Modeling the role of extremely low-volatile organic compounds in β-caryophyllene secondary organic aerosol formation

Sesquiterpene emitted from nature is the main precursor for secondary organic aerosol (SOA) formation. β-caryophyllene (BCA) is the most common sesquiterpene. Autoxidation of BCA oxidation products may lead to the rapid formation of extremely low-volatile organic compounds (ELVOCs), and it could be one of the dominant SOA formation pathways. However, until now the BCA SOA formation mechanisms are missing an autoxidation pathway. In this work, we develop a semi-explicit peroxy radical autoxidation mechanism for the production of ELVOCs from the oxidation of BCA with two major oxidants (O₃ and NO₃) under dark conditions and couple it to the Master Chemical Mechanism (MCMv3.3.1). Here, SOA originating from BCA is simulated under varying environmental conditions (temperature, humidity, and NO_x levels) reported in several BCA chamber experiments. Simulations are performed with the SSH-Aerosol model accounting for multiphase chemistry, ELVOC nucleation, and condensation/evaporation. Our mechanism demonstrates a very good agreement between the modeled and observed SOA mass concentrations and size distribution.