大气典型α二羰基化合物的光谱探测方法和外场应用

Spectral Detection Techniques and Field Applications for Typical Atmospheric α-Dicarbonyl Compounds

乙二醛和甲基乙二醛是大气环境中两种最典型的α二羰基化合物,其浓度变化是大气VOCs氧化过程和反应活性的重要表征,对于研究大气VOCs氧化反应具有重要意义。大气乙二醛和甲基乙二醛具有浓度极低、寿命短、活性较强,使其浓度的准确探测具有一定的挑战性,导致外场环境的监测结果较少,缺乏大气化学反应机理分析的研究。对于α二羰基化合物的探测先后发展出化学衍生化法、质谱法等,能够有效地实现气体浓度监测,而技术也存在一定的局限。随着光学技术的进步,针对大气α二羰基化合物发展了一系列的光谱测量手段,比如差分吸收光谱、腔增强吸收光谱、激光诱导磷光、傅里叶红外光谱等技术,具有非接触、探测限低、灵敏度高、时间分辨率高等特点。综述了乙二醛和甲基乙二醛的光谱测量技术现状和发展趋势,对方法的原理、技术要点、优缺点等进行了详细的说明,列举了技术的器件参数、反演算法、探测限等关键特征,并对其国内外相关应用予以介绍。针对高活性α二羰基化合物的标定需求,详细说明并对比分析了现有条件下常用的气流稀释法、待测物溶液温控起泡器法、加热法、大气反应法等气体标定方法。对基于光谱技术的大气α二羰基化合物外场观测实验进行汇总分析,对实验条件、浓度结果、主要结论等予以总结,表明光谱技术是乙二醛和甲基乙二醛探测的有力手段,列表说明了浓度变化与一次污染排放、VOCs氧化、二次有机气溶胶生成等反应的相关性;重点讨论了甲醛、乙二醛、甲基乙二醛混合比率,得出不同环境下的混合比数值范围,表明RGF在BVOCs环境下数值较低,高混合比可能预示着人工源VOCs的影响。

Glyoxal and methylglyoxal are two typical types ofα-dicarbonyl compounds in the atmospheric environment.The concentration variation is an important characterization of the oxidation process and reaction activity of atmospheric VOCs,which is of great significance for studying the oxidation reaction of the atmosphere.However,the characteristics of extremely low concentrations,short lifetime,and strong activity of glyoxal and methylglyoxal bring out certain challenges to accurately detecting their concentrations,resulting in limited monitoring results of the field environment and a lack of research on the mechanism of atmospheric chemical reactions.Several methods have been developed for detectingα-dicarbonyl compounds,such as chemical derivatization and mass spectrometry,which can effectively achieve gas concentration monitoring,but the technology also has certain limitations.In recent years,with the advancement of optical technology,a series of spectral methods has developed,such as Differential Optical Absorption Spectroscopy,Cavity Enhanced Absorption Spectroscopy,Laser-Induced Phosphorescence,Fourier transform infrared,and other technologies,which have the characteristics of non-contact detection,low detection limit,high sensitivity,and high time resolution.This article summarizes the current status and development trends of spectral technology and provides a detailed explanation of the principle,key procedures,advantages,and disadvantages of the method.The article also lists the key features of the technology,such as device parameters,retrieval algorithm,detection limit,and relevant applications.At the same time,for the calibration requirements for the high activityα-dicarbonyl compounds,commonly used calibration methods,such as airflow dilution,temperature-controlled bubbler method,heating method,and atmospheric reaction method,were detailed and described and made a comparison.Finally,the field observation experiments ofα-dicarbonyl compounds were summarized,including the experimental conditions,concentration results,and main conclusions,which indicated that spectral technology is a powerful tool for glyoxal and methylglyoxal detection.Some analysis of the correlation between concentration changes and primary pollution emissions,VOC oxidation,and secondary organic aerosol generation are carried out.The mixing ratio of formaldehyde,glyoxal,and methylglyoxal was mainly discussed,and the range of mixing ratio values under different environments was obtained.Some results indicate that RGF has lower values in BVOC environments,and a high mixing ratio may indicate the impact of artificial VOC sources.