双光路DOAS技术获取近地面大气污染气体和气溶胶的方法及应用研究

The atmospheric complex pollution becomes more and more serious, which results in atmospheric enhanced oxidation and accelerated transformation of gases into particles. It is urgent to develop a novel method to measure near-ground atmospheric pollution gases and aerosols simultaneously in a large scale. This project aims to develop a novel method to real-time, online and simultaneous determination concentrations of near-ground atmospheric pollution gases and aerosols basing on differential optical absorption spectroscopy (DOAS), combining double optical path technique. The broadband xenon arc lamp is as light source of double optical path DOAS system. The differential optical absorption spectra are attained accurately using this system. The atmospheric concentrations of trace gases are retrieved basing on differential principle. The aerosol extinction coefficients are obtained by removal the contribution of polluted gas and Rayleigh scattering. The model is set to retrieve the aerosol using multispectral extinction data basing on Mie scattering theory. The aerosol size distribution and number density spectra distribution are retrieved by using aerosol extinction coefficients which have been got by DOAS system. Mass extinction efficiency (MEE) which linked between the aerosol optical property and the aerosol amount in the atmosphere is also analyzed in this work. This project also gives its variation with aerosol size and relative humidity. Inversion method and remote sensing system are used the daily emissions of gases and aerosols. The interaction mechanisms, diffusion, transport and deposition of atmospheric pollution are discussed in this work. The research results not only can provide technique support to controll the haze weather, but also study atmospheric heterogeneous gas/particle chemical reaction to provide the raw data. The research will also promote further development and application of the DOAS technique.

大气复合污染日趋严重，造成大气氧化性增强，气体向颗粒物的转化在加快，亟待一种大范围对其同时监测的新方法。本项目拟以差分吸收光谱法（DOAS）为基础，结合双光路设计技术，开展实时、在线、同时获取近地面大气污染气体和气溶胶的新方法研究。通过构建以宽带氙弧灯为光源双光路DOAS系统，精确解析大气污染气体和气溶胶特征吸收光谱；反演大气污染气体浓度；在消除瑞利散射影响后，基于Mie散射理论，反演气溶胶的宽波段消光系数；利用多光谱消光数据，反演大气气溶胶粒子尺寸和数密度谱分布等；并对单位质量粒子的消光效率(MEE)进行研究，给出其与粒子尺寸、相对湿度间的变化规律。最终把遥测系统和反演方法应用于大气污染气体和气溶胶的日常排放实时监测中，研究其相互作用机理，分析扩散、传输和沉降过程。为整治我国灰霾天气，研究大气气相/粒子非均相化学反应提供科学依据。项目的研究还将推动DOAS技术的进一步发展和应用。

针对我国大气复合污染日趋严重，导致大气氧化性增强，气体向颗粒物的转化在加快，项目以差分吸收光谱法（DOAS）为基础，结合双光路设计技术，开展实时、在线同时获取近地面大气污染气体和气溶胶特性的光谱新方法研究。（1）双光路DOAS测量系统的设计与集成。构建了以宽带氙弧灯为光源的双光路差分吸收光谱系统，根据大气污染气体和气溶胶分布特点，合理设置监测系统长光程和短光程，并进行性能测试和数值模拟。（2）大气污染气体浓度和气溶胶消光系数反演算法研究。基于能见度数据，实现系统校准，精确解析大气总的消光系数。基于差分思想，获得大气痕量气体浓度，去除瑞利散射以及气体吸收对消光系数的影响后，解析出气溶胶颗粒物的消光系数。并探讨了气溶胶颗粒物消光系数随着波长变化规律。（3）基于核函数准则，利用均匀球型粒子的电磁场Mie散射理论来反演气溶胶微物理特性，获得了气溶胶粒子体积谱分布，利用体积谱与数密度谱的关系，反演了气溶胶粒子的数密度谱分布。（4）外场实验。基于300nm至650 nm波段范围内的消光系数，获得了颗粒物的在0.1μm至1.25 μm粒径范围的数密度谱分布。该研究为探索气溶胶颗粒物的微物理特性和分析大气气相/粒子非均相化学反应提供科学依据。项目的研究还将推动DOAS技术的进一步发展和应用。