Recently, the important progress of NO3 radical detection research is made by Pinhua XIE research group of Anhui Institute of Optics & Fine Mechanics. The results were published online in Journal of Quantitative Spectroscopy & Radiative Transfer (Elsevier) on July 13.
Nitrate radical (NO3) is a significant nocturnal trace gas in the atmosphere. It has special oxidative capacity for such volatile organic compounds (VOC) (especially) as terpene, dimethyl sulfide(DMS)and alkene et al,and the key role And italso plays a key role in the non-photochemical conversion of NOx(NO/NO2) to HNO3 and the formation of nitrate aerosol.Therefore, accurate measurement of its concentration in the atmosphere has a great significance to the study of nocturnal atmospheric chemistry.
Renzhi HU, and Dan WANG et al developed a cavity ring-down spectroscopy (CRDS) instrument for measuring atmospheric NO3 radical. In this new instrument, they used the modulation diode laser as the light source, and combined it with high-reflectivity optical cavity to reach a high sensitive detection. Given of the high aerosol concentration in China, it is necessary to design a suitable sampling system to reduce the loss of NO3 radicals during sampling,and a set of calibration system to calibrating accurately thesampling loss. The instrument achieves an effective absorption path length of approximately 20 km, and the detection limit of 3.2ppt@10s, which can satisfythe measurement demands in the domesticatmospheric environment.
In the fall and winter of 2014(HOPE - J3A comprehensive experiments),the nocturnal atmospheric NO3 radical is detected in Beijing and the change rules of NO3 radical is studied. Combining of NO2, O3 and NO data, nocturnal loss mechanism of NO3 radical at a suburb site in Beijing is briefly analyzed.
It shows that the cavity ring-down spectroscopy system for NO3 radical detection provides a powerful means of monitoring for atmospheric chemistry research at night and can be applied to atmosphere environment and smog chamber experiment.
This work is funded by theStrategic Priority Research Programof the Chinese Academy of Sciences
The article links: http://www.sciencedirect.com/science/article/pii/S0022407315002484
Diode laser cavity ring-down spectroscopy for in situ measurement of NO3 radical in ambient air
(a) CRD-NO3 detection system (b) Laser wavelength optimization
(c) Calibration of inlet loss (d) HOPE - J3A field measurement
Imaged by Renzhi HU
Keywords: NO3 radical; Cavity ring-down spectroscopy (CRDS);_Atmospheric monitoring; Diode laser