| Total reactive nitrogen, which is often referred to as NOy, a collective name for NOx?NO+NO2?, NO3, HONO, HNO3, N2O5, PNs?totalperoxynitrates, R02N02?,ANs?total alkyl nitrates, RON02?, and aerosol nitrates, etc., plays an important role in atmospheric chemistry and has a strong influence on air quality. The presence of NOy has a considerable impact on the abundance of 03, hydroxyl and hydrogen per-oxy radicals ?OH and H02?, and the formation processes of photochemical smog and secondary organic aerosol ?SOA?. This thesis presents the development of a cavity ring-down spectroscopy ?CRDS? system used to detect NO, N02, RN02 ?PNs+ANs? and NO3 in ambient air.The first chapter introduced the chemical process referred to NO, NO2, RNO2 and NO3 in the atmosphere. Brief description of different techniques used to detect N02 were presented. Principles of the CRDS technique were also presented.In the second chapter, a two-channel cavity ring-down spectrometer ?TD-CRDS?based on 405 nm diode laser has been built for in situ, real-time measurement of N02,total RNO2 ?peroxy nitrates and alkyl nitrates? and NO. A detection limit of 0.092 ppbv in 1 sec for NO2 has been obtained.In the third chapter, we conducted a cavity ring-down spectrometer operating at 662 nm for the detection of NO3. We obtained a detection limit of 1 pptv at 1 sec.In the fourth chapter, we realized ambient detection of NOy using the CRDS in-struments. We took two periods of detection of RNO2 NO2 in the winter of 2015,and the possible causes of two independent heavy smog events were also investigated.A 6-day long measurement was conducted at urban site of Hefei by using the 405 nm CRDS instrument compared with a commercial molybdenum converted chemilumines-cence ?Mo-CL? instrument. Continuous ambient detection of NO and N03 were also carried out using the 405 nm and 662 nm CRDS instruments, respectively.In the last chapter, a brief conclusion of the experiments and perspectives for future studies were presented. |
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