Hygroscopic Phase Transitions of Atmospheric Particles

这项工作的目的是了解与硫酸盐混合的复杂有机材料的化学和吸湿相变之间的联系。复杂的有机材料将包括实验室中不同类型的次级有机气溶胶(SOA)产生的材料，以及俄克拉荷马州大平原南部天然存在的材料(即野外活动)。第一个目标是测量SOA有机硫酸盐混合粒子的潮解相对湿度(DRH)和结晶相对湿度(CRH)。第二个目标是将有机成分的可变性与混合颗粒的相变行为的可变性联系起来。吸湿相变使气溶胶粒子在低非均相化学反应性和高非均相化学反应性状态之间以及光散射低和高光散射状态之间切换。由于最近的环境测量、建模和实验室研究的结合，这些影响正变得越来越量化。结果表明，大气颗粒物中的硫酸盐含量是理解和预测吸湿相变的基础。其他化学成分，如酸度、硝酸盐或有机物质也有调节作用。进一步取得进展的一个关键挑战是更好地了解有机材料对硫酸盐相变的影响；以前的实验室工作主要集中在硫酸盐与一种或几种有机分子的混合上。然而，大气颗粒物是由硫酸盐和多种不同类型的有机分子混合而成的。这种混合物的行为预计将与更简单的组成截然不同，特别是在相变方面，因为多组分的熵意味着，如果存在晶体-水相变，将只有硫酸盐的相变。夏季本科生项目将扩大未被代表的群体在科学中的参与。已经制定了从历史上的黑人学院和大学以及波多黎各大学进行招聘的计划。他还开发了一个气溶胶计算器网站，在这个项目中，首席调查员将继续开发该网站。其动机是创建一个对新学生(以及专业人员)有用的网站，以便仔细和彻底地理解气溶胶科学和技术的复杂性。该网站为学习和探索气雾剂的性质提供了现成的界面(即因特网浏览器等网络浏览器)。网站和网络浏览器的使用使该网站可以在世界各地访问，从而使这一教育工具得以广泛传播。

The objective of the work is to understand the connections between chemistry and hygroscopic phase transitions for complex organic materials mixed with sulfate. The complex organic materials will include both those produced by different types of secondary organic aerosol (SOA) in the laboratory and those naturally present in the Southern Great Plains, Oklahoma (i.e., field campaign). The first goal is to measure the values of the deliquescence relative humidity (DRH) and crystallization relative humidity (CRH) of mixed SOA organic-sulfate particles. The second goal is to connect the variability of the organic composition to the variability in the phase-transition behavior of the mixed particles. Hygroscopic phase transitions switch aerosol particles between states of lower and higher heterogeneous chemical reactivity and between states of lower and higher light scattering. These effects are becoming increasingly quantified as a result of a combination of recent ambient measurements, modeling, and laboratory studies. What emerges is that the sulfate content of atmospheric particles is the anchor point for understanding and predicting the hygroscopic phase transitions. Other chemical components such as acidity, nitrate, or organic material have a modulating influence. A key challenge for further progress is a better understanding of the effects of organic material on sulfate phase transitions; previous laboratory work has largely focused on sulfate mixed with a single up to several types of organic molecules. Atmospheric particles, however, consist of a mixture of sulfate with a multitude of different types of organic molecules. Such mixtures are expected to behave quite differently than simpler compositions, especially in regard to phase transitions, because the entropy of the multitude implies that crystal-aqueous phase transitions, when present, will be those solely of sulfate.A summer undergraduate project will broaden the participation of underrepresented groups in the sciences. A program is in place for recruitment from Historically Black Colleges and Universities and the University of Puerto Rico. He has also developed an AerosolCalculator website, and in this project the principal investigator will continue with its development. The motivation is to create a site useful for new students (as well as professionals) to develop a careful and thorough understanding of the complexities of aerosol science and technology. The website provides a ready interface (i.e., a web browser such as Internet Explorer) for the learning and exploration of the properties of aerosols. The use of a website and a web browser makes the site accessible worldwide, allowing for broad dissemination of this educational tool.