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Author: Hongmin Yu Publisher: ISBN: Category : Atmospheric aerosols Languages : en Pages : 28
Book Description
Biomass burning organic aerosol (BBOA), organic aerosol that derived from burning of biomass fuels, has been a major research focus because of its special role in the global budget of atmospheric chemistry and radiative forcing. Due to its chemical complexity, there are gaps in our knowledge about the chemical aging processes of BBOA in the atmosphere. Since many photochemical aging experiments on BBOA are usually conducted for only a few hours, less is known about the photo-aging pathways of the system over an extended timescale. This study presents the analyses of three BBOA filter samples derived from three types of fuels that were photolytically aged over a timeframe of up to ~3.5 days. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Offline-Aerosol Mass Spectrometry (Offline-AMS) were used to measure the chemical changes in the aqueous sample extracts and evaluate how those changes can relate to their specific fuel type. This study finds an overall increase in oxidation states and decrease in the nitro group (NO2) compounds in the samples. The level of levoglucosan, a tracer organic species of BBOA, is also observed to decrease in the sample mixture due to photolysis alone for the first time. Several unique chemical characteristics were observed for each sample, which possibly relate to their individual fuel type. In order to further support those observations and obtain a full picture of the chemical compositions of the samples, future studies will focus on examining the acetonitrile extracts of our samples, investigating the corresponding on-line AMS data set, and applying more analytical methods to the sample extracts.
Author: Hongmin Yu Publisher: ISBN: Category : Atmospheric aerosols Languages : en Pages : 28
Book Description
Biomass burning organic aerosol (BBOA), organic aerosol that derived from burning of biomass fuels, has been a major research focus because of its special role in the global budget of atmospheric chemistry and radiative forcing. Due to its chemical complexity, there are gaps in our knowledge about the chemical aging processes of BBOA in the atmosphere. Since many photochemical aging experiments on BBOA are usually conducted for only a few hours, less is known about the photo-aging pathways of the system over an extended timescale. This study presents the analyses of three BBOA filter samples derived from three types of fuels that were photolytically aged over a timeframe of up to ~3.5 days. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Offline-Aerosol Mass Spectrometry (Offline-AMS) were used to measure the chemical changes in the aqueous sample extracts and evaluate how those changes can relate to their specific fuel type. This study finds an overall increase in oxidation states and decrease in the nitro group (NO2) compounds in the samples. The level of levoglucosan, a tracer organic species of BBOA, is also observed to decrease in the sample mixture due to photolysis alone for the first time. Several unique chemical characteristics were observed for each sample, which possibly relate to their individual fuel type. In order to further support those observations and obtain a full picture of the chemical compositions of the samples, future studies will focus on examining the acetonitrile extracts of our samples, investigating the corresponding on-line AMS data set, and applying more analytical methods to the sample extracts.
Author: Sean Herbert Kessler Publisher: ISBN: Category : Languages : en Pages : 134
Book Description
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: Publisher: ISBN: Category : Languages : en Pages : 49
Book Description
Multiphase OH and O3 oxidation reactions with atmospheric organic aerosol (OA) can influence particle physicochemical properties including composition, morphology, and lifetime. Chemical aging of initially insoluble or low soluble single-component OA by OH and O3 can increase their water-solubility and hygroscopicity, making them more active as cloud condensation nuclei (CCN) and susceptible to wet deposition. However, an outstanding problem is whether the effects of chemical aging on their CCN activity are preserved when mixed with other organic or inorganic compounds exhibiting greater water-solubility. In this work, the CCN activity of laboratory-generated biomass burning aerosol (BBA) surrogate-particles exposed to OH and O3 is evaluated by determining the hygroscopicity parameter, [kappa], as a function of particle type, mixing state, and OH/O3 exposure applying a CCN counter (CCNc) coupled to an aerosol flow reactor (AFR). Levoglucosan (LEV), 4-methyl-5-nitrocatechol (MNC), and potassium sulfate (KS) serve as representative BBA compounds that exhibit different hygroscopicity, water solubility, chemical functionalities, and reactivity with OH radicals, and thus exemplify the complexity of mixed inorganic/organic aerosol in the atmosphere. The CCN activities of all of the particles were unaffected by O3 exposure. Following exposure to OH, [kappa] of MNC was enhanced by an order of magnitude, from 0.009 to ~0.1, indicating that chemically-aged MNC particles are better CCN and more prone to wet deposition than pure MNC particles. No significant enhancement in [kappa] was observed for pure LEV particles following OH exposure. [kappa] of the internally-mixed particles was not affected by OH oxidation. Furthermore, the CCN activity of OH exposed MNC-coated KS particles is similar to the OH unexposed atomized 1:1 by mass MNC: KS binary-component particles. Our results strongly suggest that when OA is dominated by water-soluble organic carbon (WSOC) or inorganic ions, chemical aging has no significant impact on OA hygroscopicity. The organic compounds exhibiting low solubility behave as if they are infinitely soluble when mixed with a sufficient amount of water-soluble compounds. At and beyond this point, the particles' CCN activity is governed entirely by the water-soluble fraction and not influenced by the oxidized organic fraction. Our results have important implications for heterogeneous oxidation and its impact on cloud formation given that atmospheric aerosol is a complex mixture of organic and inorganic compounds exhibiting a wide-range of solubilities.
Author: Sherri W. Hunt Publisher: ACS Symposium ISBN: 9780841233638 Category : Science Languages : en Pages : 0
Book Description
This book highlights new cross-disciplinary advances in aerosol chemistry that involve more than one phase, for example, unique chemical processes occurring on gas-solid and liquid-solid interfaces.
Author: Clemens Mensink Publisher: Springer Nature ISBN: 3030220559 Category : Science Languages : en Pages : 490
Book Description
Current developments in air pollution modeling are explored as a series of contributions from researchers at the forefront of their field. This newest contribution on air pollution modeling and its application is focused on local, urban, regional and intercontinental modeling; emission modeling and processing; data assimilation and air quality forecasting; model assessment and evaluation; atmospheric aerosols. Additionally, this work also examines the relationship between air quality and human health and the effects of climate change on air quality. This work is a collection of selected papers presented at the 36th International Technical Meeting on Air Pollution Modeling and its Application, held in Ottawa, Canada, May 14-18, 2018. The book is intended as reference material for students and professors interested in air pollution modeling at the graduate level as well as researchers and professionals involved in developing and utilizing air pollution models.
Author: Mihalis Lazaridis Publisher: Springer Science & Business Media ISBN: 9400701624 Category : Science Languages : en Pages : 368
Book Description
This book’s main objective is to decipher for the reader the main processes in the atmosphere and the quantification of air pollution effects on humans and the environment, through first principles of meteorology and modelling/measurement approaches. The understanding of the complex sequence of events, starting from the emission of air pollutants into the atmosphere to the human health effects as the final event, is necessary for the prognosis of potential risk to humans from specific chemical compounds and mixtures of them. It fills a gap in the literature by providing a solid grounding in the first principles of meteorology and air pollution, making it particularly useful for undergraduate students. Its broad scope makes it a valuable text in many related disciplines, containing a comprehensive and integrated methodology to study the first principles of air pollution, meteorology, indoor air pollution, and human exposure. Problem-solving exercises help to reinforce concepts.
Author: Jan Zalasiewicz Publisher: Cambridge University Press ISBN: 110847523X Category : Medical Languages : en Pages : 385
Book Description
Reviews the evidence underpinning the Anthropocene as a geological epoch written by the Anthropocene Working Group investigating it. The book discusses ongoing changes to the Earth system within the context of deep geological time, allowing a comparison between the global transition taking place today with major transitions in Earth history.
Author: Christopher Yung-Ta Lim Publisher: ISBN: Category : Languages : en Pages : 101
Book Description
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.
Author: Rolf Müller (physicien.) Publisher: Royal Society of Chemistry ISBN: 1849730024 Category : Science Languages : en Pages : 347
Book Description
In recent years, several new concepts have emerged in the field of stratospheric ozone depletion, creating a need for a concise in-depth publication covering the ozone-climate issue. This monograph fills that void in the literature and gives detailed treatment of recent advances in the field of stratospheric ozone depletion. It puts particular emphasis on the coupling between changes in the ozone layer and atmospheric change caused by a changing climate. The book, written by leading experts in the field, brings the reader the most recent research in this area and fills the gap between advanced textbooks and assessments.
Author: Hongmin Yu
Author: Hongmin Yu
Author: Sean Herbert Kessler
Author: 
Author: Sherri W. Hunt
Author: Clemens Mensink
Author: Mihalis Lazaridis
Author: Jan Zalasiewicz
Author: Christopher Yung-Ta Lim
Author: 
Author: Rolf Müller (physicien.)