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

从直接的气溶胶气候效应来看，大气气溶胶吸收是影响太阳能量平衡的主要因素之一。吸收主要由三种主要化合物推动，烟尘、矿物粉尘和褐碳。然而，这些人为的和天然的化合物变得有效的相对量现在是众所周知的。因此，本提案的目的是在电子显微镜对许多单一颗粒的化学成分和结构进行量化的基础上，量化烟尘、有机碳和矿物粉尘的吸收效果。作为感兴趣的区域，地中海东部之所以被选中，是因为在春季，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最复杂混合物盛行。拟议的工作将结合第三方资助的飞机和地面测量活动进行，该活动提供了一个独特的机会，可从第三方获取大量大气、气溶胶和云量测的有关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：将根据化学性质确定气溶胶颗粒类型并对其进行量化。化学成分的粒度分布将通过2.5-微米以下气溶胶颗粒的相对化学成分和单独的粒度分布测量，以及直接通过专用的大颗粒收集技术来估计。B)分成挥发性/耐火性成分：根据电子显微镜，挥发性和耐火性成分将在单个颗粒内进行识别和量化。将确定耐火材料的类型。C)基于单个颗粒的粉尘/烟尘吸收分配的评估：老化的气溶胶颗粒的吸收分数将通过其化学和形态特性来确定。吸收组分的体积贡献将通过图像分析和元素映射来确定。相应的吸收颗粒数丰度将被用来确定粉尘和烟尘的贡献。烟尘颗粒的微观结构和化学成分将被用来确定主要烟尘来源的贡献。D)探索粉尘来源和粉尘吸收之间的潜在联系：通过粉尘化学成分模拟的吸收将与粉尘来源有关，其依据是一年一次的气溶胶成分时间序列，以便捕捉季节周期。综上所述，拟议的项目将在吸收分配、污染/混合环境中粉尘对辐射强迫的潜在贡献、与粉尘来源的可能联系以及烟尘来源分配方面产生新的和详细的见解。

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.