Matching Items (4)
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- All Subjects: Mars (Planet)
- All Subjects: Particulate matter
- Creators: Clarke, Amanda
Description
Understanding and predicting climate changes at the urban scale have been an important yet challenging problem in environmental engineering. The lack of reliable long-term observations at the urban scale makes it difficult to even assess past climate changes. Numerical modeling plays an important role in filling the gap of observation and predicting future changes. Numerical studies on the climatic effect of desert urbanization have focused on basic meteorological fields such as temperature and wind. For desert cities, urban expansion can lead to substantial changes in the local production of wind-blown dust, which have implications for air quality and public health. This study expands the existing framework of numerical simulation for desert urbanization to include the computation of dust generation related to urban land-use changes. This is accomplished by connecting a suite of numerical models, including a meso-scale meteorological model, a land-surface model, an urban canopy model, and a turbulence model, to produce the key parameters that control the surface fluxes of wind-blown dust. Those models generate the near-surface turbulence intensity, soil moisture, and land-surface properties, which are used to determine the dust fluxes from a set of laboratory-based empirical formulas. This framework is applied to a series of simulations for the desert city of Erbil across a period of rapid urbanization. The changes in surface dust fluxes associated with urbanization are quantified. An analysis of the model output further reveals the dependence of surface dust fluxes on local meteorological conditions. Future applications of the models to environmental prediction are discussed.
ContributorsTahir, Sherzad Tahseen (Author) / Huang, Huei-Ping (Thesis advisor) / Phelan, Patrick (Committee member) / Herrmann, Marcus (Committee member) / Chen, Kangping (Committee member) / Clarke, Amanda (Committee member) / Arizona State University (Publisher)
Created2019
Description
On Mars, sedimentary deposits reveal a complex history of water- and wind-related geologic processes. Central mounds – kilometer-scale stacks of sediment located within craters – occur across Mars, but the specific processes responsible for mound formation and subsequent modification are still uncertain. A survey of central mounds within large craters was conducted. Mound locations, mound offsets within their host craters, and relative mound heights were used to address various mound formation hypotheses. The results suggest that mound sediments once filled their host craters and were later eroded into the features observed today. Mounds offsets from the center of their host crater imply that wind caused the erosion of central mounds. An in depth study of a single central mound (Mt. Sharp within Gale crater) was also conducted. Thermal Emission Imaging System Visible Imaging Subsystem (THEMIS-VIS) mosaics in grayscale and false color were used to characterize the morphology and color variations in and around Gale crater. One result of this study is that dunes within Gale crater vary in false color composites from blue to purple, and that these color differences may be due to changes in dust cover, grain size, and/or composition. To further investigate dune fields on Mars, albedo variations at eight dune fields were studied based on the hypothesis that a dune’s ripple migration rate is correlated to its albedo. This study concluded that a dune’s minimum albedo does not have a simple correlation with its ripple migration rate. Instead, dust devils remove dust on slow-moving and immobile dunes, whereas saltating sand caused by strong winds removes dust on faster-moving dunes.
On the Moon, explosive volcanic deposits within Oppenheimer crater that were emplaced ballistically were investigated. Lunar Reconnaissance Orbiter (LRO) Diviner Radiometer mid-infrared data, LRO Camera images, and Chandrayaan-1 orbiter Moon Mineralogy Mapper near-infrared spectra were used to test the hypothesis that the pyroclastic deposits in Oppenheimer crater were emplaced via Vulcanian activity by constraining their composition and mineralogy. The mineralogy and iron-content of the pyroclastic deposits vary significantly (including examples of potentially very high iron compositions), which indicates variability in eruption style. These results suggest that localized lunar pyroclastic deposits may have a more complex origin and mode of emplacement than previously thought.
On the Moon, explosive volcanic deposits within Oppenheimer crater that were emplaced ballistically were investigated. Lunar Reconnaissance Orbiter (LRO) Diviner Radiometer mid-infrared data, LRO Camera images, and Chandrayaan-1 orbiter Moon Mineralogy Mapper near-infrared spectra were used to test the hypothesis that the pyroclastic deposits in Oppenheimer crater were emplaced via Vulcanian activity by constraining their composition and mineralogy. The mineralogy and iron-content of the pyroclastic deposits vary significantly (including examples of potentially very high iron compositions), which indicates variability in eruption style. These results suggest that localized lunar pyroclastic deposits may have a more complex origin and mode of emplacement than previously thought.
ContributorsBennett, Kristen Alicia (Author) / Bell, James F. (Thesis advisor) / Christensen, Phillip (Committee member) / Clarke, Amanda (Committee member) / Robinson, Mark (Committee member) / Whipple, Kelin (Committee member) / Arizona State University (Publisher)
Created2016
Description
To investigate the impacts of an energy efficiency retrofit, indoor air quality and resident health were evaluated at a low‐income senior housing apartment complex in Phoenix, Arizona, before and after a green energy building renovation. Indoor and outdoor air quality sampling was carried out simultaneously with a questionnaire to characterize personal habits and general health of residents. Measured indoor formaldehyde levels before the building retrofit routinely exceeded reference exposure limits, but in the long‐term follow‐up sampling, indoor formaldehyde decreased for the entire study population by a statistically significant margin. Indoor PM levels were dominated by fine particles and showed a statistically significant decrease in the long‐term follow‐up sampling within certain resident subpopulations (i.e. residents who report smoking and residents who had lived longer at the apartment complex).
ContributorsFrey, S.E. (Author) / Destaillats, H. (Author) / Cohn, S. (Author) / Ahrentzen, S. (Author) / Fraser, M.P. (Author)
Created2015
Description
Chemical and physical interactions of flowing ice and rock have inexorably shaped planetary surfaces. Weathering in glacial environments is a significant link in biogeochemical cycles – carbon and strontium – on Earth, and may have once played an important role in altering Mars’ surface. Despite growing recognition of the importance of low-temperature chemical weathering, these processes are still not well understood. Debris-coated glaciers are also present on Mars, emphasizing the need to study ice-related processes in the evolution of planetary surfaces. During Earth’s history, subglacial environments are thought to have sheltered communities of microorganisms from extreme climate variations. On Amazonian Mars, glaciers such as lobate debris aprons (LDA) could have hosted chemolithotrophic communities, making Mars’ present glaciers candidates for life preservation. This study characterizes glacial processes on both Earth and Mars.
Chemical weathering at Robertson Glacier, a small alpine glacier in the Canadian Rocky Mountains, is examined with a multidisciplinary approach. The relative proportions of differing dissolution reactions at various stages in the glacial system are empirically determined using aqueous geochemistry. Synthesis of laboratory and orbital thermal infrared spectroscopy allows identification of dissolution rinds on hand samples and characterization of carbonate dissolution signals at orbital scales, while chemical and morphological evidence for thin, discontinuous weathering rinds at microscales are evident from electron microscopy. Subglacial dissolution rates are found to outpace those of the proglacial till plain; biologically-mediated pyrite oxidation drives the bulk of this acidic weathering.
Second, the area-elevation relationship, or hypsometry, of LDA in the midlatitudes of Mars is characterized. These glaciers are believed to have formed ~500 Ma during a climate excursion. Hypsometric measurements of these debris-covered glaciers enable insight into past flow regimes and drive predictions about past climate scenarios. The LDA in this study fall into three major groups, strongly dependent on basal elevation, implying regional and climatic controls on ice formation and flow.
I show that biologically-mediated mineral reactions drive high subglacial dissolution rates, such that variations within the valley can be detected with remote sensing techniques. In future work, these insights can be applied to examining Mars’ glacial regions for signs of chemical alteration and biosignatures.
Chemical weathering at Robertson Glacier, a small alpine glacier in the Canadian Rocky Mountains, is examined with a multidisciplinary approach. The relative proportions of differing dissolution reactions at various stages in the glacial system are empirically determined using aqueous geochemistry. Synthesis of laboratory and orbital thermal infrared spectroscopy allows identification of dissolution rinds on hand samples and characterization of carbonate dissolution signals at orbital scales, while chemical and morphological evidence for thin, discontinuous weathering rinds at microscales are evident from electron microscopy. Subglacial dissolution rates are found to outpace those of the proglacial till plain; biologically-mediated pyrite oxidation drives the bulk of this acidic weathering.
Second, the area-elevation relationship, or hypsometry, of LDA in the midlatitudes of Mars is characterized. These glaciers are believed to have formed ~500 Ma during a climate excursion. Hypsometric measurements of these debris-covered glaciers enable insight into past flow regimes and drive predictions about past climate scenarios. The LDA in this study fall into three major groups, strongly dependent on basal elevation, implying regional and climatic controls on ice formation and flow.
I show that biologically-mediated mineral reactions drive high subglacial dissolution rates, such that variations within the valley can be detected with remote sensing techniques. In future work, these insights can be applied to examining Mars’ glacial regions for signs of chemical alteration and biosignatures.
ContributorsRutledge, Alicia Marie (Author) / Christensen, Philip R. (Thesis advisor) / Shock, Everett (Committee member) / Clarke, Amanda (Committee member) / Sharp, Thomas (Committee member) / Whipple, Kelin (Committee member) / Arizona State University (Publisher)
Created2015