复合污染大气环境中OH自由基测量干扰的定量研究  

Quantitative study on the interference of OH radical measurement in the air pollution complex

作　　者：马雪飞 谭照峰 陆克定[1] 张远航[1] Xuefei Ma;Zhaofeng Tan;Keding Lu;Yuanhang Zhang(State Key Joint Laboratory of Environmental Simulation and Pollution Control,College of Environmental Sciences and Engineering,PekingUniversity,Beijing 100871,China;Institute of Energy and Climate Research,IEK-8:Troposphere,Forschungszentrum Jülich GmbH,Jülich 52428,Germany)

机构地区：[1]北京大学环境科学与工程学院,环境模拟与污染控制国家重点实验室,北京100871 [2]Institute of Energy and Climate Research,IEK-8:Troposphere,Forschungszentrum Jülich GmbH,Julich 52428,Germany

出　　处：《科学通报》2022年第31期3724-3736,共13页Chinese Science Bulletin

基　　金：北京市自然科学基金杰出青年科学基金(JQ19031)资助。

摘　　要：大气OH自由基的原位测量是定量表征大气氧化性的有效方式,也是检验和改进大气化学机制的重要手段.由于大气OH自由基活性强、浓度低,其准确测量是大气领域研究的重要挑战之一.激光诱导荧光(laser-induced fluorescence,LIF)技术因其高灵敏度和高选择性而成为最为广泛应用的技术.但是,已有研究表明,在高挥发性有机物(volatile organic compounds,VOCs)条件下,采用传统光谱调制法的LIF仪器可能存在测量干扰,且干扰来源未知.本研究基于北京大学激光诱导荧光系统(Peking University laser-induced fluorescence,PKU-LIF),开发了化学调制法,通过定量化学背景值分离干扰,从而实现OH自由基准确测量.在2016年北京冬季观测中,首次实现了基于化学调制法和光谱调制法的OH自由基同步测量,获取了两套OH自由基浓度时间序列.考虑到两套自由基的不确定性为31%,两种方法的测量结果呈高度一致(相关斜率:0.88±0.01),表明在冬季观测期间,PKU-LIF基于传统光谱调制法测量并无显著干扰.但是,采用LIF技术测量OH自由基是否受到干扰以及干扰的程度与具体的仪器设计和所处环境条件密切相关,因此未来应用LIF技术进行复杂环境大气中OH自由基浓度测量时,应增加化学调制法来排除或定量干扰,实现OH自由基的无干扰测量.OH radical is the most important gas-phase oxidant in the troposphere,which oxidizes the primary pollutants to secondary pollutants and causes the regional secondary pollution.Hence,it is crucial to acquire comprehensive knowledge of the radical chemistry to mitigate the secondary air pollution.However,the well-established photochemistry is insufficient to describe the chemical processes in the complex air mixture.For instance,the model severely underpredicts OH radical concentration in forest areas.In situ measurement of OH radical is an efficient way to quantify the atmospheric oxidation capacity and improve our understanding of atmospheric chemical mechanisms.While due to its high reactivity and low concentration,measurement of OH radical is one of the most challenging tasks in the atmospheric research.Laser-induced fluorescence(LIF)is the most widely used technique to measure OH due to its high sensitivity and selectivity.However,studies have shown that under high volatile organic compounds(VOCs)conditions,LIF technique based on traditional spectral modulation methods may suffer from interference,whose origin has not yet been known.In this study,based on the Peking University Laser-Induced Fluorescence system(PKU-LIF),a chemical modulation method was developed,to separate interference by quantifying the chemical background signals,through chemical removing of the ambient OH prior to be sampled into the detection cell,thereby enabling accurate measurement of OH radical.During the winter campaign in Beijing in 2016,simultaneous OH radical measurement based on both the chemical modulation method and the spectral modulation method was achieved for the first time,and two sets of OH radical concentrations were obtained.It was found that,the two sets of OH radical concentrations agreed within the combined uncertainties of 31%(correlation slope:0.88±0.01),indicating that there was no significant interference in the measurement of OH based on the traditional spectral modulation method during this winter campaign.It i

关 键 词：OH自由基 激光诱导荧光技术 测量干扰 光谱调制法 化学调制法 

分 类 号：X831[环境科学与工程—环境工程]