基于迭代算法的大气HONO和NO_(2)开放光路宽带腔增强吸收光谱测量  

Measurements of atmospheric HONO and NO_(2) utilizing an open-path broadband cavity enhanced absorption spectroscopy based on an iterative algorithm

作　　者：孟凡昊 秦敏[1] 方武 段俊 唐科 张鹤露 邵豆 廖知堂 谢品华[1,2] Meng Fan-Hao;Qin Min;Fang Wu;Duan Jun;Tang Ke;Zhang He-Lu;Shao Dou;Liao Zhi-Tang;Xie Pin-Hua(Key Laboratory of Environmental Optics and Technology,Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,China;University of Science and Technology of China,Hefei 230026,China;College of Electrical and Opto-Electronic Engineering,West Anhui University,Lu’an 237012,China)

机构地区：[1]中国科学院合肥物质科学研究院,安徽光学精密机械研究所,环境光学与技术重点实验室,合肥230031 [2]中国科学技术大学,合肥230026 [3]皖西学院电气与光电工程学院,六安237012

出　　处：《物理学报》2022年第12期2-9,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:41875154,42175151,U21A2028);安徽省重点研究与开发计划(批准号:202104i07020010)资助的课题。

摘　　要：气态亚硝酸(HONO)作为羟基(OH)自由基的重要前体物,在大气中浓度低、寿命短、易损耗且活性强,针对大气HONO的高灵敏度测量具有一定的挑战.本文介绍了基于迭代算法的开放光路宽带腔增强吸收光谱(OP-BBCEAS)技术应用于大气HONO和NO_(2)的测量.常规BBCEAS技术通过将经滤膜过滤后的环境空气由泵压入/抽入光学腔内进行测量,尽管可以减小气溶胶消光对测量的影响,但针对一些活性组分的测量则需要考虑光学腔和采样造成的吸附损耗和二次生成等壁效应.本文采用OP-BBCEAS技术,开放光路的测量模式避免了上述壁效应的影响,基于迭代反演算法通过多次迭代确定有效吸收光程,然后采用差分光学吸收光谱的光谱拟合方法对光谱中HONO和NO_(2)的吸收进行定量,克服了气溶胶颗粒Mie散射消光和光源波动的宽带变化影响.在轻度(PM_(2.5)<75μg/m^(3))和中度(PM_(2.5)>75μg/m^(3))不同气溶胶污染状况下测量了实际大气HONO和NO_(2)浓度,并同时与常规封闭腔BBCEAS系统开展了测量对比.不同PM_(2.5)污染程度下两台BBCEAS系统测量的HONO和NO_(2)浓度均显著性相关(R^(2)>0.99),HONO和NO_(2)浓度的测量差异(HONO≤4.0%,NO_(2)≤6.5%)均小于系统测量误差(HONO:8.1%,NO_(2):7.5%),验证了迭代反演算法应用于OP-BBCEAS系统实际大气测量的可行性.Nitrous acid(HONO),as an important precursor of hydroxyl(OH)radical,has a low concentration,short lifetime,easy loss and high reactivity in the atmosphere.Thus,the high sensitivity detection of atmospheric HONO is a challenge.In this paper,we report an open-path broadband cavity enhanced absorption spectroscopy(OP-BBCEAS)system based on the iterative algorithm for simultaneous measurement of atmospheric HONO and NO_(2).In the conventional BBCEAS system,a pump is used to drive the ambient air into the optical cavity through the filter membrane for measurement,which can reduce the influence of aerosol particle extinction.However,the influence of wall loss and secondary formation caused by the optical cavity and sampling should be considered for reactive component measurements.The OP-BBCEAS with open-path configuration is adopted in this paper to avoid being influenced by wall effect.The effective absorption optical path is calculated by the iterative retrieval algorithm through multiple iterations,and the absorption of HONO and NO_(2) are then quantified by the spectral fitting method of differential optical absorption spectroscopy,which removes the broadband change influence of the Mie scattering extinction by aerosol particles and the light intensity fluctuation.The atmospheric HONO and NO_(2) with light(PM_(2.5)<75μg/m^(3))and moderate(PM_(2.5)>75μg/m^(3))aerosol loading are measured by the OP-BBCEAS system based on iterative algorithm,and compared with the counterparts by the conventional close-path BBCEAS system.The concentrations of HONO and NO_(2) measured by the two BBCEAS systems are in good agreement(R^(2)>0.99)for different PM2.5 concentration levels,and the measurement differences of HONO and NO_(2) concentrations(HONO≤4.0%,NO_(2)≤6.5%)are less than the systematic measurement errors(HONO:8.1%,NO_(2):7.5%),which verifies the feasibility of iterative algorithm applied to OP-BBCEAS system for atmospheric measurement.

关 键 词：宽带腔增强吸收光谱 开放光路 迭代算法 差分吸收光谱 

分 类 号：X831[环境科学与工程—环境工程]