Experimental and Modeling Study of Heterogeneous Ice Nucleation on Mineral Aerosol Particles and Its Impact on a Convective Cloud PDF Download
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Author: Thibault Hiron
Publisher:
ISBN:
Category : Impact
Languages : en
Pages :
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Author: Thibault Hiron
Publisher:
ISBN:
Category : Impact
Languages : en
Pages :
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Author: Sarah Sihvonen
Publisher:
ISBN:
Category :
Languages : en
Pages :
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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: Constantin Andronache
Publisher: Elsevier
ISBN: 012810550X
Category : Science
Languages : en
Pages : 302
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Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling
Author: Alessia Nicosia
Publisher:
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Category :
Languages : en
Pages : 0
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Heterogeneous ice nucleation is one element inside the overall complexity of the Earth's atmosphere, however, it has a profound impact on our representation of cloud properties: this process affects the optical thickness and lifetime of mixed-phase clouds and cirrus clouds, and it is responsible for a significant proportion of precipitations formed globally. Heterogeneous ice nucleation is related to the presence of specific aerosol particles, named ice nuclei particles (INP), with the unique ability of lowering the energy barrier required for the formation of ice crystals, especially where cloud's temperatures are >-38 °C. In the last decades, significant advancements have been made to the fundamental understanding of ice nucleation, however the lack of knowledge on the cloud ice phase still contributes to major uncertainties in climate model prediction of radiative forcing. This is partly due to limited observational data quantifying INP distributions and properties all over the world, especially in remote locations. In the first part of this thesis, field observations of ice nucleating particles have been performed at the Italian Climate Observatory “O. Vittori” on Mountain Cimone (2165 m above sea level), in the spring 2014 and autumn 2015, within the Bacchus and Air Sea Lab projects. For the first time we report the results of offline INP measurements, performed at a high altitude site within the Mediterranean basin. In the period 19-29 May 2014, a parallel campaign took place at the low-altitude station San Pietro Capofiume, a rural site in the Po Valley. The two campaigns were concerned, for a few days, by a Saharan Dust transport Event, which was recorded simultaneously at the high and the low-level station. We investigated the ambient number concentration of INP under condensation freezing activation mechanism (at -18 °C and above water saturation). In the second part of this thesis, we present the observations that were performed during the Arctic campaign Parcs-Maca, in the period of transition among the polar night and the polar day. We could characterise for the first time the ice nucleating and physical/chemical properties of the Arctic Primary Marine Aerosol, in a laboratory-controlled generation approach, that was combined to a mesocosm experiment. The aim of the mesocosm experiment was to adopt a multidisciplinary approach to study the effect of marine pollution on marine emissions. We found a moderate but significant decrease of the ice nuclei concentration in the polluted seawater (with respect to the control seawater) recorded in the freezing range between -8.5 and -19 °C and activated through immersion-freezing. Within the seaspray our measurements have indicated a relation among INP active at warm temperature (above -15 °C through immersion-freezing) and a calcium enrichment detected in PM1 filters (and followed by an apparent Chloride depletion). On the basis of our observations, and the results reported from other studies, a few suggestions on the nature of these marine ice nuclei have been suggested. In summary, the measurements made for this thesis provide new information on the concentrations of ice nuclei in ambient aerosol particles in remote regions (a high-altitude observatory in the central Mediterranean region) and in relation to a specific source (the Arctic sea spray).
Author: Zaminhussein Abdulali Kanji
Publisher:
ISBN: 9780494609897
Category :
Languages : en
Pages : 490
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The indirect aerosol effect contributes to major uncertainties in determining the radiation budget of the earth. A large uncertainty is due to the formation of ice clouds onto natural or anthropogenic aerosols. Field studies have shown that mineral type particles are often associated with ice crystals in the mid-upper troposphere and given the long residence time in the atmosphere of dust particles (∼2 weeks in the absence of precipitation), their contribution to ice formation processes is not fully defined.It was concluded that there is no single value for the onset of ice formation in the atmosphere via deposition freezing. The associated contact angles show that there is a distribution of active sites on IN and that not all active sites have the same affinity for initiation of ice formation even within the same aerosol type. This work provides evidence that deposition mode nucleation can be an alternate pathway to homogeneous nucleation when mineral aerosols are present in the troposphere since the high T-low RH conditions required for deposition mode nucleation are more easily encountered in the atmosphere than the low T-high RH required for homogeneous nucleation.In order to probe ice formation onto natural mineral dust in a setting where it could be suspended as aerosol, a new continuous flow diffusion chamber (CFDC) was built. This allowed investigations of the effects of total aerosol surface area and particle size. The CFDC was also used in an international inter-comparison of ice nucleation instrumentation to compare efficiencies of soot, biological aerosol (bacteria) and samples of natural desert dusts from different regions of the world. The laboratory observations were parameterized using nucleation rates (Jhet) and contact angles (theta) as described by classical nucleation theory.For both this experimental technique and a static one developed during the candidate's Masters degree, mineral dust particulate proved to be the most efficient ice nuclei (IN) activating at RH with respect to ice (RH i) as low as 105% at T=233 K. The efficiency varied with particle size and aerosol surface area (SA). Large particles or higher SA activated at lower RHi than small particles or lower SA. The static chamber was sensitive to the first ice event out of a large SA and therefore gave true onset RHi, which was lower than the onset defined by the CFDC studies, which was not sensitive to a single ice event. In addition the static chamber used a broader size range of particulate matter, including super micron particles while the CFDC particles sizes were restricted to below 0.5 microm. Soot and organic coated dust particles were inefficient IN compared to pure dust. Soot aerosols showed some efficiency at T
Author: Katherine Marak
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Aerosol particles can facilitate heterogenous ice formation in the troposphere and stratosphere by acting as ice nuclei, modulating cloud formation/dissipation, precipitation, and their microphysical properties. Heterogeneous ice nucleation is driven by ice embryo formation on the particle surface, which can be influenced by features of the surface such as crystallinity, surface structure, lattice structure, defects, and functional groups. Probing for deeper understanding of what surface features have the greatest impact on heterogeneous freezing is significant and can be done with synthetic and modified materials. To characterize the effect of crystallinity, pores, and surface functional groups towards ice nucleation, samples of comparable silica systems, specifically, quartz, ordered and non-ordered porous amorphous silica samples with a range of pore sizes (2-11 nm), and non-porous functionalized silica spheres were used as models for mineral dust aerosol particles (Chapter 2). The results suggest that crystallinity has a larger effect than porosity on ice nucleation activity, as all of the porous silica samples investigated had lower onset freezing temperatures and lower ice nucleation activities than quartz. Our findings also suggest that pores alone are not sufficient to serve as effective active sites, and need some additional chemical or physical property, like crystallinity, to nucleate ice in immersion mode freezing. The addition of a low density of organic functional groups to non-porous samples showed little enhancement compared to the inherent nucleation activity of silica with native surface hydroxyl groups. The density of functional groups investigated in this work suggests that a different arrangement of surface groups may be needed for enhanced immersion mode ice nucleation activity. In summary, crystallinity dictates the ice nucleation activity of silica samples rather than porosity or low-density surface functional groups. Silver and gold nanoparticles with thiol ligands of different functionalities (alkane, carboxylic acid and alcohol) were investigated for immersion ice nucleation activities (Chapter 3). The alcohol ligand nanoparticles of both silver and gold had significantly higher activities than the alkane thiol ligand, with a 4.5 oC and 10.7 oC difference in median freezing temperature respectively. Silver nanoparticles capped with thiol alcohol ligands were also tested for aggregation and oxidative stability. The silver nanoparticles are oxidatively stable for at least 2 years. We have also shown that aggregates of nanoparticles have likely caused the activity for all of the silver and gold samples, as ice nucleation activity strongly diminished when large aggregates (>200 nm) were filtered from solution. Investigating the ice nucleation activity of synthetic ZSM-5 samples with varying Si:Al helps to clarify ice nucleation activity of natural mineral dust samples, which are often aluminosilicate based materials (Chapter 4). Additionally, ammonium is a very common cation in the atmosphere, and its effects on ice nucleation activity are still being studied. Ice nucleation temperature increases with increasing Al content. Additionally, when ammonium is the cation that is strongly adsorbed to the surface and in pores, initial freezing temperatures are reduced by up to 6 oC. Seeing a drastic decrease in ice nucleation activity in the presence of ammonium, suggests that the cation can interact with the surface to block active sites. In addition to ice nucleation, dust samples can affect human health. The goal of Chapter 5 is to present risk assessments for trace element concentrations in PM10 dusts from simulated road material and township roads with/without oil and gas produced water brine (O&GPWB) treatment. PM10 trace metal quantification was conducted by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and compared to values from EDS analysis on PM2.5. Among adults, PM10 inhalation lifetime cancer risks (CRinh range: 2.39E+01 to 7.73E+01) and hazard quotients for As, Ni and Pb exposure were elevated for O&GPWB, SFSR and RRA. Cumulative Pb dose for the O&GPWB-treated roads was 71 ng/kg by age 21, compared with 37 ng/kg for non-treated roads. Our results may be consistent with elevated blood lead (Pb) concentrations above state averages in this rural O&G producing region.
Author: Esther Chong
Publisher:
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Category :
Languages : en
Pages :
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The mechanism of ice nucleation continues to be an ongoing discussion within the scientific community. The debate centers around two central questions: how an aerosol particle interacts with water and what characteristics of the particle promote ice nucleation. Understanding of aerosol-cloud interactions, whether it is the formation of cloud condensation nuclei or ice nuclei, has been a source of some of the highest uncertainty in determining the radiative budget of the Earth. The complexity of atmospheric aerosol particles makes it difficult to decide on which particular characteristics on a particle affects its ice nucleation activity. To study specific features, we used model metal oxide systems to control as many variables as possible. By systematically determining which properties and to what extent they affect ice nucleation, we may extrapolate the mechanism of ice nucleation and decrease the uncertainty around aerosol-cloud interactions. The metal oxide systems included aluminum, iron, titanium, and manganese oxide, which are all found as components in mineral dust. As one of the most prevalent ice nucleating particles in the atmosphere, mineral dust is an ideal atmospheric particle for us to simulate with our model systems. A combination of X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were used to characterize our model systems. The aluminum oxides were chosen to study the effect of crystallinity and lattice matching on ice nucleation. The three most crystalline samples, corundum [[alpha]-Al2O3], gibbsite [Al(OH)3], and bayerite [Al(OH)3], were also found to have the highest ice nucleation activity. Then, calculations of the lattice match of the aluminum oxides with respect to hexagonal ice found that the best ice nucleating particle was corundum [[alpha]-Al2O3], which had the highest lattice match along the a- and b-axis. Therefore, a combination of high crystallinity and high lattice match with hexagonal ice correlated with a high ice nucleation activity. Then, iron oxides were studied to expand further on the aluminum oxide system by exploring if the lattice match is a viable property to determine ice nucleation activity despite the difference in composition. Overall, wüstite [FeO] had a high lattice match and the highest ice nucleation activity among the iron oxide samples. Because wüstite [FeO] was milled for the ice nucleation experiments, the effect of milling on ice nucleation was also studied. By comparing milled and 20 [mu]m sieved of both wüstite [FeO] and MnO, we saw that physical defects formed by the mill had minimal improvements on the ice nucleation activity of MnO. XPS showed that milled wüstite [FeO] had more exposed hydroxyls at the surface compared to the sieved wüstite [FeO]. In contrast, milled and sieved MnO showed similar concentrations of oxygen and hydroxyl species. Thus, the high lattice match and the exposure of hydroxyl groups after milling were the leading factors to wüstite [FeO]'s high ice nucleation activity. The last two systems, titanium and manganese oxide, were chosen to confirm that the lattice match trend could be applied to a variety of particles. For the titanium oxides, Ti2O3 was the best ice nucleating particle, but the lattice match was not high. We hypothesize that the dissociation and adsorption of water at the surface of titanium oxides could affect their ice nucleation. The manganese oxides followed the lattice match trend. MnO had the highest ice nucleation activity and the highest lattice match. Thus, the data compilation of all four metal oxides found that a high lattice match with hexagonal ice has a reasonably strong correlation with the immersion ice nucleation activity. The commonality of the lattice match trend between these metal oxide systems has implications of more properties that are good indicators for the ice nucleation activity over a wide range of compounds. If enough of these properties are identified, then it would be possible for cloud models better to predict the ice nucleation activity of complex atmospheric particles and decrease the uncertainty of aerosol-cloud interactions.
Author: Dennis Niedermeier
Publisher:
ISBN:
Category :
Languages : en
Pages : 90
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Author:
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Languages : en
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This study reports on heterogeneous ice nucleation activity of predominantly organic (or coated with organic material) anthropogenic particles sampled within and around the polluted environment of Mexico City. The onset of heterogeneous ice nucleation was observed as a function of particle temperature (Tp), relative humidity (RH), nucleation mode, and particle chemical composition which is influenced by photochemical atmospheric aging. Particle analyses included computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). In contrast to most laboratory studies employing proxies of organic aerosol, we show that anthropogenic organic particles collected in Mexico City can potentially induce ice nucleation at experimental conditions relevant to cirrus formation. The results suggest a new precedent for the potential impact of organic particles on ice cloud formation and climate.
Author: Ulrike Lohmann
Publisher: Cambridge University Press
ISBN: 1316586251
Category : Science
Languages : en
Pages : 419
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An Introduction to Clouds provides a fundamental understanding of clouds, ranging from cloud microphysics to the large-scale impacts of clouds on climate. On the microscale, phase changes and ice nucleation are covered comprehensively, including aerosol particles and thermodynamics relevant for the formation of clouds and precipitation. At larger scales, cloud dynamics, mid-latitude storms and tropical cyclones are discussed leading to the role of clouds on the hydrological cycle and climate. Each chapter ends with problem sets and multiple-choice questions that can be completed online, and important equations are highlighted in boxes for ease of reference. Combining mathematical formulations with qualitative explanations of underlying concepts, this accessible book requires relatively little previous knowledge, making it ideal for advanced undergraduate and graduate students in atmospheric science, environmental sciences and related disciplines.
