Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 73-81). Also available on the World Wide Web.

Mine tailings can be rich in sulphide minerals and may form acid mine drainage (AMD) through reaction with atmospheric oxygen and water. AMD contains elevated levels of metals and arsenic (As) that could be harmful to animals and plants. An oxygen-consuming layer of organic material and plants on top of water-covered tailings would probably reduce oxygen penetration into the tailings and thus reduce the formation of AMD. However, wetland plants have the ability to release oxygen through the roots and could thereby increase the solubility of metals and As. These elements are released into the drainage water, taken up and accumulated in the plant roots, or translocated to the shoots. The aim was to examine the effects of plant establishment on water-covered mine tailings by answering following questions: A) Is plant establishment on water-covered mine tailings possible? B) What are the metal and As uptake and translocation properties of these plants? C) How do plants affect metal and As release from mine tailings, and which are the mechanisms involved? Carex rostrata Stokes, Eriophorum angustifolium Honck., E. scheuchzeri Hoppe, Phragmites australis (Cav.) Steud., Salix phylicifolia L. and S. borealis Fr. were used as test plants. Influences of plants on the release of As, Cd, Cu, Pb, Zn and in some cases Fe in the drainage water, and plant element uptake were studied in greenhouse experiments and in the field. The results obtained demonstrate that plant establishment are possible on water-covered unweathered mine tailings, and a suitable amendment was found to be sewage sludge. On acidic, weathered tailings, a pH increasing substance such as ashes should be added to improve plant establishment. The metal and As concentrations of the plant tissue were found to be generally higher in roots than in shoots. The uptake was dependent on the metal and As concentrations of the tailings and the release of organic acids from plant roots may have influenced the uptake. The metal release from tailings into the drainage water caused by E. angustifolium was found to depend greatly on the age and chemical properties of the tailings. However, no effects of E. angustifolium on As release was found. Water from old sulphide-, metal- and As-rich tailings with low buffering capacity were positively affected by E. angustifolium by causing higher pH and lower metal concentrations. In tailings with relatively low sulphide, metal and As contents combined with a low buffering capacity, plants had the opposite impact, i.e. a reduction in pH and elevated metal levels of the drainage water. The total release of metal and As from the tailings, i.e. drainage water together with the contents in shoots and roots, was found to be similar for C. rostrata, E. angustifolium and P. australis, except for Fe and As, where the release was highest for P. australis. The differences in metal and As release from mine tailings were mainly found to be due to the release of O2 from the roots, which changes the redox potential. Release of organic acids from the roots slightly decreased the pH, although did not have any particular influence on the release of metal and As. In conclusion, as shown here, phytostabilisation may be a successful technique for remediation of mine tailings with high element and sulphide levels, and low buffering capacity.

Oil sands operators are being faced with the challenge of reclaiming the large volumes of slurry tailings created during oil sands processing. New regulations mandate that operators must minimize fluid tailings by capturing fines in dedicated disposal areas, leading to a ‘trafficable’ or solid deposit. Adding a polyacrylamide polymer to the tailings and thinly spreading them over a sloped disposal area (a process developed by Shell Canada Energy known as the atmospheric fines drying or AFD process) has been shown to enhance the dewatering of tailings which leads to a dry deposit at a much faster rate than traditional methods. Hydroponic experiments using the emergent aquatic macrophytes cattail (Typha latifolia L.) and common reed (Phragmites australis (Cav.) Trin. ex Steud.) were conducted to investigate the phytotoxicity of waters formed during AFD processing. The phytotoxicity of AFD release waters was compared to the phytotoxicity of traditional mature fine tailings (MFT) reclaim water through the monitoring of plant water uptake and whole plant fresh weight over the course of the experiment. It was found that there are no significant differences between the phytotoxicity observed in the MFT and AFD treatments and it was also found that spring runoff melt water from the AFD deposits is less phytotoxic than the original release water. Two additional hydroponic studies using cattail and common reed were also conducted. The first examined the phytotoxic effects attributable solely to the naphthenic acids isolated from Shell’s Muskeg River Mine tailings, and the second evaluated the phytotoxic effects of amending mature fine tailings with gypsum. It was found that the gypsum amended tailings caused greater phytotoxicity in cattail and common reed than tailings without gypsum added. Furthermore, both species were tolerant to growing in nutrient media spiked with naphthenic acids (40 mg/L). The phytotoxicity experiments conducted also demonstrated that common reed is consistently more tolerant to growing in water associated with oil sands tailings and is therefore the more appropriate choice for use in reclamation strategies involving wetland plants. Mass spectrometry was used to determine the naphthenic acid molecular profiles for Shell oil sands tailings. Using low resolution mass spectrometry, no detectable features or changes to the composition of naphthenic acids attributable to Shell processing were found. High-resolution mass spectrometry provided insight into possible plant mediated changes and biodegradation of naphthenic acids. It appears as though, to some extent, cattail is able to dissipate naphthenic acids, which could explain the susceptibility of cattail to the phytotoxic effects of naphthenic acids. Further research is required to determine whether the changes observed in the naphthenic acid mixture are due to microbial degradation and/or a phytotoxic response of the plants studied.

Taiwan is an island surrounded by sea. Due to the topography, the coastal wetlands distribute almost around the west seashore, and some at the estuary of the east seashore. The coastal wetland is a transitional area between territory ecosystem and marine ecosystem. The environment of the coastal wetland is influenced by tide and season, thus the distribution of vegetations here exhibits a dynamic equilibrium. This study attempts to investigate the distribution and composition of the vegetation and the appearance of the habitat environment at the coastal wetland of Taiwan. According to the results, 173 species belonging to 50 families have been recorded. This indicates that the diversity of the marsh vegetation at the coastal wetland is low. Most of the species belong to Gramineae, Compositae and Cyperaceae. Paspalum vaginatum and Phragmites karka are the most dominant plant at coastal marsh environments. According to the results of detrended correspondence analysis (DCA) and cluster analysis (CA), 16 vegetation types including one subtype and one transitional type are classified. The habitats of these vegetation types can be classified into five types, namely tidal fresh water marsh, fresh water-salt marsh, wet meadow, salt marsh and submerged environment. Most of these vegetation types have only one major dominant species. The distribution of the marsh vegetation features a belting pattern, which is mainly limited by the maximum of their salt tolerance from coastal toward inland, or estuary toward headwaters. Subsequently, it can by influenced by soil moisture and pH value. Furthermore, the vegetations are influenced by many additional environmental factors, resulting in a mosaic distribution of vegetation types. The marsh vegetation is processing at an unstable and developing period. Because the coastal wetland is seriously disturbed by human activities, the environmental variation becomes greater. Therefore, the transitional vegetations were observed frequently. Finally, the development pressure due to economic demand is the major cause that makes coastal wetland disappeared. It is urgently needed to protect this sensitive natural resource.

Thesis (M.S.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 99-106). Also available via World Wide Web.

Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [110]-119).

Thesis (M.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 66-71). Also available in electronic format on the Internet.

Thesis (Ph.D.)--University of Central Florida, 2009. / Adviser: Pedro F. Quintana-Ascencio. Includes bibliographical references.

Theses (M.S.)--Marshall University, 2004. / Title from document title page. Includes abstract. Includes vita. Document formatted into pages: contains ix, 146 pages. Bibliography: p. 118-121.

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