Preprints
https://doi.org/10.5194/egusphere-2024-2762
https://doi.org/10.5194/egusphere-2024-2762
09 Sep 2024
 | 09 Sep 2024

Measurement of NO and NH3 Concentrations in Atmospheric Simulation Chamber Using Direct Absorption Spectroscopy

Nakwon Jeong, Seungryong Lee, Soonho Song, Daehae Kim, Miyeon Yoo, and Changyeop Lee

Abstract. In urban atmospheric chemistry, nitrogen oxides and ammonia in the atmosphere are major species participating in the secondary aerosol formation process, causing severe environmental problems such as decreased visibility and acid rain. In order to respond effectively to particulate matter problems, the correlation of precursors should be identified in detail. This study used UV-C light to convert gaseous substances into particulate substances in the atmospheric simulation chamber to simulate the photochemical reaction. The effects of several operating variables, such as UV-C light intensity, relative humidity, and initial concentrations of O2, NO, and NH3, on the NH4NO3 formation were investigated. Since atmospheric gas species are short-lived, they require a measurement technique with an ultra-fast response and high sensitivity. Therefore, the concentrations of NO and NH3 were measured using Direct Absorption Spectroscopy techniques with the wavenumber regions of 1926 and 6568 cm-1, respectively. NO and NH3 were precisely measured with an error rate of less than 3 % with the reference gas. The results show that NO and NH3 were converted over 98 % when UV-C light intensity was 24 W and relative humidity was about 30 % at 1 atm, 296 K. It also showed that higher UV-C light intensity, O3 concentration, and relative humidity induced higher conversion rates and secondary aerosol generation. In particular, it was experimentally confirmed that the secondary aerosol generation and growth process was greatly influenced by relative humidity.

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This study explores the formation of NH4NO3, a key component of atmospheric aerosols, by...
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