formation of secondary organic aerosol in/on cloud droplets. Clouds are formed through adiabatic expansion inside a 1.2 cubic meter all-FEP Teflon cloud/reaction chamber that is suspended in a 3.5 cubic meter stainless steel vessel that can withstand full vacuum. Air is simultaneously extracted from the reaction/cloud chamber and the surrounding vacuum vessel such that a slight positive pressure is always maintained to keep the 0.05 mm thick FEP walls taut. Air cooled with a chilled water heat exchanger and/or heated with a resistive heater is circulated around the reaction/cloud chamber to maintain the walls at about the same temperature as the air inside to minimize convection, humidity gradients, and droplet evaporation. The reaction/cloud chamber rotates on a horizontal axis at about 7 rpm to minimize settling losses of the large droplets. Water soluble precursor gases such as glyoxal can either be directly injected or formed through gas phase photochemistry driven by solar simulating lamps. Monodisperse particles are injected prior to cloud formation and their growth during the experiment is used to quantify in-cloud aerosol production. Results from preliminary cloud processing experiments will be presented.