NO3自由基在夜间大气环境化学中有重要作用。以月亮直射光作为光源，使用CCD光栅光谱仪采集合肥地区的直射月光谱，并结合自动寻星赤道仪对月亮进行跟踪。应用被动差分吸收光谱技术探测夜间大气中NO3自由基柱含量。分析了影响光谱反演的主要因素，并采用逐线积分方法计算了特定水汽含量和温度条件下的水汽吸收截面参与反演，减少了水汽对NO3自由基反演的干扰。使用大气质量因子将斜柱浓度转换成了垂直柱浓度，最终得到合肥地区实验期间NO3自由基垂直柱浓度不高于1.7×1014 molecule/cm2，接近黎明时，探测到大气中NO3自由基的柱浓度迅速下降。

Nitrate radical plays (NO3) an important role in the nighttime atmosphere. By using direct moonlight as light source, a passive differential optical absorption spetroscopy (DOAS) system with automatic star-finder system and CCD spectrometer, is developed to measure the nighttime NO3 vertical column abundance of NO3. Water vapor cross section is calculated using a line-by-line approach with considering the dependence of cross section on the temperature and water vapor amounts. By using air mass factor(AMF), the vertical column density (VCD) of NO3 radical is converted from slant column density (SCD). The max value of SCD is under 1.7×1014 molecule/cm2. As the sun rises, the observed column abundance decreases rapidly.