The Aging Of Organic Aerosol In The Atmosphere

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The Aging of Organic Aerosol in the Atmosphere

Author : Sean Herbert Kessler
Publisher :
ISBN 13 :
Total Pages : 134 pages
Book Rating : 4.:/5 (86 download)

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Book Synopsis The Aging of Organic Aerosol in the Atmosphere by : Sean Herbert Kessler

Download or read book The Aging of Organic Aerosol in the Atmosphere written by Sean Herbert Kessler and published by . This book was released on 2013 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Photolytic Aging of 4-nitrophenol

Author : Lydia Dolvin
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (115 download)

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Book Synopsis Photolytic Aging of 4-nitrophenol by : Lydia Dolvin

Download or read book Photolytic Aging of 4-nitrophenol written by Lydia Dolvin and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic aerosols in the atmosphere have a large impact on global climate and human health. Understanding the lifetimes and fates of these organics in the atmosphere is imperative for optimizing climate models and characterizing their contributions to net atmospheric warming. The warming and cooling properties of aerosols are related to their abilities to absorb or scatter light. Brown carbon is a type of organic aerosol that is of particular interest due to its ability to absorb light in the visible range. These absorption and scattering properties can change, however, if the aerosols are subjected to photolytic or chemical aging. These aging processes are limiting factors on an aerosol’s atmospheric lifetime. In the atmosphere aerosols exist in the dry and aqueous phase. Aqueous aerosols may be found in cloud-water systems, where photolytic and chemical aging can still take place. The literature reports characterizations of different secondary organic aerosol (SOA) component lifetimes in these cloud-water systems, but often does not investigate these lifetimes in “dirty” systems where more than one type of SOA molecule exists. This overlooks the potential for interactions between aerosols of different compositions and ages. In this work, we investigate the photolytic lifetimes of 4-nitrophenol under atmospheric cloud-water conditions. We characterize these lifetimes both alone and in a mixed system with a-pinene SOA by analyzing the kinetics of 4-nitrophenol photolysis. The presence of SOA seems to have an important impact on the photolytic lifetimes of 4-nitrophenol, with fresh SOA accelerating the rate of photo-decay and aged SOA slowing it. We hypothesize that OH radicals produced as photo-products contribute to the photo-decay of this brown carbon when in a system with other organic SOA.

Atmospheric Aerosols

Author : Olivier Boucher
Publisher : Springer
ISBN 13 : 9401796491
Total Pages : 322 pages
Book Rating : 4.4/5 (17 download)

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Book Synopsis Atmospheric Aerosols by : Olivier Boucher

Download or read book Atmospheric Aerosols written by Olivier Boucher and published by Springer. This book was released on 2015-05-18 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook aims to be a one stop shop for those interested in aerosols and their impact on the climate system. It starts with some fundamentals on atmospheric aerosols, atmospheric radiation and cloud physics, then goes into techniques used for in-situ and remote sensing measurements of aerosols, data assimilation, and discusses aerosol-radiation interactions, aerosol-cloud interactions and the multiple impacts of aerosols on the climate system. The book aims to engage those interested in aerosols and their impacts on the climate system: graduate and PhD students, but also post-doctorate fellows who are new to the field or would like to broaden their knowledge. The book includes exercises at the end of most chapters. Atmospheric aerosols are small (microscopic) particles in suspension in the atmosphere, which play multiple roles in the climate system. They interact with the energy budget through scattering and absorption of solar and terrestrial radiation. They also serve as cloud condensation and ice nuclei with impacts on the formation, evolution and properties of clouds. Finally aerosols also interact with some biogeochemical cycles. Anthropogenic emissions of aerosols are responsible for a cooling effect that has masked part of the warming due to the increased greenhouse effect since pre-industrial time. Natural aerosols also respond to climate changes as shown by observations of past climates and modelling of the future climate.

Laboratory Studies of the Multiday Oxidative Aging of Atmospheric Organic Aerosol

Author : Christopher Yung-Ta Lim
Publisher :
ISBN 13 :
Total Pages : 101 pages
Book Rating : 4.:/5 (11 download)

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Book Synopsis Laboratory Studies of the Multiday Oxidative Aging of Atmospheric Organic Aerosol by : Christopher Yung-Ta Lim

Download or read book Laboratory Studies of the Multiday Oxidative Aging of Atmospheric Organic Aerosol written by Christopher Yung-Ta Lim and published by . This book was released on 2019 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fine particulate matter (PM, or "aerosol") in the atmosphere affects the Earth's radiative balance and is one of the most important risk factors leading to premature mortality worldwide. Thus, understanding the processes that control the loading and chemical composition of PM in the atmosphere is key to understanding air quality and climate. However, the chemistry of organic aerosol (OA), which comprises a significant fraction of submicron atmospheric PM, is immensely complex due to the vast number of organic compounds in the atmosphere and their numerous reaction pathways. Laboratory experiments have generally focused on the initial formation of OA from volatile organic compounds (VOCs), but have neglected processes that can change the composition and loading of OA over longer timescales ("aging"). This thesis describes several laboratory studies that better constrain the effect of two important aging processes over timescales of several days, the oxidation of gas phase species to form secondary OA (condensation) and the reaction of gas phase radicals with organic molecules in the particle phase (heterogeneous oxidation). First, the oxidation of biomass burning emissions is studied by exposing particles and gases present in smoke to hydroxyl radicals (OH). Increases in organic aerosol mass are observed for all fuels burned, and the amount of OA formed is explained well by the extent of aging and the total concentration of measured organic gases. Second, the effect of particle morphology on the rate of heterogeneous oxidation is examined by comparing the oxidation of particles with thin organic coatings to the oxidation of pure organic particles. Results show that morphology can have a strong impact on oxidation kinetics and that particles with high organic surface area to volume ratios can be rapidly oxidized. Third, the molecular products from the heterogeneous OH oxidation of a single model compound (squalane) are measured. Formation of a range of gas-phase oxygenated VOCs is observed, indicating the importance of fragmentation reactions that decrease OA mass, and providing insight into heterogeneous reaction mechanisms. The results from this work emphasize that the concentration and composition of OA can change dramatically over multiple days of atmospheric oxidation.

Mastering SQL Server 2008

Author : Michael Lee
Publisher : John Wiley & Sons
ISBN 13 : 0470467398
Total Pages : 795 pages
Book Rating : 4.4/5 (74 download)

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Book Synopsis Mastering SQL Server 2008 by : Michael Lee

Download or read book Mastering SQL Server 2008 written by Michael Lee and published by John Wiley & Sons. This book was released on 2009-01-16 with total page 795 pages. Available in PDF, EPUB and Kindle. Book excerpt: As Microsoft’s bestselling database manager, SQL Server is highly flexible and customizable, and has excellent support—the 2008 version offers several significant new capabilities. This book offers accurate and expert coverage on the updates to SQL Server 2008 such as its enhanced security; the ability to encrypt an entire database, data files, and log files without the need for application changes; a scalable infrastructure that can manage reports and analysis of any size and complexity; and its extensive performance data collection.

Observations of Secondary Organic Aerosol Production and Soot Aging Under Atmospheric Conditions Using a Novel Environmental Aerosol Chamber

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Author : Crystal Glen
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (778 download)

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Book Synopsis Observations of Secondary Organic Aerosol Production and Soot Aging Under Atmospheric Conditions Using a Novel Environmental Aerosol Chamber by : Crystal Glen

Download or read book Observations of Secondary Organic Aerosol Production and Soot Aging Under Atmospheric Conditions Using a Novel Environmental Aerosol Chamber written by Crystal Glen and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Atmospheric Aging of Monoterpene Secondary Organic Aerosol

Author : Stephen Anthony Mang
Publisher :
ISBN 13 :
Total Pages : 286 pages
Book Rating : 4.:/5 (27 download)

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Book Synopsis Atmospheric Aging of Monoterpene Secondary Organic Aerosol by : Stephen Anthony Mang

Download or read book Atmospheric Aging of Monoterpene Secondary Organic Aerosol written by Stephen Anthony Mang and published by . This book was released on 2008 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:

OH-initiated Heterogeneous Aging of Highly Oxidized Organic Aerosol

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)

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Book Synopsis OH-initiated Heterogeneous Aging of Highly Oxidized Organic Aerosol by :

Download or read book OH-initiated Heterogeneous Aging of Highly Oxidized Organic Aerosol written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The oxidative evolution (?aging?) of organic species in the atmosphere is thought to have a major influence on the composition and properties of organic particulate matter, but remains poorly understood, particularly for the most oxidized fraction of the aerosol. Here we measure the kinetics and products of the heterogeneous oxidation of highly oxidized organic aerosol, with an aim of better constraining such atmospheric aging processes. Submicron particles composed of model oxidized organics--1,2,3,4-butanetetracarboxylic acid (CH10O8), citric acid (C6H8O-- ), tartaric acid (C4H6O6), and Suwannee River fulvic acid--were oxidized by gas-phase OH in a flow reactor, and the masses and elemental composition of the particles were monitored as a function of OH exposure. In contrast to our previous studies of less-oxidized model systems (squalane, erythritol, and levoglucosan), particle mass did not decrease significantly with heterogeneous oxidation. Carbon content of the aerosol always decreased somewhat, but this mass loss was approximately balanced by an increase in oxygen content. The estimated reactive uptake coefficients of the reactions range from 0.37 to 0.51 and indicate that such transformations occur at rates corresponding to 1-2 weeks in the atmosphere, suggesting their importance in the atmospheric lifecycle of organic particulate matter.

Real-time Measurements of Secondary Organic Aerosol Formation and Aging from Ambient Air in an Oxidation Flow Reactor in the Los Angeles Area

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Author :
Publisher :
ISBN 13 :
Total Pages : 23 pages
Book Rating : 4.:/5 (958 download)

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Book Synopsis Real-time Measurements of Secondary Organic Aerosol Formation and Aging from Ambient Air in an Oxidation Flow Reactor in the Los Angeles Area by :

Download or read book Real-time Measurements of Secondary Organic Aerosol Formation and Aging from Ambient Air in an Oxidation Flow Reactor in the Los Angeles Area written by and published by . This book was released on 2016 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Environmental Simulation Chambers: Application to Atmospheric Chemical Processes

Author : Ian Barnes
Publisher : Springer Science & Business Media
ISBN 13 : 9781402042317
Total Pages : 492 pages
Book Rating : 4.0/5 (423 download)

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Book Synopsis Environmental Simulation Chambers: Application to Atmospheric Chemical Processes by : Ian Barnes

Download or read book Environmental Simulation Chambers: Application to Atmospheric Chemical Processes written by Ian Barnes and published by Springer Science & Business Media. This book was released on 2006-01-13 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book gives in the first instance descriptions of different types of so-called environment chambers or photoreactors used mainly for the simulation and/or investigation of important chemical processes occurring in the atmosphere. The types of reactor described include outdoor and indoor chambers, temperature regulated chambers and glass and Teflon foil chambers The practical use of chambers is demonstrated in contributions by leading scientists in the field of atmospheric chemistry using, in many cases, current results. The types of atmospherically relevant investigations described include the measurement of reactivities, the measurement of radicals, the measurement of photolysis frequencies and products, kinetic and product studies on the oxidation of different types of hydrocarbons by important oxidant species (OH, N03, 03), formation of secondary organic aerosol from hydrocarbon oxidation etc. A special section includes contributions from eastern European countries which highlight some of the environmental research being performed in these countries. An abridged version of a specially commissioned review by the JRC Ispra on the status of environmental research in eastern European countries is also included in this section.

Atmospheric Aerosol Aging Involving Organic Compounds and Impacts on Particle Properties

Author : Chong Qiu
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (868 download)

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Book Synopsis Atmospheric Aerosol Aging Involving Organic Compounds and Impacts on Particle Properties by : Chong Qiu

Download or read book Atmospheric Aerosol Aging Involving Organic Compounds and Impacts on Particle Properties written by Chong Qiu and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the first part of this dissertation, we study the aging of soot, a representative type of primary aerosols, in the presence of OH-initiated oxidation products of toluene. Monodisperse soot particles are introduced into an environmental chamber where toluene is oxidized by OH radicals. The variations in soot particle properties are simultaneously monitored, including particle size, mass, organic mass faction, hygroscopicity, and optical properties. The changes in particle properties are found to be largely governed by the thickness of the organic coating that is closely related to reaction time and initial reactant concentrations. Derived from particle size and mass, the effective density increases while dynamic shape factor decreases as the organic coating grows, suggesting a compaction of the soot morphology. As the organic coating grows, the particles become more hygroscopic and have enhanced light scattering and absorption. The second part discusses the potential reactions between amines and some aerosol constituents and alteration of aerosol properties. The reactions between alkylamines and ammonium sulfate/bisulfate have been studied using a low-pressure fast flow reactor coupled to a mass spectrometer at 293 K. Alkylamines react with ammonium sulfate/bisulfate to form alkylaminium sulfates, suggesting the existence of alkylaminium salts in particle phase. We have extended our study to characterize the physicochemical properties of alkylaminium sulfates. The hygroscopicity, thermostability, and density of five representative alkylaminium sulfates have been measured by an integrated aerosol analytical system. All alkylaminium sulfate aerosols show monotonic size growth when exposed to increasing relative humidity. Mixing ammonium sulfate with alkylaminium sulfates lowers the deliquescence point corresponding to ammonium sulfate. Alkylaminium sulfates are thermally comparable to or more stable than ammonium sulfate. The densities of alkylaminium sulfate particles are lower than that of ammonium sulfate. Our results suggest that the organic compounds can effectively alter the composition and properties of atmospheric aerosols, considerably influencing the impacts of aerosols on air quality, climate forcing, and human health. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149291

Atmospheric Aerosols

Author : Claudio Tomasi
Publisher : John Wiley & Sons
ISBN 13 : 3527336451
Total Pages : 706 pages
Book Rating : 4.5/5 (273 download)

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Book Synopsis Atmospheric Aerosols by : Claudio Tomasi

Download or read book Atmospheric Aerosols written by Claudio Tomasi and published by John Wiley & Sons. This book was released on 2017-03-20 with total page 706 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ein Blick auf die morphologischen, physikalischen und chemischen Eigenschaften von Aerosolen aus den unterschiedlichsten natürlichen und anthropogenen Quellen trägt zum besseren Verständnis der Rolle bei, die Aerosolpartikel bei der Streuung und Absorption kurz- und langwelliger Strahlung spielen. Dieses Fachbuch bietet Informationen, die sonst schwer zu finden sind, und vermittelt ausführlich die Kenntnisse, die erforderlich sind, um die mikrophysikalischen, chemischen und Strahlungsparameter zu charakterisieren, die bei der Wechselwirkung von Sonnen- und Erdstrahlen so überaus wichtig sind. Besonderes Augenmerk liegt auf den indirekten Auswirkungen von Aerosolen auf das Klima im Rahmen des komplexen Systems aus Aerosolen, Wolken und der Atmosphäre. Auch geht es vorrangig um die Wirkungen natürlicher und anthropogener Aerosole auf die Luftqualität und die Umwelt, auf die menschliche Gesundheit und unser kulturelles Erbe. Mit einem durchgängig lösungsorientierten Ansatz werden nicht nur die Probleme und Gefahren dieser Aerosole behandelt, sondern auch praktikable Lösungswege aufgezeigt.

Regional Influence of Wildfires on Aerosol Chemistry in the Western US and Insights Into Atmospheric Aging of Biomass Burning Organic Aerosol

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Author :
Publisher :
ISBN 13 :
Total Pages : 17 pages
Book Rating : 4.:/5 (986 download)

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Book Synopsis Regional Influence of Wildfires on Aerosol Chemistry in the Western US and Insights Into Atmospheric Aging of Biomass Burning Organic Aerosol by :

Download or read book Regional Influence of Wildfires on Aerosol Chemistry in the Western US and Insights Into Atmospheric Aging of Biomass Burning Organic Aerosol written by and published by . This book was released on 2017 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Formation and Degradation of Secondary Organic Aerosol Material

Author : Alison Mariko Fankhauser
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (115 download)

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Book Synopsis Formation and Degradation of Secondary Organic Aerosol Material by : Alison Mariko Fankhauser

Download or read book Formation and Degradation of Secondary Organic Aerosol Material written by Alison Mariko Fankhauser and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We utilize the current state of knowledge surrounding IEPOX SOA formation in an attempt to elucidate a unifying mechanism. However, model results suggest that significant gaps remain in our understanding of formation and aging processes, especially oligomerization. Finally, we consider microbial consumption of aerosol organics in the atmosphere. Observations of culturable cells in aqueous aerosols and cloud water suggest that they may be actively metabolizing aqueous media while they are airborne, which could have significant impacts on aerosol and cloud properties. Metabolic rates of cells cultured from atmospheric samples are incorporated into GAMMA. While there is a substantial decrease in the concentration of organic species for particles in which cells reside, the overall effect on populations of particles is negligible, and bacterial metabolism is not expected to measurably alter the organic content of the atmosphere.

Atmospheric and Aerosol Chemistry

Author : V. Faye McNeill
Publisher : Springer
ISBN 13 : 3642412157
Total Pages : 267 pages
Book Rating : 4.6/5 (424 download)

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Book Synopsis Atmospheric and Aerosol Chemistry by : V. Faye McNeill

Download or read book Atmospheric and Aerosol Chemistry written by V. Faye McNeill and published by Springer. This book was released on 2014-07-08 with total page 267 pages. Available in PDF, EPUB and Kindle. Book excerpt: Christian George, Barbara D’Anna, Hartmut Herrmann, Christian Weller, Veronica Vaida, D. J. Donaldson, Thorsten Bartels-Rausch, Markus Ammann - Emerging Areas in Atmospheric Photochemistry. Lisa Whalley, Daniel Stone, Dwayne Heard - New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory. Neil M. Donahue, Allen L. Robinson, Erica R. Trump, Ilona Riipinen, Jesse H. Kroll - Volatility and Aging of Atmospheric Organic Aerosol. P. A. Ariya, G. Kos, R. Mortazavi, E. D. Hudson, V. Kanthasamy, N. Eltouny, J. Sun, C. Wilde - Bio-Organic Materials in the Atmosphere and Snow: Measurement and Characterization. V. Faye McNeill, Neha Sareen, Allison N. Schwier - Surface-Active Organics in Atmospheric Aerosols.

Establishing Chemical Mechanisms and Estimating Phase State of Secondary Organic Aerosol From Atmospherically Relevant Organic Precursors

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Author : Shashank Jain
Publisher :
ISBN 13 :
Total Pages : 352 pages
Book Rating : 4.:/5 (13 download)

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Book Synopsis Establishing Chemical Mechanisms and Estimating Phase State of Secondary Organic Aerosol From Atmospherically Relevant Organic Precursors by : Shashank Jain

Download or read book Establishing Chemical Mechanisms and Estimating Phase State of Secondary Organic Aerosol From Atmospherically Relevant Organic Precursors written by Shashank Jain and published by . This book was released on 2016 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic aerosol (OA) is a ubiquitous component of atmospheric particulate that influences both human health and global climate. A large fraction of OA is secondary in nature (SOA), being produced by oxidation of volatile organic compounds (VOCs) emitted by biogenic and anthropogenic sources. Despite the integral role of SOA in atmospheric processes, there remains a limited scientific understanding of the chemical and physical changes induced in SOA as it ages in the atmosphere. This thesis describes work done to increase the knowledge of processes and properties of atmospherically relevant SOA. In the work presented in this thesis, I have worked on improving an existing innovative, soft ionization aerosol mass spectrometer and utilized it to establish chemical mechanisms for oxidation of atmospherically relevant organic precursors (i.e., Green Leaf Volatiles). I discovered that SOA formation from cis-3-hexen-1-ol is dominated by oligomer and higher molecular weight products, whereas the acetate functionality in cis-3-hexenylacetate inhibited oligomer formation, resulting in SOA that is dominated by low molecular weight products. One of the most important factors contributing to uncertainties in our estimations of SOA mass in the atmosphere, remains our basic assumption that atmospheric SOA is liquid-like, which we have found to be untrue. Hence, I developed a methodology to estimate the phase state of SOA and identified new parameters that can have significant influence on the phase state of atmospheric aerosol. This simplified method eliminates the need for a Scanning Mobility Particle Sizer (SMPS) and directly measures Bounce Factor (BF) of polydisperse SOA using only one multi-stage cascade Electrostatic Low Pressure Impactor (ELPI). The novel method allows for the real time determination of SOA phase state, permitting studies of the relationship between SOA phase, oxidative formation and chemical aging in the atmosphere. I demonstrated that SOA mass loading (CSOA) influences the phase state significantly. Results show that under nominally identical conditions, the maximum BF decreases by approximately 30% at higher CSOA and suggests that extrapolation of experiments not conducted at atmospherically relevant SOA levels to simulate the chemical properties may not yield results that are relevant to our natural environment. My work has provided a better understanding of the mechanisms of aerosol formation at atmospheric concentrations, which is necessary to understand its physical properties. This improved understanding is fundamental to accurately model aerosol formation in the atmosphere, and subsequently evaluate their large-scale effect on human health and environment.

OH-initiated Heterogeneous Oxidation of Atmospheric Organic Aerosols

Author : Ingrid Jennifer George
Publisher :
ISBN 13 : 9780494609651
Total Pages : 0 pages
Book Rating : 4.6/5 (96 download)

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Book Synopsis OH-initiated Heterogeneous Oxidation of Atmospheric Organic Aerosols by : Ingrid Jennifer George

Download or read book OH-initiated Heterogeneous Oxidation of Atmospheric Organic Aerosols written by Ingrid Jennifer George and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The chemical aging of organic aerosols by OH-initiated heterogeneous oxidation was investigated using both model organic and ambient aerosol particles. Organic aerosol particles were exposed to OH radicals in an aerosol flow tube and the modification of their chemical composition and particle properties was studied. Overall, this work has shown that OH-initiated heterogeneous oxidation enhanced the degree of oxidation and the Cloud Condensation Nucleus (CCN) activity of organic aerosol particles for equivalent OH exposure timescales of a few days to a week. The modification of the hygroscopicity of model primary and secondary organic aerosols from chemical aging was investigated by measuring the CCN activity of organic aerosols exposed to OH radicals. Primary organic aerosols, initially CCN inactive, became as CCN active as secondary organic aerosols due to heterogeneous reaction, where surface tension reduction played a major role. The CCN activity for model secondary organic aerosols was also enhanced due to OH oxidation, but changes were less dramatic than for the model primary organic aerosols. Aerosol Mass Spectrometer (AMS) measurements showed that the heterogeneous uptake kinetics of OH radicals onto model primary organic aerosols was efficient. The heterogeneous reaction of organic aerosols with OH led to the production of high molecular weight particle-phase species with the addition of multiple oxygenated functional groups. These results were consistent with the observed increase in particle density with OH exposure. With the exception of solid organic aerosols, the particle volume and mass of organic particles were reduced by less than 20% from OH oxidation at high OH exposures due to volatilization of particle-phase reaction products. The degree of oxidation of the organic fraction of urban ambient aerosols was significantly enhanced for an equivalent atmospheric OH exposure time of 4 days for a daily average atmospheric OH concentration of 2x10 6 cm-3. Ambient aerosol particles sampled from a sparsely populated, forested region were initially more oxygenated than the urban aerosol particles and did not become more oxidized from reaction with OH radicals.