Issue 14, 2016

Investigations on HONO formation from photolysis of adsorbed HNO3 on quartz glass surfaces

Abstract

During the last few decades, nitrous acid (HONO) has attracted significant attention as a major source of the OH radical, the detergent of the atmosphere. However, the different daytime sources identified in the laboratory are still the subject of controversial discussion. In the present study, one of these postulated HONO sources, the heterogeneous photolysis of nitric acid (HNO3), was studied on quartz glass surfaces in a photo flow-reactor under atmospherically relevant conditions. In contrast to other investigations, a very low HNO3 photolysis frequency for HONO formation of J(HNO3 → HONO) = 2.4 × 10−7 s−1 (0° SZA, 50% r.h.) was determined. If these results can be translated to atmospheric surfaces, HNO3 photolysis cannot explain the significant HONO levels in the daytime atmosphere. In addition, it is demonstrated that even the small measured yields of HONO did not result from the direct photolysis of HNO3 but rather from the consecutive heterogeneous conversion of the primary photolysis product NO2 on the humid surfaces. The secondary NO2 conversion was not photo-enhanced on pure quartz glass surfaces in good agreement with former studies. A photolysis frequency for the primary reaction product NO2 of J(HNO3 → NO2) = 1.1 × 10−6 s−1 has been calculated (0° SZA, 50% r.h.), which indicates that renoxification by photolysis of adsorbed HNO3 on non-reactive surfaces is also a minor process in the atmosphere.

Graphical abstract: Investigations on HONO formation from photolysis of adsorbed HNO3 on quartz glass surfaces

Associated articles

Article information

Article type
Paper
Submitted
20 jan 2016
Accepted
09 mrt 2016
First published
09 mrt 2016
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2016,18, 9616-9625

Investigations on HONO formation from photolysis of adsorbed HNO3 on quartz glass surfaces

S. Laufs and J. Kleffmann, Phys. Chem. Chem. Phys., 2016, 18, 9616 DOI: 10.1039/C6CP00436A

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