1. Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
2. Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230026, China
3. CAS Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
4. Science and Technology on Optical Radiation Laboratory, Beijing 100854, China
Abstract：Substituents form BTX (benzene, toluene, xylene, etc) by replacing the H atom on the benzene ring. The unfixed π-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 O2, 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 cm2·molecule-1) in the deep ultraviolet band of 195～208 nm, which is about nine times the cross-section size (2.6×10-18 cm2·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 SO2, NH3, CS2, 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, SO2 and NH3 under laboratory conditions. The experimental results show that the detection limit of the spectral retrieval using the 195～208 nm band reaches 17.6 μg·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 relative error is less than 5%. In the actual field condition, a portable differential optical absorption spectroscopy (DOAS) system was used to obtain the atmospheric measurement spectrum of 190～300 nm, and the DOAS method was applied to analyze and combine with the GPS information to obtain the pollution concentration distribution of benzene in a chemical industrial park. The experimental results show that the deep ultraviolet band of 195～208 nm can also be adapted to the quantitative analysis of benzene. And compared with the retrieval results of the 240～260 nm band, the correlation coefficient of the two retrieval bands has reached 0.98 and the relative error is less than 10%.
Key words：Differential optical absorption spectroscopy; DOAS; Benzene; Deep ultraviolet
叶凯迪，秦 敏，方 武，段 俊，唐 科，孟凡昊，张鹤露，谢品华，徐文斌. 深紫外波段苯的差分光学吸收光谱DOAS定量方法研究[J]. 光谱学与光谱分析, 2021, 41(10): 3007-3013.
YE Kai-di, QIN Min, FANG Wu, DUAN Jun, TANG Ke, MENG Fan-hao, ZHANG He-lu, XIE Pin-hua, XU Wen-bin. Study on the Measurement of C6H6 in the 195～208 nm Band Based on Differential Absorption Spectroscopy. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(10): 3007-3013.
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