Application of the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM) to Simulation of Air Quality in the Northeast USA

BRYAN PLACE, Karl Seltzer, Chris Allen, Benjamin Murphy, K. Wyat Appel, Ivan Piletic, Emma D'Ambro, Rebecca Schwantes, Matthew Coggon, Sara Farrell, Emily Saunders, Lu Xu, Golam Sarwar, William Hutzell, William R. Stockwell, Ana Torres-Vasquez, Jonathan Pleim, Havala Pye, United States Environmental Protection Agency

     Abstract Number: 316
     Working Group: Carbonaceous Aerosol

Abstract
The Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM) aims to provide a transparent link between the emissions and transformations of reactive organic carbon (ROC) in the atmosphere. As such, one of the main achievements of the mechanism is to couple gas-phase reactions and products with the particle-phase and better represent atmospheric secondary organic aerosol (SOA) formation. In this work, we present an initial evaluation of CRACMM version 1.0 implemented within the Community Multiscale Air Quality (CMAQ) model using the Northeast USA Summer 2018 as the testing domain. We discuss the mechanism performance in context of previously well-established chemical mechanism such as Carbon Bond 6 and RACM2 and evaluate the model outputs against multi-network observations of ozone, organic carbon, particulate matter, and hazardous air pollutants. Box modeling is used to provide insight into how changes in the mechanistic representation of various systems affects the prediction of oxidants and precursors to SOA. We find that the CRACMM mechanistic representation of ROC chemistry including autoxidation, multigenerational oxidation, and treatment of semi-and intermediate volatility compounds produces levels of SOA similar to top-down algorithms. These initial evaluations thus indicate that CRACMM could provide a fully bottom-up replacement for empirical SOA parameterizations in CMAQ that can be used for source apportionment.