| Nitrous acid (HONO) is an important OH reservoir species during nighttime and it is readily photolyzed after dawn releasing substantial OH radical into the planetary boundary layer (PBL). HONO + hν (λ < 370 nm) → OH + NO. Up to the ppb level of HONO has been observed above urban areas. It is still uncertain on the role that HONO chemistry plays in O3 production in urban areas. Furthermore, the details regarding the HONO production mechanism and the quantification of HONO sources are still not well established, especially for areas enriched with NOx and VOC emissions. In this presentation measurements of the HONO concentration using chemical ionization mass spectrometry in a US Urban Center, Houston, TX will be reported. Discussions will be made on the implications on HONO formation on the radical production. |