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

R. Bröske (1) , J. Kleffmann (1) , P. Wiesen (1)

1 Physikalische Chemie/FB 9

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 ?-pinene, limonene or catechol and OH radicals with toluene or limonene, respectively. The aerosols were sampled on filters and exposed to humidified NO₂ mixtures under atmospheric conditions. The estimated upper limits for the uptake coefficients of NO₂ and the reactive uptake coefficients NO₂ ?HONO are in the range of 10^?6 and 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 ?-pinene, limonene or catechol, respectively. The upper limits for the reactive uptake coefficients NO₂ \rightarrow HONO were in the range of 7×10^?7 ?9×10^?6. The results from the present study show that heterogeneous formation of nitrous acid on secondary organic aerosols (SOA) is unimportant for the atmosphere.

Domaines: Océan, Atmosphère

R. Bröske, J. Kleffmann, P. Wiesen. Heterogeneous conversion of NO₂ on secondary organic aerosol surfaces: A possible source of nitrous acid (HONO) in the atmosphere?. Atmospheric Chemistry and Physics Discussions, 2003, 3 (1), pp.597-613. ⟨hal-00300898⟩