强烟尘水滴干扰下DOAS法在线测量NO质量浓度的研究

DOAS Method for On-line Measurement of NO Concentration Interfered by High Density of Dust and Water Droplets

在高浓度烟尘、水汽液滴和NO共存的工况下,采用差分吸收光谱法研究和分析了不同质量浓度NO的吸收光谱特性,提出了一种基于差分吸收光谱法的NO质量浓度反演算法;同时,利用信噪比对小波分解时小波母函数的选取进行了比较.结果表明:在对NO吸收光谱进行小波分解后,即使在干扰颗粒质量浓度较大时,某些特征波长点处的小波系数高频细节分量与未受干扰的NO吸收光谱的小波系数高频细节分量有较好的重合;通过对小波分解时小波母函数选取的比较,可以获得适用于此反演算法的最优小波母函数sym10,它可以有效消除烟尘、水汽液滴的干扰影响,而且测量误差在允许范围内,能够满足烟尘排放监测要求.

With simultaneous existence of dust and water droplets in high densities,absorption spectrums of NO were analyzed using differential optical absorption spectroscopy（DOAS）,based on which a new reverse method for calculation of NO mass concentration was proposed.Simultaneously,optimal mother wavelet was chosen by comparing corresponding signal to noise ratios.Wavelet transform results show that there do exist some characteristic points,where the high-frequency components of wavelet coefficient are not affected by any interference,even if the interference comes from high density of dust or water droplets.Among all the mother wavelets,the one sym10 is found to be optimal for the new reverse method,which may help to eliminate the interference of dust and water droplets,reduce the measurement error,and finally satisfy the requirement of dust emission.