Formation of photo-oxidants and processing of organic species in aerosol liquid water

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The goal of this project is to improve the understanding of how highly reactive, condensed phase species in the atmosphere influence the chemistry and composition of atmospheric particles. Many reactions in particles and droplets are driven by highly reactive photo-oxidants that are formed within the condensed phase when certain organic and inorganic molecules absorb sunlight. The results of this research will help to elucidate the role of these species in the formation, transformation, and loss of particulate organics and assist with regulatory efforts to reduce particulate matter air pollution.The objectives of the project are to: (1) Measure the concentrations and kinetics (i.e., formation rates and lifetimes) of the triplet states of light-absorbing organic compounds (3C*), singlet molecular oxygen (1O2*), and hydroxyl radical (•OH) in relatively dilute water extracts of fine particles collected over the course of a year in Davis, California; (2) Develop new methods to quantify photo-oxidant concentrations under the very concentrated aerosol liquid water conditions present in the ambient atmosphere; (3) Explore the importance of 3C* and 1O2* in transforming organic species in particles; and (4) Integrate the results to improve the community’s understanding of photo-oxidants in particles and drops. The principal investigators plan to work with a collaborator to model the particle- and gas-phase chemistry in biomass-burning plumes and explore the role of condensed phase photo-oxidants in the formation and evolution of organic aerosols.This effort includes the mentoring of a postdoctoral fellow and both graduate and undergraduate students, and activities with middle and high school students to improve their understanding of particulate matter air pollution.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.