Ozone-initiated Reactions Research Articles

A model to evaluate ozone distribution and reaction byproducts in aircraft cabin environments.

Ozone and byproducts of ozone-initiated reactions are among the primary pollutants in aircraft cabins. However, investigations of the spatial distribution and reaction mechanisms of these pollutants are insufficient. This study established a computational fluid dynamics-based model to evaluate ozone and byproduct distribution, considering ozone reactions in air, adsorption onto surfaces, and byproduct desorption from surfaces. The model was implemented in an authentic single-aisle aircraft cabin and validated by measurements recorded during the aircraft cruise phase. Ozone concentrations in the supply air-dominated area were approximately 50% higher than that in the passenger breathing zone, suggesting that human surfaces represent a significant ozone sink. The deposition velocity onto human bodies was 21.83 m/h, surpassing 3.97 m/h on other cabin interior surface areas. Our model provides a mechanistic tool to analyze ozone and byproduct concentration distributions, which would be useful for assessing passenger health risks and for developing strategies for healthier aircraft cabin environments.

New insight into photodegradation mechanisms, kinetics and health effects of p-nitrophenol by ozonation in polluted water

P-nitrophenol (p-NP) is a recalcitrant organic compound attracted great environmental attention, but its degradation mechanism is indeterminacy, which challenges its treatment, migration, transformation and ecological impact in the environment. In the present study, the aqueous-phase decomposition process of p-NP initiated by O3 has been investigated by a theoretical calculation method. The detailed possible reaction pathways for the oxidative degradation of p-NP by ozone have been proposed. The chemical reaction thermodynamics results show that the reaction barriers of all ozone-initiated pathways are below 15 kcal·mol−1, indicating that ozone can completely initiate the oxidation of p-NP under natural conditions. However, the kinetic results show that the initiation reaction of p-NP by ozone alone is relatively slow compared to the reaction by OH. Interestingly, under ultraviolet (UV) radiation, the dissolved ozone interacts with water and produces two active radicals: OH and HO2. The reaction rate of p-NP initiated with OH is much higher than that with ozone, implying that the OH produced in the photochemical process can improve the removal efficiency of p-NP. The intermediates generated in the ozone-initiated reaction have been found to decompose into small molecule organic acids, aldehydes and ketones. The potential carcinogenicities and teratogenicities of the transformation products have also been studied, and some of them still have carcinogenic activity, which deserve further attention. In addition, to our knowledge, this may be the first computational chemistry study on the degradation of p-NP initiated by HO2. All the results provide a new fundamental understanding for the migration and transformation of p-NP in water environment, and indicate that further assessment is needed for the impact of p-NP and especially its transformation products on the ecological environment in a significant way.

Indoor air chemistry: Terpene reaction products and airway effects.

Reactive chemistry is ubiquitous indoors with a wealth of complex oxidation reactions; some of these are initiated by both homogeneous and heterogeneous reaction of ozone with unsaturated organic compounds and subsequent the hydroxyl radical, either in the gas-phase or on reactive surfaces. One major focus has been the reaction of common and abundant terpene-based fragrances in indoor air emitted from many wood-based materials, a variety of consumer products, and citrus fruits and flowers. Inhalation of the terpenes themselves are generally not considered a health concern (both acute and long-term) due to their low indoor air concentrations; however, their gas- and surface reactions with ozone and the hydroxyl radical produce a host of products, both gaseous, i. a. formaldehyde, and ultrafine particles formed by condensation/nucleation processes. These reaction products may be of health concern. Human cell bioassays with key reaction products from ozone-initiated terpene reactions have shown some inflammatory reactions, but results are difficult to interpret for human exposure and risk assessment. Acute effects like sensory irritation in eyes and airways are unlikely or present at very low intensity in real life conditions based on rodent and human exposure studies and known thresholds for sensory irritation in eyes and airways and derived human reference values for airflow limitation and pulmonary irritation. Some fragrances and their ozone-initiated reaction products may possess anti-inflammatory properties. However, long-term effects of the reaction products as ultrafine particles are poorly explored. Material and product surfaces with high ozone deposition velocities may significantly impact the perceived air quality by altered emissions from both homogeneous and heterogeneous surface reactions.

VOCs and aldehydes source identification in European office buildings - The OFFICAIR study

Indoor air quality (IAQ) measurements were carried out in two field campaigns (summer and winter) in European office buildings (approximately 140 office rooms) in eight countries, as part of the EU-funded OFFICAIR project. A source identification study was performed with principal component analysis (varimax rotation) on a database containing volatile organic compound (VOC) and aldehyde concentration data during summer and winter monitoring campaigns. The common indoor and outdoor sources of VOCs and aldehydes were identified through a critical evaluation based on checklist data and knowledge of material and product emissions from the literature.The dominant source of variance, accounting for 29% and 26% of the explained variance in the summer and winter campaigns, respectively, was attributed to the ingress of outdoor air into indoor environments. The other most relevant sources for variance were directly or indirectly associated with building materials, such as flooring materials (in particular carpets), wood-based products and various types of paint. Ozone-initiated indoor air chemistry played a key role only during summer, in which a specific source linked to ozone-initiated reactions was clearly identified. Other indoor sources explained less than 10% of the variance, such as printer emissions in both campaigns and cleaning products in winter.

A practical method and its applications to prioritize volatile organic compounds emitted from building materials based on ventilation rate requirements and ozone-initiated reactions

Volatile organic compounds emissions from building materials can be a major pollution source in low-occupant-density spaces. Composite-style indoor air quality references, which reflect the combined effects of multiple volatile organic compounds, can be used to determine ventilation rate requirements based on building material emissions. The lowest concentration of interest concept was adopted to implement the idea. Twenty-eight building materials selected from the National Research Council of Canada database were subjected to emission modelling, resulting in 101 volatile organic compounds as a starting volatile organic compound pool. A method was proposed to generate a volatile organic compound priority list that determines ventilation rate requirements while considering ozone-initiated reactions. Three priority lists were obtained based on three lowest concentration of interest schemes, i.e., AFSSET, AgBB and EU-LCI, with each consisting of 17–21 volatile organic compounds that were most likely to attribute to large ventilation rate requirements. Also, analyses of selected volatile organic compounds showed that the changes in the composition of the priority lists due to ozone-initiated reactions could be ignored at a typical indoor ozone concentration level. The application of priority lists was discussed for source control and air cleaning device testing. This paper provides a method to prioritize the chemicals based on ventilation rate requirements with a goal of developing volatile organic compound control strategies at building design stage.

Limonene and its ozone-initiated reaction products attenuate allergic lung inflammation in mice

Inhalation of indoor air pollutants may cause airway irritation and inflammation and is suspected to worsen allergic reactions. Inflammation may be due to mucosal damage, upper (sensory) and lower (pulmonary) airway irritation due to activation of the trigeminal and vagal nerves, respectively, and to neurogenic inflammation. The terpene, d-limonene, is used as a fragrance in numerous consumer products. When limonene reacts with the pulmonary irritant ozone, a complex mixture of gas and particle phase products is formed, which causes sensory irritation. This study investigated whether limonene, ozone or the reaction mixture can exacerbate allergic lung inflammation and whether airway irritation is enhanced in allergic BALB/cJ mice. Naïve and allergic (ovalbumin sensitized) mice were exposed via inhalation for three consecutive days to clean air, ozone, limonene or an ozone–limonene reaction mixture. Sensory and pulmonary irritation was investigated in addition to ovalbumin-specific antibodies, inflammatory cells, total protein and surfactant protein D in bronchoalveolar lavage fluid and hemeoxygenase-1 and cytokines in lung tissue. Overall, airway allergy was not exacerbated by any of the exposures. In contrast, it was found that limonene and the ozone–limonene reaction mixture reduced allergic inflammation possibly due to antioxidant properties. Ozone induced sensory irritation in both naïve and allergic mice. However, allergic but not naïve mice were protected from pulmonary irritation induced by ozone. This study showed that irritation responses might be modulated by airway allergy. However, aggravation of allergic symptoms was observed by neither exposure to ozone nor exposure to ozone-initiated limonene reaction products. In contrast, anti-inflammatory properties of the tested limonene-containing pollutants might attenuate airway allergy.

Ozone deposition velocities on cotton clothing surface determined by the field and laboratory emission cell

Interfacial ozone-initiated chemistry can greatly influence human exposure to reactants and products in the indoor environment. As the nearest reaction interface to human body, clothing assumes an important role in the generation of ultrafine particles and volatile organic compounds when reacting with indoor ozone. However, little is known about the kinetics of ozone-clothing reactions. This investigation developed a convenient method to examine the reaction kinetic parameters of ozone-clothing reactions by using a field and laboratory emission cell. Deposition velocity can be determined in a short period by this method. The study found that the deposition velocity and reaction rate constant for ozone-cotton vest reactions were not significantly affected by the ozone concentration, air flow velocity and long soiling duration (>6 h) of the vest. However, whether or not the vest had been soiled with skin oil is key to the magnitude of the deposition velocity and reaction rate constant. The ozone deposition velocities on soiled cotton vest surface are approximately constant under typical indoor conditions. The deposition velocity and reaction rate constant of ozone-initiated reactions with soiled cotton vest are 0.79 ± 0.17 and 2.43 ± 0.71 cm/s, respectively, at room temperature.

Ozone-initiated terpene reaction products in five European offices: replacement of a floor cleaning agent.

Cleaning agents often emit terpenes that react rapidly with ozone. These ozone-initiated reactions, which occur in the gas-phase and on surfaces, produce a host of gaseous and particulate oxygenated compounds with possible adverse health effects in the eyes and airways. Within the European Union (EU) project OFFICAIR, common ozone-initiated reaction products were measured before and after the replacement of the regular floor cleaning agent with a preselected low emitting floor cleaning agent in four offices located in four EU countries. One reference office in a fifth country did not use any floor cleaning agent. Limonene, α-pinene, 3-carene, dihydromyrcenol, geraniol, linalool, and α-terpineol were targeted for measurement together with the common terpene oxidation products formaldehyde, 4-acetyl-1-methylcyclohexene (4-AMCH), 3-isopropenyl-6-oxo-heptanal (IPOH), 6-methyl-5-heptene-2-one, (6-MHO), 4-oxopentanal (4-OPA), and dihydrocarvone (DHC). Two-hour air samples on Tenax TA and DNPH cartridges were taken in the morning, noon, and in the afternoon and analyzed by thermal desorption combined with gas chromatography/mass spectrometry and HPLC/UV analysis, respectively. Ozone was measured in all sites. All the regular cleaning agents emitted terpenes, mainly limonene and linalool. After the replacement of the cleaning agent, substantially lower concentrations of limonene and formaldehyde were observed. Some of the oxidation product concentrations, in particular that of 4-OPA, were also reduced in line with limonene. Maximum 2 h averaged concentrations of formaldehyde, 4-AMCH, 6-MHO, and IPOH would not give rise to acute eye irritation-related symptoms in office workers; similarly, 6-AMCH, DHC and 4-OPA would not result in airflow limitation to the airways.

Ozone-initiated VOC and particle emissions from a cleaning agent and an air freshener: Risk assessment of acute airway effects

Emissions of volatile organic compounds and ultrafine particles from a kitchen cleaning agent (cream) and plug-in air freshener were investigated in a 20m3 walk-in climate chamber at low (~5ppb) and high ozone (~50ppb) test concentrations and 0.6 air exchange rate. The products emitted terpenes, inter alia limonene, dihydromyrcenol, geraniol, linalool, and glycol ethers. The ozone-initiated reaction products of these compounds were measured by air sampling on Tenax TA followed by thermal desorption GC–MS and air sampling on DNPH cartridges followed by liquid extraction and HPLC–UV analysis. Particle formation was monitored simultaneously. A number of oxygenated and poly-oxygenated reaction products were identified and risk assessed for acute airway effects: formaldehyde, acetaldehyde, acetone, 4-acetyl-1-methylcyclohexene, 6-methyl-5-heptene-2-one, 3-isopropenyl-6-oxo-heptanal, and 4-oxo-pentanal. These compounds generally increased initially at the high ozone concentration, while the terpenes decayed, concurrent with their consumption of ozone. At high ozone concentration, the plug-in air freshener resulted in concentrations of formaldehyde and 4-oxopentanal that may give rise to concern about sensory irritation and airflow limitation, respectively. At high ozone concentration, the kitchen cleaning agent and air freshener resulted in peak particle mass concentrations at 81μg/m3 (8.5×105 #/cm3) and 24μg/m3 (2.3×104 #/cm3), respectively. At low ozone concentration, the particle concentration peaked at 4μg/m3 (1.0×105 #/cm3) after the application of the kitchen cleaning agent, while no increase was observed for the air freshener. The particles, in view of their organic composition and concentration, are not considered to cause acute airway effects. Testing under realistic conditions that mimic user pattern behavior is warranted to obtain acute and longer-term exposure data at realistic indoor ozone concentrations.

SOA Formation Potential of Emissions from Soil and Leaf Litter

Soil and leaf litter are significant global sources of small oxidized volatile organic compounds, VOCs (e.g., methanol and acetaldehyde). They may also be significant sources of larger VOCs that could act as precursors to secondary organic aerosol (SOA) formation. To investigate this, soil and leaf litter samples were collected from the University of Idaho Experimental Forest and transported to the laboratory. There, the VOC emissions were characterized and used to drive SOA formation via dark, ozone-initiated reactions. Monoterpenes dominated the emission profile with emission rates as high as 228 μg-C m(-2) h(-1). The composition of the SOA produced was similar to biogenic SOA formed from oxidation of ponderosa pine emissions and α-pinene. Measured soil and litter monoterpene emission rates were compared with modeled canopy emissions. Results suggest surface soil and litter monoterpene emissions could range from 12 to 136% of canopy emissions in spring and fall. Thus, emissions from leaf litter may potentially extend the biogenic emissions season, contributing to significant organic aerosol formation in the spring and fall when reduced solar radiation and temperatures reduce emissions from living vegetation.

Adjuvant and Inflammatory Effects in Mice After Subchronic Inhalation of Allergen and Ozone-Initiated Limonene Reaction Products

Inhalation of ozone (O3), a highly toxic environmental pollutant, produces airway inflammation and exacerbates asthma. However, in indoor air, O3 reacts with terpenes (cyclic alkenes), leading to formation of airway irritating pollutants. The aim of the study was to examine whether inhalation of the reaction products of O3 and the terpene, limonene, as well as limonene and low-level O3 by themselves, induced allergic sensitization (formation of specific immunoglobulin [Ig] E) and airway inflammation in a subchronic mouse inhalation model in combination with the model allergen ovalbumin (OVA). BALB/cJ mice were exposed exclusively by inhalation for 5 d/wk for 2 wk and thereafter once weekly for 12 wk. Exposures were low-dose OVA in combination with O3, limonene, or limonene/O3 reaction products. OVA alone and OVA + Al(OH)3 served as control groups. Subsequently, all groups were exposed to a high-dose OVA solution on three consecutive days. Serum and bronchoalveolar lavage fluid were collected 24 h later. Limonene by itself did not promote neither OVA-specific IgE nor leukocyte inflammation. Low-level O3 promoted eosinophilic airway inflammation, but not OVA-specific IgE formation. The reaction products of limonene/O3 promoted allergic (OVA-specific IgE) sensitization, but lung inflammation, which is a characteristic of allergic asthma, was not observed. In conclusion, the study does not support an allergic inflammatory effect attributed to O3-initiated limonene reaction products in the indoor environment.

Study of Ozone-Initiated Limonene Reaction Products by Low Temperature Plasma Ionization Mass Spectrometry

Limonene and its ozone-initiated reaction products were investigated in situ by low temperature plasma (LTP) ionization quadrupole time-of-flight (QTOF) mass spectrometry. Helium was used as discharge gas and the protruding plasma generated ~850ppb ozone in front of the glass tube by reaction with the ambient oxygen. Limonene applied to filter paper was placed in front of the LTP afterglow and the MS inlet. Instantly, a wide range of reaction products appeared, ranging from m/z 139 to ca. 1000 in the positive mode and m/z 115 to ca. 600 in the negative mode. Key monomeric oxidation products including levulinic acid, 4-acetyl-1-methylcyclohexene, limonene oxide, 3-isopropenyl-6-oxo-heptanal, and the secondary ozonide of limonene could be identified by collision-induced dissociation. Oligomeric products ranged from the nonoxidized dimer of limonene (C20H30) and up to the hexamer with 10 oxygen atoms (C60H90O10). The use of LTP for in situ ozonolysis and ionization represents a new and versatile approach for the assessment of ozone-initiated terpene chemistry.

Effects of essential oils on the formation of formaldehyde and secondary organic aerosols in an aromatherapy environment

This study aimed to examine the formation of secondary air pollutants (formaldehyde and secondary organic aerosols (SOAs)) in aromatherapy workplaces in which aromatic and volatile organic compounds were the dominant handling materials. A representative aromatherapy workplace with a split air-conditioner ventilation system was selected. Levels of various indoor pollutants, including total volatile organic compounds (TVOC), terpenes, ozone, particle size distribution, and formaldehyde, were measured. The results indicated that the levels of TVOC and terpenes that evaporated from essential oils increased considerably during periods of aromatherapy in the spa space. This study demonstrated that formaldehyde and SOAs were generated through ozone-initiated reactions with the major constituents of essential oils (terpenes) in an environment with low ozone concentrations (17.2–21.4 ppb). Variations in formaldehyde concentration (0.021–0.024 ppm) were in significant during the aromatherapy process. Secondary organic particles with diameters of 30–130 nm were present in significant levels during periods of aromatherapy. Generated formaldehyde and nano-sized SOAs should not be neglected in aromatherapy environmental settings because of their potential health effects. The results suggest that various control strategies for decreasing exposure to indoor secondary air pollutants may be used, such as improving ventilation systems, indoor decorations, or materials in aromatherapy workplaces.

Ozone-Initiated Particle Formation, Particle Aging, and Precursors in a Laser Printer

An increasing number of researchers have hypothesized that ozone may be involved in the particle formation processes that occur during printing, however no studies have investigated this further. In the current study, this hypothesis was tested in a chamber study by adding supplemental ozone to the chamber after a print job without measurable ozone emissions. Subsequent particle number concentration and size distribution measurements showed that new particles were formed minutes after the addition of ozone. The results demonstrated that ozone did react with printer-generated volatile organic compounds (VOCs) to form secondary organic aerosols (SOAs). The hypothesis was further confirmed by the observation of correlations among VOCs, ozone, and particles concentrations during a print job with measurable ozone emissions. The potential particle precursors were identified by a number of furnace tests, which suggested that squalene and styrene were the most likely SOA precursors with respect to ozone. Overall, this study significantly improved scientific understanding of the formation mechanisms of printer-generated particles, and highlighted the possible SOA formation potential of unsaturated nonterpene organic compounds by ozone-initiated reactions in the indoor environment.

Airway effects of repeated exposures to ozone-initiated limonene oxidation products as model of indoor air mixtures

Repeated low-level indoor air exposure to volatile organic compounds (VOCs) may influence the reporting of sensory irritation in the eyes and airways. The ozone-initiated reaction products of limonene, an abundant VOC, were used as a model of indoor air mixtures to study upper airway (sensory) irritation, bronchoconstrictive and alveolar level effects after repeated exposures. Mice were exposed 1h/day for 10 consecutive days to: air, limonene (52ppm/289mg/m3); ozone (0.1ppm/0.2mg/m3); a reaction mixture of limonene (52±8ppm) and ozone (0.5, 2.5 and 3.9ppm) resulting in ∼0.05ppm residual ozone. Neither the limonene nor the ozone exposures alone showed consistent effects on the respiratory parameters. In the limonene/ozone groups, the respiratory rate decreased concentration-dependently with an extrapolated no-effect-level of ∼0.3ppm admixed ozone. Both sensory irritation and airflow limitation were conspicuous effects of the mixtures; sensory irritation appeared rapidly and airflow limitation developed slowly during each exposure. The effects of these parameters did not change with increasing number of exposures. No firm conclusion could be drawn about alveolar level effects. Cells in bronchoalveolar lavage were unchanged irrespective of exposure to air, ozone, and limonene with and without ozone. In conclusion, the study indicated that repeated exposures to ozone-initiated limonene mixtures did not cause sensitization of sensory irritation and airflow limitation. Bronchoalveolar lavage after exposures to ozone, and limonene with and without ozone, respectively, did not show airway inflammation.

Tobacco smoke aging in the presence of ozone: A room-sized chamber study

a b s t r a c t Exposure to tobacco pollutants that linger indoors after smoking has taken place ( thirdhand smoke , THS ) can occur over extended periods and is modulated by chemical processes involving atmospheric reactive species. This study investigates the role of ozone and indoor surfaces in chemical transformations of tobacco smoke residues. Gas and particle constituents of secondhand smoke (SHS) as well as sorbed SHS on chamber internal walls and model materials (cotton, paper, and gypsum wallboard) were charac- terized during aging. After smoldering 10 cigarettes in a 24-m 3 room size chamber, gas-phase nicotine was rapidly removed by sorption to chamber surfaces, and subsequently re-emitted during ventilation with clean air to a level of w10% that during the smoking phase. During chamber ventilation in the presence of ozone (180 ppb), ozone decayed at a rate of 5.6 h ! 1 and coincided with a factor of 5 less nicotine sorbed to wallboard. In the presence of ozone, no gas phase nicotine was detected as a result of re-emission, and higher concentrations of nicotine oxidation products were observed than when ventilation was performed with ozone-free air. Analysis of the model surfaces showed that heteroge- neous nicotine-ozone reaction was faster on paper than cotton, and both were faster than on wallboard. However, wallboard played a dominant role in ozone-initiated reaction in the chamber due to its large total geometric surface area and sink potential compared to the other substrates. This study is the first to show in a room-sized environmental chamber that the heterogeneous ozone chemistry of sorbed nicotine generates THS constituents of concern, as observed previously in bench-top studies. In addition to the main oxidation products (cotinine, myosmine and N-methyl formamide), nicotine-1-oxide was detected for the first time.

Secondary organic aerosol formation from ozone-initiated reactions with nicotine and secondhand tobacco smoke

We used controlled laboratory experiments to evaluate the aerosol-forming potential of ozone reactions with nicotine and secondhand smoke. Special attention was devoted to real-time monitoring of the particle size distribution and chemical composition of SOA as they are believed to be key factors determining the toxicity of SOA. The experimental approach was based on using a vacuum ultraviolet photon ionization time-of-flight aerosol mass spectrometer (VUV-AMS), a scanning mobility particle sizer (SMPS) and off-line thermal desorption coupled to mass spectrometry (TD-GC-MS) for gas-phase byproducts analysis. Results showed that exposure of SHS to ozone induced the formation of ultrafine particles (<100 nm) that contained high molecular weight nitrogenated species ( m/ z 400–500), which can be due to accretion/acid–base reactions and formation of oligomers. In addition, nicotine was found to contribute significantly (with yields 4–9%) to the formation of secondary organic aerosol through reaction with ozone. The main constituents of the resulting SOA were tentatively identified and a reaction mechanism was proposed to elucidate their formation. These findings identify a new component of thirdhand smoke that is associated with the formation of ultrafine particles (UFP) through oxidative aging of secondhand smoke. The significance of this chemistry for indoor exposure and health effects is highlighted.

Temperature dependence of yields of secondary organic aerosols from the ozonolysis of &amp;lt;i&amp;gt;α&amp;lt;/i&amp;gt;-pinene and limonene

Abstract. Secondary organic aerosol (SOA) formation has been investigated as a function of temperature and humidity for the ozone-initiated reaction of the two monoterpenes α-pinene (243–313 K) and limonene (253–313 K) using the 84.5 m3 aerosol chamber AIDA. This paper gives an overview of the measurements done and presents parameters specifically useful for aerosol yield calculations. The ozonolysis reaction, selected oxidation products and subsequent aerosol formation were followed using several analytical techniques for both gas and condensed phase characterisation. The effective densities of the SOA were determined by comparing mass and volume size distributions to (1.25±0.10) g cm−3 for α-pinene and (1.3±0.2) g cm−3 for limonene. The detailed aerosol dynamics code COSIMA-SOA proved to be essential for a comprehensive evaluation of the experimental results and for providing parameterisations directly applicable within atmospheric models. The COSIMA-assisted analysis succeeded to reproduce the observed time evolutions of SOA total mass, number and size distributions by adjusting the following properties of two oxidation product proxies: individual yield parameters (αi), partitioning coefficients (Ki), vapour pressures (pi) and effective accommodation coefficients (γi). For these properties temperature dependences were derived and parameterised. Vapour pressures and partitioning coefficients followed classical Clausius – Clapeyron temperature dependences. From this relationship enthalpies of vaporisation were derived for the two more and less volatile product proxies of α-pinene: (59±8) kJ mol−1 and (24±9) kJ mol−1, and limonene: (55±14) kJ mol−1 and (25±12) kJ mol−1. The more volatile proxy components had a notably low enthalpy of vaporisation while the less volatile proxy components gave enthalpies of vaporisation comparable with those of typical products from α-pinene oxidation, e.g. pinonaldehyde and pinonic acid.

Theoretical Studies on the Kinetics and Mechanisms of Reactions for Methyl Vinyl Ether and Ozone

The interconversion between the two distinct isomers of methyl vinyl ether (MVE), the formation of the primary ozonides from O3-initated reactions of MVE, the transformation between the primary ozonides, and the subsequent fragmentation were studied using quantum chemical methods at the BHandHLYP/6311++G(d,p) level of theory for optimized geometries and frequency calculations and at the QCISD/631G(d,p) level for the single point energy calculations. The rate coefficients were calculated for the temperature range 280440 K by using the canonical transition state theory (TST). For ozone addition to MVE, there are two different possibilities discussed on the basis of two different possible orientations for ozone attack. The results of the theoretical study indicate that although the synperiplanar-MVE is 7.11 kJ/mol more stable than the antiperiplanar-MVE, the antiperiplanar-MVE plays a more important role in formation of the primary ozonides because the primary ozonides formed from the ozone addition antiperiplanar-MVE are more stable and the energy barriers corresponding to transition states are lower. The interconversion between the primary ozonides formed from the ozone addition to antiperiplanar-MVE is the most accessible compared with the transformations between other primary ozonides. The cleavage of the primary ozonides mainly leads to the formation of the CH2OO, which is in agreement with the experimental estimates. The calculated overall rate constant for the ozone-initiated reactions is 4.81017cm3/(molecules) at 298.15 K, which agrees with the experimental value for ethyl vinyl ether.

Secondary organic aerosol from ozone-initiated reactions with terpene-rich household products

We analyzed secondary organic aerosol (SOA) data from a series of small-chamber experiments in which terpene-rich vapors from household products were combined with ozone under conditions analogous to product use indoors. Reagents were introduced into a continuously ventilated 198 L chamber at steady rates. Consistently, at the time of ozone introduction, nucleation occurred exhibiting similar behavior to atmospheric events. The initial nucleation burst and growth was followed by a period in which approximately stable particle levels were established, reflecting a balance between new particle formation, condensational growth, and removal by ventilation. Airborne particles were measured with a scanning mobility particle sizer (SMPS, 10–400 nm) in every experiment and with an optical particle counter (OPC, 0.1–2.0 μm) in a subset. Parameters for a three-mode lognormal fit to the size distribution at steady state were determined for each experiment. Increasing the supply ozone level increased the steady-state mass concentration and yield of SOA from each product tested. Decreasing the air-exchange rate increased the yield. The steady-state fine-particle mass concentration (PM 1.1) ranged from 10 to >300 μg m −3 and yields ranged from 5% to 37%. Steady-state nucleation rates and SOA mass formation rates were ∼10 cm −3 s −1 and ∼10 μg m −3 min −1, respectively.