Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR

Abstract

Abstract. HONO formation has been proposed as an important OH radical source in simulation chambers for more than two decades. Besides the heterogeneous HONO formation by the dark reaction of NO 2 and adsorbed water, a photolytic source has been proposed to explain the elevated reactivity in simulation chamber experiments. However, the mechanism of the photolytic process is not well understood so far. As expected, production of HONO and NO x was also observed inside the new atmospheric simulation chamber SAPHIR under solar irradiation. This photolytic HONO and NO x formation was studied with a sensitive HONO instrument under reproducible controlled conditions at atmospheric concentrations of other trace gases. It is shown that the photolytic HONO source in the SAPHIR chamber is not caused by NO 2 reactions and that it is the only direct NO y source under illuminated conditions. In addition, the photolysis of nitrate which was recently postulated for the observed photolytic HONO formation on snow, ground, and glass surfaces, can be excluded in the chamber. A photolytic HONO source at the surface of the chamber is proposed which is strongly dependent on humidity, on light intensity, and on temperature. An empirical function describes these dependencies and reproduces the observed HONO formation rates to within 10 %. It is shown that the photolysis of HONO represents the dominant radical source in the SAPHIR chamber for typical tropospheric O 3 /H 2 O concentrations. For these conditions, the HONO concentrations inside SAPHIR are similar to recent observations in ambient air.

Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols

“…This is a large (270 m 3 ) chamber made of double-walled thin (125 mm and 250 mm film thickness) Teflont film. 332 The space between the walls is flushed with clean air to reduce diffusion of outside gases into the chamber. Despite flushing the chamber with clean air overnight so that all measurable trace gas concentrations were below their detection limits, photolytic production of HONO as well as NO 2 and NO was still observed upon exposure to sunlight.…”

Comparison of three aerosol chemical characterization techniques utilizing PTR-ToF-MS: a study on freshly formed and aged biogenic SOA

“…The chamber is equipped with a louvre system; thus experiments could be performed under dark conditions focusing on O 3 and NO 3 oxidation (roof closed) or as photooxidation experiments utilizing sunlight (roof open). More details on SAPHIR can be found in Rohrer et al (2005).…”

“…In this work, an intercomparison campaign was performed in the atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction chamber; Rohrer et al, 2005) to investigate biogenic SOA (BSOA) formation and aging. The focus of this work is on the comparison of three different aerosol characterization techniques, the ACM-PTRToF-MS, the TD-PTR-ToF-MS and the CHARON-PTRToF-MS.…”

A new plant chamber facility, PLUS, coupled to the atmosphere simulation chamber SAPHIR

“…To this clean, dry air, trace gases are added according to experimental purpose. The SAPHIR chamber is described in more detail elsewhere (Schlosser et al, 2009;Bohn et al, 2005;Rohrer et al, 2005).…”