Linking gas, particulate, and toxic endpoints to air emissions in the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM)

Abstract. Chemical mechanisms describe the atmospheric transformations of organic and inorganic species connect air emissions to secondary such as ozone, fine particles, hazardous pollutants (HAPs) like formaldehyde. Recent advances in our understanding several chemical systems shifts drivers chemistry warrant updates used transport models Community Multiscale Air Quality (CMAQ) modeling system. This work builds on Regional Atmospheric Chemistry Mechanism version 2 (RACM2) develops Multiphase (CRACMM) 1.0, which demonstrates a fully coupled representation leading ozone aerosol (SOA) with consideration HAPs. CRACMMv1.0 includes 178 gas-phase species, 51 particulate 508 reactions spanning heterogeneous pathways. To support estimation health risks associated HAPs, nine CRACMM cover 50 % total cancer 60 non-cancer emission-weighted toxicity estimated for primary HAPs from anthropogenic biomass burning sources US, coverage higher (> 80 %) when formaldehyde acrolein are considered. In addition, new mechanism were added based importance their aerosol, or burden reactive carbon (ROC): sesquiterpenes, furans, propylene glycol, alkane-like low- intermediate-volatility compounds (9 species), oxygenated (16 aromatic hydrocarbons (2 slowly reacting carbon. Intermediate- lower-volatility increase ROC by 40 compared current operational mechanisms. Autoxidation, reaction particularly effective producing SOA, was C10 larger alkanes, hydrocarbons, monoterpene including second-generation aldehydes. Integrating radical SOA put additional constraints both enabled implementation previously unconsidered pathways phenolic furanone compounds, predicted account ∼ 30 hydrocarbon under typical conditions. found span atmospherically relevant range number, number oxygens per carbon, oxidation state slight high bias hydrogens total, 11 emitted implemented precursors CMAQv5.3.3 representations, resulting bottom-up prediction is required accurate source attribution design control strategies. available CMAQv5.4.