大气NO3自由基和N2O5是夜间大气氧化反应能力的重要指标，其准确探测备受关注。系统标定是浓度准确测量的前提，考虑损耗随时间及环境条件变化显著特性，本项目基于腔衰荡光谱高灵敏度探测系统，同时利用氮氧化物间化学反应，拟发展一种满足外场测量条件下损耗实时准确修正的绝对定标方法。在此基础上，探究高纯度标气源合成方法，解决NO2高精度准确定量、系统同步定标及实时损耗修正等难题；并与相对定标方法对比及进行外场测试，进一步验证该方法的准确性。本项目可应用于普遍采样仪器，为大气NO3自由基、N2O5准确测量提供重要手段；同时有助于准确掌握夜间对流层大气氧化容量，为我国区域性灰霾夜间形成机制研究提供有力支撑。

he NO3 radical and N2O5 are the important indicators of atmospheric oxidation ability at night，and their accurate detection have drawn much attention. Calibration of the concentration is the premise of accurate detection. Taking account of the significant characteristics of loss change with time and environmental conditions, an absolute calibration method is proposed to meet the requirement of accurate measurement of loss under field conditions based on the high-sensitivity detection system of cavity ring-down spectroscopy and making use of chemical conversion of nitrous oxides. Exploring the synthesis method of high-purity standard gas, on this basis, the problem of accurate determination of NO2, simultaneous calibration of two gases and real-time calibration are solved. The accuracy of this calibration method was further verified by comparison with the relative calibration method under laboratory conditions and the field measurement conditions. In the end, the project can be applied to the universal sampling instrument to realize the highly sensitive detection of NO3 radical and N2O5 in the atmosphere. Moreover, the significance of this project lies in accurately grasping nocturnal atmospheric oxidation capacity in the troposphere and providing stronger support for regional haze formation mechanism research.