Development of cavity enhanced absorption spectrometer for nitrate radical
Abstract
Nitrate radical (NO3) is an important trace species in atmospheric chemistry by regulating the oxidation of volatile organic compounds (VOCs) and determining partition of nitrogen oxide species between NOx (NOx = NO + NO2) and NOz (sum of all reactive nitrogen oxides except NOx) under the nocturnal atmospheric condition. Due to its high reactivity thus results low abundance, ambient NO3 detection has been achieved via limited measurement techniques (e.g. differential optical absorption spectroscopy, chemical ionization mass spectroscopy, laser induced fluorescence and cavity applied spectroscopy) characterized by high performance (i.e. high accuracy, low detection limit, and high time resolution, etc.) home-built instruments. So far, most of the successful ambient measurements of NO3 were conducted from an aircraft, tall tower and/or mountain top where the effective sampling of the nocturnal residual layer were capable. With this respect, we developed a field deployable instrument based on the cavity enhance absorption spectroscopic (CEAS) technique with LED (Light Emitting Diode) as incoherent broad band light source; a special designed cage system was applied for the robust performance in extreme operating condition such as vibration and pressure drops. Our newly developed instrument measures NO3 from the optical extinction at a wavelength range around 662nm and the cavity characteristics such as cavity loss are defined by the light attenuation ratio with the condition of cavity filled with helium and zero air. The finest conditions of spectral fitting for NO3 retrieval, acquisition time, and following detection limit were demonstrated during the presentation. In addition, test results for the pressure dependency and feasibility of NO3 reactivity measurements with targeted VOCs (i.e. rate constant for reactive loss) will be also included.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A33P2917N
- Keywords:
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- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE