基于单颗粒分析的大气一次棕碳颗粒物的来源识别与老化机制研究

棕碳是大气中除黑碳之外另一类重要的吸光性物质，其来源、分布和光学特性是当前气溶胶领域的研究热点。然而，目前针对华北冬季灰霾大气中丰富的一次源棕碳颗粒的微观表征仍然缺乏。本项目拟基于多种微观技术手段识别纳米级一次棕碳颗粒并对其在大气输送过程中的微观特征变化进行系统分析。首先，在我国华北的邯郸农村和北京城区布设采样点，收集民用煤和生物质燃烧新鲜排放和经大气传输老化过程的一次棕碳单颗粒样品；其次，综合利用透射电镜和多功能纳米红外光谱仪等多种手段分析一次棕碳颗粒在不同大气环境中的丰度、形貌、粒径、化学组分、混合状态和复折射率等特征，揭示不同来源的一次棕碳颗粒在大气传输过程中的老化机制；最后，构建不同老化程度的一次棕碳颗粒微观模型，并利用Mie理论模型探究老化过程对棕碳颗粒光学特性的影响规律。本项目将为理解一次棕碳颗粒对华北冬季灰霾形成的作用机制提供直接证据，为更好地评估棕碳的气候效应提供观测依据。

Brown carbon (BrC) has been proved to be another important light-absorbing substance in the atmosphere besides black carbon, and its source, distribution, and optical properties are the hot scientific topics in the field of aerosol research. However, the microscopic characterization of primary BrC is still lacking. This project plans to select the Handan rural site and the Beijing urban site in the NCP, which are affected by the local fresh emission and regional transport of polluted air masses, respectively. Field observations will be simultaneously conducted during the heating season to collect individual particle samples. The individual particle samples collected at the two sites will be analyzed using transmission electron microscopy and nanoIR spectrometer to identify primary BrC particles and characterize their composition, morphology, particle size, mixing state, refractive index, and relative abundance. By comparing the difference of microscopic information of primary BrC particles at the two sites, we intend to acquire the key parameters to identify the sources of primary BrC particles, reveal the aging mechanism of primary BrC particles in atmospheric transportation. Furthermore, the Mie theory model will be used to calculate the optical properties of aged BrC particles at the two sites to clarify the influence of aging processes on the optical characteristics of BrC. This project will be helpful to further understand the micro-characteristics of BrC and its roles in winter haze formation in the NCP and further provide an observation basis for assessing the climatic effects of BrC in China.