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Author: Delanie Losey Publisher: ISBN: Category : Languages : en Pages :
Book Description
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: Delanie Losey Publisher: ISBN: Category : Languages : en Pages :
Book Description
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
Book Description
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: Sarah Sihvonen Publisher: ISBN: Category : Languages : en Pages :
Book Description
Aerosol particles impact the climate by serving as the seeds to form water droplets and ice to form clouds. However, these aerosol-cloud interactions are the least understood aspect of our understanding of the climate system. Mineral dust aerosol is the largest global source of ice nucleating particles. During atmospheric transport, mineral dust can be exposed to sulfuric acid, which has been shown to decrease the ice nucleation activity of these particles. Many explanations for this observation, such as chemical changes to the surface or product formation that blocks active sites, have been suggested. Our research focused on building a molecular picture of these surfaces to understand why sulfuric acid exposure reduces the ice nucleation activity of clay minerals such as kaolinite. We performed studies using X-ray diffraction and solid state NMR that investigate the changes that clay minerals undergo as a result of acid exposure. We are the first to show that the formation of a product on the surface of kaolinite was responsible for the decreased ice nucleation activity, not surface changes to the mineral itself. We continued to study aerosol-cloud interactions by using parcel models that explore the impact of ice growth surface kinetics on the competition between heterogeneous and homogeneous ice nucleation in clouds. We found that impaired growth of ice favors homogeneous freezing. The parcel models will be expanded to include our work on clay minerals to explore the impact of chemical aging of ice nuclei on overall cloud properties. We also studied the effect of acidic-processing on coal fly ash samples. Coal fly ash has been found to have a similar atmospheric impact as mineral dust, but is studied to a lesser extent. Like mineral dust, coal fly ash can serve as a source of bioavailable iron to phytoplankton in nutrient limited regions of the ocean. Fly ash has also been found to serve as an ice nucleating material. We performed aqueous sulfuric acid-treatment on fly ash samples representative of the types produced in the United States. We found that a soluble salt, gypsum (hydrated calcium sulfate), formed on three out of four samples. The most iron rich sample did not react with sulfuric acid. However, acidic-processing was shown to increase the amount of soluble iron which has implications for the biogeochemical cycle. These results also demonstrate that further work investigating these fly ash systems is warranted. In addition to our work on ice nucleation, we constructed a photoacoustic spectrometer to measure the absorbance of aerosol particles to study the optical properties of atmospheric aerosol. These measurements will aid in understanding the interactions of aerosol particles with light and the radiative balance of the planet.
Author: Paul E. Wagner Publisher: Springer ISBN: 9783540501084 Category : Science Languages : en Pages : 764
Book Description
These proceedings give a rather complete overview of the most recent research in the areas of fundamental processes and phase transitions, cloud droplet and ice nucleation in the atmosphere, and aerosol formation and aerosol characteristics in the atmosphere. Nine review papers on topics of special importance are supplemented by about 200 summaries on topics of greatest current importance. The volume should be of interest to scientists working in the atmospheric and environmental sciences, in chemistry and in physics, as well as to engineers working in these areas.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Abstract : Atmospheric aerosols play a vital role in the Earth's energy budget-directly by scattering and absorbing solar radiation and indirectly by acting as cloud condensation nuclei and ice-nucleating particles [1, 2]. The cloud formation potential of aerosol is driven by multiple factors, including surface properties, size distribution, composition, mixing state, phase state, and morphology [3]. The interaction of aerosols with clouds alters the aerosol's physicochemical properties. Those properties can also evolve during transport due to atmospheric processing, in turn, affect the aerosol's ice nucleation and cloud formation activities. This thesis presents experimental studies to understand the role of physicochemical properties of aerosol on the formation of ice. To get a detailed understanding of the aerosol effect on ice nucleation, we conducted controlled ice nucleation experiments on a known surface (muscovite mica) with controlled properties (e.g., surface cations) as well as ice nucleation experiments on complex atmospheric particles, which were characterized with multimodal microspectroscopic techniques. The results from controlled experiments suggest that the ice nucleation activity of a surface can be modified by simply changing the surface cations. In contrast, ice nucleation experiments with complex atmospheric particles indicates a more complicated dependence on the physicochemical properties.
Author: Valerie Alstadt Publisher: ISBN: Category : Languages : en Pages :
Book Description
The composition and properties of aerosol particles present in the atmosphere have broad implications for both climate and human health. Aerosol particles interact with water and form cloud condensation nuclei or ice nuclei; however, the effect of these interactions on climate are not well understood. Additionally, the heterogeneous chemistry of aerosol particles can affect atmospheric particle composition and ice nucleation activity. Particle size and local aerosol composition also have important implications for human health. Of particular interest are mineral dust particles as these particles may undergo long range transport after entering the atmosphere through desert winds. These particles can interact with other atmospheric pollutants, which may alter their surface properties. We investigated the adsorption of one such pollutant, acetic acid, on the surface of the mineral kaolinite before and after the addition of water vapor using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). To determine the conformation of the resulting adsorbates on the surface, we used molecular modeling to determine the theoretical frequencies of possible surface conformations. This research determined that the type of adsorbate on the surface of the treated particles varied with the addition of water as some conformations were more energetically stable in the presence of water than others.Further work focused on water adsorption on the nanoscale and the energetics of water desorption. We studied the effects of surface defects on water adsorption on the surface of sodium chloride using Atomic Force Microscopy (AFM) and Temperature Program Desorption Spectroscopy (TPDS). This research provided insight into the energetics of how water binds to sodium chloride and how water binds onto water layers at cold temperatures. As the surface properties and composition of particles with good ice nucleation activity in the atmosphere are unclear, we also studied the immersion freezing activity of multi-walled carbon nanotubes in order to determine whether ice nucleation occurred on the outer surface, inner pore, or edge of the carbon nanotube. Using additional characterization methods, we determined that freezing occurred inside the nanotube and that freezing began at different temperatures depending on the size of the inner diameter. This research provided insight into how soot and the spherules that comprise soot could be an effective ice nucleus depending on size. On the local level, we have studied the changes in atmospheric particle composition in University Park, PA before and after local power plants converted from coal to natural gas consumption. Particle measurements were taken fourteen times in a two-year period and Transmission Electron Microscopy (TEM) was performed in order to determine how particle composition changed and whether or not the number of fractal particles changed. The long-term aim of this study was to provide specific information on the local composition of PM2.5 particles.
Author: Robert Parker Publisher: ISBN: Category : Languages : en Pages :
Book Description
Aerosol particles undergo numerous phase transitions in the atmosphere as the relative humidity is varied. Understanding the location and occurrence of these phase transitions is essential for understanding the morphology and successful modeling of aerosol particles. Some phase transitions that are possible are deliquescence, efflorescence, separation, and mixing. To investigate the phase transitions of organic aerosol particles, model systems composed of either phenylglyoxylic acid or 3,4-dimethoxyphenylacetic acid with either ammonium sulfate, ammonium chloride, or sodium sulfate were studied. Using optical microscopy, these systems have revealed a hysteresis between the location of separation and mixing phase transitions. To our knowledge this hysteresis has never been reported before. Additionally a history effect has been observed in which the immediate RH and time history of the aerosol particle influences the location of the mixing phase transition. The existence of these two phenomena, in addition to their atmospheric implications, are discussed.
Author: Rekha Kale Publisher: Scitus Academics LLC ISBN: 9781681171326 Category : Aerosols Languages : en Pages : 0
Book Description
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: National Research Council Publisher: National Academies Press ISBN: 0309133505 Category : Science Languages : en Pages : 222
Book Description
Changes in climate are driven by natural and human-induced perturbations of the Earth's energy balance. These climate drivers or "forcings" include variations in greenhouse gases, aerosols, land use, and the amount of energy Earth receives from the Sun. Although climate throughout Earth's history has varied from "snowball" conditions with global ice cover to "hothouse" conditions when glaciers all but disappeared, the climate over the past 10,000 years has been remarkably stable and favorable to human civilization. Increasing evidence points to a large human impact on global climate over the past century. The report reviews current knowledge of climate forcings and recommends critical research needed to improve understanding. Whereas emphasis to date has been on how these climate forcings affect global mean temperature, the report finds that regional variation and climate impacts other than temperature deserve increased attention.
Author: Publisher: Walter de Gruyter GmbH & Co KG ISBN: 1501519379 Category : Science Languages : en Pages : 215
Book Description
Atmospheric aerosols are an important and a highly complex component of the Earth’s atmosphere that alter the radiative forcing and the chemical composition of the gas phase. These effects have impacts on local air quality and the global climate. Atmospheric Aerosol Chemistry outlines research findings to date in aerosol chemistry and advances in analytical tools used in laboratory studies for studying their surface and bulk reactivity.
Author: Delanie Losey
Author: Delanie Losey
Author: Emma Tackman
Author: Sarah Sihvonen
Author: Paul E. Wagner
Author: 
Author: Valerie Alstadt
Author: Robert Parker
Author: Rekha Kale
Author: National Research Council
Author: