Indoor secondary organic aerosol formation : influence of particle controls, mixtures, and surfaces
Year: 2009
Type: article
Abstract: Ozone (O₃) and terpenoids react to produce secondary organic aerosol (SOA). This work explored novel ways that these reactions form SOA indoors, with five \ninvestigations, in two categories: investigations of (i) the impacts of particle controls on \nindoor SOA formation, and (ii) two fundamental aspects of indoor SOA formation. \nFor category (i), two investigations examined the particle control devices of ion \ngenerators, which are air purifiers that are ineffective at removing particles and emit \nozone during operation. With a terpenoid source present (an air freshener), ion \ngenerators acted as steady-state SOA generators, both in a 15 m³ chamber and 27 m³ \nroom. The final investigation in category (i) modeled how heating, ventilating, and air-conditioning \n(HVAC) systems influence SOA formation. Influential HVAC parameters \nwere flow rates, particle filtration, and indoor temperature for residential and commercial \nmodels, as well as ozone removal by particle-laden filters for the commercial model. \nFor category (ii), the first investigation measured SOA formation from ozone \nreactions with single terpenoids and terpenoid mixtures in a 90 L Teflon-film chamber, at \nlow and high ozone concentrations. For low ozone, experiments with only d-limonene \nyielded the largest SOA number formation, relative to other mixtures, some of which had \nthree times the effective amount of reactive terpenoids. This trend was not observed for high ozone experiments, and these results imply that ozone-limited reactions with d-limonene \nform byproducts with high nucleation potential. The second investigation in category (ii) explored SOA formation from ozone \nreactions with surface-adsorbed terpenoids. A model framework was developed to \ndescribe SOA formation due to ozone/terpenoid surface reactions, and experiments in a \n283 L chamber determined the SOA yield for ozone/d-limonene surface reactions. The \nobserved molar yields were 0.14–0.16 over a range of relative humidities, and lower relative humidity led to higher SOA number formation from surface reactions. Building materials on which ozone/d-limonene surface reactions are predicted to lead to \nsubstantial SOA formation are those with initially low surface reactivity, such as glass, \nsealed materials, or metals. The results from category (ii) suggest significant, previously unexplored mechanisms of SOA number formation indoors.
Author: Michael S. Waring
Language: English
Subfield: Health, Toxicology and Mutagenesis
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2147675325