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Using Machine Learning to Develop a Calibration Model for Low-Cost Air Quality Sensors Deployed during a Dust Event (open access)

Using Machine Learning to Develop a Calibration Model for Low-Cost Air Quality Sensors Deployed during a Dust Event

Low-cost sensors have the potential to create dense air monitoring networks that help enhance our understanding of pollution exposure and variability at the individual and neighborhood-level; however, sensors can be easily influenced by environmental conditions, resulting in performance inconsistencies across monitoring settings. During summer 2020, 20 low-cost particulate sensors were deployed with a reference PM2.5 monitor in Denton, Texas in preparation for calibration. However, from mid to late-summer, dust transported by the Saharan Air Layer moved through the North Texas region periodically, influencing the typical monitoring pattern exhibited between low-cost sensors and reference instruments. Traditional modeling strategies were adapted to develop a new approach to calibrating low-cost particulate sensors. In this study, data collected by sensors was split according to a novel dust filter into dust and non-dust subsets prior to modeling. This approach was compared with building a single model from the data, as is typically done in other studies. Random forest and multiple linear regression algorithms were used to train models for both strategies. The best performing split-model strategy, the multiple linear regression models split according to dust and non-dust subsets (combined R2 = 0.65), outperformed the best performing single-model strategy, a random forest model (R2 = 0.49). …
Date: May 2021
Creator: Hickey, Sean
System: The UNT Digital Library

Wildfire Influence on Rainfall Chemistry and Deposition in Texas during the 2011-2014 Drought

From 2011 to 2014, one of the most severe and intense droughts in Texas recorded history led to widespread wildfires across the state, with unknown effects on atmospheric nutrient and pollutant deposition. The objectives of this research were to: (1) characterize the frequency, magnitude, and spatiotemporal distribution of Texas wildfires (2011-2014); (2) identify smoke occurrence and source regions at eight Texas National Atmospheric Deposition Program (NADP) National Trends Network (NTN) sites (2011); and (3) quantify the influence of wildfire on weekly rainwater chemistry and deposition in 2011 at three NADP sites (Sonora, LBJ Grasslands, Attwater Prairie NWR). Data on large wildfires, smoke occurrence, and rainfall chemistry and deposition were coupled with principal component and back-trajectory analysis to address these objectives. Between 2011-2014, 72% of all wildfires occurred in 2011, accounting for 90% of the total area burned. In total, there were 17 extreme wildfires (i.e., in the 95th percentile of hectares burned), of which 11 occurred in 2011. Wildfire activity was concentrated in West Texas ecoregions and consumed primarily shrub/scrub and grassland/herbaceous land cover. Although West Texas experienced the most wildfires, smoke at the NADP locations in 2011, the "high-fire year," was more frequent in East Texas due to regional …
Date: August 2021
Creator: Williamson, Thomas
System: The UNT Digital Library
Hurricane Harvey and the Devastation of Dispossession (open access)

Hurricane Harvey and the Devastation of Dispossession

Disaster science is a procedural field often construed as producing blanket policies that attempt to cover everyone, but the complexity of human lived experiences must have a space to exist within disaster science if its research and findings are to be effective. This thesis illustrates that disaster policies and publications often leave out the most vulnerable communities—those in greatest need of collective support. Through critically analyzing beautification through green space, discussing photovoice interviews, and by deconstructing public preparedness documents published by Harris County Office of Homeland Security and Emergency Management (HCOHSEM), it is clear that accumulation by dispossession filters down through not only property and money but also access to green spaces and a healthy life. By dispossessing low-income communities of their right to green spaces and life, those communities end up in places that are environmentally dangerous, leaving them at a disadvantage in the disaster preparedness and recovery process. This thesis serves as a case study highlighting how HCOHSEM failed to provide low-income communities with assistance prior to, during, and after Hurricane Harvey. The lessons from these gaps in protective measures show that public policies need to be malleable to ensure residents of any community are covered. Though no …
Date: December 2021
Creator: Espinoza, Samantha
System: The UNT Digital Library

Particulate Matter Accumulation to Urban Rock Pigeon (Columba livia) Feathers

This research investigates particulate matter (PM) deposition to rock pigeons (Columba livia) in urban environments within Denton County, Texas. Pigeon habitat was characterized within a 2-km radius at eight locations using the 2016 National Land Cover Database (NLCD). In summer 2020, feathers were sampled from 10 rock pigeons at two locations (n = 20) differing in degree of urban development. Birds were captured using walk-in funnel traps baited with bird seed. Based on molt pattern and appearance, four old flight feathers were identified and sampled from each bird. New primary feathers were obtained from each population as reference samples. Feathers were washed three times with double deionized water and acetone, and the solution vacuum filtered through a glass microfiber filter to collect all particles >1.5 µm in diameter. Particulate matter mass was determined by gravimetric analysis and calculated per unit feather surface area. Relative PM accumulation rates were significantly different between the populations. Characteristics of urban land cover, proximity to and types of emissions sources, wind exposure, and building density were drivers of variability in PM deposition to feather surfaces. The results from this study should be useful for subsequent research to help identify best practices for using feathers collected …
Date: August 2021
Creator: Ellis, Jennifer Lee
System: The UNT Digital Library
GIS-Based Analysis of Local Climate Zones in Denton, Texas (open access)

GIS-Based Analysis of Local Climate Zones in Denton, Texas

This study implemented a GIS-based analysis of local climate zones (LCZ) in Denton, TX with data sets from 2009, 2011, 2015, and 2016. The LCZ scheme enables evaluation of distinct regions' thermal characteristics with greater granularity than conventional urban-rural dichotomies. Further, the GIS-based approach to LCZ mapping allows use of high-resolution lidar data, the availability of which for the study area enabled estimation of geometric and surface cover parameters: height of roughness elements, sky-view factor, and building surface fraction. Pervious surface fraction was estimated from National Landcover Database impervious imagery. A regular grid was used to estimate per-cell mean values for each parameter, and with a decision-making algorithm (if/then statements) two maps were produced (2011 and 2015) and six LCZ identified in each: LCZ 6 (open low-rise), LCZ 8 (large low-rise), LCZ 9 (sparsely built), LCZ A (dense trees), LCZ B (scattered trees), and LCZ C (bush/scrub). Post-processing was carried out to ensure identified zones met the spatial minimum for qualification as LCZ. Landsat Collection 2 Level 2 surface temperature products from various seasons of 2011 and 2015 were acquired to examine LCZ thermal differentiability, and preliminary surface urban heat island intensity values were estimated. Particular attention was afforded to …
Date: December 2021
Creator: Michel, Daniel
System: The UNT Digital Library
App Stole My Gayborhood? A Transforming Ethos at the Intersection of Queer Urban Life and Cyberspace(s) (open access)

App Stole My Gayborhood? A Transforming Ethos at the Intersection of Queer Urban Life and Cyberspace(s)

This thesis demonstrates a queer perspective stemming from a qualitative analysis of data gathered in interviews with LGBTQ+ people to analyze a transforming ethos of gayborhoods and queer desires. In particular, the research focuses on the interactive relationship between self-identified lesbian, gay, bisexual, transgender, and queer (LGBTQ+) participants; the cyberspace(s) of LGBTQ+ mobile-dating applications (apps); and tangible urban places. The topic of gayborhood demise and whether such places are worth saving has been debated by scholars and journalists for the last decade. The demise of gayborhoods is often thought to be a symptom of neoliberal urban processes such as gentrification within the context of the post-gay era and broader societal acceptance of homosexuality. This means the question of "if the gayborhood is worth saving" is inherently imbedded in an assumption that homosexuality is not viewed or treated as different or lesser than heterosexuality. In this imagined post-gay era, gayborhoods are declining because the dangers posed to the LGBTQ+ population are purported to no longer exist, so there is no longer a need for designated queer and/or safe places. This research destabilizes the assumptions embedded within the conception of the post-gay era by asking whether the gayborhood meets the needs and …
Date: May 2021
Creator: Stucky, Farrell
System: The UNT Digital Library

Behind the Curtain of Public Space: Revealing the Narratives of Corporate Street Hawking in Globalizing Accra

All street hawkers are not the same in many Newly Industrialized Countries (NICs) of the global south as often portrayed by the media and documented in extant literature. This perception has created a gap in knowledge as researchers explore street hawking activities in NICs. In this study, I investigated a new informality trend of street hawking is coming into being within the capital city of Accra, Ghana. As governance is increasingly becoming entrepreneurial, informal activities are gradually becoming formal. Formal and registered businesses are increasingly capitalizing on hawking activities to occupy public spaces. The advent of the informality trend, I term corporate street hawking opens up new issues for the political economy, labor, and urban studies. By employing semi-structured interviews with 47 street hawkers in Accra, this paper sought to investigate three broadly interrelated questions. First, how do neoliberal policies impact the production of public space in Accra? Second, is corporate street hawking a form of creative destruction? Finally, how do corporate street hawkers practice agency within Accra?
Date: December 2021
Creator: Ansah, Hilary Ama
System: The UNT Digital Library

A Multi-Proxy Approach to Identifying Marine Overwash Sedimentation and Terrestrial Flood Sedimentation in a Coastal Lake in Southeastern Texas

This research project focuses on using a multiproxy approach to discriminate between overwash and non-hurricane marsh sediments within the bed of a coastal lake. 3 marsh cores were collected in an area of McFaddin National Wildlife Refuge just south of Clam Lake that are known to contain 4 hurricane overwash deposits, Ike, Rita, Carla, and Audrey. LOI and XRF analysis were used to determine the signature of the hurricane overwash layers. 3 more cores were collected from Clam Lake where there are no visible sand layers. The elemental signature of the overwash layers found in the marsh cores was used to run a hierarchical cluster analysis on the lake cores. This was able to determine the effectiveness of XRF's ability to distinguish between hurricane overwash and marsh sediments. The combination of cluster analysis, LOI, and XRF can tentatively identify hurricane overwash deposits in a coastal lake, however, it is more successful in the marsh cores. Results in the lake cores are somewhat inconsistent and uncertain, possibly because there may have not been enough overwash deposits to identity or that the XRF analysis needs more distinct sand layers to distinguish between overwash and marsh.
Date: August 2021
Creator: Beaubouef, Chelsea E.
System: The UNT Digital Library

Spatial-Temporal Assessment of Irrigation Application Changes and Soil Moisture Analysis Using SMAP Maps

Due to inadequate long-term and large-scale observation approach for observation of soil moisture across the globe, this study intends to unveil the importance of using simulated soil moisture fields from land surface models, forced with observed precipitation and near-surface meteorology in monitoring drought and formulating effective water management practices for continued production irrigation applications. This study shows that socio-economic and ecosystem effects can be determined by evaluating spatial-temporal changes in irrigation applications. Thus, it facilitates understanding of the importance of water management and how water, energy, and carbon flows protect our climate and environment. By using Soil Moisture Active Passive (SMAP) in monitoring soil moisture, the information obtained is critical in providing early drought warnings, particularly in those parts of the United States that experience flash agricultural droughts. Further, this study highlights that frequent and reliable soil moisture measurements from SMAP helped improve the predictive capability of weather and climate models.
Date: December 2021
Creator: Unal, Kerra E.
System: The UNT Digital Library