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Multivariate Relative Rate Measurements Of Reactions Between Volatile Organic Compounds Vocs And Atmospheric Radicals
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Book Synopsis Multivariate Relative Rate Measurements of Reactions Between Volatile Organic Compounds (VOCs) and Atmospheric Radicals by : Jacob T. Shaw
Download or read book Multivariate Relative Rate Measurements of Reactions Between Volatile Organic Compounds (VOCs) and Atmospheric Radicals written by Jacob T. Shaw and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Kinetics of Atmospheric Reactions of Biogenic Volatile Organic Compounds by : Marie Coy Killian
Download or read book Kinetics of Atmospheric Reactions of Biogenic Volatile Organic Compounds written by Marie Coy Killian and published by . This book was released on 2013 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: Biogenic volatile organic compounds (VOCs) react with Cl and OH radicals and the resulting radicals combine with oxygen to form peroxy radicals RO2. Organic peroxy radicals can then react with NO to form NO2, a precursor of tropospheric ozone. The work presented here explored the initial reaction between Cl and thujone, a VOC emitted by Great Basin sagebrush. The rate constant for the reaction of thujone + Cl at 296 K was measured with the method of relative rates with FTIR for detection of reactants. LEDs were used to photolyze Cl2 to generate Cl in the reaction cell. Thujone was also photolyzed by the LEDs and therefore the relative rates model was revised to account for this photolysis. With toluene as the reference compound, the rate constant for thujone + Cl at 296 K is 2.62 ± 1.90 × 10-12 molecules-1 s-1, giving an atmospheric lifetime of 0.5-2.6 minutes for thujone.
Book Synopsis Volatile Organic Compounds in the Atmosphere by : Ralf Koppmann
Download or read book Volatile Organic Compounds in the Atmosphere written by Ralf Koppmann and published by John Wiley & Sons. This book was released on 2008-04-15 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: Every day, large quantities of volatile organic compounds (VOCs) are emitted into the atmosphere from both anthropogenic and natural sources. The formation of gaseous and particulate secondary products caused by oxidation of VOCs is one of the largest unknowns in the quantitative prediction of the earth’s climate on a regional and global scale, and on the understanding of local air quality. To be able to model and control their impact, it is essential to understand the sources of VOCs, their distribution in the atmosphere and the chemical transformations which remove these compounds from the atmosphere. In recent years techniques for the analysis of organic compounds in the atmosphere have been developed to increase the spectrum of detectable compounds and their detection limits. New methods have been introduced to increase the time resolution of those measurements and to resolve more complex mixtures of organic compounds. Volatile Organic Compounds in the Atmosphere describes the current state of knowledge of the chemistry of VOCs as well as the methods and techniques to analyse gaseous and particulate organic compounds in the atmosphere. The aim is to provide an authoritative review to address the needs of both graduate students and active researchers in the field of atmospheric chemistry research.
Book Synopsis Studies of the Atmospheric Chemistry of Volatile Organic Compounds and of Their Atmospheric Reaction Products by : Roger Atkinson
Download or read book Studies of the Atmospheric Chemistry of Volatile Organic Compounds and of Their Atmospheric Reaction Products written by Roger Atkinson and published by . This book was released on 2004 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Atmospheric Reactions of Volatile Organic Compounds and Their Products by : Jillian Dolores Baker
Download or read book Atmospheric Reactions of Volatile Organic Compounds and Their Products written by Jillian Dolores Baker and published by . This book was released on 2004 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Yields and Reactions of Intermediate Compounds Formed from the Initial Atmospheric Reactions of Selected VOCs by :
Download or read book Yields and Reactions of Intermediate Compounds Formed from the Initial Atmospheric Reactions of Selected VOCs written by and published by . This book was released on 2000 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Atmospheric Transformation of Volatile Organic Compounds by :
Download or read book Atmospheric Transformation of Volatile Organic Compounds written by and published by . This book was released on 2008 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: To be able to understand and predict the concentration of a target compound in the atmosphere one must understand the atmospheric chemistry involved. The transformation of volatile organic compounds (VOCs) in the troposphere is predominantly driven by the interaction with the hydroxyl and nitrate radicals. The hydroxyl radical exists in daylight conditions and its reaction rate constant with an organic compound is typically very fast. The nitrate radical drives the nighttime chemistry. These radicals can scavenge hydrogen from an organic molecule generating secondary products that are often overlooked in detection schemes. Secondary products can be more stable and serve as a better target compound in detection schemes. The gas-phase reaction of the hydroxyl radical (OH) with cyclohexanol (COL) has been studied. The rate coefficient was determined to be (19.0+4.8) x 10-12cm3 molecule-1 s-1 (at 297+3 oK and 1 atmosphere total pressure) using the relative rate technique with pentanal, decane, and tridecane as the reference compounds. Assuming an average OH concentration of 1 x 106 molecules cm-3, an atmospheric lifetime of 15 h is calculated for cyclohexanol. Products of the OH + COL reaction were determined to more clearly define cyclohexanol's atmospheric degradation mechanism. The observed products were: cyclohexanone, hexanedial, 3-hydroxycyclohexanone, and 4-hydroxycyclohexanone. Consideration of the potential reaction pathways suggests that each of these products is formed via hydrogen abstraction at a different site on the cyclohexanol ring.
Book Synopsis Volatile Organic Compounds in the Atmosphere by : R M Harrison
Download or read book Volatile Organic Compounds in the Atmosphere written by R M Harrison and published by Royal Society of Chemistry. This book was released on 2007-10-31 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interest in volatile organic compounds (VOCs) as air pollutants has increased dramatically in recent years. This book covers a number of very topical issues concerning VOCs, including stratospheric ozone depletion due to CFCs, and the properties of alternative substances; the role of VOCs in the photochemical formation of lower atmosphere (tropospheric) ozone; and the problem of the direct toxicity of VOCs such as benzene and formaldehyde. This Issue reviews our current knowledge of VOCs, drawing upon the expertise of renowned experts and major national and international research programmes. It examines man-made and natural sources, as well as pathways and chemical reactions in the atmosphere. It also looks closely at the sources and concentrations of VOCs indoors, where humans are most likely to be exposed to them. Volatile Organic Compounds in the Atmosphere describes techniques used for the calculation of emissions inventories and strategies for control, and explores the many Government policy matters relating to VOCs. It provides readers with in-depth, clearly explained coverage of the many complex scientific and policy issues surrounding VOCs in the atmosphere.
Book Synopsis Pamphlets on Employment-Minnesota by :
Download or read book Pamphlets on Employment-Minnesota written by and published by . This book was released on 1900 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Atmospheric Chemistry of Volatile Organic Compounds by :
Download or read book Atmospheric Chemistry of Volatile Organic Compounds written by and published by . This book was released on 1995 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: The relative hydroxyl (OH) reaction rates from the simulated atmospheric oxidation of several acetates and other oxygenated organic compounds have been measured. The OH radical was from the photolysis of methyl nitrite in air. The reaction products of 2-ethoxyethyl acetate with OH identified and quantified and a reaction mechanism is proposed. The measured rate constants (x10( -11)cm(3)molecule( -1)s( -1)) are: 6.77+/-0.50 for trans-4-octene, 1.40+/-0.07 for 4-methyl-2-pentanone, 6.70+/-0.23 for trans-2-heptene, .342+/-0.087 for n-propyl acetate, .571+/-0.094 for n-butyl acetate, 0.753+/-0.048 for n-pentyl acetate, 1.056+/-0.131 for 2-ethoxyethyl acetate, 1.356+/-0.232 for 2-ethoxyethyl isobutyrate, 2.722+/-.206 for 2-ethoxyethyl methacrylate, 4.34+/-.385 4-penten-1-yl acetate, and 3.33+/-0.122 for 3-ethoxyacrylic acid ethyl ester.
Book Synopsis Nitrous Acid, Hydroxyl Radicals, and Peroxy Radicals by : Brandon Bottorff
Download or read book Nitrous Acid, Hydroxyl Radicals, and Peroxy Radicals written by Brandon Bottorff and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hydroxyl radical (OH) and peroxy radicals (HO2 and RO2) are key species that drive the oxidation of trace gases and control the fate of several tropospheric pollutants. Reactions of these radical species with volatile organic compounds (VOCs) and nitrogen oxides (NO + NO2 = NOx) establish a fast radical-propagation cycle that can lead to a net production of harmful secondary pollutants such as ozone (O3) and secondary organic aerosols (SOA). Attempts to develop accurate control strategies for these pollutants require an in-depth understanding of radical chemistry, however recent measurements of radical concentrations have shown discrepancies with predictive models.This work will describe measurements of radicals made by the Indiana University Laser- Induced Fluorescence-Fluorescence Assay by Gas Expansion (LIF-FAGE) instrument that has been described previously, and will also detail the development and initial measurements made by a Laser-photofragmentation/Laser-induced fluorescence (LP/LIF) instrument capable of nearsimultaneous detection of OH and nitrous acid (HONO), an important radical precursor. In particular, this work will detail measurements of OH, and HO2 made by the LIF-FAGE instrument in a forested environment in northern Michigan as part of the 2016 Program for Research on Oxidants, Photochemistry, and Transport (PROPHET) field campaign. An extensive set of supporting measurements, including photolysis rates and mixing ratios of NOx, VOCs, and other trace gases was used to constrain a zero dimensional box to assess our current understanding of atmospheric chemistry in remote environments characterized by high VOC mixing ratios and low mixing ratios of NOx.In addition, the development and initial field deployment of the LP/LIF instrument will be detailed. This will include a discussion on a novel calibration method based on determining the photofragmentation efficiency (PE) of HONO by the 355-nm photolysis laser, and also includes initial measurements of HONO and OH in both a forested and urban setting. Lastly, HONO mixing ratios in the indoor environment will be analyzed through measurements made as part of the House Observations of Microbial and Environmental Chemistry (HOMEChem) field campaign. HONO behavior during a variety of common household activities will be assessed and measurements from the LP/LIF instrument are compared to simultaneous measurements from a chemical ionization mass spectrometry (CIMS) instrument. The agreement between the two instruments gives confidence in both measurement techniques and also suggests that HONO concentrations can be well mixed in indoor environments.
Book Synopsis Measurements of Atmospheric Radicals in Ambient and Indoor Environments by : Colleen Marciel Fontelera Rosales
Download or read book Measurements of Atmospheric Radicals in Ambient and Indoor Environments written by Colleen Marciel Fontelera Rosales and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydroxyl (OH), hydroperoxy (HO2), and peroxy (RO2) radicals are key to atmospheric oxidation, critically altering the chemistry of the air we breathe. Radical reactions initiate oxidation of volatile organic compounds (VOCs), which in the presence of nitrogen oxides (NOx) can form ozone and secondary organic aerosols (SOA)-air pollutants affecting human health and welfare in ambient and indoor environments.In ambient environments with high mixing ratios of biogenic VOCs and low mixing ratios of NOx, measurements using our current instrumental technique for radicals have shown discrepancies with modeled predictions. Here, these discrepancies were investigated during the Indiana Radical, Reactivity, and Ozone Production Intercomparison II (IRRONIC II) field campaign. Intercomparisons between different radical measurement techniques were done (1) between their individual calibration techniques and (2) between ambient radical measurements of each instrument. All instruments proved able to measure OH, HO2, and RO2 at levels encountered in forests and agreed with each other within stated uncertainties. The agreement between measurements in this unpolluted, forested area with elevated levels of biogenic emissions instilled confidence in the accuracy of our radical measurement techniques.Previously, there have been few direct measurements of radicals in indoor environments, compared to ambient environments. However, these radicals critically affect mechanisms involving indoor pollutants, e.g., VOCs, ozone, and SOA. In this study, radical chemistry involving terpene-based and bleach cleaners were investigated during HOMEChem (House Observations of Microbial and Environmental Chemistry) and iRACE (Indoor Radical and Aerosol Chemistry Experiments). In iRACE, secondary oxidation products, radicals, and new particle (aerosol) formation were observed immediately after using a terpene-based cleaner. Radical and aerosol concentrations reached levels comparable to outdoor traffic-impacted areas, emulating "indoor smog" for 10-15 minutes and respiratory tract deposition comparable to that from the inhalation of traffic-associated aerosol in an urban street canyon. Meanwhile, in HOMEChem, indoor sunlight was found to induce bleach-initiated radical chemistry and enhance radical production indoors, similar to levels expected outdoors. These developments in our understanding of secondary chemistry-driven indoor air pollution (as opposed to direct emissions) serve to help inform regulations regarding cleaning product formulations and improve our cleaning practices indoors.
Book Synopsis Measurements and Model Predictions of Hydroxyl Radical, Peroxy Radicals, and Nitrous Acid by : Emily Kathleen Reidy
Download or read book Measurements and Model Predictions of Hydroxyl Radical, Peroxy Radicals, and Nitrous Acid written by Emily Kathleen Reidy and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hydroxyl radical (OH) is the dominant oxidant in the atmosphere, controlling the lifetimes of volatile organic compounds (VOCs) and contributing to the formation of ozone (O3) and secondary organic aerosols (SOA). The oxidation of VOCs by OH propagates a radical cycle between OH, the hydroperoxy radical (HO2), and organic peroxy radical (RO2). Due to its importance in the atmosphere, there is a substantial body of literature investigating ROX (≡ OH + HO2 + RO2) chemistry in the outdoor environment, but few measurements occurring indoors, where people spend the majority of their time. This work includes the first measurements of OH and HO2 in a residential environment during use of a gas stove. Emissions from the gas stove quickly create a complex indoor atmosphere with unexpectedly high concentrations of OH and HO2, suggesting missing radical sources in indoor spaces.In more pristine regions, there has been significant disagreement between measurements and modeled concentrations of ROX. While progress has been made in improving OH agreement in deciduous forests, HO2 and RO2 model disagreement persists. Measurements of radicals spanning three forested campaigns are compared through a chemical coordinate analysis and suggest that newly proposed radical loss pathways still cannot account for the discrepancies between model and measurements.Finally, measurements of radical species and their major precursors in a coniferous forest emphasize the importance of nitrous acid (HONO) on ROX concentrations. HONO photolyzes to form OH and NO, producing a substantial amount of total ROX. HONO concentrations are particularly difficult to model, as there are numerous sources of varying importance in different environments. While common chemical mechanisms only include gas-phase reactions of HONO, heterogeneous reactions were added in order to characterize sources of HONO in the remote, forested environment. Overall, this work discusses missing sources and sinks of radicals and their major precursor, HONO, in indoor spaces, deciduous, and coniferous forests, addressing gaps in our understanding of radical chemistry that impact the formation of secondary air pollution.
Book Synopsis Kinetic Studies of the Reactions of Several Atmospheric Pollutants with Hydroxyl Radicals Using the Relative Rate by : Michael Tai Phan
Download or read book Kinetic Studies of the Reactions of Several Atmospheric Pollutants with Hydroxyl Radicals Using the Relative Rate written by Michael Tai Phan and published by . This book was released on 2016 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Study of Volatile Organic Compounds (VOC) in the Cloudy Atmosphere by : Miao Wang
Download or read book Study of Volatile Organic Compounds (VOC) in the Cloudy Atmosphere written by Miao Wang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volatile Organic Compounds (VOC), including saturated, unsaturated, and other substituted hydrocarbons, play a major role in atmospheric chemistry. They are primarily emitted by anthropogenic and biogenic sources into the atmosphere; they are also transformed in situ by chemical reactions, and more specifically, by photo-oxidation leading to the formation of ozone (O3) and Secondary Organic Aerosol (SOA). By altering the organic fraction of aerosol particles, VOC modify the Earth's radiative balance through a direct effect (absorption and scattering of solar radiation) or through indirect effect by altering cloud microphysical properties. They also present a direct effect on human health and on the environment.During their atmospheric transport, VOC and their oxidation products, Oxygenated Volatile Organic Compounds (OVOC), may partition between the gaseous and aqueous phases depending on their solubility. Clouds have a significant effect on tropospheric chemistry by redistributing trace constituents between phases and by providing liquid water in which aqueous phase chemistry can take place. Indeed, during the cloud lifetime, chemical compounds and particularly VOC are efficiently transformed since clouds favor the development of complex “multiphase chemistry”. The latter presents several particularities. First, photochemical processes inside the droplets are important in the transformation of chemical compounds. Second, aqueous chemical reactions are efficient and can be faster than the equivalent reactions in the gas phase. This can be related to the presence of strong oxidants such as hydrogen peroxide H2O2 or Transition Metal Ions (TMI), which participate in the formation of radicals such as hydroxyl radicals (HO•) that favor oxidation processes. Furthermore, the presence of viable microorganisms has been highlighted and shown to participate in transformations of the chemical species. Finally, these transformations in clouds are also strongly perturbed by microphysical processes that control formation, lifetime and dissipation of clouds. These processes will redistribute the chemical species between the different reservoirs (cloud water, rain, particle phase, gaseous phase, and solid ice phase). In this frame, the transformation of VOC in the cloud medium can lead to the production of secondary compounds contributing to SOA formation, reported as “cloud aqSOA”. This secondary organic aerosol mass produced during the cloud lifetime could explain in part the ubiquity of small dicarboxylic and keto acids and high molecular-weight compounds measured in aerosol particles, fog water, cloud water, or rainwater at many locations, as they have neither substantial direct emission sources nor any identified important source in the gas phase. This aqSOA mass stays in the particle phase after cloud evaporation implying a modification of the (micro)physical and chemical properties of aerosol particles (particle size, chemical composition, morphology). This leads to modifications of their impacts on consecutive cloud or fog cycles (aerosol indirect effects) and of their interactions with incoming radiation by scattering/absorbing (aerosol direct effect). (...).
Book Synopsis The Hydroxyl Radical Reaction Rate Constant and Atmospheric Transformation Products of 2-Butanol and 2-Pentanol by :
Download or read book The Hydroxyl Radical Reaction Rate Constant and Atmospheric Transformation Products of 2-Butanol and 2-Pentanol written by and published by . This book was released on 1998 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant to +2-butanol (2BU, CH3CH2CHOHch3 and 2-pentanol (2PE, CH3CH2CH2CHOHch3. 2BU and 2PE react with OH yielding bimolecular rate constants of (8.1 +/- 2.0) x 10(exp -12 cm3/molecule/s and (11.9 +/- 3.0) x 10(exp-12) cm3/molecule/s, respectively, at 297 +/- 3 K and 1 atmosphere total pressure. Both 2BU and 2PE OH rate constants reported here are in agreement with previously reported values. In order to more clearly define these alcohols' atmospheric reaction mechanisms, an investigation into the OH + alcohol reaction products was also conducted. The OH + 2BU reaction products and yields observed were: methyl ethyl ketone (MEK, 60 +/- 2%, CH3CH2C(=O)CH3 and acetaldehyde (29 +/- 4%, HC(=O)CH3. The OH + 2PE reaction products and yields observed were: 2-pentanone (2PO, 4 +/- 4%, CH3C(=O)CH2CH2CH3, propionaldehyde (14 +/- 2%, HC(=O)CH2CH3, and acetaldehyde 40 +/- 4%, HC(=O)CH3. The alcohols' reaction mechanisms are discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. Labeled (O-18) 2BU/OH reactions were conducted to investigate 2BUs atmospheric transformation mechanism details. The findings reported here can be related to other structurally similar alcohols and may impact regulatory tools such as ground level ozone-forming potential calculations (incremental reactivity).
Book Synopsis Theories of Molecular Reaction Dynamics by : Niels E. Henriksen
Download or read book Theories of Molecular Reaction Dynamics written by Niels E. Henriksen and published by Oxford University Press, USA. This book was released on 2008 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with a central topic at the interface of chemistry and physics - the understanding of how the transformation of matter takes place at the atomic level. Building on the laws of physics, the book focuses on the theoretical framework for predicting the outcome of chemical reactions. The style is highly systematic with attention to basic concepts and clarity of presentation. Molecular reaction dynamics is about the detailed atomic-level description of chemical reactions. Based on quantum mechanics and statistical mechanics or, as an approximation, classical mechanics, the dynamics of uni- and bi-molecular elementary reactions are described. The book features a detailed presentation of transition-state theory which plays an important role in practice, and a comprehensive discussion of basic theories of reaction dynamics in condensed phases. Examples and end-of-chapter problems are included in order to illustrate the theory and its connection to chemical problems.
