The photochemical reaction of NO2 with organics may be a source of atmospheric HONO during the daytime. Here, the conversion of NO2 to HONO on polycyclic aromatic hydrocarbons (PAHs) under solar irradiation under aerobic and anaerobic conditions was investigated using a flow tube reactor coupled to a NOx analyzer. O2 played an inhibition role in NO2 uptake and HONO formation on PAHs, as shown by 7%-45% and 15%-52% decrease in NO2 uptake coefficient (γ) and HONO yield (YHONO), respectively. The negative effect of O2 on the reaction between NO2 and PAHs should be attributed to three reasons. First, O2 could compete with NO2 for the available sites on PAHs. Second, the quenching of the triple excited state of PAHs (3PAHs*) by O2 inhibited the NO2 uptake. Third, NO3- formed under aerobic conditions reduced the conversion efficiency of NO2 to HONO. The environmental implications suggested that the NO2 uptake on PAHs could contribute to a HONO source strength of 10-120 ppt h-1 in the atmosphere.
Keywords: Chemical composition; HONO; NO2 uptake; Nitrogen-containing species; Oxidizing gas; Photochemical mechanism.
© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.