AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Laboratory Studies of ClNO2 Production from N2O5 Uptake on Saline Playa Dusts
CASSANDRA GASTON, Dhruv Mitroo, Thomas Gill, Savannah Haas, Kerri Pratt, Haley Royer, University of Miami
Abstract Number: 117 Working Group: Aerosol Chemistry
Abstract Nitryl chloride (ClNO2), formed when dinitrogen pentoxide (N2O5) reacts with chloride-containing aerosol, photolyzes to produce chlorine radicals that facilitate the formation of tropospheric ozone. ClNO2 has been measured in continental areas; however, the sources of particulate chloride required to form ClNO2 in inland regions remain unclear. Dust emitted from saline playas (e.g., dried lakebeds) contains salts that can potentially form ClNO2 in inland regions. Here, we present the first laboratory measurements demonstrating the production of ClNO2 from playa dusts. N2O5 reactive uptake coefficients (γN2O5) ranged from ~10-3 to 10-1 and ClNO2 yields (φClNO2) on playa dusts were >50% for all playas tested except one. In general, as the soluble ion fraction of playa dusts increases, γN2O5 decreases and φClNO2 increases. We attribute this finding to a transition from aerosol surfaces dominated by silicates that react efficiently with N2O5 and produce little ClNO2 to aerosols that behave like deliquesced chloride-containing salts that generate high yields of ClNO2. Molecular bromine (Br2) and nitryl bromide (BrNO2) were also detected, highlighting that playas facilitate the heterogeneous production of brominated compounds. Our results suggest that parameterizations and models should be updated to include playas as an inland source of aerosol chloride capable of efficiently generating ClNO2.