This project is comprised of a series of studies to measure the uptake coefficients for semi-volatile organic compounds (SVOC) on secondary organic aerosols (SOA) formed from the oxidation of a variety of gas phase precursors. The rationale for these investigations is that SOA growth is better described by a kinetically limited mechanism than one based on equilibrium phase partitioning, and that uptake coefficients for various SVOC on typical atmospheric SOA are needed in order to model SOA growth more accurately. However, uptake coefficients data on SOA are limited. The activities therefore include studies of the generation and composition of SOA formed from oxidation of SOA precursors by nitrate radical or/and ozone inside a large-volume, slow-flow aerosol flow tube; studies of the uptake of organic nitrates and SVOC on SOA as well as studies of possible evaporation of SOA components using attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR); measurements of absolute uptake coefficients of organic nitrates and SVOC on SOA using a Knudson cell and a coated wall fast flow reactor; characterization of the uptake of organic nitrates and SVOC on self-assembled monolayers; and analysis of SOA using nano-secondary ion mass spectrometry (nano-SIMS). The research will yield information important in assessing the relative importance of kinetically limited mechanisms versus equilibrium partitioning in SOA growth.
Broader impacts include providing kinetic data and molecular insights on the uptake of semi-volatile organic compounds onto secondary organic aerosol, disseminating results broadly through publications, summer teacher workshops, hosted lab tours for students and the general public, visits of researchers to local schools, training of undergraduate and graduate students and postdoctoral fellows, continued involvement of underrepresented groups in the principal investigator's research activities, and development of new experiments for the undergraduate curriculum at UC-Irvine.
