Heterogeneous conversion of NO₂ on secondary organic aerosol surfaces: A possible source of nitrous acid (HONO) in the atmosphere?

• Main Authors: R. Bröske, J. Kleffmann, P. Wiesen
• Format: Article
• Language: English
• Published: Copernicus Publications 2003-01-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/3/469/2003/acp-3-469-2003.pdf
• ISSN: 1680-7316; 1680-7324

The heterogeneous conversion of NO₂ on different secondary organic aerosols (SOA) was investigated with the focus on a possible formation of nitrous acid (HONO). In one set of experiments different organic aerosols were produced in the reactions of O₃ with alpha-pinene, limonene or catechol and OH radicals with toluene or limonene, respectively. The aerosols were sampled on filters and exposed to humidified NO₂&nbsp; mixtures under atmospheric conditions. The estimated upper limits for the uptake coefficients of NO₂&nbsp; and the reactive uptake coefficients NO_2&nbsp; -> HONO are in the range of 10^-6and 10^-7, respectively. The integrated HONO formation for 1 h reaction time was <10¹³ cm^-2 geometrical surface and <10¹⁷ g^-1 particle mass. In a second set of experiments the conversion of NO₂ into HONO in the presence of organic particles was carried out in an aerosol flow tube under atmospheric conditions. In this case the aerosols were produced in the reaction of O₃ with beta-pinene, limonene or catechol, respectively. The upper limits for the reactive uptake coefficients NO₂-> HONO were in the range of 7 x 10^-7- 9 x 10^-6. The results from the present study show that heterogeneous formation of nitrous acid on secondary organic aerosols (SOA) is unimportant for the atmosphere.