ClNO<sub>2</sub> Production from N<sub>2</sub>O<sub>5</sub> Uptake on Saline Playa Dusts: New Insights into Potential Inland Sources of ClNO<sub>2</sub>

Published on 2019-06-12T14:48:23Z (GMT) by
Nitryl chloride (ClNO<sub>2</sub>), formed when dinitrogen pentoxide (N<sub>2</sub>O<sub>5</sub>) reacts with chloride-containing aerosol, photolyzes to produce chlorine radicals that facilitate the formation of tropospheric ozone. ClNO<sub>2</sub> has been measured in continental areas; however, the sources of particulate chloride required to form ClNO<sub>2</sub> in inland regions remain unclear. Dust emitted from saline playas (e.g., dried lakebeds) contains salts that can potentially form ClNO<sub>2</sub> in inland regions. Here, we present the first laboratory measurements demonstrating the production of ClNO<sub>2</sub> from playa dusts. N<sub>2</sub>O<sub>5</sub> reactive uptake coefficients (γ<sub>N2O5</sub>) ranged from ∼10<sup>–3</sup> to 10<sup>–1</sup> and ClNO<sub>2</sub> yields (φ<sub>ClNO2</sub>) were >50% for all playas tested except one. In general, as the soluble ion fraction of playa dusts increases, γ<sub>N2O5</sub> decreases and φ<sub>ClNO2</sub> increases. We attribute this finding to a transition from aerosol surfaces dominated by silicates that react efficiently with N<sub>2</sub>O<sub>5</sub> and produce little ClNO<sub>2</sub> to aerosols that behave like deliquesced chloride-containing salts that generate high yields of ClNO<sub>2</sub>. Molecular bromine (Br<sub>2</sub>) and nitryl bromide (BrNO<sub>2</sub>) 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 ClNO<sub>2</sub>.

Cite this collection

Mitroo, Dhruv; Gill, Thomas E.; Haas, Savannah; Pratt, Kerri A.; Gaston, Cassandra J. (2019): ClNO2 Production from N2O5 Uptake on Saline

Playa Dusts: New Insights into Potential

Inland Sources of ClNO2. ACS Publications. Collection.