Investigation on heterogeneous reactions of reactive oxidized nitrogen species with urban particles using iodide-chemical ionization mass spectrometry

Abstract We investigated the heterogeneous reactions of HNO 3 and NO 2 on the surface of ambient urban particulate matter, which were conducted in a Teflon bag under dark conditions. Iodide-chemical ionization mass spectrometry, a real-time mass spectrometry approach, was used to measure HNO 3 and HONO, while NO and NO 2 were measured by a NO/NO x monitor and a cavity attenuated phase shift spectroscopy-NO 2 monitor, respectively, in real-time. In experiments examining the heterogeneous reaction of HNO 3 on the surface of the urban particles, no formation of NO and NO 2 was observed under dark conditions (initial surface concentration of urban aerosols, 8.6 × 10 7 nm 2 cm −3 ), but the formation of NO, NO 2 , and HONO was observed after irradiation by black lights. Since a similar phenomenon was also observed without introduction of the particulate matter, the heterogenous reaction with light was concluded to have occurred on the inner surface of the Teflon bag. In experiments examining the heterogeneous reaction of NO 2 on the surface of urban particles, HONO was likely formed on the surfaces of the urban particles, but the yield of HONO suggested that the reaction on the urban particles was less efficient than that on the surface of soot particles. Graphical Abstract