| Summary: | 博士 === 國立臺灣大學 === 生物環境系統工程學系暨研究所 === 91 === Since spatial or temporal measurements of soil physical and chemical properties generally do not explain the underlying governing processes directly, knowledge of soil properties and vegetation distributions is essential in recovering habitats. Statistical analysis is a science tool to help us find out the relationship. This work mainly introduced by three chapters. The first chapter investigated soil samples collected from Kuan-Tu wetlands, Taiwan. Factor analysis was performed to explain the impact of various environmental factors on this coastal wetland located in suburban Taipei. The results indicated that the latent factors were heavy metals, salinity, and organic matters. Factor scores were computed and cluster analysis was implemented using factor scores to classify the Kuan-Tu wetlands into four regions by plant types short marshes, rice paddy fields, tall marshes, and drier area. Multivariate analysis of the spatial patterns of the soil quality and vegetation types in the habitat showed that properties of soil determine types of vegetation and accumulation of contaminants in the soil. Sediment from tall marshes area accumulated more Ni, Cu, Pb, Cd, Zn, Fe, except Mn, than sediment from short marshes area. The methodology and results concerning the Kuan-Tu wetlands may be applicable to other wetlands to interpret the relationship between soil properties and plant classification.
The second chapter used the conclusions by chapter one. The canonical discriminant analysis was used to improve an existing vegetation classification scheme by identifying the physical-chemical properties of sediment in Kaun-Tu wetlands, Taiwan. And predictive discriminant analysis was used to examine the ability of the models constructed in predicting class membership with unknown sediment properties into known classes. Multivariate analysis of the spatial patterns of the soil quality and vegetation types in the habitat showed that different properties of soil grow different types of vegetation and absorbs contaminants differently. And controlling these critical variables can feasibly conserve a suitable habitat for wetland biology. The most important aspects of managing Kuan-Tu wetland for migrant birds in the winter were controlling plant succession, maintaining the tillage of rice paddies to ensure stable food supply and reducing the effects of contaminants. The methodology and results provide useful information concerning the Kuan-Tu wetlands and may be applicable to other wetlands with similar properties or experiencing similar environmental issues.
Because have not real testing of the bioaccumulation in conclusions of chapter one and two. So in chapter third we demonstrate the potential of water hyacinth (Eichhornia crassipes Mart. Solms.), for the phytoremediation of five trace elements - cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), and nickel (Ni). The ability of water hyacinth to take up and translocate the five trace elements from roots to shoots was studied by field sampling. Translocation ability, defined as the quantity of Cu, Pb, Cd, Ni, and Zn translocated in the plant’s tissues, was expressed as a root/shoot ratio. The ratio results were in the order of Cu＞Pb＞Cd＞Ni＞Zn. Water hyacinth had high bioconcentration factors of trace elements, when grown in water environments with low concentrations of the five elements, indicating that Cu＞Pb＞Zn＞Cd＞Ni, and had low bioconcentration factors when grown in sediment environment with low concentrations of these trace element, except copper. Generally, the concentration of these five elements in the roots was 3 to15 times higher than those in the shoots. The concentrations in the root tissue were found in the order of Cu＞Zn＞Ni＞Pb＞Cd. Water hyacinth was thus found to be a promising candidate for phytoremediation of wastewater polluted by Cu, Pb, Zn, and Cd. The absorption capacity for water hyacinth was 0.24 kg/ha for Cd, 5.42 kg/ha for Pb, 21.62 kg/ha for Cu, 26.17 kg/ha for Zn, and 13.46 kg/ha for Ni.
|
|---|
