A net ozone production rate detection system based on dual-channel cavity ring-down spectroscopy

A newly constructed cavity ring-down spectroscopy (OPR-CRDS) for measuring net photochemical ozone production rates was developed. The system consists of two chambers (a reaction chamber and a reference chamber) and a dual-channel Ox-CRDS detector. The inner surfaces of both chambers are coated with Teflon film to minimize the wall loss of Ox. It was found that even though the photolysis frequency (J value) decreased by 10%, the decrease in the P(O₃) caused by the ultraviolet-blocking film coating was less than 3%. The two chambers had a good consistency in the mean residence time and the measurement of NO₂ and Ox under the condition of no sunlight. The detection limit of the OPR-CRDS was determined to be 0.20 ppbv/hr. To further verify the accuracy of the system, the observed values of the OPR-CRDS were compared with the calculation results based on radical (OH, HO₂, and RO₂) reactions, and a good correlation was obtained. Finally, the developed instrument was applied to the comprehensive field campaign at an urban site in the Yangtze River Delta (China), the time series and change characteristics of the P(O₃) were required directly, and the good environmental adaptability and stability of the OPR-CRDS system were demonstrated. It is expected that the new instrument will be beneficial to investigations of the relationship between P(O₃) and its precursors.