California Air Resources Board

Principal Investigator/Author: David Cocker

Contractor: University of California, Riverside

Contract Number: 18RD009

Project Status: Completed

Relevant CARB Programs: Atmospheric Processes

Topic Areas: Chemistry & Reactivity, Modeling

Research Summary:

A major fraction of fine particulate matter (PM2.5) in the atmosphere is comprised of secondary organic aerosol (SOA), which is created in the atmosphere from the oxidation of a variety of volatile organic compounds (VOCs). Recent research concluded that non-vehicular sources (e.g., volatile consumer products or food-derived cooking emissions) of reactive gas-phase organics in urban areas may now contribute a larger fraction of the total VOC emissions. These non-vehicular sources must be better characterized to fully understand their impact on ambient ozone (O3) and SOA formation. The primary effort of this research project is to optimize SOA chamber experiments that can be used to evaluate and improve SOA formation mechanisms in regulatory or scientific modeling applications. The investigators will review the existing chamber database, perform experimental comparison of SOA yield determination for several key SOA systems by conducting identical VOC oxidation experiments in two chamber facilities: California Institute of Technology (Caltech) and University of California, Riverside (UCR). The proposed research project will also characterize SOA precursors that are emitted from a variety of VOC sources, such as consumer products (CPs), and the chemicals to be tested will be selected based on their chemical composition and potential importance to both ozone and SOA formation. The resulting environmental chamber datasets will be used to evaluate the predictive capabilities of the SOA formation mechanisms using selected SOA models. The results from this project will aid in the improvement of regulatory air quality models used to develop the State Implementation Plan and enhance our ability to develop regulatory strategies that reduce ambient O3 and PM2.5.

Keywords: secondary organic aerosol (SOA), volatile organic compounds (VOCs), particulate matter (PM), emissions, emission sources, ozone (O3), chamber experiment, modeling