SGER: Development of Scanning Electron Microscope Techniquesto Ascertain the Microscopic Mixing Characteristics of Atmospheric Aerosols

大多数大气颗粒的化学分析都是在散装样品上进行的。然而，颗粒组成的变化强烈影响大气转化、能见度降低和颗粒污染物的命运。此外，了解燃烧产物的微观混合特性对于理解燃烧中的颗粒形成至关重要。随着计算机控制的扫描和x射线探测器的发展，可以测量像碳这样轻的元素，扫描电子显微镜（SEM）在这方面有很大的应用前景。然而，需要做更多的开发工作，以确保元素分析准确地反映气溶胶的组成。本研究的目的是利用电子显微镜对大气气溶胶进行精确的单粒子分析。已知成分的单分散气溶胶将用于1)进行电子束对大气气溶胶主要成分损伤的研究，2)减少电子束损伤的测试方法，以及3)验证现有的定量方法。扫描电镜测量碳的潜力也将被评估。所开发的技术将来将用于确定决定气溶胶对水的吸收的元素特征。

Most chemical analyses of atmospheric particles are carried out on bulk samples. However, particle by particle variations in composition strongly influence atmospheric transformations, visibility degradation, and the fate of particulate pollutants. In addition, knowledge of the microscopic mixing characteristics of combustion products is essential to understanding particle formation in combustion. With the development of computer- controlled scanning and x-ray detectors which measure elements as light as carbon, the scanning electron microscope (SEM) has a great deal of promise for this application. However, more development work is needed to assure that the elemental analysis accurately reflects the composition of the aerosol. The goal of this research is to obtain accurate single particle analyses of atmospheric aerosols with an electron microscope. Monodisperse aerosols of known composition will be used to 1) conduct studies of electron beam damage to major components of atmospheric aerosols, 2) test methods to reduce beam damage, and 3) validate existing quantitation methods. The potential of the SEM for measuring carbon will also be assessed. The techniques developed will be used in the future to identify the elemental characteristics determining the uptake of water by aerosols.