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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Remediation of trace metal contaminated soils / Remediation if trace metal

Tejowulan, Raden Sri. January 1999 (has links)
The chelating agent ethylene diamine tetraacetic acid (EDTA) is promising. The ligand is more effective in removing the metal contaminants from soils than HCl. In a batch experiment, EDTA released a large portion of metals from soils to soil extracts. A batch method was also developed for recovering the metal contaminants in the resulting EDTA soil-extracts. Using an anion exchange resin (AER) AG 3-x4, up to 99% of the Cd, Cu, Pb, and Zn were removed from the leachates. / To increase the efficacy of the extraction method we tested different reagent, amount, and technical application strategies using soil columns. Mixing the reagent with the whole soil column was found to be the most efficient method for the application of the chelating agent for the purpose of metal extraction from soils. It was found that EDTA was superior to citric acid in removing Cd, Cu, Pb, and Zn from the soils investigated. Up to 27% more Cd, 23% more Cu, 42% more Pb, and 21% more Zn were removed by the EDTA and the removal was further increased with the addition of an acid/salt solution (1.0 M HCl and 1.0 M KCl) to the columns. Other promising results are that the AER in columns is an effective method for extracting metals from EDTA soil-extracts with different properties. The resin column method was found to be more efficient than the resin batch procedure. / The results of the simulated field experiment confirmed that the remediation of contaminated soils can be achieved using EDTA. The majority of the contaminated soils were decreased to the point that they could be reused for commercial and/or residential use. / Computer models can be used to predict the possible metal speciation and interaction with solid surfaces in soils. Using the MINEQL+ program, the models estimated that most of the metal species in the soil extracts (in the presence of EDTA, chloro, hydroxo, and carbonato ligands and humate and hydrous ferric oxide (HFO) solid phases) were present as soluble metal-EDTA complexes. It appears that the metal-EDTA complexes found in the systems are very stable over a wide range of soil pH. Our surface complexation models also indicated that the EDTA is much stronger than the humate and the HFO solid phases in forming complexes with the metals. As a consequence, the adsorption of the Cd, Cu, Pb, and Zn by the solid surfaces was negligible in the presence of EDTA. (Abstract shortened by UMI.)
32

Remediation of brine-contaminated soil using calcium nitrate, gypsum, and straw

Nielsen, Jennifer I. 23 April 2013 (has links)
Salt-affected soils from point source brine contamination are common in the active oil field in SE Saskatchewan. A remediation process that included dewatering by sub-surface tile drains, application of surface amendments (calcium nitrate and straw), and growing forages has been successful but not previously examined. In a field study of two remediation sites, the changes in vegetation, soil salinity, and groundwater were assessed using geo-referenced electromagnetic (EM) maps (EM38h, EM38v, and EM31v), piezometers, and soil sampling. A laboratory soil core leaching experiment studied the effect of gypsum, calcium nitrate, and straw at various rates on the remediation of a brine-contaminated soil. All treatments including the control reduced the electrical conductivity (EC) to non-saline values (<4 dS m-1). The sodium adsorption ratio (SAR) was reduced to <13 with the high rates of gypsum and calcium nitrate. The fastest and most effective treatments were comprised of all rates of gypsum and the highest rate of calcium nitrate.
33

Effect of rate-limited interfacial tension reductions on the displacement of residual NAPLs during surfactant flushing

Loverde, Laura Elizabeth 12 1900 (has links)
No description available.
34

Transformation of 2,4,6-trinitrotoluene (TNT) by the aquatic plant myriophyllum spicatum

Comstock, Kelly K. 08 1900 (has links)
No description available.
35

Natural language, computer-assisted learning and language-impaired children

Ward, Robert David January 1987 (has links)
No description available.
36

Methylmercury Production in Riverbank Sediments of the South River, Virginia (USA) and Assessment of Biochar as a Mercury Treatment Option

Paulson, Krista 24 January 2015 (has links)
Mercury (Hg) is a toxic element which bioaccumulates in the food chain when methylated and poses a health risk to the human population mainly through fish consumption. It is released into the environment through both natural and anthropogenic processes. Remediation of river systems contaminated with Hg presents challenges due to complexities associated with dynamic transport and deposition processes and cyclic methylation. The South River watershed in Virginia, USA contains elevated concentrations of Hg within sediment and floodplain soils as a result of historical releases from a textile manufacturing plant from 1929-1950. Methylation of Hg is a bacterially mediated process which is controlled by the availability of electron donors, electron acceptors and Hg, amongst other factors. To evaluate the factors controlling Hg methylation at the South River site, four column experiments were conducted that involved saturating site sediments with South River water, followed by subjecting the columns to influent solution containing differing organic carbon and sulfate amendments. These amendments included acetate, lactate, and lactate combined with excess SO42- and the production of MeHg relative to a control was monitored both spatially and temporally. Production of MeHg was observed in all four columns, with the lowest mass found in the effluent generated by the control column (8.7 ng L-1), and a slightly higher mass in the acetate and lactate amended column effluents (53.7 ng L-1 and 30.1 ng L-1 reached respectively). The aqueous MeHg in the column amended with lactate and SO42- reached a maximum of 4910 ng L-1 near the output of the column. The results from these column experiments suggest that excess SO42- did not inhibit methylation under saturated flow conditions in the South River sediments. The bacterial species Desulfovibrio putealis, Geobacter spp., Desulfobacterium and Desulfosporosinus were identified in the column sediments and are potential contributors to the observed Hg methylation. Experiments were conducted to evaluate the potential removal of Hg and MeHg from sediment pore water. The experiments consisted of two columns connected in series. The first column contained Hg-bearing sediment with South River water as an influent solution to provide a source of Hg for the treatment column. The effluent from the first column was then connected to a treatment column which contained 1:1 volume ratio of biochar and silica sand. This treatment column was loaded with Hg for 182 pore volumes, disconnected, and then subjected to new influent solutions consisting of first background river water and then simulated acid rain water. The purpose was to determine the potential of the biochar material to retain Hg under saturated flow conditions. No significant release of Hg was observed in the column effluent with the South River water. After the influent was switched to simulated acid rain water (pH ~ 4.6), there was an increase in Hg concentrations in the column effluent for one sampling period, but then the unfiltered and 0.45 ???m filtered Hg concentrations returned to < 8.5 ng L-1. Total Hg extractions on the biochar column material at four locations suggested that the majority of the Hg in the column resided in the first 5 cm of material even after influent perturbations, with a maximum of 0.26 ???g g-1 dry weight in the 2 cm closest to the influent. Mercury sequential extraction results on the biochar material at the termination of the column revealed the majority (67%) of the Hg on the biochar material was removed with 12 M HNO3 (F4 fraction), followed by 0.1 M KOH (F3 fraction) at 31%. Less than 1.2% of the THg was removed after subjecting the biochar material to deionized water (F1 fraction) and 0.01M HCl + 0.1M CH3COOH (F2 fraction). A solid-phase analysis of MeHg on the same biochar material resulted in a concentration of 0.20 ng g-1 dry weight, or <0.08% of total solid-phase Hg. These results suggest that application of biochar may represent an effective approach for treating Hg in passive flow through systems.
37

The electrokinetic bioremediation of hydrocarbons from the sub-surface

Carter, Penny C. January 2007 (has links)
Hydrocarbon contamination of soil from accidental spills and negligence represents a major cause of sub-surface contamination. There are numerous physical, chemical and biological techniques available for contaminant remediation. However, many of these methods can be difficult to implement at sites where access to soils, or delivery of treatments, requires substantial excavation works and disruption (for example where contamination is located beneath or adjacent to building structures and underground services). An innovative technology that may provide a solution for the remediation of subsurface contamination without causing interim damage is that of electrokinetic remediation. Electrokinetic remediation is the application of a low voltage, direct current (of the order of mA/cm<sup>2</sup>) between electrodes placed in a contaminated soil system. The production of an electric field causes a number of electrically-induced processes to occur that can promote soil remediation, principally: electromigration, electroosmosis, electrophoresis, and electrolysis. This study examined the use of electrokinetics coupled with biodegradation to remediate kerosene and transformer oil from sub-surface soils. The principal investigations carried out within this study included: the use of electroosmosis as an in situ flushing technique; use of electrokinetics to deliver surfactants into the soil to promote mobilisation of contaminants within the sub-surface; and the use of electrokinetics to create optimum conditions for biodegradation by the delivery of nutrients and electron acceptors, the removal of toxic metabolites, and by controlling the pH and moisture content of the soil. As an integral part of the research, a field trial was designed and set up to determine whether electrokinetics could be used to promote the biodegradation of transformer oil from the subsurface. This was one of the first field trials in the UK for the electrokinetic remediation of hydrocarbon contaminants. The results of the study support the use of electrokinetics as a field tool for the enhancement of remediation in the sub-surface. Laboratory-scale studies showed the potential to mobilise the more soluble hydrocarbons (such as toluene and xylene) in the soil, to deliver enhancing agents (e.g. surfactants and nutrients) and to remove toxic metabolites. The field-scale experiment demonstrated the concept of a relatively low cost treatment cell on-site and provided some evidence that biodegradation of the transformer oil was promoted. Consequently, it is suggested that electrokinetics, with the correct engineering controls in place, provides a valuable method of optimising the biodegradation of hydrocarbons in the sub-surface.
38

Remediation study for a salt-affected soil impacted by the oil and gas industry

Guo, Ying 11 1900 (has links)
An agricultural land was adversely affected by salt released by the oil and gas industry. Remediation was needed to recover the land to agricultural productivity. Field-scale and laboratory-scale experiments were conducted to identify a practical and reliable remediation technique that could be used to treat the salt-contaminated farmland. Different approaches, including leaching and drainage interventions, gypsum application, zeolite application, alluing or ripping, sanding and combinations of these approaches, were tested to evaluate the removal of sodium and chloride from salt-affected soils. Electrical conductivity (EC), sodium adsorption ratio (SAR) and remediation time were three important diagnostic parameters in the evaluation. It was found that the integrated application of alluing, gypsum addition and leaching achieved the best remediation for the fine textured soil containing a high concentration of sodium and chloride. Chemical amendments must be applied prior to leaching when treating severely sodic soils.
39

Old gas stations - new fuel for environmental awareness

Man-Bourdon, Alexandre 05 1900 (has links)
According to Environment Canada, across the country there are currently over 1400 abandoned gas station sites that are contaminated. Unbeknownst to local residents, many of these sites are undergoing remediation. Temporary interventions called remedial landscapes can be designed by landscape architects to communicate to the public the remediation activities, which are otherwise hidden from view. Environmental psychologists note that pro-environmental behaviour stems from increased awareness of environmental degradation. Furthermore, by presenting first hand information in the form of a landscape, people can make their own decisions concerning their role in unsustainable practices. This thesis posits that by experiencing remedial landscapes, people will change their environmental attitudes and or behaviours. Remedial landscapes also offer opportunities for public art and further exploration of alternative forms of remediation. It includes not only precedent studies of other remedial landscapes, but a public perception survey concerning a gas station undergoing remediation in Kerrisdale, Vancouver. The survey indicated that the remediation of contaminated sites is a community concern and that the remediation should be made more visible. Participants also agreed that the use of a designed landscape would be a viable tool for communicating the status of the site. This research informed a set of design guidelines for the Kerrisdale ‘test site.’ A remedial landscape has been designed using these guidelines and is included as part of the thesis.
40

Persulfate activation by major soil minerals

Ahmad, Mushtaque, January 2008 (has links) (PDF)
Thesis (M.S. in environmental engineering)--Washington State University, December 2008. / Title from PDF title page (viewed on Apr. 17, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 15-18).

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