New Particle Formation and Growth Dynamics for ?-Pinene Ozonolysis in a Smog Chamber and Implications for Ambient Environments

Secondary organic aerosol (SOA) plays an important role in the Earth's energy balance and air quality. Understanding the formation of SOA accompanying the oxidation of volatile organic compounds (VOCs) remains incomplete because of the complex reactions and partitioning mechanisms. In this study, we investigated new particle formation (NPF) of SOA derived from alpha-pinene ozonolysis in the Harvard Environmental Chamber using the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) with the condensing species as two products, one of lower volatility (LVOC, 0.01 mu g m-3) and one of higher volatility (SVOC, 1.0 mu g m-3). A module for the classical nucleation theory was included. The surface tension (sigma), bulk diffusivity (Db), and mass accommodation coefficient (alpha) were varied until convergence between the simulated and observed particle number size distributions. alpha of LVOC was constrained as 0.03-0.1 with the reported sigma of alpha-pinene-ozonolysis-derived SOA and Tolman surface correction (similar to 23.0-27.5 mN m-1) and Db from 10-15.5 to >10-11 cm2 s-1. The observed particle number size distribution of alpha-pinene ozonolysis was well-simulated to derive the physical parameters, including sigma, Db, and alpha, suggesting the possible application to group the reported complex oxidation products and further application for other atmospheric-related oxidations for quantifying NPF.