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Author: Wiesje Mooiweer
Publisher: ProQuest
ISBN: 9781109180466
Category : Atmospheric aerosols
Languages : en
Pages : 182
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Book Description
Particulates that form the atmospheric aerosol play a significant role in determining Earth's climate, both directly through scattering and absorption of solar radiation, and indirectly by impacting cloud formation processes. They are present in a large range of sizes, concentrations, chemical compositions, and compositional inhomogeneities, complicating our ability to quantify the aerosol's direct and indirect effects. This work investigates the dependence of aerosol light scattering on relative humidity (RH) and chemical composition, and the effect of organic material on scattering enhancement and implied particle growth characteristics. It utilizes measurements carried out in the Elk Mountain/Laramie Aerosol Characterization Experiment (EMLACE), in which observations were made at both a clean high-altitude mid-continental site (Elk Mountain, WY) in summer (2006), and in a small urban environment (Laramie, WY) during both summer (2005) and winter (2006). High time resolution measurements of scattering extinction from both dry and humidified PM 1 aerosols were obtained together with time resolved measurements of PM 1 volatile aerosol chemical composition and mass loading. Variabilities in particle chemical composition and optical behavior with location and season are documented. Scattering extinction is positively correlated with aerosol mass loading. Enhanced scattering, due to water uptake by the particles at high RH, is described by a scattering enhancement factor (f(RH)), which is found to be smaller with increasing mass fraction of organic material. Observed f(RH) values are interpreted in terms of mass weighted contributions (f(RH high) Inorg and f(RH high) Org) from the particulate inorganic and organic material at high RH. Analyses show that whereas f(RH high) Inorg varies continually, depending on the physical and chemical properties of the aerosol, the experimental data can, in general, be adequately interpreted using a value of 1.0 for f(RH high) Org (though values up to 1.1 are occasionally indicated), suggesting that organic material does not significantly promote increased scattering at high RH. Numerical values of f(RH high) Inorg and f(RH high) Org were used to develop an empirical parameterization of changes in aerosol optical properties with increasing RH, based solely on variations in particulate chemical composition. This parameterization successfully reconstructs variations in f(RH) for the observed ambient aerosols over the entire range of RH values employed in the experiments.
Author: Wiesje Mooiweer
Publisher: ProQuest
ISBN: 9781109180466
Category : Atmospheric aerosols
Languages : en
Pages : 182
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Book Description
Particulates that form the atmospheric aerosol play a significant role in determining Earth's climate, both directly through scattering and absorption of solar radiation, and indirectly by impacting cloud formation processes. They are present in a large range of sizes, concentrations, chemical compositions, and compositional inhomogeneities, complicating our ability to quantify the aerosol's direct and indirect effects. This work investigates the dependence of aerosol light scattering on relative humidity (RH) and chemical composition, and the effect of organic material on scattering enhancement and implied particle growth characteristics. It utilizes measurements carried out in the Elk Mountain/Laramie Aerosol Characterization Experiment (EMLACE), in which observations were made at both a clean high-altitude mid-continental site (Elk Mountain, WY) in summer (2006), and in a small urban environment (Laramie, WY) during both summer (2005) and winter (2006). High time resolution measurements of scattering extinction from both dry and humidified PM 1 aerosols were obtained together with time resolved measurements of PM 1 volatile aerosol chemical composition and mass loading. Variabilities in particle chemical composition and optical behavior with location and season are documented. Scattering extinction is positively correlated with aerosol mass loading. Enhanced scattering, due to water uptake by the particles at high RH, is described by a scattering enhancement factor (f(RH)), which is found to be smaller with increasing mass fraction of organic material. Observed f(RH) values are interpreted in terms of mass weighted contributions (f(RH high) Inorg and f(RH high) Org) from the particulate inorganic and organic material at high RH. Analyses show that whereas f(RH high) Inorg varies continually, depending on the physical and chemical properties of the aerosol, the experimental data can, in general, be adequately interpreted using a value of 1.0 for f(RH high) Org (though values up to 1.1 are occasionally indicated), suggesting that organic material does not significantly promote increased scattering at high RH. Numerical values of f(RH high) Inorg and f(RH high) Org were used to develop an empirical parameterization of changes in aerosol optical properties with increasing RH, based solely on variations in particulate chemical composition. This parameterization successfully reconstructs variations in f(RH) for the observed ambient aerosols over the entire range of RH values employed in the experiments.
Author: Sotiria Koloutsou-Vakakis
Publisher:
ISBN:
Category :
Languages : en
Pages : 324
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Book Description
Recent model predictions indicate that sulfate aerosol particles cause radiative forcing of the same magnitude but of opposite sign than the forcing caused by anthropogenic greenhouse gases. The spatial and temporal variability of parameters used in the models are highly uncertain resulting in uncertain model predictions of the aerosol radiative forcing. Such parameters related to aerosol particle properties and direct radiative forcing are: the hygroscopic growth factor (f(RH)), the upscatter fraction ($beta$), and the mass scattering efficiency, ($alpha$). These three parameters can be estimated from regional measurements of total light scattering and back-scattering coefficients as functions of relative humidity, particle composition and size, and wavelength of light. To take and validate such measurements: (i) an ambient aerosol monitoring station was designed and built for continuous ambient aerosol measurements, south of Bondville, in Central Illinois, U.S.A., (ii) instrumentation that measures aerosol particle light scattering coefficients under controlled relative humidity conditions was designed, built, calibrated and tested, (iii) a model was developed that estimates hygroscopic particle growth under the assumption of thermodynamic equilibrium and for metastable particles, (iv) experiments with laboratory generated aerosol particles were completed to calibrate the instrumentation and test the models, and (v) tests for closure were completed using the experimental and modeled results. Examination of the measurements to date, showed that about 95% of the aerosol gravimetric mass (dp $le$ 1 $mu$m), at Bondville, that is identifiable with ion chromatography consists of NH$sb4sp+$ and SO$sb4sp{2-}$. Mean values and standard deviations for f(RH) were in the range 1.1 $pm$ 0.4 to 2.3 $pm$ 1.1 depending on wavelength and direction of scattering. Mean values and standard deviations for b were in the range 7.0% $pm$ 1.4% to 21.7% $pm$ 4.18% depending on relative humidity and wavelength. $rmalphasb{sosbsp{4}{2-}}$ (estimated with multiple linear regression) was 8.25 m$sp2$/g. A model, was developed to test closure. The model integrates results from thermodynamic equilibrium calculations and experimental data on metastable particles, with light scattering modeling. Tests for closure indicated that the water insoluble component of the aerosol, which is not accounted for by ion chromatography, can be very important in modifying the optical properties of the aerosol.
Author: George W. Griffing
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 2
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Book Description
Author: Ernie R. Lewis
Publisher: American Geophysical Union
ISBN: 0875904173
Category : Science
Languages : en
Pages : 423
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Book Description
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 152. Sea salt aerosol (SSA) exerts a major influence over a broad reach of geophysics. It is important to the physics and chemistry of the marine atmosphere and to marine geochemistry and biogeochemistry generally. It affects visibility, remote sensing, atmospheric chemistry, and air quality. Sea salt aerosol particles interact with other atmospheric gaseous and aerosol constituents by acting as sinks for condensable gases and suppressing new particle formation, thus influencing the size distribution of these other aerosols and more broadly influencing the geochemical cycles of substances with which they interact. As the key aerosol constituent over much of Earth's surface at present, and all the more so in pre-industrial times, SSA is central to description of Earth's aerosol burden.
Author: Alan P. Waggoner
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 56
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Book Description
Author: Panel on Aerosol Radiative Forcing and Climate Change
Publisher: National Academies Press
ISBN: 0309588871
Category : Science
Languages : en
Pages : 180
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Book Description
This book recommends the initiation of an "integrated" research program to study the role of aerosols in the predicted global climate change. Current understanding suggest that, even now, aerosols, primarily from anthropogenic sources, may be reducing the rate of warming caused by greenhouse gas emissions. In addition to specific research recommendations, this book forcefully argues for two kinds of research program integration: integration of the individual laboratory, field, and theoretical research activities and an integrated management structure that involves all of the concerned federal agencies.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 5
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Book Description
Ambient aerosols are frequently composed of hygroscopic inorganic salts such as chlorides, sulfates and nitrates in either pure or mixed forms. Such inorganic salt aerosols exhibit the properties of deliquescence and efflorescence in air. The phase transformation from a solid particle to a saline droplet usually occurs spontaneously when atmospheric relative humidity reaches a level specific to the chemical composition of the aerosol particle. Conversely, when relative humidity decreases and becomes low enough, a saline droplet will evaporate and suddenly crystallize, expelling all its water content. Information on the composition and temperature dependence of these properties is required in mathematical models for describing the dynamic and transport behavior of ambient aerosols. Experiments are carried out in the temperature range 5--35°C, using single particles individually suspended in an electrodynamic cell that can be evacuated and back filled with water vapor. The phase transformation of the aerosol particle is monitored by laser light scattering and the relative humidity at the transition point is determined by directly measuring the water vapor pressure in the cell. Results are obtained for particles containing either a single salt or a preselected mixture of NaCl, KCl, NaNO3, Na2SO4 and (NH4)2SO4, which are common constituents of ambient aerosols. A theoretical model on the composition and temperature dependence of the deliquescence properties is developed for single and two-salt aerosol systems.
Author: Jeffery S. Marshall
Publisher: Cambridge University Press
ISBN: 1107032075
Category : Mathematics
Languages : en
Pages : 361
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Book Description
This is targeted at professionals and graduate students working in disciplines where flow of adhesive particles plays a significant role.
Author: John H. Seinfeld
Publisher: John Wiley & Sons
ISBN: 1118591364
Category : Science
Languages : en
Pages : 1249
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Book Description
Thoroughly restructured and updated with new findings and new features The Second Edition of this internationally acclaimed text presents the latest developments in atmospheric science. It continues to be the premier text for both a rigorous and a complete treatment of the chemistry of the atmosphere, covering such pivotal topics as: * Chemistry of the stratosphere and troposphere * Formation, growth, dynamics, and properties of aerosols * Meteorology of air pollution * Transport, diffusion, and removal of species in the atmosphere * Formation and chemistry of clouds * Interaction of atmospheric chemistry and climate * Radiative and climatic effects of gases and particles * Formulation of mathematical chemical/transport models of the atmosphere All chapters develop results based on fundamental principles, enabling the reader to build a solid understanding of the science underlying atmospheric processes. Among the new material are three new chapters: Atmospheric Radiation and Photochemistry, General Circulation of the Atmosphere, and Global Cycles. In addition, the chapters Stratospheric Chemistry, Tropospheric Chemistry, and Organic Atmospheric Aerosols have been rewritten to reflect the latest findings. Readers familiar with the First Edition will discover a text with new structures and new features that greatly aid learning. Many examples are set off in the text to help readers work through the application of concepts. Advanced material has been moved to appendices. Finally, many new problems, coded by degree of difficulty, have been added. A solutions manual is available. Thoroughly updated and restructured, the Second Edition of Atmospheric Chemistry and Physics is an ideal textbook for upper-level undergraduate and graduate students, as well as a reference for researchers in environmental engineering, meteorology, chemistry, and the atmospheric sciences. Click here to Download the Solutions Manual for Academic Adopters: http://www.wiley.com/WileyCDA/Section/id-292291.html
Author: Kristin Di Monte
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Light extinction by atmospheric aerosol particles and their interactions with water are heavily dependent on their chemical composition, morphology, and mixing state. Both properties are crucial for determining the impact aerosol particles have on our climate. Since light extinction directly impacts visibility as well as climate, measurements of the extinction at varying relative humidities (RH) are needed in order to improve climate models. In this work we have measured the relative humidity dependence of aerosol light extinction and water uptake at 643 nm for particles of varying ammonium sulfate/organic compositions. Internal as well as external mixtures of levoglucosan, sucrose, and adipic acid with ammonium sulfate are investigated using cavity ring-down spectroscopy (CRDS). Optical growth factor (fRH) and hygroscopicity parameters ([kappa]) are reported for each aerosol system.
