Compositional Evolution of Secondary Organic Aerosol as Temperature and Relative Humidity Cycle in Atmospherically Relevant Ranges

Abstract

Atmospheric secondary organic aerosols (SOA) play an important role in the global particulate matter budget, and their chemical compositions determine critical properties that impact radiative forcing and human health. During temporal and spatial transport, atmospheric particles undergo ambient temperature and relative humidity (RH) changes or cycles that may transform their chemical compositions. Here, we report compositional evolution of SOA from α-pinene ozonolysis in a smog chamber as the temperature and RH cycle within atmospherically relevant ranges (5–35 °C; 10–80% RH). The results suggest that the organic vapor condensation is limited during cooling, in contrast to volatility-based predictions, likely due to high viscosity of the α-pinene SOA particles and the potential enrichment of semivolatile products in the particle surface region. Combining a number of online and offline aerosol bulk and molecular-level measurements, we determine that particle-phase reactions occur reversibly and irreversibl...