Observation and comparison of HONO and H2O2 during early summer in Seoul, Korea

Nitrous acid (HONO) is a key source of OH radical and hydrogen peroxide (H₂O₂) is an important indicator for OH abundance, which is responsible for atmospheric oxidative capacity, and are both important photochemical indicator species. Research of the sources and behavior of these trace gases is important in order to understand the oxidative mechanisms that lead to urban ozone and aerosol formation. Despite the importance of these gases, especially in the urban conditions in South Korea, currently they are not well understood because of their high reactiveness and low concentration in the atmosphere. In this study, HONO and H₂O₂ measurement was conducted at Korea University (37°35'06.5"N 127°01'34.6"E) located in Seoul, Korea from June 1 to June 27 of 2018 using High Efficiency Diffusion Scrubber with Ion Chromatography (HEDS-IC) and Quantum Cascade-Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS). QC-TILDAS has a short response time (1 10 Hz) and a low detection limit ( 0.1 ppbv). Concentrations varied from the detection limit to 2.51 ppbv for HONO and 2.45 ppbv for H₂O₂ with average values of 0.51 ppbv and 0.52 ppbv. Both HONO and H₂O₂ concentrations showed typical diurnal values, low for HONO and high for H₂O₂ during the afternoon, and were well correlated with O₃. HONO showed positive correlation with NO₂.