Aqueous Chemistry of Organic Peroxy (RO2) Radicals

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

This project is funded by the Environmental Chemical Sciences Program in the Division of Chemistry. The research team (led by Professor Jesse Kroll and Professor William Green) will carry out experimental and modeling studies of the chemical reactions of organic peroxy radicals in atmospheric droplets. The atmosphere includes a wide range of organic (carbon-containing) compounds, emitted from sources such as vehicles, wildfires, and plants, and these undergo chemical reactions during their time in the atmosphere. Nearly all these reactions make organic peroxy radicals, highly reactive chemicals whose subsequent reactions help determine the impact of the organic compounds on air quality and climate. Most past studies of peroxy radicals have focused on their chemistry in the gas phase, but their chemistry in cloud droplets and fine particles is less well understood. Therefore, this project will study the chemical reactions that these radicals will undergo within liquid water. Laboratory studies will measure reaction products under different atmospheric conditions, and computational studies will focus on predicting reaction rates and products. Graduate and undergraduate students will be involved in this research, and the team will participate in MIT-wide research opportunity programs aimed at students from traditionally underrepresented groups. The aim of this project is to gain a predictive, mechanistic understanding of the chemistry of organic peroxy (RO2) radicals in the atmospheric aqueous phase (cloud droplets and deliquesced aerosol particles). The project will examine aqueous-phase RO2 chemistry in detail, via both laboratory experiments (to measure reaction product distributions) and computational studies (to predict reaction kinetics, mechanisms, and solvent effects). Laboratory work will center on the OH oxidation of multifunctional, water-soluble species, with careful control of reaction conditions (chemical environment, RO2 co-reactants) and the use of online mass spectrometry to measure reaction products in real time. Studies will be carried out first in the dilute bulk aqueous phase, then in the concentrated (high ionic strength, low pH) bulk aqueous phase, and finally in deliquesced particles. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.