Generation and Quantification of Ultrafine Particles through Terpene/Ozone Reaction in a Chamber Setting

Abstract

Terpene/ozone reactions produce gas-and condensed-phase products and thus contribute to both indoor and outdoor aerosol. These reactions may be important in indoor settings, where terpenes are generated from indoor sources and ambient ozone can reach significant levels. Moreover, airway irritation has been observed in mice exposed to terpene oxidation products (OPs). The aim of this study was to characterize a system for generating and quantifying ultrafine particles formed through terpene/ozone reactions in preparation for inhalation toxicology experiments. Two common monoterpenes, α-pinene and d-limonene, and a hemiterpene, isoprene, were investigated. Ozone and gas-phase terpene were introduced continuously into a reaction flow tube, from which reaction products entered a plexiglass chamber. Particle number, mass, and size distribution (∼15-750 nm) were monitored in the chamber for various reactant concentrations and air exchange rates (AERs). In all experiments, ozone was the limiting reagent and the reaction rate was much more rapid than the AER. Particles formed rapidly and in high concentrations in the pinene and limonene systems. Particle formation was slower in the isoprene system and fewer particles were formed; moreover, particle diameters were smaller. In all 3 systems, progressive growth of particles was observed due to condensation and coagulation processes. The isoprene system displayed instability with respect to aerosol characteristics and did not reach steady-state conditions. In the pinene system, ozone concentration was a strong predictor of steady-state particle number and mass concentration and particle diameter. The particle number was greater at higher AERs, but particles were smaller. This study is the first to incorporate measurement of ultrafine particles formed from terpene/ozone reactions into a controlled exposure Address correspondence to Annette C. Rohr, EPRI, 3412 Hillview Avenue, Palo Alto, CA 94304-1395. E-mail: arohr@epri.com chamber setting. Following system characterization, we will conduct mouse exposures to further investigate the respiratory effects of gas-and particle-phase terpene OPs.

Interactions of forests with secondary air pollutants: Some challenges for future research

“…The oxidation of biogenic VOCs can be an important first step in the generation of secondary organic aerosol (SOA) particles , Rohr et al, 2007, a process that has long been associated with forests, leading to the characteristic 'blue haze' observed over forested areas. Reactions with sesquiterpenes (e.g.…”

Indoor and Outdoor Particle Number and Mass Concentrations in Athens. Sources, Sinks and Variability of Aerosol Parameters

“…Smaller particles, mostly in the submicrometer range, are emitted generally through combustion processes, while coarse particles' main source is resuspension caused by people presence and movement (Morawska and Zhang, 2002;He et al, 2004). Secondary particles may also be formed in indoor environments through gas-to-particle conversion (Rohr et al, 2003).…”

Quantification of Ozone Levels in Indoor Environments Generated by Ionization and Ozonolysis Air Purifiers

“…In fact, new ultrafine particles are likely to be created if an ozonolysis air purifier is used in a room with a large concentration of gaseous unsaturated VOCs, such as terpenes. [22][23][24] The level of O 3 required to efficiently kill bacteria is also harmful to humans. Indeed, U.S. Environmental Protection Agency (EPA) provided a comprehensive assessment of the effectiveness and health consequences of O 3 generation indoors stating that, "at concentrations that do not exceed public health standards, O 3 is generally ineffective in controlling indoor air pollution."…”