Marine & Environmental Sciences Faculty Articles

The Role of Hydrates, Competing Chemical Constituents, and Surface Composition on ClNO2Formation

Document Type

Article

Publication Title

Environmental Science and Technology

ISSN

0013936X

Publication Date

1-1-2021

Keywords

aerosol, air quality, dinitrogen pentoxide, halogen, heterogeneous reaction, hygroscopicity, mineral dust, nitryl chloride

Abstract

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.

DOI

10.1021/acs.est.0c06067

Volume

55

Issue

5

First Page

2869

Last Page

2877

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