Secondary Organic Aerosol Formation Initiated by Îł-Terpineol Ozonolysis and Exposure Quantified by the Secondary Intake Fraction
Secondary Organic Aerosol Formation Initiated by Îł-Terpineol Ozonolysis and Exposure Quantified by the Secondary Intake Fraction

Author: Yanan Yang

Publisher:

Published: 2017

Total Pages: 338

ISBN-13:

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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. Îł-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 Îł-terpineol with these oxidants, SOA formation has the potential to increase in-door fine particle concentrations. However, SOA formation from Îł-terpineol has not been systematically quantified. Therefore, the purpose of this work was to quantify SOA formation owing to Îł-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 Îł-terpineol with high ozone (~25 ppm) to ensure rapid and complete ozonolysis for high (0.84 h8́21), moderate (0.61 h8́21) and low (0.36 h8́21) 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 Îł-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 Îł-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 Îł-terpineol ranging from 20 ppb to 200 ppb with excess ozone (~25ppm). In this system, ozone can either initiate reactions with Îł-terpineol to produce organic peroxy radicals (RO28́9) or react with NO2 to produce NO3, which can react with Îł-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, Îł-terpineol, or Îł-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.

Formation of Secondary Organic Aerosol Due to Terpenoid Ozonolysis in Ventilated Settings
Formation of Secondary Organic Aerosol Due to Terpenoid Ozonolysis in Ventilated Settings

Author: Somayeh Youssefi

Publisher:

Published: 2015

Total Pages: 482

ISBN-13:

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The average American spends 18 hours indoors for every hour spent outdoors. There-fore, the quality of air indoors is important and can impact human health. The ozonolysis of monoterpenes impacts indoor pollutant exposure because those reactions generate second-ary organic aerosols (SOA), which are condensed phase airborne particulate matter. Ozone (OR3R) typically infiltrates indoors with outdoor air, and monoterpenes (CR10RHR16R) are unsaturated hydrocarbons emitted from consumer products, such as air fresheners and cleaning agents. Organic aerosol mass formation owing to terpene oxidation can be parameterized with aerosol mass fraction (AMF). The AMF is the ratio of the produced SOA mass to the terpene mass that is oxidized, and it is not constant and increases concurrent with more or-ganic aerosol being available. Prior to this work, prediction of indoor-formed SOA was limited in accuracy because indoor models assumed a constant AMF. As such, the first main objective of this work was to develop an improved indoor formation model that could account for varying AMFs, which was validated with field and laboratory measurements in the literature. Furthermore, current available AMF data in the literature were from atmospheric studies and were measured mostly in unventilated smog chambers for ozone-excess conditions, which is not realistic in most indoor settings. Therefore, the second main objective of this work was to determine the impact of the building air exchange rate (hP-1P), which is the volume normalized airflow through a space, on the AMF of SOA formed due to monoterpene ozonolysis. To do so, two series of experiments were performed with limonene and [alpha]-pinene in a chamber at different air exchange rates (AER) and at realistic concentrations to study the AER and initial reactants' concentrations on SOA formation and the AMF. Limonene ozonolysis AMFs ranged from 0.026 to 0.47, and [alpha]-pinene AMFs ranged from 0.071 to 0.25. Results indicated that as AER increased, the AMF strongly decreased for limonene, but for [alpha]-pinene the impact was in the opposite direction and weaker. Also, for limonene ozonolysis, the ratio of ozone-limonene initial concentrations affected SOA formation positively. These differences arise due to molecular structural differences: Limonene has two double bonds, and secondary ozone chemistry with the remaining exocyclic bond in the SOA phase is the driving factor; [alpha]-pinene only has one, and resulting AER impacts are due to removal of concentrations and competing loss effects. Moreover, limonene has a greater potential to influence indoor SOA concentrations than [alpha]-pinene. Finally, the first and second objectives focused only on aerosol mass formation, but experiments revealed differences in the resulting aerosol size distributions and number for-mation. For instance, the peak number concentration was decreased for both limonene and [alpha]-pinene ozonolysis as the AER increased. It is due to the fact that exchange of air with outdoors shortens residence time of reactants and continuous removal of indoor air causes a non-equilibrium condition between the gaseous and the particle phases. In the third and final objective of this dissertation, I developed a model to predict the size distribution evolution, which can be used in the future to explore the drivers of the evolution of the SOA size distribution indoors.

The Ozonolysis of A-terpineol in an Aqueous Environment
The Ozonolysis of A-terpineol in an Aqueous Environment

Author: Dani Leviss

Publisher:

Published: 2016

Total Pages: 82

ISBN-13:

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Ozone is a major atmospheric pollutant, a central component of smog, a lung irritant, and able to react with abundant organic atmospheric aerosols. The gas phase ozonolysis of volatile organic compounds has been extensively studied and shown to be a major pathway for the formation of secondary organic aerosol (SOA). Although recent work indicates that aqueous processes account for a major fraction of SOA, little is known about aqueous phase ozonolysis. In the present research, we studied the ozonolysis of a-terpineol in aqueous solutions to model the chemistry of atmospheric droplets at varied ozone concentrations (131, 480, and 965 ppb). 1 H Nuclear Magnetic Resonance Spectroscopy (NMR) monitored the experimental progress of this reaction, and one-and two-dimensional NMR along with Gas Chromatography-Mass Spectrometry (GCMS) and Infrared Spectroscopy (IR) identified products. (What follows are illustrations of chemical structures for a-terpineol, cis-lactol, trans-lactol and lactone.) The second-order rate coefficient of the aqueous reaction is 9.93 x 106 M-1 s-1 with a lifetime of 5.2 min, 15 times shorter than in the gas phase (lifetime of 79 min). Formation of products of decreased volatility suggests ozonolysis of a-terpineol yields more condensible secondary organic material and therefore potentially increased impact on climate, visibility, and health.

Secondary Organic Aerosol from Ozone-initiated Reactions with Terpene-rich Household Products
Secondary Organic Aerosol from Ozone-initiated Reactions with Terpene-rich Household Products

Author:

Publisher:

Published: 2008

Total Pages:

ISBN-13:

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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 behavior similar 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 to 400 nm) in every experiment and with an optical particle counter (OPC, 0.1 to 2.0?m) 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 (PM1.1) ranged from 10 to> 300 mu g m-3 and yields ranged from 5percent to 37percent. Steady-state nucleation rates and SOA mass formation rates were on the order of 10 cm-3 s-1 and 10 mu g m-3 min-1, respectively.

Chemistry of Secondary Organic Aerosol
Chemistry of Secondary Organic Aerosol

Author: Lindsay Diana Yee

Publisher:

Published: 2013

Total Pages: 466

ISBN-13:

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The photooxidation of volatile organic compounds (VOCs) in the atmosphere can lead to the formation of secondary organic aerosol (SOA), a major component of fine particulate matter. Improvements to air quality require insight into the many reactive intermediates that lead to SOA formation, of which only a small fraction have been measured at the molecular level. This thesis describes the chemistry of secondary organic aerosol (SOA) formation from several atmospherically relevant hydrocarbon precursors. Photooxidation experiments of methoxyphenol and phenolic compounds and C12 alkanes were conducted in the Caltech Environmental Chamber. These experiments include the first photooxidation studies of these precursors run under sufficiently low NOx levels, such that RO2 + HO2 chemistry dominates, an important chemical regime in the atmosphere. Using online Chemical Ionization Mass Spectrometery (CIMS), key gas-phase intermediates that lead to SOA formation in these systems were identified. With complementary particle-phase analyses, chemical mechanisms elucidating the SOA formation from these compounds are proposed. Three methoxyphenol species (phenol, guaiacol, and syringol) were studied to model potential photooxidation schemes of biomass burning intermediates. SOA yields (ratio of mass of SOA formed to mass of primary organic reacted) exceeding 25% are observed. Aerosol growth is rapid and linear with the organic conversion, consistent with the formation of essentially non-volatile products. Gas and aerosol-phase oxidation products from the guaiacol system show that the chemical mechanism consists of highly oxidized aromatic species in the particle phase. Syringol SOA yields are lower than that of phenol and guaiacol, likely due to unique chemistry dependent on methoxy group position. The photooxidation of several C12 alkanes of varying structure n-dodecane, 2-methylundecane, cyclododecane, and hexylcyclohexane) were run under extended OH exposure to investigate the effect of molecular structure on SOA yields and photochemical aging. Peroxyhemiacetal formation from the reactions of several multifunctional hydroperoxides and aldehyde intermediates was found to be central to organic growth in all systems, and SOA yields increased with cyclic character of the starting hydrocarbon. All of these studies provide direction for future experiments and modeling in order to lessen outstanding discrepancies between predicted and measured SOA.

The Influence of Formation Temperature on Secondary Organic Aerosol Volatility
The Influence of Formation Temperature on Secondary Organic Aerosol Volatility

Author: Katherine Smith

Publisher:

Published: 2018

Total Pages:

ISBN-13: 9780355967500

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The volatility of secondary organic aerosol (SOA) formed from the dark ozonolysis of [alpha]-pinene in a flow tube at temperatures ranging from 275 to 298 K has been characterized by thermally induced evaporation. The SOA was heated from the formation temperature (T[subscript f]) in a thermodenuder and the temperature-dependent volume loss was measured. The resulting thermograms for the SOA formed at the different temperatures were nearly identical when considered as a function of [delta]T (= T – T[subscript f]), rather than absolute temperature. A kinetic model of aerosol evaporation was used to derive T[subscript f]-specific effective volatility distributions for the SOA. The derived distributions indicate SOA formed at lower temperatures is composed of compounds having higher effective volatilities compared to that formed at higher temperatures. However, the increased abundance of compounds having higher effective volatilities at lower T[subscript f] cannot be explained solely due to increased partitioning into the particle phase due to a decrease in vapor pressures. Instead, much of the dependence on T[subscript f] likely results from T-dependent changes in the fraction of the particles that is monomers versus dimers (or higher order oligomers). The relatively short formation time (