Morphology and Optical Properties of Aerosol Particles Coated with Palmitic Acid PDF Download
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Author: Joshua Haines
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The morphology of aerosol particles influences the reactions that occur during atmospheric aging, as well as altering their contributions to the direct and indirect effects. In order to study the morphology of aerosol particles coated with organic compounds, we have condensed palmitic acid onto ammonium sulfate, quartz, and kaolinite particles with a coating oven. Using transmission electron microscopy, we have determined that the coated particles consist of a core particle with palmitic acid non-uniformly surrounding this core. This particle morphology matches atmospherically relevant particles. However, to our knowledge, particles with this morphology have not been created through the use of a coating oven. The optical properties of the coated particles are characterized through cavity ring-down spectroscopy and compared to Mie scattering calculations. For thick coatings, Mie scattering theory is effective at predicting the extinction cross section of the observed particles. We discuss the atmospheric relevance of the observed particles and their impact on climate-aerosol interactions.
Author: Joshua Haines
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The morphology of aerosol particles influences the reactions that occur during atmospheric aging, as well as altering their contributions to the direct and indirect effects. In order to study the morphology of aerosol particles coated with organic compounds, we have condensed palmitic acid onto ammonium sulfate, quartz, and kaolinite particles with a coating oven. Using transmission electron microscopy, we have determined that the coated particles consist of a core particle with palmitic acid non-uniformly surrounding this core. This particle morphology matches atmospherically relevant particles. However, to our knowledge, particles with this morphology have not been created through the use of a coating oven. The optical properties of the coated particles are characterized through cavity ring-down spectroscopy and compared to Mie scattering calculations. For thick coatings, Mie scattering theory is effective at predicting the extinction cross section of the observed particles. We discuss the atmospheric relevance of the observed particles and their impact on climate-aerosol interactions.
Author: Daniel Veghte
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Major factors that affect climate change depend on gas and particulate phase components in the atmosphere. Gas phase species have been studied in great detail and are well understood, causing a warming effect on the atmosphere. The less understood major contributing factor in the atmosphere are aerosol particles, which range in size from nanometers up to microns. Aerosol particles can directly scatter and absorb light and also have secondary effects such as acting as a surface for gas phase reactions to occur or seed particles for cloud formation. Aerosol particles can cause health problems ranging from serious cardiovascular to respiratory effects. All Climate and health effects of aerosol particles are dependent on particle composition, morphology, concentration, and size. Since a large variety of particulate types exist in the atmosphere, we have focused on understanding the effect of mineral dust composition and morphology. Mineral dust is important because it is the second largest emission by mass. In order to study the optical properties of aerosol particles, we built a cavity ring-down spectrometer and developed methods to interpret the excinction cross section results for particles with a varied shape. We have studied the major components of mineral dust that include calcium carbonate, hematite, quartz, aluminosilicate clay minerals, and feldspars, along with a heterogeneous dust sample. We have found that non-absorbing species that have surface roughness and an aspect ratio close to one (such as calcite, quartz and feldspar) can be treated as spheres. Aerosol particles that are absorbing (hematite) that have an aspect ratio near one with a roughened surface need to be treated with more complex models; otherwise the extinction cross section will be underrepresented. For aerosol particles that are non-absorbing but have a high aspect ratio (aluminosilicate clay minerals), additional modeling parameters are also needed that will account for shape and orientation. We have used Arizona Test Dust to determine if the models we have developed can be used to model the optical properties of a heterogeneous mixture. We have shown that the extinction cross section of the Arizona Test Dust can be modeled as long as individual components are treated independently and significant error would be introduces if all species were treated as spheres.Organic aerosol particles are chemically complex species that originate from primary or secondary emissions. We have described mixed organic/ammonium sulfate particles in the submicron regime using TEM to understand phase separation. When the organic component has a high aqueous solubility, all particles exhibit a homogeneous morphology while at low aqueous solubility all particles exhibit a phase separated structure. Intermediate solubility organics show a size dependent morphology. For pimelic and succinic acid, small particles (under approximately 200 nm) have a homogeneous structure while the larger particles exhibit phase separated structures. We have studied samples collected in Ulaanbaatar, Mongolia to better understand the types of particles and the effect of aging on these particles in an urban environment. The majority of the particles are soot, small spheres, or mineral dust. When we compared the monthly particle composition, we saw that there was an increased aging of the particles during the winter months due to pollution and a lower boundary layer leading to reduced atmospheric mixing. By understanding the particle composition present in areas and modeling the optical properties of individual particle types, better models can be created to give insight into aerosol particles affects on the atmosphere.
Author: Kristin Di Monte
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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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.
Author: Delanie Losey
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Aerosol particle morphology can influence the water uptake, heterogeneous chemistry, and optical properties of the particle. This morphology is known to be dependent on the composition of the particle as well as relative humidity. Recent studies have pointed out the importance of pH in aerosol particles. The pH of systems being investigated during phase transition studies have not investigated the role of pH, which could lead to the deprotonation of the organic component and would affect phase transitions. To investigate the influence of high pH and therefore deprotonation on the phase transitions of 3-methylglutaric acid:ammonium sulfate, sodium hydroxide was used to make solutions with pHs below the pKa1, between the pKa1 and pKa2, and above pKa2 of 3-methylglutaric acid. Using optical microscopy and an environmental chamber, the separation relative humidity (SRH), mixing relative humidity (MRH), efflorescence relative humidity (ERH) and deliquescence relative humidity (DRH) were recorded for each system. As the pH of the system was increased, the SRH decreased. This was attributed to the increased solubility of the organic component in water when it was deprotonated. The ERH also changed to higher values with added sodium hydroxide. The MRH and DRH values, however, remained constant over all pH. A previously unobserved hysteresis was found between SRH and MRH and the atmospheric implications are discussed. The influence of low pH was also explored in a similar manner, but through addition of concentrated sulfuric acid. Stoichiometric amounts of sulfuric acid was added to six different organic:ammonium sulfate systems to change the salt identity to letovicite, (NH4)3H(SO4)2, and ammonium bisulfate, NH4HSO4. An experiment at low pH was also conducted for each system. In every case, the addition of sulfuric acid led to an overall decrease in SRH, as expected with changing salt identity. Furthermore, at the lowest pH studied the SRH of four of the six systems were so low that phase separation would not occur in atmospherically relevant conditions. Also, phase separation could occur with no inorganic salt present at all. The ERH and DRH for each system also were affected. These results could affect mass transfer and water uptake for systems at low pH, and can be further explored by investigating the role of pH in particle viscosity and submicron aerosol morphology. Fly ash can undergo aging in the atmosphere through interactions with sulfuric acid and water. These reactions can lead to physical and chemical changes caused by reaction products or chemical leaching. These changes could influence the amount of soluble material on the particle as well as the ability of the particle to nucleate ice. Both of these affect the fly ash particles ability to serve as a cloud nucleus. The extent of these changes is expected to be linked to the chemical composition of the fly ash so three fly ash types were investigated. The effect of water- and acid-treatment were assessed using X-ray diffraction, attenuated total reflectance infrared spectroscopy, transmission electron microscopy with selected area electron diffraction and energy dispersive spectroscopy, inductively coupled plasma-atomic emission spectroscopy, Brunauer-Emmett-Teller surface area analysis, and immersion freezing. The results show the presence of soluble material on fly ash and indicate that sulfuric-acid treatment has major physical and chemical effects on fly ash. These effects are dependent on composition of the fly ash. Acid-treatment results in gypsum being created and a variety of metals to be leached, and these changes did affect the immersion ice nucleation activity of the samples. Further studies of these effects on deposition mode freezing are expected for the future.
Author: Emma Tackman
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Aerosol particles are a diverse class of materials that permeate the atmosphere with implications for global climate and human health. Atmospheric aerosols are released into the environment from many sources and continue to undergo atmospheric processing which introduces further variation into particle populations. This surfeit of sources and atmospheric trajectories leads to a wide variety in the properties in aerosol particles such as composition, shape, size, morphology, and reactivity. The methods measuring properties of aerosol particles is itself an important and developing field of study with direct applications in bettering our understanding of aerosol behaviors and atmospheric chemical systems. This work presents a critical analysis of existing microscopy-based measurements and provides new methods, applications, and recommendations for improving the assessment of aerosol properties. Chemical properties of aerosol particles include aqueous particle acidity and the O:C ratio of organic constituents. A new method for measuring the internal pH of aqueous aerosol microdroplets was developed and presented here using carbon quantum dots as a pH sensitive fluorophore. This technique was validated using a complex organic mixture representing various functional groups found in atmospheric organic material. The influence of organic O:C ratio on phase separation for proxy organic/inorganic mixed aerosol particles was assessed for microdroplets and nanoparticles. For optical microscope experiments, sucrose was added to organic/inorganic mixtures to systematically increase the O:C ratio of the system and was observed to suppress phase separation. Similarly, particles made up of combinations of carboxylic acids at particular O:C ratios and inorganic salts are analyzed using TEM for size dependence of phase separation at the nanoscale. Generally, large particles are able to phase separate while small particles remain homogeneous, or well mixed, and the transition region between the two regimes was examined. TEM is used in several studies to consider aerosol particle spreading and morphology at atmospherically relevant sizes. Inorganic particles were found to spread along the surface of a substrate. Particles with an organic coating also spread on the substrate but additionally lost volume, possibly due to outgassing of residual volatile species in storage or physical deformation during the impaction process. Results were compared to measurements of the same particles suspended in a gas flow and sizing discrepancies between the two methods were found, mostly attributed to the presence of a substrate in microscope assays. Further, the influence of generation parameters on the final morphologies of particles was determined for particles made under low and high relative humidity conditions with wet and dry seed particles. Wet seeds were found to restructure due to humidity cycling and spread less on the surface than dry seeds, while wet and dry coated particles were influenced similarly by the impaction process. Wet seeded organic particles also showed a new textured morphology, emphasizing the utility of microscope measurements of individual aerosol particles.
Author: Rekha Kale
Publisher: Scitus Academics LLC
ISBN: 9781681171326
Category : Aerosols
Languages : en
Pages : 0
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Atmospheric Aerosols is a vital problem in current environmental research due to its importance in atmospheric optics, energetics, radiative transfer studies, chemistry, climate, biology and public health. Aerosols can influence the energy balance of the terrestrial atmosphere, the hydrological cycle, atmospheric dynamics and monsoon circulations. Because of the heterogeneous aerosol field with large spatial and temporal variability and reduction in uncertainties in aerosol quantification is a challenging task in atmospheric sciences. Keeping this in view the present study aims to assess the impact of aerosols on coastal Indian station Visakhapatnam and the adjoining Bay of Bengal. An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or not. Examples of natural aerosols are fog, forest exudates and geyser steam.
Author: Jennifer A. Faust
Publisher: Elsevier
ISBN: 0128136421
Category : Science
Languages : en
Pages : 492
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Book Description
Physical Chemistry of Gas-Liquid Interfaces, the first volume in the Developments in Physical & Theoretical Chemistry series, addresses the physical chemistry of gas transport and reactions across liquid surfaces. Gas–liquid interfaces are all around us, especially within atmospheric systems such as sea spry aerosols, cloud droplets, and the surface of the ocean. Because the reaction environment at liquid surfaces is completely unlike bulk gas or bulk liquid, chemists must readjust their conceptual framework when entering this field. This book provides the necessary background in thermodynamics and computational and experimental techniques for scientists to obtain a thorough understanding of the physical chemistry of liquid surfaces in complex, real-world environments. 2019 PROSE Awards - Winner: Category: Chemistry and Physics: Association of American Publishers Provides an interdisciplinary view of the chemical dynamics of liquid surfaces, making the content of specific use to physical chemists and atmospheric scientists Features 100 figures and illustrations to underscore key concepts and aid in retention for young scientists in industry and graduate students in the classroom Helps scientists who are transitioning to this field by offering the appropriate thermodynamic background and surveying the current state of research
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309445655
Category : Science
Languages : en
Pages : 227
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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: National Research Council
Publisher: National Academies Press
ISBN: 030916463X
Category : Science
Languages : en
Pages : 222
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Scientists and engineers have long relied on the power of imaging techniques to help see objects invisible to the naked eye, and thus, to advance scientific knowledge. These experts are constantly pushing the limits of technology in pursuit of chemical imagingâ€"the ability to visualize molecular structures and chemical composition in time and space as actual events unfoldâ€"from the smallest dimension of a biological system to the widest expanse of a distant galaxy. Chemical imaging has a variety of applications for almost every facet of our daily lives, ranging from medical diagnosis and treatment to the study and design of material properties in new products. In addition to highlighting advances in chemical imaging that could have the greatest impact on critical problems in science and technology, Visualizing Chemistry reviews the current state of chemical imaging technology, identifies promising future developments and their applications, and suggests a research and educational agenda to enable breakthrough improvements.
Author: British Road Federation
Publisher:
ISBN:
Category : Roads
Languages : en
Pages : 36
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