Development of onsite measurement system of atmospheric nitrous acid

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Nitrous acid (HONO) is a significant source of hydroxyl (OH) radicals and an indoor pollutant. HONO is difficult to accurately measure since the species is prone to losses due to its high reactivity and solubility. Thus, this research concentrates on the development of a measurement system utilizing cavity ring down spectroscopy (CRDS) and differential optical absorption spectroscopy (DOAS). The former is used to provide a basic detection limit of HONO and to determine HONO’s absorption cross-section in the mid-IR region while the latter is used to increase the sensitivity of the system and improve on the detection limit. The study also includes examination of the effects of temperature, carrier gas flow rate and reactant amount on the HONO synthesis. Current results show an encouraging detection limit and that the reaction synthesis yields HONO of satisfactory purity.