深紫外波段苯的差分光学吸收光谱DOAS定量方法研究  

Study on the Measurement of C_(6)H_(6) in the 195~208 nm Band Based on Differential Absorption Spectroscopy

作　　者：叶凯迪 秦敏 方武 段俊 唐科 孟凡昊[1,2] 张鹤露 谢品华 徐文斌[4] YE Kai-di;QIN Min;FANG Wu;DUAN Jun;TANG Ke;MENG Fan-hao;ZHANG He-lu;XIE Pin-hua;XU Wen-bin(Key Laboratory of Environment Optics and Technology,Anhui Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Hefei 230031,China;Science Island Branch of Graduate School,University of Science and Technology of China,Hefei 230026,China;CAS Center for Excellence in Regional Atmospheric Environment,Institute of Urban Environment,Chinese Academy of Sciences,Xiamen 361021,China;Science and Technology on Optical Radiation Laboratory,Beijing 100854,China)

机构地区：[1]中国科学院安徽光学精密机械研究所,中国科学院环境光学与技术重点实验室,安徽合肥230031 [2]中国科学技术大学科学岛分院,安徽合肥230026 [3]中国科学院区域大气环境研究卓越创新中心,中国科学院城市环境研究所,福建厦门361021 [4]光学辐射重点实验室,北京100854

出　　处：《光谱学与光谱分析》2021年第10期3007-3013,共7页Spectroscopy and Spectral Analysis

基　　金：国家重点研发计划项目(2017YFC0209900,2016YFC0201002);中国科学院重点部署项目(KFZD-SW-320);安徽省科技重大专项(16030801120)资助。

摘　　要：取代基通过取代苯环上的H原子形成不同苯系物(苯、甲苯、二甲苯等),其共有结构苯环上的不固定π键电子受到激发,使得苯系物在紫外波段240~280 nm具有明显的特征吸收结构,鉴于此大气中的苯及相关的苯系物可以通过差分光学吸收光谱(DOAS)方法来进行定量,但采用该波段测量需要考虑以下问题:首先是氧气(O_(2))的吸收干扰问题,苯(C_(6)H_(6))在该波段的吸收截面与O_(2)在243~287 nm Herzzberg带相互重叠,且O_(2)的特征光谱结构随O_(2)的浓度不同而变化,导致O_(2)的吸收光学密度与O_(2)的浓度不成线性关系。其次,苯系物结构上的相似性使其在紫外波段的特征吸收结构差别较小并且相互重叠,从而对C_(6)H_(6)的拟合产生干扰。此外,除了O_(2)和苯系物以外,还有臭氧(O_(3))、二氧化硫(SO_(2))等干扰。C_(6)H_(6)在195~208 nm的深紫外波段具有较大的吸收截面(2.417×10^(-17)cm^(2)·molecule-1),为240~260 nm处截面大小(2.6×10^(-18)cm^(2)·molecule^(-1))的9倍左右,针对C_(6)H_(6)在深紫外195~208 nm波段的吸收特征,开展便携式DOAS定量方法研究,采用该波段进行C_(6)H_(6)的光谱定量分析并应用到实际的外场观测。通过建立C_(6)H_(6)与干扰气体SO_(2),氨(NH_(3)),二硫化碳(CS_(2))和一氧化氮(NO)的差分吸收截面的二维相关性矩阵,获取C_(6)H_(6)光谱定量的最优反演波段。通过开展实验室条件下C_(6)H_(6),SO_(2)和NH_(3)不同浓度配比的混气实验对195~208 nm波段反演C_(6)H_(6)的效果进行评估。实验结果显示,采用195~208 nm波段进行光谱反演的探测限为17.6μg·m^(-3),光谱反演浓度与理论浓度的相对测量误差均小于5%且RSD(相对标准偏差)小于3%,同时与240~260 nm波段反演结果进行对比,相对误差小于5%。在外场实际情况下,利用便携式DOAS系统获取190~300 nm的大气测量光谱,通过DOAS方法解析并结合GPS信息,获得了某化工园区C_(6)H_(6)的污染浓度分布Substituents form BTX(benzene,toluene,xylene,etc)by replacing the H atom on the benzene ring.The unfixedπ-bond electrons on the benzene ring of the common structure are stimulated,which makes BTX have a distinct characteristic absorption structure in the ultraviolet band of 240~280 nm.BTX in this atmosphere can be quantified by the differential optical absorption spectroscopy(DOAS)method.However,problems need to be taken into consideration when adopting the measurement of this band,such as the non-linear absorption of O_(2),cross interference between BTX due to the existence of similar absorption structures,and overlapping absorption interference of other gases.Benzene has a large absorption cross-section(2.417×10^(-17)cm^(2)·molecule^(-1))in the deep ultraviolet band of 195~208 nm,which is about nine times the cross-section size(2.6×10^(-18)cm^(2)·molecule^(-1))at 240~260 nm.Therefore,according to the characteristics of benzene in the deep ultraviolet 195~208 nm band,a portable differential optical absorption spectrum(DOAS)quantitative method is studied.This band is used to carry out the quantitative spectral analysis of benzene for the first time and applied to the actual field observation.The optimal retrieval band of benzene spectral quantification is obtained by establishing the two-dimensional correlation matrix of the differential absorption cross sections of benzene and the interfering gases SO_(2),NH_(3),CS_(2),and NO.Furthermore,the effect of retrieval of benzene in 195~208 nm band was evaluated by carrying out mixed gas experiments with different concentrations of benzene,SO_(2)and NH_(3)under laboratory conditions.The experimental results show that the detection limit of the spectral retrieval using the 195~208 nm band reaches 17.6μg·m^(-3),the relative measurement error between the measured concentration of the spectral retrieval and the configured concentration is less than 5%and the relative standard deviation(RSD)is less than 3%.Compared with the retrieval results in the 240~260 nm band,the

关 键 词：差分光学吸收光谱 DOAS 苯 深紫外 

分 类 号：O433.4[机械工程—光学工程]