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An investigation on the effects of herbaceous plants on the biogeochemistry of wetland sediments.

机译：草本植物对湿地沉积物生物地球化学影响的研究。

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摘要

Wetlands are among the most productive ecosystems and play important ecological, environmental and hydrological functions on local, regional and global scales and plants represent a vital component in sustaining the healthy functioning of wetland systems. In this thesis, my research focus was the effects of herbaceous plants on the biogeochemistry of wetland sediments.; In my greenhouse microcosm experiments, it was observed that wetland plant transpiration could significantly concentrate dissolved species. Results showed that under normal drainage and transpiration conditions, diurnal variations in plant transpiration alone do not results in comparable variations in the concentrations of dissolved species in the rhizosphere due the "memory" effect. However, significant variations could occur in pores under strong influence of plant roots, as indicated by results obtained with microelectrodes.; Chromium is a widely used toxic heavy metal. Hexavalent chromium could be reduced to trivalent chromium which under normal pH conditions, forms precipitation and is less toxic. I investigated the roles of plants on the reduction and removal of hexavalent chromium. Plant transpiration could enhance the loading of chromium toward the rhizosphere where it could be reduced. Abiotic reduction, possibly driven by organic materials from plants and bacteria, was found to be responsible fir the reduction of hexavalent chromium.; It was also found that both Typha latifolia and Phragmites australis could actively uptake Cl- on Br-, two widely used tracers. The effect of transpiration on the Br concentration profile in sediments, and hence on its uptake kinetics, was highlighted in this research.; Wetlands also represent one of the major sources of atmospheric methane, which is the second most important greenhouse gas. A one-dimensional, process-based methane emission model from rice paddy systems was developed and tested. Rice paddy systems were selected because they represent one of the manageable sources of methane. Effects of rice plants on the production, oxidation and emission of methane was highlighted in this model and it could enable the examination of the consequences of changes in agricultural practices and environmental conditions on methane fluxes and the evaluation of potential mitigation options.
机译：湿地是生产力最高的生态系统之一，并在地方，区域和全球范围内发挥重要的生态，环境和水文功能，而植物则是维持湿地系统健康运行的重要组成部分。本文的研究重点是草本植物对湿地沉积物生物地球化学的影响。在我的温室缩影实验中，观察到湿地植物的蒸腾作用可以显着地浓缩溶解的物种。结果表明，在正常排水和蒸腾条件下，由于“记忆”效应，仅植物蒸腾的昼夜变化不会导致根际中溶解物质浓度的变化。然而，如通过微电极获得的结果所示，在植物根的强烈影响下，孔隙中可能会发生显着变化。铬是一种广泛使用的有毒重金属。六价铬可以还原为三价铬，在正常的pH条件下会形成沉淀，并且毒性较小。我调查了植物在减少和去除六价铬中的作用。植物的蒸腾作用可增加铬向根际的负载量，并可以减少。非生物性还原可能是由植物和细菌中的有机物推动的，这是六价铬还原的原因。还发现香蒲和芦苇都可以积极吸收被广泛使用的两种示踪剂Br-上的Cl-。这项研究强调了蒸腾作用对沉积物中溴浓度分布的影响，并因此对其吸收动力学的影响。湿地也代表了大气中甲烷的主要来源之一，后者是第二重要的温室气体。开发并测试了稻田系统基于过程的一维甲烷排放模型。选择稻田系统是因为它们代表了甲烷的可管理来源之一。该模型强调了水稻对甲烷产生，氧化和排放的影响，它可以检验农业实践和环境条件的变化对甲烷通量的影响，并评估潜在的缓解方案。

著录项

  • 作者

    Xu, Shangping.;

  • 作者单位

    Princeton University.;

  • 授予单位 Princeton University.;
  • 学科 Engineering Environmental.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 198 p.
  • 总页数 198
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 环境污染及其防治;
  • 关键词

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