10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Not Fade Away: Photolytic Brown Carbon Formation in Aqueous Aerosol
DAVID DE HAAN, Devoun Stewart, Tobin Gramyk, Alexia De Loera, Duncan Ugland, Christian Carmona, Antonio Rojas, University of San Diego
Abstract Number: 1435 Working Group: Aerosol Chemistry
Abstract Based on results from bulk aqueous phase lab experiments, it is now commonly assumed that brown carbon formed by small, water-soluble aldehydes + ammonium salts are quickly destroyed by sunlight. However, recent cloud chamber studies showing more intense browning with solar simulator lights turned on suggest that this common assumption does not apply to evaporating aqueous aerosol, where brown carbon is more likely to be formed by radical polymerization pathways. Here, we present results of small-chamber and steady-state aerosol experiments where we quantify the amount of brown carbon formed as a function of UV or sunlight exposure and other variables. In deliquesced ammonium sulfate aerosol at 50% RH, we find that 90 min of sunlight destroys brown carbon formed by methylglyoxal + methylamine dark reactions. However, if hydrogen peroxide is added as an OH radical source, more brown carbon is formed in sunlight than in dark reactions (with or without hydrogen peroxide), further evidence of rapid photolytic brown carbon production. We will report on studies of additional chemical systems that form brown carbon, including glyoxal + SO2.