激光捕获协同激光诱导击穿拉曼光谱的超细大气颗粒物原位在线多组分分析方法研究

Ultrafine particulate matter (<1 μm) pollution seriously endangers people's health, and has become a hot issue of global concern. How to analyze the elements, molecules, and the intermediate free radicals of the single ultrafine particle is the main problem and technical bottleneck for accurately tracing and effectively controlling the particulate matter pollution. Motivated by the urgent requirement for the in-situ, on-line and multi-component analysis of the ultrafine particulate matter, we would build a system combining laser trapping with laser-induced breakdown Raman spectroscopy in this project. The hollow laser trapping technique would be employed to capture the ultrafine particulate matter, and the laser-induced breakdown Raman spectroscopy would be used for the multi-component analysis of the trapped single ultrafine particulate matter. On the basis of this system, we would do the following researches. First, we would study on the mechanical mechanism of ultrafine atmospheric particulate matter in the hollow light field in order to improve the ultrafine particle trapping stability. Second, we would study on the mechanism of the plasma generation and evolution on the atmospheric particles in order to improve the signal-to-noise ratio of the laser-induced breakdown Raman spectroscopy signal. At the same time, the complex spectrum analysis algorithm would be developed in order to simultaneously extract the laser-induced breakdown spectra and Raman spectra fast and accurately. And finally, the elements, molecules, and the intermediate free radicals of the ultrafine particle would be analyzed based on the laser-induced breakdown spectra and Raman spectra. This project would provide a new idea and a new method to reveal the formation mechanism of the ultrafine atmospheric particulate pollutants and to infer their sources.

超细大气颗粒物（<1μm）污染严重危害人类健康，已成为全球关注的热点问题。如何实时原位分析单个超细悬浮颗粒物的元素和分子组成以及中间自由基是大气颗粒污染物精准溯源与综合防控的主要难题和技术瓶颈。本项目从单个超细悬浮颗粒物原位在线多组分同时分析的实际需求出发，构建激光捕获协同激光诱导击穿拉曼光谱系统，采用空心激光原位捕捉超细悬浮颗粒物，协同激光诱导击穿拉曼光谱进行超细大气颗粒物原位在线多组分分析。在此基础上，重点研究超细大气颗粒物在空心光场中的受力机制和大气颗粒物上的激光诱导等离子体产生与演化机制，提高超细大气颗粒物捕获的稳定性和激光诱导击穿拉曼光谱的信噪比。进一步发展复杂光谱解析方法，快速准确提取激光诱导击穿光谱与拉曼光谱，最终实现单个超细大气颗粒物实时原位多组分现场分析。本项目将为揭示超细大气颗粒污染物的形成机制以及推断污染物的来源提供新思路和新方法。

超细大气颗粒物污染严重危害人类健康，已成为全球关注的热点问题。如何实时原位分析单个超细悬浮颗粒物的元素和分子组成以及中间自由基是大气颗粒污染物精准溯源与综合防控的主要难题和技术瓶颈。本项目从单个超细悬浮颗粒物原位在线多组分同时分析的实际需求出发，进行了以下研究工作：（1）构建了激光捕获协同激光诱导击穿光谱系统，采用热致非线性效应导致的交叉相位调制技术得到尺寸可调的空心光束，进一步将空心光束准直聚焦后进行颗粒物原位捕捉，最后利用激光诱导击穿光谱对已经捕获的颗粒物进行原位多组分分析。（2）研究了颗粒物的捕获稳定性和捕获效率与颗粒物尺寸、颗粒物的吸光度、激光功率、空心光束尺寸的关系，明确了超细大气颗粒物在空心光场中的受力机制，并发展了一种三维操控颗粒物的方法，即通过改变空心光束尺寸可以使颗粒物沿着激光传播方向前后移动，通过旋转楔形棱镜可以实现颗粒物在垂直光传播方向的平面上进行旋转。这就为颗粒物的原位分析奠定了基础。（3）研究了大气颗粒物激光诱导等离子体产生与演化机制，证实了大气颗粒物上等离子产生的“二步”机制，即激光首先激发空气产生空气等离子体，空气等离子体进一步激发颗粒物产生颗粒物等离子体。这就为提高和优化激光诱导击穿光谱的信噪比提供了重要的参考和依据。（4）以炭黑颗粒物为样品，模拟大气颗粒物吸附过程，使其吸附不同浓度的多种重金属污染物。对吸附了重金属污染物的炭黑颗粒进行原位捕获和单颗粒多组分分析，优化实验参数，获得了高信噪比的单颗粒激光诱导击穿光谱。（5）基于随机森林算法发展了一种复杂光谱解析方法，利用多变量提取的思路实现了快速准确提取激光诱导击穿光谱，最终实现了单个炭黑颗粒上的多种重金属污染物的同时高精度定量分析。本项目提出并实现了单个大气污染物原位多组分同时高精度定量分析，将为揭示超细大气颗粒污染物的形成机制以及推断污染物的来源提供新思路和新方法。