Emissions of certain low vapor pressure-volatile organic compounds (LVP-VOCs) are considered exempt to volatile organic compounds (VOC) regulations due to their low evaporation rates. However, these compounds may still play a role in ambient secondary organic aerosol (SOA) and ozone formation. The LVP-VOCs selected for this work are categorized as intermediate-volatility organic compounds (IVOCs) according to their vapor pressures and molecular formulas. In this study, the evaporation rates of 14 select IVOCs are investigated with half of them losing more than 95% of their mass in less than one month. Further, SOA and ozone formation are presented from 11 select IVOCs and 5 IVOC-containing generic consumer products under atmospherically relevant conditions using varying radical sources (NO x and/or H 2 O 2) and a surrogate reactive organic gas (ROG) mixture. Benzyl alcohol (0.41), n-heptadecane (0.38), and diethylene glycol monobutyl ether (0.16) are determined to have SOA yields greater than 0.1 in the presence of NO x and a surrogate urban hydrocarbon mixture. IVOCs also influence ozone formation from the surrogate urban mixture by impacting radical levels and NO x availability. The addition of lab created generic consumer products has a weak influence on ozone formation from the surrogate mixture but strongly affects SOA formation. The overall SOA and ozone formation of the generic consumer products could not be explained solely by the results of the pure IVOC experiments.

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 irreversibly throughout the temperature/RH cycles, substantially modifying concentrations of the SOA constituents and forming new products. Further, the presence of water is found to enhance the SOA O/C ratios prominently during cooling (high RH). These findings have important implications for understanding the chemical evolution of SOA in the atmosphere through their lifetime and long-range transport.

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