Mercury distribution in tropical soil profiles related to origin of mercury and soil processes
Mercury distribution in tropical soil profiles related to origin of mercury and soil processes
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DOI：
10.1016/j.scitotenv.2008.04.001
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发表时间：
2008-08-15
影响因子：
9.8
通讯作者：
Guedron, Stephane
中科院分区：
文献类型：
--
作者：
Grimaldi, Catherine;Grimaldi, Michel;Guedron, Stephane
这项研究的目的是提高我们对热带土壤汞含量[Hg]的垂直和横向变化的理解。除了与人为汞源的距离外，最常见的决定因素是含汞相的丰度。土壤过程（风化、质量或水的转移）决定了载体相的丰度。我们假设土壤过程也对汞的分布有直接的影响，并且根据该元素的岩石成因或大气成因的不同，影响是不同的。我们比较了法属圭亚那森林中两种类型的土壤（oxisol和ululsol），在相隔几十米的地方，显示出非常不同的汞含量。研究表明，[Hg]的垂直剖面与[Hg-大气]的变化密切相关，而[Hg-成岩]的变化不大。由于两种土壤之间的水力导电性对比，表层沉积物中hg -大气的渗透有利于渗透到氧化土中3英寸以下的深度，并且仅限于氧化土的上层。汞主要是在终极层的互质层中形成的。在母质递进风化过程中，由于次生矿物的不平衡作用，在土壤表面附近限制了汞的相对堆积。储存在土壤中的汞-大气或汞-岩石的再活化是含汞阶段的化学或颗粒侵蚀的一个功能，特别活跃于终极土壤的上层，那里在降雨期间发生横向流动。观察到的铁或粘土含量与[Hg]之间的相关性可能是由汞对这些载体相的亲和力引起的，但也可能反映了风化和转移过程，这些过程共同影响了汞的命运以及土壤的矿物学和化学成分。(c) 2008 Elsevier B.V.版权所有
The aim of the study is to improve our understanding of the vertical and lateral variations in the mercury content [Hg] of tropical soils. In addition to the distance to anthropogenic sources of Hg, the most frequently evoked determining factor is the abundance of Hg-bearing phases. Soil processes (weathering, mass or water transfer) determine the abundance of carrier phases. We assume that soil processes also have a direct impact on the distribution of Hg and that the impact is different according to the lithogenic or atmospheric origin of this element. We compare two types of soil (oxisol and ultisol) in the French Guiana forest, at localities a few tens of metres apart and exhibiting very different Hg contents. We show that vertical profiles of [Hg] are strongly related to the variations of [Hg-atmospheric], whereas [Hg-lithogenic] varies little. The penetration of Hg-atmospheric from the surface deposits is favoured down to a depth of 3 in in the oxisol and limited to the upper horizons of the ultisol because of contrasted hydraulic conductivity between the two soils. Hg is primarily of lithogenic origin in the alteritic horizons of the ultisol. The relative accumulation of Hg-lithogenic during the progressive weathering of parental material is limited near the soil surface by the disequilibrium of secondary minerals. Remobilization of Hg-atmospheric or Hg-lithogenic stored in the soil is a function of the chemical or particulate erosion of Hg-bearing phases, particularly active in the upper horizons of the ultisol, where lateral flow occurs during rain events. The correlations observed between the iron or clay contents and [Hg] can be caused by the affinity of Hg for these carrier phases, but may also reflect the weathering and the transfer processes which affect together the fate of Hg and the mineralogical and chemical composition of the soil. (c) 2008 Elsevier B.V. All rights reserved.