Dissertations / Theses on the topic 'Atmospheric hazard'

Thesis: Ph. D. in Geophysics, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2020
Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 245-268).
In this Thesis, we investigate natural and engineered processes related to the assessment of the seismic hazard from the impact of anthropogenic operations on the stability of pre-existing geological faults. We do so by developing simulation tools that coupled multiphase flow and geomechanics, and apply them at the field scale using geologically realistic representations of the subsurface. In a first contribution at the scale of individual fractures, we study the impact of confining stress on the capillary pressure behavior during drainage through rough fractures, where we find that capillary pressure variations are sensitive to the degree of confining stress and the degree of spatial correlation of the fracture aperture.
By solving the elastic contact problem and simulating slow two-phase displacements through the fracture gap, we uncover the universality class of avalanche size in fluid displacement, and find that it is consistent with a process controlled by self-organized criticality. In a second contribution at the scale of hundreds of kilometers, we address the importance of long-term, large-scale crustal deformation on the spatiotemporal distribution of Slow Slip Events (SSEs) in the Guerrero Gap, putting forward an alternative explanation for SSE nucleation, interval time and arrest. We show, by means of finite element simulations with rate-state friction, that fault geometry and crustal deformation control the nucleation and arrest of SSEs, via normal stress changes along the subducting slab that act as a mechanism for SSE stabilization. In a third contribution, we develop a two-way coupled multiphase flow and geomechanics model that rigorously accounts for the fluid-solid interaction.
We do so by coupling two well-established open-source simulators, the open-source finite element mechanical simulator PyLith and the finite volume open source flow simulator MATLAB Reservoir Simulation Toolbox (MRST). We employ the fixed-stress split of the fully-coupled problem, which renders the sequential iterative scheme unconditionally stable. We validate our implementation using analytical solutions for single-phase flow for a range of model parameters, and find excellent agreement in all cases. We then apply our simulator to synthetic cases to illustrate the impact of CO₂ injection on earthquake triggering on a pre-existing fault, demonstrating that poroelastic effects can have a strong fault-weakening effect even through impermeable geologic strata. In the two final contributions in this thesis, we apply the coupled multiphase flow and geomechanics simulator described above to assess seismic hazard from fluid injection at the reservoir scale.
In our first application, we revisit the classical experiment in earthquake control from water injection at the Rangely oil field, Colorado. The coupled flow-geomechanics simulations on a geologically constrained structural model of the Rangely field, along with reservoir-pressure and seismological data, provide an unique opportunity to understand the mechanisms responsible for the observed seismicity. In particular, our analysis allows us to separate the contributions to fault destabilization from direct pore pressure diffusion and poroelastic effects and to elucidate the fundamental role of fluid flow along the fault. In our second field-scale application, we investigate the impact of industrial-scale CO₂ storage on the stability of, and potential leakage along, pre-existing faults in the Gulf of Mexico (GoM).
We do so by performing 3D numerical simulations of coupled flow and geomechanics using high-fidelity geological models of the Miocene section of the GoM, both at the field scale (10s of km) and at the regional scale (100s of km). We pay particular attention to the frictional and hydraulic properties of unlithified sedimentary faults, and incorporate a detailed, physics-based, probabilistic representation of clay and sand smearing to populate the flow properties of normal faults. We then investigate different scenarios of injection-well location in relation with faults' geometry and architecture, representing geologic settings corresponding to "open" and "closed" reservoirs.
The results of our flow-geomechanics simulations suggest that CO₂ injection results in small fault destabilization, and vanishingly small probability of leakage along faults--supporting the notion that large-scale (100s of Mt) CO₂ injection in the GoM is feasible, but that well location is key for the success of individual Carbon Capture and Storage (CCS) projects.
by Josimar Alves da Silva Junior.
Ph. D. in Geophysics
Ph.D.inGeophysics Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences

Radon gas may be a major air quality hazard issue inside the home. Radon (222Rn) comes from the natural breakdown of radioactive uranium (238U) via radium (226Ra) in soil, rocks, and water. Radon and its progeny contribute more than 50% of the total radiation dose to the human population due to inhalation; it can result in severe and fatal lung disease. This investigation has determined the radon concentrations in seventy-seven domestic houses in a mountainous area of Hamadan in Iran which were monitored using track-etch detectors of type CR-39 exposed for three month periods. The arithmetic mean radon concentration in Hamadan buildings was determined to be 80 Bqm-3 and also an average indoor annual effective dose equivalent for the Hamadan city population was calculated as 1.5 mSv. Maximum radon concentrations were noted during the winter and spring season. In addition to this, 28 water wells were monitored by utilizing a Sarad Doseman detector at hourly intervals over extended periods. Radon measurements were also carried out in the nearby Alisadr show cave, using Solid State Nuclear Track etch Detectors (SSNTDs) during the winter and the spring periods. In the cave, the average annual effective geometric and arithmetic mean dose for guides was 28.1 and 34.2 mSv respectively. The dose received by visitors was very low. Hamadan city is built on alluvial fan deposits which are the source of the local water supply. The data from the wells shows that the groundwater in these alluvial deposits influences the flux of radon. The atmospheric radon concentration measurement in wells above the water surface ranged from 1,000 Bqm-3 to 36,600 Bqm-3. There is evidence that radon-rich ground waters play a significant role in the transport of radon through the alluvial fan system. There is evidence that the radon concentrations in homes in Hamadan are greatly influenced by the porous nature of the underlying geology and the movement of groundwater within the alluvial fan.

White Island and Ruapehu are currently the most active volcanoes in New Zealand. During non-eruptive periods, intense quiescent degassing through fumaroles can occur. The current project studies the quiescent degassing plumes, including aerosol sampling on White Island and dispersion modelling of SO₂ and PM₁₀ from White Island and Ruapehu volcanoes. Aerosol sampling from fumaroles at the crater floor on White Island volcano was carried out on 9 February and 6 April 2005. The exposed filters were analysed for various anions and cations and the particle mass concentration and molar concentration determined. Major elemental constituents were sodium and chlorine (Na⁺: 413 µg m⁻³, Cl⁻: 1520 µg m⁻³), which show best correlation at both sampling sessions. Other ions detected, with little correlation, are Ca²⁺, PO₄³⁻ and to a certain extent Mg²⁺. Other constituents found, which cannot correlate explicitly to other ions, are K⁺, NH₄⁺, NO₃⁻, and SO₄²⁻. SEM study of one exposed filter was performed and mainly NaCl particles could be distinguished due to their well-defined cubic shape. The Air Pollution Model (TAPM) was used for dispersion modelling of SO₂ (models 1-4) and PM₁₀ (models 5 and 6) from White Island and Ruapehu volcanoes. Annual modelling was performed using different parameters of emission rate, exit temperature and exit velocity. The resulting plume dispersions show relatively low concentrations at ground level ≤10 m), particularly for the models of PM₁₀ dispersion. TAPM calculated the highest SO₂ ground level concentrations with model 4, where the NES values of 350 and 570 µg m⁻³ were exceeded several times. The data was then used for detailed hazard assessment of urban population in the North Island. The meteorological data from annual modelling was used for model evaluation and compared with observation data from different weather stations by statistical calculations. Overall, TAPM performed well with most good and very good results. To evaluate SO₂ dispersion modelling, airborne plume measurements were carried out on 22 November 2006 by plume traverses at 3, 10 and 20 km. Although there is some variation, the calculated correlation coefficients indicate good model results for two plume traverses at 3 and 20 km and one plume traverse at 10 km. The meteorological data was also used for model evaluation, and the results indicate good model performance. TAPM is therefore suggested for future studies when more observation data are available to verify the calculated model data.

Atmospheric features, such as tropical cyclones, act as a driving mechanism for many of the major hazards affecting coastal areas around the world. Accurate and efficient quantification of tropical cyclone surge hazard is essential to the development of resilient coastal communities, particularly given continued sea level trend concerns. Recent major tropical cyclones that have impacted the northeastern portion of the United States have resulted in devastating flooding in New York City, the most densely populated city in the US. As a part of national effort to re-evaluate coastal inundation hazards, the Federal Emergency Management Agency used the Joint Probability Method to re-evaluate surge hazard probabilities for Flood Insurance Rate Maps in the New York – New Jersey coastal areas, also termed the New York Bight. As originally developed, this method required many combinations of storm parameters to statistically characterize the local climatology for numerical model simulation. Even though high-performance computing efficiency has vastly improved in recent years, researchers have utilized different “Optimal Sampling” techniques to reduce the number of storm simulations needed in the traditional Joint Probability Method. This manuscript presents results from the simulation of over 350 synthetic tropical cyclones designed to produce significant surge in the New York Bight using the hydrodynamic Advanced Circulation numerical model, bypassing the need for Optimal Sampling schemes. This data set allowed for a careful assessment of joint probability distributions utilized for this area and the impacts of current assumptions used in deriving new flood-risk maps for the New York City area.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003.
Includes bibliographical references (p. 132-144).
This work provides a statistical description of the near-Earth asteroids (NEAs) in terms of number, orbital parameters, reflectance spectra, albedos, diameters, and terrestrial and lunar collision rates. I estimate the size and shape of the NEA population using survey data from the Lincoln Near-Earth Asteroid Research project including more than 1300 NEA detections. The NEA population is more highly inclined than previously estimated and the total number of NEAs with absolute magnitudes (H) brighter than 18 is 1227 +170/-90. The absolute magnitude and orbital parameter distributions for the NEAs are combined with reflectance spectra and albedo measurements. I obtain a debiased estimate of the fraction of NEAs in each of 10 taxonomic complexes, and a debiased average albedo for each. The number of NEAs larger than 1 km is 1090 +/- 180. Next, I determine the impact frequency, collision velocity distribution and collision energy distribution for impacts of NEAs into the Earth and Moon. Globally destructive collisions ([approx.] 1021 J) of asteroids 1 km or larger strike the Earth once every 0.60 +/- 0.1 Myr on average. Regionally destructive collisions with impact energy greater than 4x1018 J ([approx.] 200 m diameter) strike the Earth every 47,000 +/- 6,000 years. The rate of formation of craters expected from the NEAs is found to be in close agreement with the observed number of craters on the Earth and Moon.
(cont.) These results combine the largest set of NEA discovery statistics from a single survey, the largest set of physical data on NEAs, and corrections for observational bias. The result is a comprehensive estimate of the total NEA population in terms of orbital parameters, absolute magnitudes, albedos, and sizes. This improved description of the NEAs will help us to plan surveys to find and study the remaining undiscovered NEAs, to connect the NEAs to their origins in the main-belt, to connect the NEAs to meteorite samples, to compare the lunar and terrestrial cratering record to the current population of potential impactors, and to understand the magnitude of the NEA impact hazard to the Earth's biosphere.
by Joseph Scott Stuart.
Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 106-119).
Portland, Oregon, lies within an active tectonic margin, which puts the city at risk to hazards from earthquakes and volcanic eruptions. The young Juan de Fuca microplate is subducting under North America, introducing not only arc magmatism into the overlying plate, but also interplate and intraplate seismicity related to the subduction zone. Large crustal earthquakes are also probable in Portland because of the oblique strike-slip Portland Hills Fault zone. These hazards create risk to Portland residents and infrastructure because of pre-existing vulnerabilities. Much of Portland's downtown area, including the government and business districts, is at risk of ground shaking infrastructure damage, liquefaction and landslides due to earthquakes. Additionally, the city is within 110 km of three active Cascadia stratovolcanoes, two of which pose hazards from tephra and lahars. Though the city is under the umbrella of four emergency response plans-city, county, state and federal-there are critical gaps in mitigation strategies, emergency exercises and community education and outreach. Portland cannot prevent earthquakes or volcanic eruptions, but the city can reduce its vulnerability to these hazards.
by Alexandra M. Jordan.
S.B.

Landslides pose a persistent threat to El Salvador's population, economy and environment. Government officials share responsibility in managing this hazard by alerting populations when and where landslides may occur as well as developing and enforcing proper land use and zoning practices. This thesis addresses gaps in current knowledge between identifying precisely when and where slope failures may initiate and outlining the extent of the potential debris inundation areas. Improvements on hazard maps are achieved by considering a series of environmental variables to determine causal factors through spatial and temporal analysis techniques in Geographic Information Systems and remote sensing. The output is a more dynamic tool that links high resolution geomorphic and hydrological factors to daily precipitation. Directly incorporable into existing decision support systems, this allows for better disaster management and is transferable to other developing countries.

Пчелінцев О. С. Оцінка та шляхи зниження техногенного навантаження на атмосферне повітря в промислових регіонах : кваліфікаційна робота магістра спеціальністю 183 «Технології захисту навколишнього середовища» / наук. керівник К. В. Бєлоконь. Запоріжжя. ЗНУ, 2021. 78 с.
UA : Проведено оцінку ризику для здоров’я населення від забруднення атмосферного повітря Заводського району м. Запоріжжя. Проаналізовані заходи щодо зниження негативного впливу викидів промислових підприємств на здоров’я населення м. Запоріжжя.
EN : An assessment of the risk to public health from air pollution of the Zavodskoy district of Zaporizhzhia was carried out. Analyzed measures to reduce the negative impact of industrial emissions on the health of the population of Zaporizhzhia.

Донець В. В. Шляхи зниження негативного впливу викидів промислових підприємств на здоров’я населення м. Запоріжжя : кваліфікаційна робота магістра спеціальності 183 «Технології захисту навколишнього середовища» / наук. керівник Є. А. Манідіна. Запоріжжя : ЗНУ, 2020. 124 с.
UA : Розглянуті найбільш поширені забруднюючі речовини, які надходять в атмосферне повітря від стаціонарних джерел, та якість атмосферного повітря у м. Запоріжжі. Проведено оцінку ризику для здоров’я населення від забруднення атмосферного повітря Заводського району м. Запоріжжя. Проаналізовані заходи щодо зниження негативного впливу викидів промислових підприємств на здоров’я населення м. Запоріжжя.
EN : The most common air pollutants from stationary sources, its dynamic of emissions into the air and their impact on human health were considered. The estimation for citizens health risk from air pollution in Zavodskoy district, Zaporizhzhia city was carried out. Measures have been developed to reduce the negative impact of industrial emissions on the health of the population of Zaporizhzhia.

碩士
朝陽科技大學
工業工程與管理系碩士班
90
The goal of this study is to develop a portable oxygen detector in order to decrease the hazards caused by oxygen deficient when working in a confined space. According to domestic reports about confined space related fatality in these five years, 32% of disasters were caused by oxygen deficient or hazardous atmosphere produced by harmful gases. This shows a necessity in developing a pocket-sized and easy carried oxygen alarm for workers who work in confined spaces so as to mend and improve the working model in gas detection, warning and rescue in manholes work field. This study integrates a Galvanic-type sensor and a microprocessor to build an oxgen detector. The working model was built, tested, and calibrated in laboratory and was field-tested at 44 chosen telecommunication manholes. Meanwhile, onsite workers were interviewed in order to realize the factors of contingency that produce oxygen deficient and gases damage. Results show works’ gross neglect of safety preparations and lack of adequate life-saving equipments and training were leaks of work safety in manholes. Most contractors have, different work type from the provider of telecommunication service, longer period of time stay in and work in the manholes. Furthermore, most contractors are not equipped with gas detector and are not properly trained. Imperceptibly, they are security risks of the labour safety. The working model has been tested and proven to have adequate accuracy and stability. According to opinions of the interviewed workers, the device receives positive appraisal and needs to be revised for better use in preventing related hazards.

This research investigates the spread of fire and smoke in buildings as well as occupant egress. There are existing deterministic models for these. While deterministic models provide averages of a process, stochastic models give the broad spectrum of all possible scenarios of the process giving the distribution function. The spread of smoke was first modelled by adding a noise component to the equation of an existing deterministic model. Later a deterministic model was developed and stochastic expressions derived using the Markov chain methodology. Though the Markov chain is a discrete process, it was used in approximating smoke spread which is a continuous process. The spread of fire was investigated using network analysis. Various methods of modelling the spread of a phenomenon in a network were compared.

Landfalling tropical cyclones bring tremendous coastal and inland hazard, which depends strongly on the evolution of the wind field after the landfall. This work investigates the inland evolution of the tropical cyclone wind field via idealized numerical simulation experiments and existing theories explaining the physics of storms over the ocean. The complicated landfall process is idealized as a transient response of a mature axisymmetric tropical cyclone to instantaneous surface forcings associated with landfall.

First, idealized landfall experiments are performed in the f-plane Bryan Cloud Model (CM1), where surface drag coefficient and evaporative fraction are individually or simultaneously modified systematically beneath an axisymmetric mature storm. Surface drying stabilizes the eyewall and consequently weakens the overturning circulation, thereby reducing inward angular momentum transport that slowly decays the low-level wind field only within the inner-core. In contrast, surface roughening first weakens the entire low-level wind field rapidly and enhances the overturning circulation dynamically despite the concurrent thermodynamic stabilization of the eyewall; thereafter, the storm gradually decays in a manner similar to drying. As a result, total precipitation temporarily increases with roughening but uniformly decreases with drying. Storm inner size and outer size decrease monotonically and rapidly with surface roughening, while the radius of maximum wind can increase with moderate surface drying.

Second, the extent to which existing intensity theory formed for tropical cyclones over the ocean can explain the intensity response to idealized landfall is explored in this work. Existing theoretical predictions for the equilibrium response and transient response of storm intensity are compared against the simulated response found in previous idealized simulations. The equilibrium and transient response of storm intensity to combined surface forcings can be reproduced by the product of their individual responses, in line with traditional potential intensity theory. The intensification theory of Emanuel (2012) is generalized for predicting the weakening process and found capable of reproducing the transient intensity decay. Specifically, the rapid initial decay of near-surface wind can be captured by how kinetic energy is instantaneously reduced by surface friction, where the decay is a function of surface roughness.

Third, existing structural theory and TC radial length scale formed or identified for storms over the ocean are tested against the idealized landfall experiment where surface is individually dried or roughened. The equilibrium storm radial length scale can predict the transient response of storm size to surface roughening throughout the decay evolution. For surface drying experiments, TC size scales with the intensity after around 12h. The E04 wind field model can generally capture the transient response of TC low-level wind field to individual surface drying and roughening, from radius of maximum wind speed to the outer region. The E04 prediction for these two types of experiments exhibits limited dependence on the subsidence cooling rate applied in the model.

Overall, though results are insufficient to explain the complicated wind field evolution of every real-world landfalling storm, it provides a fundamental understanding of how storm low-level wind fields respond to inland surface properties. This work also indicates the potential for existing theory to predict how tropical cyclone intensity evolves after landfall in the real world, which is essential for improving the forecasts on any timescale and the risk assessments.