差分吸收光谱法同时测量SO_2,NO_2及颗粒物浓度的模拟

Simulation of Concentration Measurement of SO_2,NO_2 and Particles Simultaneously by Differential Optical Absorption Spectroscopy

雾霾天气已经影响到了人们的日常生活,对雾霾成分进行测量非常重要,雾霾的主要构成成分为SO_2和NO_2及颗粒物。目前对气体及颗粒物浓度进行同时测量的研究还很少,用差分吸收光谱法(DOAS)对同时测量气体及颗粒污染物浓度进行了探索性研究。通过对多组不同配比的SO_2,NO_2及颗粒物组成成分的吸收光谱进行了模拟,由DOAS方法反演了各组分的浓度。模拟单一组分时,气体浓度从100变化至1 000ppm,SO_2浓度反演误差不大于0.17%,NO_2误差不大于0.64%,颗粒尺寸从100变化至500nm,浓度反演误差不大于2.08%。模拟气体多组分时,SO_2浓度与NO_2浓度比在1∶10到5∶1的范围内时,误差均较小,SO_2误差不超过8%,NO_2误差不超过5%,然SO_2与NO_2浓度之比大于10,NO_2的反演误差高于10%。模拟同时测量SO_2,NO_2及颗粒物浓度时,气体浓度的反演误差均在10%以内,而颗粒物浓度的反演误差对系统的信噪比依赖较大,当信噪比在40dB以上时,误差在10%以内,而信噪比低于30dB时,误差高于20%。通过上述研究结果表明,差分吸收光谱法能很好地同时测量多种气体及颗粒物浓度,用来测量分析雾霾成分。然测量环境气体吸收差异过大时,强吸收气体对弱吸收气体影响很大,信噪比较低时,颗粒浓度反演的误差也大为增加,需要更好的滤波及去噪方法。

Our daily life is disturbed seriously by the haze weather now.It is very important to measure the haze composition quantificationally.The main composition of haze is SO_2,NO_2 and particles.At present,the research of measuring gas and particle simultaneously is rare relatively.This paper use differential optical absorption spectroscopy（DOAS）to simulate the concentration measurement of gas and particle simultaneously and obtain some meaningful results.Absorption spectral of many groups of different concentration of SO_2,NO_2 and particle were simulated,and each concentration was inverted by DOAS.In the first group of single component,the concentration change from 100 to 1 000 ppm,the inverted error of SO_2 is not greater than0.17%,and which is 0.64%for NO_2.When the diameter of particle change from 100 to 500nm,the inverted error is not greater than 2.08%.In the second group of multiple gases,when the concentration ratio of SO_2 and NO_2is at the range of 1∶10and5∶1,the error of SO_2 is not bigger than 8%,and 5%for NO_2,relatively.But when the concentration of SO_2 is 10times than NO_2,the error is higher than 10%for NO_2.In the third group of gas and particle,the error of gas concentration is lower than10%,but the concentration error of particle is depended on signal to noise ratio（SNR）greatly.When SNR is higher than 40 dB,error can lower than 10% and when SNR is lower than 30 dB,the error is bigger than 20%.From these results,we can see that DOAS can measurement SO_2,NO_2 and particles simultaneously effectively,and can applied to measure and analyze haze composition.However,when the absorption strength of the gases is different greatly,the strong absorption gas influent the weak absorption gas largely.And the SNR is lower,the error of inverted particle concentration increased greatly.The solution of these problems need better filtering and noise reduction method.