Predicting the evolution of secondary organic aerosol (SOA) size distributions due to limonene ozonolysis in indoor environments

Aerosol diameter is important in determining its fate and transport. Indoors, the ozonolysis of terpenoids, such as limonene, yields secondary organic aerosol (SOA), which can range orders of magnitude in size. The generated SOA size distributions are affected by various processes, including nucleation, partitioning, coagulation, surface deposition, and air exchange; of these processes, only air exchange is not size resolved. Herein, a model was developed to predict the transient evolution of the SOA size distribution indoors due to limonene ozonolysis. The model simulates partitioning without requiring explicit knowledge of the chemical mechanism, because it instead combines the theory of the aerosol mass fraction (AMF = mass SOA formed/mass terpenoid reacted) with Fick's first law to predict the change in aerosol volume from SOA formation. We used experimental results for limonene ozonolysis from our previous work to evaluate and tune the model, and the model performed well according to standard indoor air quality model assessment methods. Its framework can be extended to other terpenoids, and its current form can be used to predict the implications of size resolved SOA formation due to ozonolysis of limonene, the most common indoor terpenoid. Further, a sensitivity analysis showed that air exchange could be one of the most influential mechanisms to control SOA indoors.