Browsing Theses (Civil and Environmental Engineering) by Subject "Environmental science"
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Biodegradation Of Petroleum And Alternative Fuel Hydrocarbons In Moderate To Cold ClimateMicrobial degradation of hydrocarbon fuels contaminating soil in the Arctic and subarctic environment is a relatively slow process. Nevertheless, due to transportation and logistical limitations in rural Alaska, biodegradation might be the best and cheapest contaminant removal option. The aim of this thesis was to investigate the environmental effects on biodegradation by naturally occurring microorganisms for some innovative hydrocarbon fuels and to determine the overall fate of hydrocarbons in soil, including degradation by fungi and bacteria, volatilization, and transport in the soil. Three major types of fuels were investigated in small scale microcosms and larger soil columns: conventional diesel as a control substance, synthetic diesel (arctic grade Syntroleum) and different types of fish oil based biodiesel. The environmental conditions investigated included different soil types (sand and gravel), different temperatures (constant 6�C, 20�C, and fluctuating between 6 and 20�C), moisture levels (from 2% to 12% GWC), fuel concentrations (from 500 to 20,000 mg fuel/kg soil) and nutrient dosages (0 or 300 mg N/kg soil). Microbial response times and growth phases were also investigated for different inoculum types. Conditions of 20�C, 300 mg N/kg soil, sand, ?4000 mg of fuel/kg soil and ?4% GWC were favorable for bioremediation, with a short lag phase lasting from one day to less than a week, and pronounced peaks of daily CO 2 production between week 2 and 3. At suboptimal conditions, all phases were extended and slow, however at low temperatures steady metabolization continued over a longer time. The relative importance of fungal and bacterial remediation varied between fuel types. Diesel fuel degradation was mainly due to bacterial activities while fish biodiesel degradation occurred largely by mycoremediation. For Syntroleum both bacterial and fungal remediation played key roles. Volatilization contributed up to 13% to overall contaminant removal. In soil columns, degradation was slower than in microcosms, due to an uneven concentration profile of contaminants, nutrients and oxygen with depth. In general, biodegradation showed promising results for soil remediation and the alternate fuel types were more biodegradable compared with conventional diesel fuel.
Detecting Methane Ebullition In Winter From Alaskan Lakes Using Synthetic Aperture Radar Remote SensingMethane (CH4) is a greenhouse gas with a high radiative forcing attribute, yet large uncertainties remain in constraining atmospheric CH4 sources and sinks. While freshwater lakes are known atmospheric CH4 sources, flux through ebullition (bubbling) is difficult to quantify in situ due to uneven spatial distribution and temporally irregular gas eruptions. This heterogeneous distribution of CH4 ebullition also creates error when scaling up field measurements for flux estimations. This thesis reviews estimates of CH4 contribution to the atmosphere by freshwater lakes presented in current literature and identifies knowledge gaps and the logistical difficulties in sampling CH 4 flux via ebullition (bubbling). My research investigates various imaging parameters of space-borne synthetic aperture radar (SAR) to constrain current CH4 emissions from northern lakes. In a GIS spatial analysis of lakes on the northern Seward Peninsula, Alaska, comparing field data of ebullition to SAR, I found that SAR L-band backscatter from lake ice was high from lakes with CH4 bubbles trapped by lake ice and low from lakes with low ebullition activity. The 'roughness' component of a Pauli polarimetric decomposition of quad-pol SAR showed a significant correlation with the percentage of lake ice area containing CH4 bubbles and with CH4 ebullition flux. This indicates that the mechanism of SAR scattering from ebullition bubbles trapped by lake ice is single bounce. I conclude that SAR remote sensing could improve our ability to quantify lake ebullition at larger spatial scales than field measurements alone, could offer between-lake comparison of CH 4 ebullition activity, and is a potential tool for developing regional estimations of lake-source CH4.
Phytoremediation strategies for recalcitrant chlorinated organicsThe purpose of the research was to investigate novel strategies for the phytoremediation of recalcitrant chlorinated organic soil contaminants. The recalcitrance of many chlorinated organics is related to chemical stability and bioavailability. Mycorrhizal fungi have the potential to enhance the degradation of such compounds through the action of lignolytic enzyme systems, and to increase the bioavailability of such compounds through increased root surface area and reach. Furthermore, the addition of surfactants has the potential to increase compound bioavailability via increased solubility. The organochlorine pesticide aldrin, and the polychlorinated biphenyl 3,3'4,4 '-tetrachlorobiphenyl (TCB) were chosen as representative recalcitrant contaminants. Feltleaf willow (Salix alaxensis) and balsain poplar (Populus balsamifera) were chosen as vegetative species likely to be useful for phytoremediation in sub-arctic ecosystems. Mixed-culture mycorrhizal fungi were first shown to be capable of taking up the hydrophobic contaminants in vitro. In the same experiments, surfactant addition increased the level of contaminant uptake. In subsequent vegetative uptake studies, mycorrhizal infection was highly correlated with the uptake of aldrin and TCB in the willow systems. In the poplar systems, this correlation was not as strong. Once taken up into the vegetative matrix of either species, most of the carbon originating from the chlorinated compounds existed as bound transformation products. Additionally, water-soluble transformation products of aldrin were formed in all of the soils tested, and such transformations were enhanced in the presence of vegetation. TCB transformation products were not detected in any of the soils tested. Surfactant addition did not impact the fate of either contaminant in the vegetative uptake studies. The surfactants, in the concentrations added, did not sufficiently solubilize the contaminants into the soil solution. The results of these studies indicated that the phytoremediation of recalcitrant chlorinated organics such as aldrin and TCB could be enhanced through the action of mycorrhizal fungi, and that surfactant addition has the potential to increase mycorrhizal uptake. Field studies were recommended, involving the use of specific degradative fungal species and effective surfactants.
Stochastic Analysis Of Response Functions Of Nitrogen In Stream WaterIn the present study, a stochastic model of nitrogen in streams is created using a new mathematical technique, Probability Density Function/Moment technique (PDF/M). The model is based on a set of four highly non-linear second order equations for nitrogen species in streams (NH$\sb3,$ NO$\sb2,$ NO$\sb3,$ and organic-N). The purpose of the PDF/M technique is to include occurrence of natural variability. The first step is to separate the stochastic terms from the non-stochastic terms and solve the resulting set of equations simultaneously. The moments of the output variables then are obtained using expectation mathematics. The moments are used in a solution of the Fokker-Planck equation to produce an analytical solution for the probability density functions of the dependent variables. Comparison of the present study to the results of the Monte Carlo method showed the application of PDF/M technique to nitrogen cycle simulation valid. <p>