大气NO3自由基及N2O5高反腔光谱探测技术定标方法研究

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.

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。

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。本项目主要解决了大气NO3自由基和N2O5高灵敏度探测标定的问题，发展了一种利用NO3自由基、NO及NO2间化学反应的绝对定标方法，为大气NO3自由基、N2O5高灵敏度探测提供了重要手段。项目研究中，针对NO2浓度准确定量测量问题，开展了激光器波长优化及腔结构合理设计，探究了衰荡时间提取算法对测量准确度的影响，采用Allan方差选取了最佳光谱采集时间，系统灵敏度达到了20ppt。针对纯度标气源制备及稳定输出研究问题，在实验室开展了N2O5固体源的合成，探究了合成方法、温度控制、干扰等问题，实现了标气源制备纯度大于95%及自由基稳定低浓度的输出。在此基础上，采用绝对损耗定标方法开展了对腔衰荡系统损耗的测量，解决了定标过程中复合反应干扰问题及定标气路设计等问题，最终获得腔衰荡系统整体传输效率约为74%±8%。开展相对损耗标定进行对比，与绝对损耗标定结果基本一致，进一步验证了CRDS系统进气效率标定的准确性。采用损耗定标修正的CRDS系统在合肥开展了NO3自由基和N2O5外场测量，验证定标准确性，实现了大气NO3自由基和N2O5高灵敏度准确测量。本项目的研究，建立了一种腔衰荡光谱系统损耗定标方法，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。本项目执行期间，发表SCI/EI论文6篇(其中SCI二区论文1篇)，培养硕士研究生1名。