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首页> 外文学位 >Role des microorganismes sur la speciation du cuivre, zinc, et aluminium dans la rhizosphere de sols forestiers.
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Role des microorganismes sur la speciation du cuivre, zinc, et aluminium dans la rhizosphere de sols forestiers.

机译：微生物对森林土壤根际中铜，锌和铝形态的影响。

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摘要

By controlling metal uptake by plants, the rhizosphere strongly influences the distribution of metals in forested ecosystems. Studies on the biogeochemistry of metals in the rhizosphere provided detailed accounts of the distribution of metals in the solid phase of this soil microenvironment. However, very few studies have investigated the speciation of metals in the soil solution despite the fact that it represents the preferential pathway of metal uptake by plants. Similarly, although the effects of roots on the biogeochemistry of metals in the rhizosphere have been extensively studied, the influence exerted by soil microorganisms has been comparatively neglected.;The thesis is composed of two chapters reviewing the latest knowledge published on this topic, of one chapter describing the methodology used for this work and of four result chapters presented as research papers. The first article describes the modelling approach used to compute the speciation of metals. The following three papers present and discuss the results of this research. The speciation results revealed that Cu is largely present in organically-complexed forms, that the speciation of Zn is dominated by the free-ion form or by organic complexes while Al is mostly found as inorganic complexes. The speciation data further revealed that the rhizosphere was systematically enriched in bioavailable metal species as compared to bulk soil. This suggested that the processes acting in the rhizosphere promoted the formation of bioavailable metal species.;Moreover, links between microbial variables and metals were also studied and indicated that the rhizospheric microorganisms exerted a significant influence on the distribution of bioavailable metals species and that this influence was larger in rhizosphere than in the bulk soil. Two microbially-driven processes were proposed to explain their influence on the bioavailability of metals in the rhizosphere. The most important microbial process was the pH change induced by the assimilation of nitrogen. This process strongly impacted on the pH of the rhizosphere and, thus, on the speciation of metals. The second process was the microbially-induced decay of soil organic matter, in particular of dead roots, through which the metals sequestered in the soil organic matter of the rhizosphere were mobilized.;The original contributions of this thesis are two-fold. First, its focus on tree roots and field sampling gave us a unique opportunity to study the rhizosphere under relevant, meaningful and representative conditions. Secondly, the data produced during this study are unique. Indeed, very few studies have documented the speciation of dissolved metals in the rhizosphere as precisely as we did. Similarly, the influence exerted by microorganisms on metal speciation in this microenvironment was demonstrated here for one of the first time. Acquiring these key informations significantly improved our understanding of the processes controlling the speciation of metals in the rhizosphere, especially by emphasizing the crucial role played by microorganisms in this microenvironment. These informations are helpful to estimate precisely the metal uptake by plants and to assess the ecological and human risk associated to the transfer of metals from soil to the vegetation.;To address this gap in knowledge, the objectives of this thesis were defined as to (1) document the liquid-phase speciation of copper (Cu), zinc (Zn) and aluminum (Al) in the rhizosphere and bulk forest soils, (2) quantify the influence of microorganisms on the speciation of Cu, Zn and Al in these soils and (3) identify the microbial variables and processes controlling the speciation of these metals in the rhizosphere. To achieve these objectives, rhizosphere and bulk soils were sampled under 18 trembling aspen trees ( Populus tremuloides Michx) equally distributed at six field sites presenting contrasted soil properties. On each soil sample, biological and chemical properties as well as the labile and bioavailable Cu, Zn and Al were measured whereas geochemical modelling was used to speciate each metal studied.;Keywords. biogeochemical cycle, forest soils, trace metals, rhizosphere, pH, microbial biomass, differential pulse anodic stripping voltammetry, ion-selective electrode, MINEQL+ 4.5, multivariate statistical analyses.
机译：通过控制植物对金属的吸收，根际强烈影响森林生态系统中金属的分布。根际中金属的生物地球化学研究提供了该土壤微环境固相中金属分布的详细说明。然而，很少有研究调查土壤溶液中金属的形态，尽管它代表了植物吸收金属的优先途径。同样，尽管已经广泛研究了根对根际中金属生物地球化学的影响，但相对忽略了土壤微生物的影响。；本文由两章组成，回顾了有关该主题的最新知识，其中一章本章描述了这项工作所使用的方法，并作为研究论文介绍了四个结果章。第一篇文章介绍了用于计算金属形态的建模方法。以下三篇论文介绍并讨论了这项研究的结果。形态结果表明，Cu主要以有机络合物形式存在，Zn的形态主要以自由离子形式或有机络合物为主，而Al主要以无机络合物形式存在。形态数据进一步表明，与块状土壤相比，根际系统地富集了可生物利用的金属物种。这表明在根际中起作用的过程促进了生物有效性金属物种的形成。此外，还研究了微生物变量与金属之间的联系，并指出，根际微生物对生物有效性金属物种的分布具有重要影响，并且这种影响在根际中比在土壤中大。提出了两个微生物驱动的过程来解释它们对根际中金属生物利用度的影响。最重要的微生物过程是氮的吸收引起的pH值变化。此过程强烈影响根际的pH值，从而影响金属的形态。第二个过程是微生物引起的土壤有机物的腐烂，特别是死根的腐烂，从而动员了根际土壤有机质中螯合的金属。本论文的最初贡献是双重的。首先，它对树根和田间采样的关注为我们提供了一个在相关，有意义和代表性条件下研究根际的独特机会。其次，在这项研究中产生的数据是唯一的。实际上，很少有研究像我们一样准确地记录了根际中溶解金属的形态。同样，这是首次证明了微生物对这种微环境中金属形态的影响。获得这些关键信息极大地提高了我们对控制根际中金属形态的过程的理解，特别是通过强调微生物在该微环境中的关键作用。这些信息有助于准确地估计植物对金属的吸收，并有助于评估与金属从土壤到植被的转移相关的生态和人类风险。为了解决这一知识空白，本论文的目标定义为（ 1）记录了根际土壤和大块森林土壤中铜（Cu），锌（Zn）和铝（Al）的液相形态，（2）定量分析了微生物对这些土壤中Cu，Zn和Al形态的影响土壤和（3）识别控制根际中这些金属形态的微生物变量和过程。为了实现这些目标，在18个颤抖的白杨树（Populus tremuloides Michx）下对根际土壤和大块土壤进行采样，这些树木平均分布在六个具有不同土壤特性的田间地点。在每个土壤样品上，测量了其生物和化学特性以及不稳定和可生物利用的Cu，Zn和Al，而地球化学模型用于指定所研究的每种金属。生物地球化学循环，森林土壤，痕量金属，根际，pH，微生物生物量，差分脉冲阳极溶出伏安法，离子选择电极，MINEQL + 4.5，多元统计分析。

著录项

  • 作者

    Cloutier-Hurteau, Benoit.;

  • 作者单位

    Universite de Montreal (Canada).;

  • 授予单位 Universite de Montreal (Canada).;
  • 学科 Biogeochemistry.;Agriculture Soil Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 235 p.
  • 总页数 235
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 肿瘤学;
  • 关键词

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