SO2气体排放的紫外成像遥感监测

工业烟囱及船舶尾气中SO2气体排放是造成大气污染的重要因素。SO2容易被氧化生成硫酸雾或硫酸盐气溶胶,产生酸雨,严重危害大气生态环境平衡及人类健康。现有的SO2光学遥感测量技术,如拉曼散射激光雷达、差分吸收激光雷达(DIAL)、傅里叶变换红外吸收光谱(FTIR)、紫外差分吸收光谱(DOAS)、高分辨光谱成像等,难以兼顾气体污染监测对高时间分辨率、高空间分辨率以及便携机动等应用需求。近年来,紫外SO2相机成像探测因探测精度高、实用性强得到迅速发展,该技术时间分辨率高、空间分辨力强,能从解析图像中直观在线获取污染气体浓度在空间的二维分布及随时间的排放率,对于监测环境污染有重要作用。基于紫外SO2相机成像探测技术,围绕SO2柱浓度探测的测量原理及影响因素、仪器设计及实验方法、反演算法及结果比对等方面开展研究。取得的成果主要有:(1)利用窄带滤光片的窄波窗口,用紫外相机测量310 nm附近的SO2紫外吸收,建立了紫外成像遥感监测理论模型,介绍了紫外成像遥感检测获取SO2浓度图像的测量原理;(2)将滤光片放置镜头前后,讨论了不同入射角对滤光片中心波长及透过率曲线的影响,发现滤光片放置镜头后,相机系统对SO2的灵敏度受入射角影响更小,对SO2浓度图像的反演误差更小;(3)分析了太阳高度角对SO2浓度图像反演的影响,阐明了SO2浓度反演曲线实时校准的不可或缺性;(4)通过理论分析设计出了紫外成像遥感探测装置,开展了基于紫外成像遥感监测SO2气体排放的实验研究,通过2-IM法拟合出了人工天空背景,获得了SO2光学厚度图像,利用标准泡进行校准,反演出了SO2浓度图像;(5)采用DOAS技术对SO2气体排放进行监测,与紫外成像遥感获得的SO2浓度进行对比表明,两方法实验结果所计算得到的浓度信息趋势相一致,从而证明紫外成像遥感监测技术测量结果的准确性,同时展现了该技术在工厂烟囱及船舶尾气污染排放遥感监测中的巨大应用前景。

Study on Ultraviolet Imaging Remote Sensing Monitoring Technology for SO2 Gas Emission

SO2 emissions from industrial smokestacks and ship exhausts is an important factor causing air pollution. SO2 is easy to be oxidized into sulfuric acid fog or sulfate aerosol, which produces acid rain and seriously endangers the balance of atmospheric, ecological environment and harms human health. The existing SO2 optical remote sensing measurement techniques, such as Raman scattering lidar, Differential absorption lidar(DIAL), Fourier transform infrared(FTIR) spectroscopy, Differential absorption spectrometer(DOAS), high-resolution spectral imaging techniques, etc., are all difficult to satisfy with the application requirements in consideration of a high temporal resolution, high spatial resolution and portable mobile, etc. In recent years, the ultraviolet SO2 camera imaging detection technology gets rapid development for its high precision and strong practicability. With features of high temporal resolution and strong spatial resolution, this technology can directly get pollution gas concentration distribution in the two-dimensional space and the emission rates over time by analyzing image’s spatial information and the correlation between SO2 concentration, which makes it play an important role in monitoring environmental pollution. This paper carries out researches based on the ultraviolet SO2 camera imaging detection technology, which focuses on the measurement principle and influencing factors, instrument design and experimental methods, inversion algorithm and result comparison. The main achievements are as follows:(1) combining the narrow-band filter’s narrow-wave window, measuring ultraviolet absorption of SO2 near 310 nm by using ultraviolet cameras, the ultraviolet imaging remote sensing theory model is established, and the measurement principle that the ultraviolet imaging remote sensing image detection technology acquires SO2 concentration is introduced;(2) the influence of different incident angle for the filter center wavelength and transmittance curve is discussed by placing the filter in front and back of the lens, from which it was found that camera system sensitivity to SO2 is less influenced by the incident angle when the filter is placed in the back of lens that;(3) the influence of solar zenith angle on SO2 concentration image inversion is analyzed, and the necessity of real-time calibration of SO2 concentration inversion curve is clarified;(4) the UV imaging remote sensing detection apparatus is designed based on the above theoretical analysis and the experiment research of UV imaging remote sensing monitoring SO2 emissions are carried out. The images of the SO2 concentration is obtained by using the 2-IM method to fit the artificial sky background by using the standard calibration of the SO2 Optical depth;(5) DOAS technology is used to monitor the SO2 emissions simultaneously. And the SO2 concentration results obtained by DOAS technology and by the UV imaging remote sensing technology are compared, which shows that the tend of the concentration information calculated by the two methods are consistent. This proves the accuracy of the measurement results of the UV imaging remote sensing monitoring technology and shows the great application prospect of this technology in remote sensing monitoring of industrial smokestacks and ship exhausts pollution.