Alumni Dissertations

 

Alumni Dissertations

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  • WE WORK, WE EAT TOGETHER: Anti-authoritarian Mutual Aid Politics in New York City, 2004-2013

    Author:
    David Spataro
    Year of Dissertation:
    2014
    Program:
    Earth & Environmental Sciences
    Advisor:
    Cindi Katz
    Abstract:

    New York City's neoliberal restructuring has fundamentally transformed the city's labor market and privatized many important aspects of a once robust municipal welfare system. In this research I examine one radical response to these changes: anti-authoritarian mutual aid groups that blend Do-It-Yourself (DIY) culture with direct action politics. These are projects where activists attempt to build strong communities of resistance by organizing collective forms of social reproduction. I find that these projects are a threat to neoliberal urbanization because they reorganize reproduction beyond the household scale while simultaneously criticizing the social relations of capitalism as the root of household insecurity. At the same time, this research reveals that mutual aid projects coming out of the white North American anarchist social movement culture are filled with conflicts and contradictions. Activists who create "geographies of autonomy" often struggle to reconcile their imperative against hierarchy with needs for a horizontal management of the commons. Additionally, I find that although these projects take social reproduction as an object of struggle, they are prone to undervalue gendered and racialized work in a way that mirrors the same neoliberal social relations which mutual aid groups seek to escape. The conflicts that ensue from these contradictions can and often lead to women and people of color (and others) withdrawing energy or support in order to create stronger forms of mutual aid. These cleavages between activists can be best understood through black feminist and Marxist feminist theories of care in social struggle. Conflicts reveal the need for mutual aid groups to develop a social practice that revalues reproduction work in social movements and celebrates those who have done it in the past and continue to do it today.

  • The Remote Sensing and Measurement of Melting Processes on Greenland and Antarctica

    Author:
    Nicholas Steiner
    Year of Dissertation:
    2012
    Program:
    Earth & Environmental Sciences
    Advisor:
    Marco Tedesco
    Abstract:

    We report measurements of melt-related processes for Antarctic and Greenland made using novel remote sensing algorithms and in-situ measurement techniques. First, persistent melting is mapped over Antarctica at high resolution using a novel melt-detection algorithm, based on wavelet-theory and multiscale analysis for the duration of the QuikSCAT satellite record (1999 through 2009). This novel approach is compared with threshold based methods, where melting is detected at 3dB below the winter mean backscatter, indicating an agreement to within 7 percent accuracy in yearly melt index [days-km2] and within 10 percent accuracy based automated weather station (AWS) comparisons due to the omission of short-duration melting events. In further comparison with Special Sensor Microwave/Image (SSMI) melting records, a higher degree of agreement (9 percent relative difference) is obtained by employing the wavelet-based approach than threshold-based (11 percent relative difference) methods. Secondly, we assess the validity of remote sensing based multispectral bathymetry from the analysis of concurrent in-situ multi-spectral and depth measurements collected over a supraglacial lake during early July 2010 in West Greenland (Lake Olivia, 69º36'35"N, 49º29'40"W). In particular, we evaluate lake bottom albedo and the water attenuation coefficient. Analysis of in-situ data (using a remotely controlled boat equipped with a GPS, sonar and a spectrometer) illustrates the exponential trend of the water-leaving reflectance with lake depth. The attenuation factors obtained are compared with those proposed in the literature. Finally, measured ablation rates at the bottom of the two lakes, collected during the summers of 2010 and 2011, are on the order of ~ 6 cm/day, versus a rate of ~ 2.5 - 3 cm/day in the case of bare ice of surrounding areas. These measurements are compared with a thermodynamic model forced with the outputs of a regional climate model. In general, the model is able to satisfactorily reproduce the measured quantities with RMSE of the order of 3 - 4 cm for the ablation and ~ 1.5 ºC in the case of water temperature. Results confirm that the ablation at the bottom of supraglacial lakes can account for close to ten percent of the total lake depth.

  • Toward A Spatial Understanding of Latin American Immigrant Worker Population Fatalities

    Author:
    Robert Stewart
    Year of Dissertation:
    2010
    Program:
    Earth & Environmental Sciences
    Advisor:
    Ines Miyares
    Abstract:

    The object of this dissertation was to conduct a geographical immigrant labor population analysis of the work spaces where Latin American immigrant worker fatal accidents occurred and were investigated by OSHA in NYC's Brooklyn and Manhattan from 1995-2004. The purpose of this analysis was to identify spatial trends and to develop a spatial profile or spatial model of these fatal accident sites. With the identification of spatial factors that are related to Latin American worker fatal accidents, OSHA could implement an improved spatial strategy for identifying hazards, issuing violations, and thus preventing these fatalities before they occur. The US Dept. of Labor/ Occupational Safety and Health Administration (OSHA) reported that the total amount of occupational fatal accidents went up from 1,729 to 1,966 in the years 1997 to 2005. In addition, in the U.S., the Hispanic worker fatality rate has increased sharply from 4.50 per 100,000 in 2003 to 4.90 in 2004. This is an 11% increase (Smith, S., et al, 2006). The New York State (NYS) Trial Lawyers Association of OSHA reported that from 1994-2004 in NYS, most of the occupational fatal accidents occurred in New York City (NYC), and in NYC most occupational fatal accidents occurred on construction sites. Sixty seven percent occurred with workers who spoke a foreign language on the job, usually Spanish. Brooklyn was reported as the county that had the most accidents in the state (NYS Trial Lawyers Assoc. of OSHA, 2005). These statistics clearly identify a need to reduce the occupational fatal accident rate, especially for Latin American immigrants in NYC. The research concludes that Latin American occupational fatal accidents do have a unique, and a statistically significant relationship with the following independent variables: union status; job size; median residential household income; and residential population density.

  • STUDY OF TROPICAL DEEP CONVECTIVE PROCESSES AND WATER VAPOR VARIATIONS USING NASA A-TRAIN DATA AND GEOSTATIONARY SATELLITE OBSERVATIONS

    Author:
    Hanii Takahashi
    Year of Dissertation:
    2013
    Program:
    Earth & Environmental Sciences
    Advisor:
    Zhengzhao "Johnny" Luo
    Abstract:

    The theme of this dissertation is to use various satellite observations to seek new insights into our understating of tropical deep convective processes and water vapor variations. Three subjects are investigated: 1) observational determination of level of neutral buoyancy (LNB) for deep convection, 2) characters and life stage view of tropical overshooting convection (OSC), and 3) variations of water vapor and clouds during East Pacific (EP)- and Central Pacific (CP)-El Niños. The first study conducts a near-global survey of LNB for tropical deep convection using CloudSat (LNB_observation) and makes comparison with the corresponding LNB based on the parcel theory using ambient sounding (LNB_sounding). The principal findings are as follows: First, although LNB_sounding provides a reasonable upper bound for convective development, ambient sounding contains limited information for predicting the actual LNB. Second, LNB_sounding significantly overestimates the "destination" height level of the detrained mass. Third, LNB_observation is consistently higher over land than over ocean, although LNB_sounding is similar between land and ocean, suggesting some fundamental differences between land and ocean convection. The second study uses CloudSat data together with ISCCP CT to study tropical OSC properties and the convective systems in which they are embedded. Our results find that, nearly 21 % of tropical deep convection is overshooting; the occurrence frequency is only slightly higher over land (~ 50.2 %) than over ocean (~ 49.8 %). Various proxies of convective strength are analyzed showing consistently that continental OSC is stronger than the oceanic counterpart. Moreover, majority (2/3) of the OSC occurs during the growing stage of the convective systems. About 1/3 occurs during the mature stage, which are more abundant over land during noontime. The third study shows that EP- and CP-El Niño events produce different patterns of water vapor and cloud anomalies over the tropical ocean. Regression of water vapor anomalies onto the Niño-3.4 sea surface temperature shows a clear "upper tropospheric amplification" of the fractional water vapor change. Furthermore, water vapor and cloud anomalies in different circulation regimes are examined. Finally, Geophysical Fluid Dynamics Laboratory AM2.1 model simulations of water vapor and clouds are compared with the satellite observations.

  • Development and Assessment of a Neural Network Approach for Retrieving Aerosol Properties from Multispectral, Multiangle Polarization Measurements

    Author:
    Alexandra Tsekeri
    Year of Dissertation:
    2012
    Program:
    Earth & Environmental Sciences
    Advisor:
    Barry Gross
    Abstract:

    Quantifying the microphysical properties of aerosols is crucial for quantifying global climate forcings. Satellite based aerosol retrievals usually rely on intensity measurements of the scattered light, but this approach has been proven inadequate for retrieving the complex refractive index and shape of aerosols, as well as the contamination from the ground surfaces. It is with these limitations in mind that we plan to improve the quality and scope of aerosol retrievals, by making use of the full capabilities of current and future polarimetric sensor systems. In order to utilize the increased information content on aerosol optical thickness (AOT), size distribution, shape and single scattering albedo (SSA), intrinsically available in multispectral-multiangle polarimetric observations, we make use of suitably constructed neural networks (NNs). We focus our analysis initially on simple retrievals over the ocean, in order to best assess the potential of the NNs as a practical approach and to identify any possible limitations. In particular, we find that, by choosing a suitable combination of inputs and outputs, based on principal component analysis (PCA), we can develop a robust NN retrieval trained on synthetic datasets. We further show the value of using cascaded NNs, to improve retrieval accuracy. Consequently, we demonstrate the potential and limitations of this approach on real aircraft instrument data from the Research Scanning Polarimeter (RSP). Discrepancies in the retrievals are found to be due to limitations from the use of spherical particle assumptions and preliminary efforts to overcome this restriction are identified. It is our belief that the value of these methods, in comparison to existing local inversion schemes, will further increase with the expected magnification of data sizes on future missions, such as the Aerosol-Cloud-Ecosystem (ACE) Mission.

  • Phosphorus transport in the Bronx River: qualitative and quantitative analysis

    Author:
    Jingyu Wang
    Year of Dissertation:
    2011
    Program:
    Earth & Environmental Sciences
    Advisor:
    Hari Pant
    Abstract:

    Phosphorus (P) is the primary limiting nutrient for algal growth in freshwater systems. Excessive P from external inputs and release from sediments could accelerate primary productivity leading to eutrophication in the water column, and consequently degrading water quality. The objectives of this study were to predict P bioavailability and estimate spatial and temporal variations in P transport in the Bronx River, New York, USA. The Bronx River originates from the Westchester Davis Brook and Kensico Dam, flowing south through Westchester County (WC) and Bronx to the estuary area where it joins the East River. The total length is about 20 miles. There are more than 100 stormwater and other discharges that flow to the river along the entire length from Westchester to the East River. The upper part of the river is freshwater, while the lower is saline. The overall goal of this research is to provide data that can help develop policies to control P runoff to the river, including regulation of P inputs from lawn fertilizers. It is hoped this data can be shared meaningfully among the United States Environmental Protection Agency (USEPA), Department of Environmental Protection (DEP), Department of Environmental Conservation (DEC), Bronx River Alliance to make the river meet the fishable/swimmable goal of the Clean Water Act. The 31P-NMR spectra showed that the dominant P species in Bronx River bed sediments were orthophosphate monoester, and lesser phosphate diesters and pyrophosphates (pyro-P). The P compounds were mostly glycerophosphate (GlyP), nucleoside monophosphates (NMP), and polynucleotides (PolyN). A few sites showed a small amount of dihydroxyacetone phosphate (DHAP), inosine monophosphate (IMP), and pyrophosphates (pyro-P). The P sorption capacity of the bed sediments of the Bronx River was very high, and the maximum values of P sorption maximum (Smax) was 476 mg kg-1, equilibrium P concentration (EPC0) was 0.73 mg L-1, and originally sorbed P (S0) was 65.6 mg kg-1. Sediments could potentially release P into the water column as the soluble reactive P (SRP) in the water column drops below EPC0 under changing hydro-climatic conditions such as the changes in pH, redox etc. Correlation analysis showed that Smax was correlated with poorly crystalline and amorphous Fe, Al, acid-extractable Ca and Mg, and organic matter suggesting their influence on P sorption capacity of the sediments. Similarly, the bed sediments contained various P pools, and rank order was: HCl-P > NaOH-P > NaHCO3-P > residueP, and the relative proportion of 3.7: 2.0: 1.4: 1 in 2006 sediment; HCl-P > NaOH-P > residue-P > NaHCO3-P, with their relative proportion of 27.8: 6.2: 2.7: 1 in sediment collected in 2007. The sediments P mineralization studies that were conducted under flooding conditions for 0, 7, 15, 30 d showed changes in the size of the P pools, indicating variations in microbial activities during incubation period. Moreover, enzyme incubation studies showed that phosphodiesterase (PDEase) hydrolyzed up to 82% of OP. Native phosphatases (NPase) hydrolyzed substantial amount of OP (up to 76%) when incubated at 37ºC, indicating that OP could be hydrolyzed under favorable temperature, and there is a potential threat to river ecosystems if global rise in temperature continues. Water samples from the river showed that the SRP concentrations were higher than EPA standard of 15 µg L-1 (SRPmax=221 µg L-1, SRPave=68 µg L-1), and TP concentrations were in a substantial amount (TPmax=1,113 µg L-1, TPave=438 µg L-1) compared with other rivers such as the Garonne River in southern France. The hydrolyzed OP by NPase was up to 100% when incubated at 37ºC indicating potential threat to water quality under changing hydro-climatic conditions. It is indicative that anthropogenic inputs such as the P fertilizer runoff from garden and golf course, sewer overflows from Hunts Point WWTP, raw sewer discharge along the river (e.g., from Yonkers), CSOs, land use changes, as well as hydro-climatic changes may cause the spatial and temporal variations on P transport in the Bronx River.

  • Numerical Study of Canopy Flows in Complex Terrain

    Author:
    Xiyan Xu
    Year of Dissertation:
    2014
    Program:
    Earth & Environmental Sciences
    Advisor:
    Chuixiang Yi
    Abstract:

    Canopy flow plays a substantial role in regulating atmosphere-biosphere exchanges of mass and energy. The worldwide FLUXNET has been developed to quantify the net ecosystem exchange of mass and energy through fluid dynamics in and above vegetation canopy using tower-based eddy covariance (EC) technique. However, EC measurements are subject to advection errors in complex terrain, particularly during nights when atmospheric stability is strong. Because EC measurements are one-dimensional (1D), three-dimensional (3D) air movement, CO2 transport, and temperature variation around the instrumented tower are unknown. We employ a Computational Fluid Dynamics (CFD) model to investigate the impact on CO2 transport of 2D and 3D characteristics of canopy flow resulting from interactions between large-scale synoptic flows and local topography, vegetation and thermal conditions. Under neutral conditions, flow distortion over a forested hill is asymmetric, with recirculation on the lee slope. The presence of vegetation and steepening slope intensifies recirculation depth and extension. The recirculation regions are responsible for CO2 build-up behind the hills. The contribution of advection to the CO2 budget is significant and topographic-dependent. Gentle slopes can cause larger advection error than steep slopes. However, the relative importance of advection to CO2 budget is slope-independent. Under calm and stable conditions, canopy flow is thermally stratified: super-stable layers above and in the deep canopy and an unstable layer inbetween. Vertical exchanges of mass, momentum, and energy are limited by the stabilities of these layers. The pattern of two drainage flows are significantly modified by the interaction between thermal stratification and slope, and are better understood with the distribution of vortices, and the sources and sinks of turbulent kinetic energy. The numerical method is applied to the alpine forest at Renon, Italy to investigate how thermo-topographic and synoptic flows interact to govern canopy flow dynamics and CO2 transport. We found that recirculation with high CO2 concentration developed only when local slope wind is enhanced by synoptic wind. There's no recirculation formed as synoptic wind direction is opposite to the local wind direction and CO2 is quite well mixed. No recirculation appears without synoptic condition under which CO2 builds up mainly at downwind locations.

  • ARSENIC IN FRACTURED BEDROCK AQUIFERS IN GREATER AUGUSTA, MAINE, USA

    Author:
    Qiang Yang
    Year of Dissertation:
    2010
    Program:
    Earth & Environmental Sciences
    Advisor:
    Yan Zheng
    Abstract:

    Thirty one percent of private well water samples (n=790) collected in 2006 from fractured meta-sedimentary bedrock aquifers in greater Augusta, Maine were found to contain >10 µg/L of arsenic. An additional 331 samples were obtained in 2007 from 4 towns representing low to high arsenic occurrence. The spatial pattern of groundwater arsenic distribution resembled the bedrock map. Arsenic exceedance rate was highest in the Silurian pelite and sandstone/limestone (~40%), and differed significantly from those in the Silurian-Ordovician sandstone (24%), the Devonian granite (15%) and the Ordovician-Cambrian volcanic rocks (9%). This was confirmed in the 4 cluster areas with a greater sampling density. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at scales of 100-101 km. The elevated arsenic concentrations were associated with high pH, fluoride, molybdenum, and low dissolved oxygen, nitrate, chloride. A logistic regression model showed that bedrock geology, soil arsenic content, pH, dissolved oxygen, nitrate and sulfate played important roles on groundwater arsenic concentrations. Water geochemistry suggested a complex mobilization mechanism of oxidation of arsenic-rich sulfide, adsorption on iron minerals, pH-dependent desorption of arsenic from iron minerals with calcite dissolution along the groundwater flow path. Geophysical logging and water sampling from bore hole and specific fractures in two wells in Manchester, Maine found that dissolved arsenic concentrations increased when the bore hole water was replaced by the water with high dissolved arsenic coming primarily from high yielding fractures near the bottom of bore hole in response to pumping. Iron particulate precipitates were common and found to be enriched in arsenic. Laboratory experiment suggested that in the bore hole arsenic was mainly settled with iron enriched particles, probably amorphous ferric oxyhydroxides, with possibly minor adsorption on the iron minerals. The association of arsenic distributions in groundwater, soil and stream sediment from national data sets examined by logistic regression models suggested that soil and stream sediment arsenic distributions had significant effects on groundwater arsenic occurrence at the national scale. Stronger correlations were found in Florida, New England and Nevada at regional scales and in greater Augusta, Maine at the local scale with higher sampling density.