The role of hydrates, competing chemical constituents, and surface composition on CLNO2 formation

Environmental Science Technology
By: , and 



Atomic chlorine (Cl) affects air quality and atmospheric oxidizing capacity. Nitryl chloride (ClNO2) – a common Cl source–forms when chloride-containing aerosols react with dinitrogen pentoxide (N2O5). A recent study showed that saline lakebed (playa) dust is an inland source of particulate chloride (Cl) that generates high ClNO2. However, the underlying physiochemical factors responsible for observed yields are poorly understood. To elucidate these controlling factors, we utilized single particle and bulk techniques to determine the chemical composition and mineralogy of playa sediment and dust samples from the southwest United States. Single particle analysis shows trace highly hygroscopic magnesium and calcium Cl-containing minerals are present and likely facilitate ClNO2 formation at low humidity. Single particle and mineralogical analysis detected playa sediment organic matter that hinders N2O5 uptake as well as 10 Å-clay minerals (e.g., Illite) that compete with water and chloride for N2O5. Finally, we show that the composition of the aerosol surface, rather than the bulk, is critical in ClNO2 formation. These findings underscore the importance of mixing state, competing reactions, and surface chemistry on N2O5 uptake and ClNO2 yield for playa dusts and, likely, other aerosol systems. Therefore, consideration of particle surface composition is necessary to improve ClNO2 and air quality modeling.

Publication type Article
Publication Subtype Journal Article
Title The role of hydrates, competing chemical constituents, and surface composition on CLNO2 formation
Series title Environmental Science Technology
DOI 10.1021/acs.est.0c06067
Volume 55
Issue 5
Year Published 2021
Language English
Publisher American Chemical Society
Contributing office(s) Eastern Mineral and Environmental Resources Science Center
Description 9 p.
First page 2869
Last page 2877
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