| Indoor air quality (IAQ) is associated with human health due to people spending most of their time indoors. Secondary organic aerosol (SOA) formation is an important source of fine airborne particles, which can cause acute airway effects and decreased lung function. SOA is a product of reactive organic gas (ROG) ozonolysis, which can be parameterized by the aerosol mass fraction (AMF). The AMF is the ratio of SOA formation mass to the reacted ROG mass, and it is positively correlated with the total organic aerosol mass concentration.;alpha-Terpineol is a terpenoid that can have a strong emission rate indoors owing to consumer product usage. It reacts strongly with oxidants such as ozone, hydroxyl radical (OH), and nitrate radical (NO3), where those radicals are produced indoors due to ozone reaction with alkenes or nitrogen dioxide (NO2), respectively. Due to the fast reaction rates of alpha-terpineol with these oxidants, SOA formation has the potential to increase in-door fine particle concentrations. However, SOA formation from alpha-terpineol has not been systematically quantified.;Therefore, the purpose of this work was to quantify SOA formation owing to alpha-terpineol ozonolysis, for two sets of experiments, one without and one with NO2 present. In the first set of 21 experiments, the SOA formation initiated by reacting 6.39 to 226 ppb alpha-terpineol with high ozone (~25 ppm) to ensure rapid and complete ozonolysis for high (0.84 h--1), moderate (0.61 h--1) and low (0.36 h--1) air exchange rates (AER) was studied in a stainless steel chamber system. The resulting SOA mass formation was parameterized with the AMF for all experiments. The impact of reacted alpha-terpineol and AERs on AMFs as well as the SOA size distribution was investigated, and different AMF models (one-product, two-product, and volatility basis set) were fit to the AMF data. Predictive modeling investigated the impact of the SOA formation from alpha-terpineol ozonolysis in residential indoor air.;Furthermore, a second set of 21 experiments in a Teflon bag operated as semi-batch reactor explored the impact of NO2 at 0 to 2000 ppb on SOA formation from alpha-terpineol ranging from 20 ppb to 200 ppb with excess ozone (~25ppm). In this system, ozone can either initiate reactions with alpha-terpineol to produce organic peroxy radicals (RO2•) or react with NO2 to produce NO3, which can react with alpha-terpineol. For analysis of results, we classified experiments by logarithmic spacing into four groups according to the initial ratio of VOC/NO2 values. SOA mass was again parameterized by the AMF as a function of the organic aerosol concentration. The impact of VOC/NO2 on SOA mass as well as the SOA size distribution was investigated, and the SOA composition for each grouping of experiments was elucidated by the kinetic modeling.;Finally, this SOA formation was put into context using the 'secondary intake fraction' (siF), which is a developed metric that evaluates SOA exposure during various human activities. The siF is defined as the up-taken mass of a secondary product for an exposed individual per unit mass of primary product emitted during human residential activities, over a given exposure time. The siF for individual intake was evaluated for SOA formation from d-limonene, alpha-terpineol, or alpha-pinene ozonolysis in five residential scenarios, including: I. Constant emission, II. Pulse emission, III. Surface cleaning, IV. Solution cleaning, and V. Skin cleaning. For a given input set, a transient model was used to predict SOA concentrations and the siF, using inputs cast as probability distributions within a Monte Carlo approach. Multiple linear regression techniques were applied to fit siF values for the five scenarios, for use in sensitivity analyses. Also, the multiple linear regression results can be used to predict the siF and the potential for human intake of SOA within exposure models. |
