The effect of environmental conditions at particle genesis stage of secondary organic aerosol formation

University Of Vermont & State Agricultural College, Burlington VT

Investigators

Abstract

This project is jointly funded by the Environmental Chemical Sciences Program in the Chemistry Division and the Atmospheric Chemistry Program of the Atmospheric and Geospace Sciences Division. Professor Giuseppe Petrucci of the University of Vermont investigates the role of water (humidity) in the formation and ageing of organic particles in the atmosphere. Leafy trees and plants release volatile organic compounds during photosynthesis and respiration. These compounds react with pollutants like ozone to produce the majority of organic particles in the atmosphere. Professor Petrucci and his group explore how humidity influences the chemical composition of particles, the phase (liquid or solid) of the particle, and their ability to scatter and/or absorb light. Understanding the chemical changes that these particles undergo once they are formed is crucial for understanding their impact on the atmosphere. This research is leading to a better understanding of the troposphere, the lowest part of the atmosphere, in terms of effects on human health, visibility, and climate. Training is provided to graduate and undergraduate students. The research team also carries out outreach to K-12 students at various levels through the University of Vermont Chemistry Camp. Determining the composition of organic particles in the atmosphere is challenging because each particle may contain hundreds of different molecules. In addition, the types of molecules may change during the particle's time in the atmosphere, which is typically five to seven days. Professor Petrucci and his group develop a novel environmental chamber setup for the study of chemical processes during particle formation. This chamber allows the use of mass spectrometric and spectroscopic techniques to study the particle's composition. These techniques also provide information on changes in particle composition due to changes in reaction conditions, like humidity. Further, using a separate approach, the researchers impinge particles at a hard surface and count how many bounce off compared to how many stick. Solid particles bounce, while liquid particles stick. The phase of the particles is compared with particle composition. Ultimately, the goal of this research is to predict the physical and optical properties of organic particles based on their chemical composition. This information is used to develop models that describe the effect of aerosols on the Earth's radiation balance and the formation and properties of clouds. The graduate, undergraduate and high school students working with Professor Petrucci gain experience in sophisticated experimental methods, and skills in chemical reaction mechanisms, aerosol science and analytical methodology.