Formation of indoor nitrous acid (HONO) by light-induced NO2 heterogeneous reactions with white wall paint
2014
Bartolomei, Vincent | Sörgel, Matthias | Gligorovski, Sasho | Alvarez, Elena Gómez | Gandolfo, Adrien | Strekowski, Rafal | Quivet, Etienne | Held, Andreas | Zetzsch, Cornelius | Wortham, Henri
Gaseous nitrogen dioxide (NO₂) represents an oxidant that is present in relatively high concentrations in various indoor settings. Remarkably increased NO₂levels up to 1.5 ppm are associated with homes using gas stoves. The heterogeneous reactions of NO₂with adsorbed water on surfaces lead to the generation of nitrous acid (HONO). Here, we present a HONO source induced by heterogeneous reactions of NO₂with selected indoor paint surfaces in the presence of light (300 nm < λ < 400 nm). We demonstrate that the formation of HONO is much more pronounced at elevated relative humidity. In the presence of light (5.5 W m⁻²), an increase of HONO production rate of up to 8.6 · 10⁹molecules cm⁻² s⁻¹was observed at [NO₂] = 60 ppb and 50 % relative humidity (RH). At higher light intensity of 10.6 (W m⁻²), the HONO production rate increased to 2.1 · 10¹⁰molecules cm⁻² s⁻¹. A high NO₂to HONO conversion yield of up to 84 % was observed. This result strongly suggests that a light-driven process of indoor HONO production is operational. This work highlights the potential of paint surfaces to generate HONO within indoor environments by light-induced NO₂heterogeneous reactions.
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