Analytical Chemistry Seminar: Alma Hodzic
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
Rethinking Secondary Organic Aerosol formation and removal in 3D models based on explicit chemistry
Dr. Alma Hodzic, NCAR, Boulder, CO
Current secondary organic aerosol (SOA) parameterizations fail to explain the observed amounts and properties of tropospheric SOA, which results in large uncertainties in their effects on radiation and climate. We use the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to simulate SOA gas-phase chemistry in various environments (urban, forest, low/high NOx). Our results show that GECKO-A predicts significant SOA mass growth in urban plumes, and formation of less volatile and more soluble organic products, than predicted by parameterizations typically used in 3D models. The results also indicate that atmospheric processing of gas-phase oxidation intermediates, which are poorly represented in 3D models, can significantly modulate SOA formation and lifetime. We discuss the possible effect of dry deposition and organic photo-fragmentation reactions on condensable organic vapors and SOA. We derive new parameterizations that reproduce GECKO-A behavior in terms of volatility, yields and solubility for use in 3D models. These parameterizations are applied at regional and global scales to re-evaluate SOA concentrations, burden and removal.