| Abstract
| - This study examines the primary and secondary productsresulting from reactions initiated by adding ozone tocomplex mixtures of volatile organic compounds (VOC).The mixtures were representative of organic species typicallyfound indoors, but the concentrations tended to behigher than normal indoor levels. Each 4-h experimentwas conducted in a controlled environmental facility (CEF,25 m3) ventilated at ∼1.8 h-1. The mixture investigatedincluded 23 VOC (no O3), O3/23 VOC, O3/21 VOC (no d-limoneneor α-pinene), and O3/terpene only (d-limonene andα-pinene). The net O3 concentration was ∼40 ppb ineach experiment, and the total organic concentration was26 mg/m3 for the 23 VOC mixture, 25 mg/m3 for the 21VOC mixture, and 1.7 mg/m3 for the d-limonene and α-pinenemixture. When the 23 VOC were added to the CEFcontaining no O3, no compounds other than those deliberatelyintroduced were observed. When O3 was added to theCEF containing the 23 VOC mixture, both gas and condensedphase products were found, including aldehydes, organicacids, and submicron particles (140 μg/m3). When O3was added to the CEF containing the 21 VOC without thetwo terpenes (O3/21 VOC condition), most of the products thatwere observed in the O3/23 VOC experiments were nolonger present or present at much lower concentrations.Furthermore, the particle mass concentration was 2−7 μg/m3, indistinguishable from the background particleconcentration level. When O3 was added to the CEFcontaining only two terpenes, the results were similar tothose in the O3/23 VOC experiments, but the particle massconcentration (190 μg/m3) was higher. The results indicatethat (i) O3 reacts with unsaturated alkenes under indoorconditions to generate submicron particles and otherpotentially irritating species, such as aldehydes and organicacids; (ii) the major chemical transformations that occurredunder our experimental conditions were driven by O3/d-limonene and O3/α-pinene reactions; and (iii) the hydroxylradicals (OH) that were generated from the O3/terpenereactions played an important role in the chemicaltransformations and were responsible for approximately 56−70% of the formaldehyde, almost all of the p-tolualdehyde,and 19−29% of the particle mass generated in theseexperiments.
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