Desert aerosol aging in polluted environments and impact on its optical properties

在气溶胶直接气候效应方面，大气气溶胶吸收是影响太阳能量平衡的主要效应之一。吸收主要由三种主要化合物驱动：煤烟、矿物粉尘和棕色碳。然而，这些人为的和天然的化合物起作用的相对数量现在是众所周知的。因此，本提案旨在通过电子显微镜对许多单粒子的化学成分和结构进行量化，从而对烟灰、有机碳和矿物粉尘的吸收效果进行量化。之所以选择东地中海作为研究区域，是因为该地区春季生物质燃烧气溶胶、人为排放、海洋气溶胶以及非洲和亚洲矿物的混合物最为复杂。拟议的工作将与第三方资助的飞机和地面测量活动一起进行，该活动提供了独特的机会，可以在第三方提供的大量大气、气溶胶和云测量中获取感兴趣区域内和上空的样本。拟议项目的主要目标是：A)气溶胶成分的一般特征：气溶胶颗粒类型将通过化学性质确定并量化。化学成分的尺寸分布将通过相对化学成分和2.5µm以下气溶胶颗粒的单独尺寸分布测量以及直接通过专门的大颗粒收集技术来估计。B)挥发性/难降解组分的划分：基于电子显微镜，将在单个颗粒中识别和定量挥发性和难降解组分。耐火材料的种类将被确定。C)基于单个颗粒的粉尘/烟尘吸收分配评估：老化气溶胶颗粒的吸收部分将通过其化学和形态特性来识别。吸收成分的体积贡献将通过图像分析和元素映射来确定。根据吸收粒子的数量丰度来确定粉尘和煤烟的贡献。烟尘颗粒的微观结构和化学成分将用于确定主要烟尘源的贡献。D)探索粉尘源和粉尘吸收之间的潜在联系：通过粉尘化学成分建立的吸收率模型将与粉尘源相关，该模型基于一年的气溶胶成分时间序列，以便捕捉季节周期。综上所述，该项目将在吸收分配、污染/混合环境中潜在的粉尘对辐射强迫的贡献、与粉尘源和烟尘源分配的可能联系等方面产生新的详细见解。

Atmospheric aerosol absorption is one of the major effects influencing the solar energy balance in terms of direct aerosol climate effect. Absorption is mainly driven by three major compounds, soot, mineral dust, and brown carbon. The relative quantities, in which these anthropogenic and natural compounds become effective, are, however, now well known. The present proposal aims therefore at a quantification of the absorbing effects of soot, organic carbon and mineral dust based on the quantification of the chemical composition and structure of many single particles by electron microscopy. As region of interest, the Eastern Mediterranean was selected because there in spring a most complex mixture of biomass burning aerosol, anthropogenic emissions, marine aerosol, and African and Asian mineral prevails. The proposed work will be performed in connection with a third-party-funded aircraft and ground-based measurement campaign, which offers the unique opportunity to obtain samples in and over the region of interest in connection with a wealth of atmospheric, aerosol and cloud measurement from third parties. Major goals of the proposed project are: A) General characterization of aerosol composition: Aerosol particle types will be identified by chemical properties and quantified. Size distributions of chemical composition will be estimated from relative chemical composition and separate size distribution measurements for sub 2.5-µm aerosol particles, as well as from a dedicated large particle collection technique directly. B) Partitioning into volatile / refractory components: Based on electron microscopy, volatile and refractory components will be identified and quantified inside single particles. Types of refractory materials will be identified. C) Assessment of dust / soot absorption partitioning based on single particles: The absorbing fraction of aged aerosol particles will be identified by their chemical and morphological properties. The volume contribution of the absorbing components will be determined by image analysis and element mapping. The according number abundance of absorbing particles will be used to determine the contribution of dust and soot. Soot particle microstructure and chemical composition will be used to determine the contribution of major soot sources. D) Exploring potential links between dust source and dust absorption: Absorption modeled through dust chemical composition will be related to dust source, based on a year-long time series of aerosol composition to allow for capturing seasonal cycles. Summarizing, the proposed project will yield new and detailed insights in absorption partitioning, potential dust contribution to radiative forcing in a polluted / mixed environment, possible connections with dust sources and soot source apportionment.