差分吸收光谱方法反演大气环境单环芳香烃有机物

差分吸收光谱技术(differential optical absorption spectroscopy, DOAS)是利用气体分子在紫外-可见光谱范围的特征吸收来测量其浓度含量，如SO₂,NO₂,O₃等。由于大气环境中的芳香烃有机物含量较低，并且其在紫外的特征吸收光谱与O₂和O₃分子的吸收谱相互重叠，交叉干扰，使得对芳香烃有机物的测量比较困难。文章利用自制的差分吸收光谱系统，采用与实际测量光程接近、经过插值的氧气分子吸收柱密度作为氧气分子吸收的参考光谱，通过最小二乘拟合去除其干扰，另外采用不同温度下的O₃吸收截面作为参考光谱修正O₃的温度效应，测量了大气环境中的苯、甲苯、二甲苯和苯酚，表明差分吸收光谱方法能满足大气环境中单环芳香烃的测量。

Retrieval of Monocyclic Aromatic Hydrocarbons with Differential Optical Absorption Spectroscopy

Differential optical absorption spectroscopy (DOAS) technique has been used to measure trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range, e.g. SO_2, NO_2, O_3 etc. However, unlike the absorption spectra of SO_2 and NO_2, the analysis of aromatic compounds is difficult and strongly suffers from the cross interference of other absorbers (Herzberg bands of oxygen, ozone and sulfur dioxide), especially with relatively low concentrations of aromatic compounds in the atmosphere. In the present paper, the DOAS evaluation of aromatic compounds was performed by nonlinear least square fit with two interpolated oxygen optical density spectra at different path lengths and reference spectra of ozone at different temperature and SO_2 cross section to correct the interference from absorbers of O_2, O_3 and SO_2. The measurement of toluene, benzene, (m,p,o)xylene and phenol with a DOAS system showed that DOAS method is suitable for monocyclic aromatic compounds monitoring in the atmosphere.