Laboratory and Mechanistic Studies of Volatile Organic Carbon Oxidation Systems in the Atmosphere PDF Download
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Author: Joshua Alexandre Moss Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Volatile Organic Compounds (VOCs) oxidize in the troposphere and significantly influence the formation of pollutants including ground-level ozone, CO2, and particulate matter (PM). Ozone and PM negatively impact human health, and all three pollutants influence Earth's climate. VOCs also dominate the OH reactivity of the atmosphere which in turn influences concentrations of other important radical species including NO[subscript x] and HO2. Chamber experiments are often conducted to measure VOC oxidation in a controlled laboratory setting, but these studies are may be complicated by vapor deposition on chamber surfaces and potential VOC decomposition in the Chemical Ionization Mass Spectrometers (CIMS) which are used to measure a broad range of oxidation products. Mechanistic simulations are also frequently performed to emulate chamber chemistry with less effort and fewer complications than may arise during a chamber experiment, but the results of these simulations are limited by uncertainties and gaps in our understanding of VOC oxidation chemistry from empirical studies. This thesis addresses uncertainties in chamber measurements and mechanisms and uses both in tandem to provide mutual benefits. Chapter 2 focuses on the development and characterization of a Total Suspended Carbon (TSC) apparatus which may be used to parametrize chamber vapor deposition.
Author: Joshua Alexandre Moss Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Volatile Organic Compounds (VOCs) oxidize in the troposphere and significantly influence the formation of pollutants including ground-level ozone, CO2, and particulate matter (PM). Ozone and PM negatively impact human health, and all three pollutants influence Earth's climate. VOCs also dominate the OH reactivity of the atmosphere which in turn influences concentrations of other important radical species including NO[subscript x] and HO2. Chamber experiments are often conducted to measure VOC oxidation in a controlled laboratory setting, but these studies are may be complicated by vapor deposition on chamber surfaces and potential VOC decomposition in the Chemical Ionization Mass Spectrometers (CIMS) which are used to measure a broad range of oxidation products. Mechanistic simulations are also frequently performed to emulate chamber chemistry with less effort and fewer complications than may arise during a chamber experiment, but the results of these simulations are limited by uncertainties and gaps in our understanding of VOC oxidation chemistry from empirical studies. This thesis addresses uncertainties in chamber measurements and mechanisms and uses both in tandem to provide mutual benefits. Chapter 2 focuses on the development and characterization of a Total Suspended Carbon (TSC) apparatus which may be used to parametrize chamber vapor deposition.
Author: James Freeman Hunter Publisher: ISBN: Category : Languages : en Pages : 110
Book Description
.Organic molecules have many important roles in the atmosphere, acting as climate and biogeochemical forcers, and in some cases as toxic pollutants. The lifecycle of atmospheric organic carbon is extremely complex, with reaction in multiple phases (gas, particle, aqueous) and at multiple timescales. The details of the lifecycle chemistry (especially the amount and properties of particles) have important implications for air quality, climate, and human and ecosystem health, and need to be understood better. Much of the chemical complexity and uncertainty lies in the reactions and properties of low-volatility oxidized intermediates that result from the oxidation of volatile organic precursors, and which have received comparatively little study thus far. This thesis describes three projects that link together the entire chain of oxidation (volatile to intermediate to condensed) in an effort to improve our understanding of carbon lifecycle and aerosol production. Laboratory studies of atmospherically relevant aerosol precursors show that the slow oxidation of intermediates is critical to explaining the yield and properties of aerosol under highly oxidized ("aged") conditions, and that the production of organic particles is significantly increased when intermediates are fully oxidized. This aging process is a strong function of molecular structure, and depends on aerosol concentration through the phenomenon of condensational trapping. Further laboratory studies of a series of (poly)cyclic 10 carbon alkanes show that structural effects are largely explained through fragmentation reactions, and that more generally, carbon-carbon bond scission is a ubiquitous and important reaction channel for oxidized intermediates. Finally, direct measurement of oxidized intermediate compounds in field studies shows that these compounds are abundant and important in the ambient atmosphere, with concentrations and properties in between those of volatile and particulate organic compounds. Together with other co-located measurements and complementary techniques, this enables estimates of emission, oxidation, and deposition to be constructed. The results from this thesis can be used to inform more sophisticated models of atmospheric organic carbon cycling, and to improve prediction of organic particulate matter concentrations.
Author: Georges Le Bras Publisher: Springer Science & Business Media ISBN: Category : Science Languages : en Pages : 348
Book Description
Oxidation and removal of atmospheric constituents involve complex sequences of reactions which can lead to the production of photo-oxidants such as ozone. In order to understand and model these complex reaction sequences, it is necessary to have a comprehensive understanding of reaction mechanisms and accurate estimates of kinetic parameters for relevant gas-phase atmospheric reactions. This book presents recent advances in the field and includes the following topics: e.g. the oxidation of simple organic compounds, NOx kinetics and mechanisms, OH radical production and rate constants for the OH attack on more complex organic compounds, peroxy and alkoxy radical reactions, photo-oxidation of aromatic and biogenic compounds, and the interaction between radical species.
Author: Georges Le Bras Publisher: Springer ISBN: 9783642592171 Category : Science Languages : en Pages : 314
Book Description
Oxidation and removal of atmospheric constituents involve complex sequences of reactions which can lead to the production of photo-oxidants such as ozone. In order to understand and model these complex reaction sequences, it is necessary to have a comprehensive understanding of reaction mechanisms and accurate estimates of kinetic parameters for relevant gas-phase atmospheric reactions. This book presents recent advances in the field and includes the following topics: e.g. the oxidation of simple organic compounds, NOx kinetics and mechanisms, OH radical production and rate constants for the OH attack on more complex organic compounds, peroxy and alkoxy radical reactions, photo-oxidation of aromatic and biogenic compounds, and the interaction between radical species.
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: National Research Council Publisher: National Academies Press ISBN: 0309046319 Category : Science Languages : en Pages : 525
Book Description
Despite more than 20 years of regulatory efforts, concern is widespread that ozone pollution in the lower atmosphere, or troposphere, threatens the health of humans, animals, and vegetation. This book discusses how scientific information can be used to develop more effective regulations to control ozone. Rethinking the Ozone Problem in Urban and Regional Air Pollution discusses: The latest data and analysis on how tropospheric ozone is formed. How well our measurement techniques are functioning. Deficiencies in efforts to date to control the problem. Approaches to reducing ozone precursor emissions that hold the most promise. What additional research is needed. With a wealth of technical information, the book discusses atmospheric chemistry, the role of oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in ozone formation, monitoring and modeling the formation and transport processes, and the potential contribution of alternative fuels to solving the tropospheric ozone problem. The committee discusses criteria for designing more effective ozone control efforts. Because of its direct bearing on decisions to be made under the Clean Air Act, this book should be of great interest to environmental advocates, industry, and the regulatory community as well as scientists, faculty, and students.
Author: National Academies of Sciences, Engineering, and Medicine Publisher: National Academies Press ISBN: 0309445655 Category : Science Languages : en Pages : 227
Book Description
Our world is changing at an accelerating rate. The global human population has grown from 6.1 billion to 7.1 billion in the last 15 years and is projected to reach 11.2 billion by the end of the century. The distribution of humans across the globe has also shifted, with more than 50 percent of the global population now living in urban areas, compared to 29 percent in 1950. Along with these trends, increasing energy demands, expanding industrial activities, and intensification of agricultural activities worldwide have in turn led to changes in emissions that have altered the composition of the atmosphere. These changes have led to major challenges for society, including deleterious impacts on climate, human and ecosystem health. Climate change is one of the greatest environmental challenges facing society today. Air pollution is a major threat to human health, as one out of eight deaths globally is caused by air pollution. And, future food production and global food security are vulnerable to both global change and air pollution. Atmospheric chemistry research is a key part of understanding and responding to these challenges. The Future of Atmospheric Chemistry Research: Remembering Yesterday, Understanding Today, Anticipating Tomorrow summarizes the rationale and need for supporting a comprehensive U.S. research program in atmospheric chemistry; comments on the broad trends in laboratory, field, satellite, and modeling studies of atmospheric chemistry; determines the priority areas of research for advancing the basic science of atmospheric chemistry; and identifies the highest priority needs for improvements in the research infrastructure to address those priority research topics. This report describes the scientific advances over the past decade in six core areas of atmospheric chemistry: emissions, chemical transformation, oxidants, atmospheric dynamics and circulation, aerosol particles and clouds, and biogeochemical cycles and deposition. This material was developed for the NSF's Atmospheric Chemistry Program; however, the findings will be of interest to other agencies and programs that support atmospheric chemistry research.
Author: Joshua Alexandre Moss
Author: Joshua Alexandre Moss
Author: Sascha Nehr
Author: James Freeman Hunter
Author: Georges Le Bras
Author: Tobias Otto
Author: Georges Le Bras
Author: Christopher Yung-Ta Lim
Author: S. Gangwal
Author: National Research Council
Author: National Academies of Sciences, Engineering, and Medicine