基于化学放大腔衰荡光谱技术的大气过氧自由基的选择性测量方法研究

Peroxy radicals are important intermediates in the reaction process of atmospheric photochemistry. The recycling process of peroxy radicals and OH radicals is the key to maintain the oxidizing properties of the atmosphere. So they have very great significance for understanding key scientific issues such as atmospheric oxidation, the formations of ozone and secondary organic aerosols. Because of their high reactivity, low concentration, intense space-time variation and the limitations of general detection methods, the research on selective measurement method of peroxy radicals in ambient atmosphere is scarce. To realize real-time observation of HO2 and RO2 radicals with high sensitivity and high time resolution, high requirements for monitoring technology are put forward..In this project, based on chemical amplification cavity ring-down spectroscopy, the selective measurement method of peroxy radicals (HO2, RO2) in the atmosphere will be studied, and the highly sensitive classification measurement of them will be realized. First, the classification sampling method of peroxy radicals will be explored, and selective sampling designs and studies of different structures and materials were carried out, in order to realize the selective sampling of HO2 and RO2. A dual-channel chemical amplification method is established, and nitrogen dioxide highly sensitive detection technology is adopted, and a highly sensitive chemical amplification detection technique for peroxy radicals is developed, and then a dual-channel chemical amplification cavity ring-down detection system of peroxy radicals is developed. And various factors affecting the amplification factor will be explored to achieve ultra-sensitive and real-time detection of HO2 and RO2. It breaks through the limitation that the chemical amplification method can only measure the total concentrations of peroxy radicals. Secondly, the calibration technology of peroxy radicals is studied and a real-time calibration system for peroxy radicals is established to realize the accurate calibration of amplification factor. At last，field measurement experiments and comparisons will be carried out, then the concentration sequences and variation characteristics of the HO2 and RO2 radicals under the typical atmospheric environment of China will be obtained accurately. It is believed that this project will solve the key detection technology bottleneck of peroxide radical selectivity measurement，promote the comprehensive development of radical chemistry research and contribute to provide advanced observational technique and scientific data for selective measurement of peroxy radicals, the deep understanding of the causes of atmospheric complex pollution, as well as realizing the coordinated control of ozone and PM2.5.

过氧自由基（HO2、RO2）是大气光化学过程中重要的中间产物，与OH自由基的循环过程是维持大气氧化性的关键，对于理解大气氧化性、臭氧及二次有机气溶胶生成等关键科学问题具有重要意义。由于活性高、浓度低、时空变化剧烈以及一般探测方法的局限性，大气过氧自由基选择性测量方法的研究相当缺乏。实现高灵敏、高时间分辨率的HO2和RO2自由基实时在线观测，对监测技术提出了很高的要求。.本项目拟基于化学放大腔衰荡光谱技术开展大气过氧自由基（HO2、RO2）选择性测量方法研究，实现HO2和RO2自由基的高灵敏分类测量。首先探究过氧自由基分类采样方法，开展不同结构和材料的选择性采样设计和研究，实现HO2和RO2自由基的选择性采样；建立双通道化学放大法，结合NO2高灵敏探测技术，开展高灵敏过氧自由基化学放大探测技术研究，研制过氧自由基双通道化学放大腔衰荡探测系统；探究影响放大因子的各种因素，实现HO2和RO2自由基的高灵敏实时探测；突破化学放大法只能测量过氧自由基总浓度的局限。其次研究过氧自由基标定技术，建立过氧自由基实时标定系统，实现过氧自由基放大因子的准确标定；最后开展外场实验及对比，准确获得我国典型大气环境下HO2和RO2自由基的浓度序列和变化特征。本项目的开展将解决过氧自由基选择性测量的关键探测技术瓶颈，实现HO2和RO2自由基外场高灵敏分类测量，促进自由基化学研究的全面开展；对于深入认识大气复合污染成因、实现臭氧和PM2.5的协同控制提供先进的探测技术和科学数据。

过氧自由基是大气光化学过程中重要的中间产物，对于理解大气氧化性、臭氧及二次有机气溶胶生成等关键科学问题具有重要意义。由于活性高、浓度低、时空变化剧烈以及一般探测方法的局限性，大气过氧自由基选择性测量方法的研究相当缺乏。.本项目开展了过氧自由基分类高灵敏探测方法研究。解决了HO2和RO2自由基分类采样、双通道化学放大、NO2高灵敏探测等难题，发展了过氧自由基化学放大-腔衰荡分类探测技术。探究了HO2自由基和RO2自由基的标准源产生方法，研制了同步光解和CH3I直接光解的过氧自由基标准源产生系统，解决了107~1010cm-3范围内过氧自由基的在线生成难题，实现了HO2和RO2自由基分类采样效率的准确标定。研究了NO、CO、化学放大反应时间和相对湿度等因素对HO2和RO2自由基化学放大因子的影响，准确定量了HO2和RO2自由基的化学放大因子。研制了过氧自由基化学放大-腔衰荡（PERCA-CRDS）探测系统，实现了对HO2和RO2自由基的分类在线测量，探测限分别为0.11ppt和0.12ppt（10s），测量误差约为15%。为了验证测量准确性，开展了PERCA-CRDS探测系统和HOx-LIF探测系统的实验室对比研究，两套系统测量结果具有较好的一致性，斜率为1.02，截距为-0.55ppt，相关性系数R2为0.99。开展了综合外场观测实验，实现了环境大气中HO2和RO2自由基高灵敏实时在线测量，准确获取了HO2和RO2自由基的浓度序列，进一步探究了基于过氧自由基观测的大气臭氧生成速率及其变化特征。.本项目的开展解决了过氧自由基化学放大法分类测量的关键探测技术瓶颈，推动了自由基化学研究的全面开展，提升了对臭氧等大气复合污染成因的精细认知，将为过氧自由基选择性测量、深入认识大气复合污染成因、实现臭氧和PM2.5的协同控制提供先进的探测技术和科学数据。