【作者】 程远；

【导师】 贺克斌；

【作者基本信息】 清华大学 ， 环境科学与工程， 2011， 博士

【摘要】 含碳气溶胶包括有机碳（OC）和元素碳（EC），在不同地域尺度上对人体健康、能见度与灰霾、大气棕色云、辐射平衡与气候变化都有重要影响，因而已成为大气环境研究领域的国际前沿和热点；但是在其采样和分析这两个最为基础的关键环节中尚存在一系列迫切需要解决的关键科学问题。本研究联合运用多通道平行采样技术和溶蚀器技术以及多种分析手段，研究了含碳气溶胶的采样和热-光学分析方法。研究结果对观测值的改善和标准方法的形成都具有十分重要的意义。根据对VOCs的去除效果、有效时间、比表面积等因素，选取蜂窝状活性炭溶蚀器开展了采样方法的研究。针对溶蚀器修正法，定量评价结果表明，本研究选用的溶蚀器能够有效消除正偏差，而且不会引入颗粒物的扩散损失、活性炭的污染等新的采样问题。针对后置石英膜修正法，后置膜OC来源的定量分解结果表明，在双层石英膜串联的采样方法中，后置膜OC虽然仅来自VOCs，但是只有在双层膜都达到吸附平衡的情况下才能较为准确地表征正偏差；在Teflon膜-石英膜串联的采样方法中，后置膜OC也来自挥发的颗粒态有机物，因此会高估正偏差。根据现有方法的主要区别，从升温程序和光学修正两个方面研究了热-光学分析方法。升温程序主要通过系统偏差和提前分割对OC、EC浓度产生影响，而且生物质燃烧的贡献会增强OC、EC浓度与升温程序的响应关系。如果惰性阶段峰值温度在580℃（IMPROVE-A升温程序）的基础上再升高，就有可能发生EC的提前解析，并导致OC浓度被高估、EC浓度被低估。OC、EC浓度与光学修正方法的响应关系主要和二次有机气溶胶（SOA）有关。基于透射修正的OC/EC比值能够反映SOA的贡献，但是基于反射修正的OC/EC比值和SOA不相关，说明透射修正更为合理。研究发现，EC也是化学组成十分复杂的混合体，而且在惰性环境中也能发生解析，说明OC、EC在热学性质方面并不存在明确的分界线。此外，发现水溶性有机物也具有吸光性，为论证棕色碳的存在提供了新的依据。更多还原

【Abstract】 Carbonaceous aerosol, consisting of organic carbon (OC) and elemental carbon(EC), has been the focus of extensive studies due to its complex effects on multiplegeographical scales, such as human health, visibility/haze, atmospheric brown clouds,radiative forcing/climate change; however, its sampling and analysis, which arefundamental to further studies, are still facing substantial challenges. In this work, thesampling and thermal-optical analysis methods of carbonaceous aerosol wereinvestigated based on a multi-channel sampler, an organic denuder, and multipleanalysis approaches. The results will be highly relevant in the improved measurement ofcarbonaceous aerosol and the establishment of standardized methods.With respect to the performance for removing VOCs, useful time and specificsurface area, an activated-carbon honeycomb denuder was selected for investigating thesampling methods. When using the denuder approach, it was demonstrated that thedenuder could effectively remove the positive artifact, and would not introduceadditional artifacts such as the particle loss due to diffusion and the contamination ofactivated-carbon material. When using the backup quartz approach, results from theapportionment of backup OC showed that all of the backup OC in the sequential-quartzmethod was from VOCs, however, it could reliably estimate the positive artifact onlywhen both the front and backup quartz filter reach equilibrium with VOCs; the backupOC in the Teflon-quartz in series method also included volatilized particulate OC, as aresult, would overestimate the positive artifact.The thermal-optical methods differ mainly with respect to temperature protocol andcharring correction method, which are investigated in this work. The discrepancybetween OC or EC concentrations defined by different temperature protocols werecaused by the systemic artifact and the early split, moreover, emissions from biomassburning would increase the discrepancy. Premature evolution of EC was found to begin when the peak inert mode temperature was increased from580℃(IMPROVE-Aprotocol), which would result in the overestimation of OC and the underestimation ofEC. The discrepancy between OC or EC concentrations defined by different charringcorrection method was mainly related to secondary organic aerosol (SOA). The OC toEC ratio calculated by results from tranmittance correction included importantinformation about the extent of SOA production, whereas the OC to EC ratio based onreflectance correction exhibited no correlation with SOA, indicating the transmittancecorrection method was more reliable.It was demonstrated that EC was also a complex aggregate of different species, andcould also evolve in the inert atmosphere, indicating that a specific boundary betweenOC and EC does not exist. Moreover, water-soluble organic carbon would alsocontribute to the light absorption, providing new evidence for the atmospheric presenceof brown carbon.更多还原