基于倍频二极管激光的汞气高精度连续监测方法研究

The current methods for monitoring mercury emissions generally face urgent problems of low accuracy and poor continuity. This project proposes a novel method that uses highly efficient double-frequency-based tunable diode lasers to replace the traditionally used mercury lamps, and the accurate and continuous mercury measurement can be guaranteed by sufficient acquirement of the characteristics of the mercury absorption spectrum. In this project, an accurate isotope-based spectral model of mercury absorption will be established with the key physical parameters accurately acquired using high-resolution spectrum measurement techniques, and the effects of different physical conditions on the mercury absorption spectrum will also be studied. On this basis, a double-frequency-based ultraviolet tunable continuous laser source will be set up by using a newly available 507 nm laser diode, and highly sensitive methods will be developed by combining the cavity enhanced spectroscopy and the wavelength modulation spectroscopy, following which we will explore a phase-shift-based technique for online calibration of absorption pathlength, and investigate methods and their principles to realize long-term stable measurement by employments of the harmonic-based frequency locking technique and the correlation spectroscopy. This research aims to develop a new mercury monitoring method with a detection limit better than 1 ng/m3 and a response time less than 10 s, which not only provides a completely new solution for the requirement of highly accurate and continuous monitoring of coal combustion mercury emissions, but also offers a novel way for the development of techniques for monitoring other industrial heavy metal pollutions, and thus have wide application prospects.

当前的汞气监测方法普遍面临精度不高和连续性不够的问题亟待解决。本项目提出解决这一问题的新思路：采用高效倍频可调谐二极管激光替代传统的汞灯光源，通过充分获取汞气特异性吸收光谱特征来实现汞气的高精度连续监测。项目结合高分辨光谱测量技术从同位素层面建立精确的汞气吸收光谱理论模型，研究不同物理条件下的汞气吸收光谱特性；在此基础上利用最新面世的507 nm二极管激光器构建高效倍频紫外可调谐连续激光光源，研究腔增强光谱结合波长调制光谱技术实现高灵敏光谱测量的有效方法，探索基于相位移动检测的吸收光程在线实时标定技术，研究基于谐波锁频和关联光谱技术的光谱稳定检测方法和原理，旨在最终发展出检测限优于1 ng/m3、响应时间小于10 s的新型汞气监测方法。研究结果不仅可为燃煤汞排放的高精度连续监测需求提供一个全新的解决方案，同时有望为其它工业重金属排放监测技术提供一个新颖的发展思路，具有广阔的应用前景。

汞污染是近年继硫氮污染和颗粒物污染之后又一广受关注的污染问题。当前的汞气监测方法通常采用单一固定波长的低压汞灯作为光源，没有实现真正的意义的光谱测量，普遍面临精度不高和连续性不够的问题。针对这一问题，本项目提出采用高效倍频可调谐二极管激光替代传统的汞灯光源，通过充分获取汞气特异性吸收光谱特征来实现汞气的高精度连续监测。. 本项目从同位素层面（涵盖汞的7种稳定同位素）建立了精确的汞气吸收光谱理论模型，利用最新面世的507 nm二极管激光器采用外腔反馈控制技术和倍频技术构建了中心波长253.7 nm的紫外可调谐连续激光光源，研究了倍频激光波长调制光谱和吸收光程延长等高灵敏光谱测量方法，研究了双波长激光同步扫描、关联光谱和光学啁啾链等实时稳定光谱测量方法，探索了基于光学调频连续波的多点气体传感方法，发展出一种新型基于二极管激光光源的汞气高精度连续监测方法，实现了ng级检测限和秒级响应时间。基于相关研究成果在Photonics Research、Optics Letters、Optics Express等光学领域权威期刊发表SCI论文9篇（含中科院物理类一区和二区论文6篇），申报国家发明专利5项（授权2项）。. 项目研究成果为汞等工业重金属污染排放监测提供了一个全新的解决方案，具有广阔的应用前景。