CAREER: Molecular Studies of Phase Separations and Internal Structure in Individual Particles

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

In this project, funded by the Environmental Chemical Sciences program of the Chemistry Division, Professor Andrew Ault of the University of Michigan is studying the properties of individual particles in the atmosphere. These particles can impact cloud formation and properties, as well as health. The tools used are advanced microscopic and spectroscopic characterization. Specifically, the project focuses on particles with two phases (organic and aqueous) and viscous/glassy particles recently observed in the atmosphere whose formation and properties are not well understood. Understanding how these particles change based on key atmospheric variables such as relative humidity and temperature will improve our ability to predict their formation, properties, and abundance in the atmosphere. This project focuses on the fundamental properties of mixed organic/inorganic particles through a series of laboratory studies in sealed environmental reaction cells coupled to two microscopes, a Raman microspectrometer and an atomic force microscopy with infrared (AFM-IR). The studies use a series of model systems (such as ammonium sulfate and dicarboxylic acids), as well a more complex mixtures, chamber-generated particles and particles from the atmosphere. The researchers probe differences within individual particles to understand microscopic changes in physical and chemical properties. Of particular interest are phase separations as a function of particle size, and acidity and reactivity in the microenvironments of phase-separated particles. An outreach program, the Detroit Research Internship Summer Experience (D-RISE), is being expanded. It enables participants to develop interactive activities, such as on particulate matter in the atmosphere, that are presented to classmates the following academic year. In addition to engaging the program participants, this also expands exposure to scientific research to underrepresented groups in the sciences at Detroit high schools. The broader impact of the studies of glassy and phase-separated aerosol are to understand if these particles take up water and nucleate cloud droplets, which is important for cloud formation and properties, as well as if they react with important gases in the atmosphere.