大气细颗粒物中毒性有机物分子水平组分分析：基于超高分辨质谱的研究

Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICRMS) provides unequaled resolving power and mass accuracy among all mass spectrometers. The extreme resolving power and mass accuracy of FT-ICRMS allows characterization of complex organic mixtures at the molecular level through accurate molecular mass determination. This has been plentifully demonstrated in characterizing natural organic matter derived from aqueous environments. Its applications in characterizing atmospheric organic aerosols have only emerged in the past few years. The project team has made the first few exploratory UHRMS studies in probing Chinese aerosols, revealing unprecedented molecular composition information. In this project, we propose to tap into the combined expertise of the project team in aerosol chemistry and ultra-high resolution mass spectrometric analysis to study the molecular composition of PM2.5 collected in the Pearl River Delta region and in a Beijing suburban area and select combustion source aerosols, and the focus will be placed on organic compound groups of either known carcinogenic toxicity, such as polycyclic organic compounds (PAHs), oxygenated PAHs, nitro-PAHs, nitrogen-containing aromatic compounds, or known to be involved in generating reactive oxygen species (ROS) in lung cells, such as quinones, and alkaloids. By seeking suitable modes and methods of ionization methods, the full range of these compound groups in the mass range of 100-1000 will be identified by taking advantage of the unique MS capability of FTICR-MS. Typical PM2.5 samples from the two sampling areas will be selected using our knowledge of major chemical constituents and PM sources. This project will produce unique sets of organic molecular composition data of typical Chinese PM2.5 that are yet unable to be achieved by other analytical techniques. Such information fills in a fundamental knowledge gap in elucidating the health effects by PM2.5.

傅里叶变换离子回旋共振质谱（FT-ICR MS）具有超高质量分辨能力和质量精确度，可以实现从分子水平表征复杂有机混合物的组成。FT-ICR MS在研究大气有机气溶胶的分子组成的应用近年来才开始。我们拟利用项目组在气溶胶化学和超高分辨质谱分析方面积累的多年经验研究大气细粒子以及部分燃烧源气溶胶的分子组成，重点着眼于具致癌毒性的有机化合物组，如多环芳烃、含氧多环芳烃、硝基多环芳烃和含氮芳香化合物；或能在肺部细胞中促进活性氧生成的有机化合物组，如醌类化合物和生物碱类。我们将探索合适的离子化方法，结合FT-ICR MS对目标有机化合物组实现分子层次上的解析。项目组将基于对气溶胶主要化学组分及污染源的认识，选取珠三角地区和北京一郊区点具有代表性的大气细粒子样品进行FT-ICR MS分析。本项目将首次获得多套典型中国大气细粒子毒性有机成分的分子组成数据，填补大气细粒子健康效应方面相关知识体系的空白。

大气细粒子对人体健康有众多负面影响，然而我们对PM2.5中不同组分的毒性却知之甚少，一个重要原因是对分子水平的化学组成所知有限。而傅里叶变换离子回旋共振质谱（FT-ICR MS）具有超高质量分辨能力和质量精确度，可以实现从分子水平表征复杂有机混合物的组成。本项目致力于利用FT-ICR MS，对北京和珠三角大量PM2.5样品，表征毒性有机物。.我们在珠三角4个采样站采集了2年PM2.5样品，和在北京郊区采样站采集了1年PM2.5样品。对所采集样品进行的化学分析包括主成分、一次源示踪物和二次有机气溶胶(SOA)示踪物等。利用详细的源示踪物信息，对北京样品进行了PMF源解析。解析出北京采样点共有10个源：生物质燃烧、烹饪源、汽车尾气、燃煤、尘土；硫酸盐二次源、硝酸盐二次源、异戊二烯的SOA、β-丁香烯的SOA、甲苯的SOA。.根据源示踪物浓度与源解析结果，挑选出20个北京样品和24个珠三角样品进行FT-ICR分析。样品采用二氯甲烷提取毒性有机物，经甲酸铵辅助ESI+离子化，成功检测出大量的分子式（一个样品最高约7000个分子式），包括多环芳烃(PAHs)、含氧PAHs、硝基PAHs和含氮芳香化合物。实验检测到众多碳数高达40和不饱和度高达30的PAHs，并且不饱和度高的PAHs在大部分样品中检测到，说明它们在大气中很重要，而且它们的存在可以用燃烧产生PAHs的机理解释。发现硝基PAHs分子数量与NO2污染浓度和母体PAHs分子数有相同的趋势，暗示硝基PAHs的产生与这两者有密切关系。发现加与不加甲酸铵的ESI+是互补的离子化方法；二氯甲烷提取极性较低、碳链较长的毒性有机物；而水可以提取氧原子多、极性高、碳链较短毒性有机物，两种溶剂提取液的同时分析可以给出覆盖比较全面的有机成分。.项目执行过程中，我们对利用多种示踪物进行源解析有了更深的了解，以及对萃取的溶剂和离子源的选择有了更深的了解。本项目首次获得了多套典型中国大气细粒子毒性有机成分的分子组成数据，填补了大气细粒子健康效应方面相关知识体系的空白。本研究的成果可以为PM2.5中毒性成分的组成提供重要信息。