Atmospheric Aging of Monoterpene Secondary Organic Aerosol PDF Download

Author: Stephen Anthony Mang
Publisher:
ISBN:
Category :
Languages : en
Pages : 286

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Author: Shexia Ma
Publisher:
ISBN: 9789535107286
Category :
Languages : en
Pages :

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Author: Sean Herbert Kessler
Publisher:
ISBN:
Category :
Languages : en
Pages : 134

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The immense chemical complexity of atmospheric organic particulate matter ("aerosol") has left the general field of condensed-phase atmospheric organic chemistry relatively under-developed when compared with either gas-phase chemistry or the formation of inorganic compounds. In this work, we endeavor to improve the general understanding of the narrow class of oxidation reactions that occur at the interface between the particle surface and the gas-phase. The heterogeneous oxidation of pure erythritol (C4H1 00 4 ) and levoglucosan (C6H1 00 5) particles by hydroxyl radical (OH) was studied first in order to evaluate the effects of atmospheric aging on the mass and chemical composition of atmospheric organic aerosol, particularly that resembling fresh secondary organic aerosol (SOA) and biomass-burning organic aerosol (BBOA). In contrast to what is generally observed for the heterogeneous oxidation of reduced organics, substantial volatilization is observed in both systems. As a continuation of the heterogeneous oxidation experiments, we also measure the kinetics and products of the aging of highly oxidized organic aerosol, in which submicron particles composed of model oxidized organics -- 1,2,3,4-butanetetracarboxylic acid (C8H100 8), citric acid (C6 H8 0 7), tartaric acid (C4H6 0 6 ), and Suwannee River fulvic acid -- were oxidized by gas-phase OH in the same flow reactor, and the masses and elemental composition of the particles were monitored as a function of OH exposure. In contrast to studies of the less-oxidized model systems, particle mass did not decrease significantly with heterogeneous oxidation, although substantial chemical transformations were observed and characterized. Lastly, the immense complexity inherent in the formation of SOA -- due primarily to the large number of oxidation steps and reaction pathways involved -- has limited the detailed understanding of its underlying chemistry. In order to simplify this inherent complexity, we give over the last portion of this thesis to a novel technique for the formation of SOA through the photolysis of gas-phase alkyl iodides, which generates organic peroxy radicals of known structure. In contrast to standard OH-initiated oxidation experiments, photolytically initiated oxidation forms a limited number of products via a single reactive step. The system in which the photolytic SOA is formed is also repurposed as a generator of organic aerosol for input into a secondary reaction chamber, where the organic particles undergo additional aging by the heterogeneous oxidation mechanism already discussed. Particles exiting this reactor are observed to have become more dramatically oxidized than comparable systems containing SOA formed by gas-phase alkanes undergoing "normal" photo-oxidation by OH, suggesting simultaneously the utility of gas-phase precursor photolysis as an effective experimental platform for studying directly the chemistry involved in atmospheric aerosol formation and also the possibility that heterogeneous processes may play a more significant role in the atmosphere than what is predicted from chamber experiments. Consideration is given for the application of these results to larger-scale experiments, models, and conceptual frameworks.

Author: Hayder Abdul-Razzak
Publisher: BoD – Books on Demand
ISBN: 9535107283
Category : Science
Languages : en
Pages : 494

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The book is divided into two sections. The first section presents characterization of atmospheric aerosols and their impact on regional climate from East Asia to the Pacific. Ground-based, air-born, and satellite data were collected and analyzed. Detailed information about measurement techniques and atmospheric conditions were provided as well. In the second section, authors provide detailed information about the organic and inorganic constituents of atmospheric aerosols. They discuss the chemical and physical processes, temporal and spatial distribution, emissions, formation, and transportation of aerosol particles. In addition, new measurement techniques are introduced. This book hopes to serve as a useful resource to resolve some of the issues associated with the complex nature of the interaction between atmospheric aerosols and climatology.

Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781723538780
Category :
Languages : en
Pages : 274

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This is the eleventh in a series of evaluated sets of rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation. The primary application of the data is in the modeling of stratospheric processes, with special emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena. Demore, W. B. and Sander, S. P. and Golden, D. M. and Hampson, R. F. and Kurylo, M. J. and Howard, C. J. and Ravishankara, A. R. and Kolb, C. E. and Molina, M. J. Jet Propulsion Laboratory NASA-CR-198863, JPL-PUBL-94-26, NAS 1.26:198863 NAS7-1260; RTOP 464-41-04-01-00...

Author: Crystal Glen
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Secondary organic aerosols (SOA) comprise a substantial fraction of the total global aerosol budget. While laboratory studies involving smog chambers have advanced our understanding of the formation mechanisms responsible for SOA, our knowledge of the processes leading to SOA production under ambient gaseous and particulate concentrations as well as the impact these aerosol types have on climate is poorly understood. Although the majority of atmospheric aerosols scatter radiation either directly or indirectly by serving as cloud condensation nuclei, soot is thought to have a significant warming effect through absorption. Like inorganic salts, soot may undergo atmospheric transformation through the vapor condensation of non-volatile gaseous species which will alter both its chemical and physical properties. Typical smog chamber studies investigating the formation and growth of SOA as well as the soot aging process are temporally limited by the initial gaseous concentrations injected into the chamber environment. Furthermore, data interpretation from such experiments is generally restricted to the singular gaseous species under investigation. This dissertation discusses the use of a new aerosol chamber designed to study the formation and growth of SOA and soot aging under atmospherically relevant conditions. The Ambient Aerosol Chamber for Evolution Studies (AACES) was deployed at three field sites where size and hygroscopic growth factor (HGF) of ammonium sulfate seed particles was monitored over time to examine the formation and growth of SOA. Similar studies investigating the soot aging process were also conducted in Houston, TX. It is shown that during the ambient growth of ammonium sulfate seed particles, as particle size increases, hygroscopic growth factors decrease considerably resulting in a significant organic mass fraction in the particle phase concluding an experiment. Observations of soot aging show an increase in measured size, HGF, mass and single scattering albedo. Ambient growth rate comparisons with chamber growth yielded similar trends verifying the use of AACES to study aerosol aging. Based on the results from this study, it is recommended that AACES be employed in future studies involving the production and growth of SOA and soot aging under ambient conditions in order to bridge the gaps in our current scientific knowledge.

Author: Mehrnaz Sarrafzadeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Atmospheric organic aerosols have a significant impact on climate and human health. However, our understanding of the physical and chemical properties of these aerosols is inadequate, thus their climate and health influences are poorly constrained. In this study, we investigated the secondary organic aerosol (SOA) formation from OH-initiated oxidation of -pinene. The majority of experiments were conducted in the York University smog chamber. The main objective was to identify the gas and particle phase products with an atmospheric pressure chemical ionization mass spectrometer (APCI-MS/MS). A wide variety of products were identified containing various functional groups including alcohol, aldehyde, carboxylic acid, ketone and nitrate. Following the chemical composition characterization of products, the shape, phase state and density of generated particles were determined. Images from a scanning electron microscope (SEM) revealed that SOA particles from -pinene were commonly spherical in shape, and adopted an amorphous semi-solid/liquid state. Additionally, the density was determined for SOA particles generated from -pinene/OH, nopinone/OH and nopinone/NO3 experiments for the first time using a tapered element oscillating microbalance-scanning mobility particle sizer (TEOM-SMPS) method. Our results showed a correlation between the determined particle density and the particle chemical composition of the respective system. This demonstrates that changes in particle density can be indicative of the changes in chemical composition of particles. We also investigated the chemical aging of oxidation products by exposing them to additional OH radicals or ozone. The observed changes in chemical composition of products and additional SOA mass production during OH-induced aging were attributed to further oxidation of gas phase intermediate products. The NOx dependence of SOA formation from -pinene photooxidation was investigated in the York University smog chamber and the Jlich Plant Atmosphere Chamber (JPAC). Consistent with previous NOx studies, SOA yields increased with increasing [NOx] at low-NOx conditions, whereas increasing [NOx] at high-NOx conditions suppressed the SOA yield. This increase was attributed to an increase of OH concentration. After removing the effect of [OH] on SOA yield in the JPAC, SOA yields only decreased with increasing [NOx]. Finally, the formation mechanisms of identified products were probed based on the information acquired throughout our study.

Author: Mark E. Davis
Publisher: Courier Corporation
ISBN: 0486291316
Category : Technology & Engineering
Languages : en
Pages : 385

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Appropriate for a one-semester undergraduate or first-year graduate course, this text introduces the quantitative treatment of chemical reaction engineering. It covers both homogeneous and heterogeneous reacting systems and examines chemical reaction engineering as well as chemical reactor engineering. Each chapter contains numerous worked-out problems and real-world vignettes involving commercial applications, a feature widely praised by reviewers and teachers. 2003 edition.

Author: Somayeh Youssefi
Publisher:
ISBN:
Category : Environmental engineering
Languages : en
Pages : 482

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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.

Author: Kenneth Stephen Docherty
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 626

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