Tracing mechanisms controlling the release of dissolved silicon in forest soil solutions using Si isotopes and Ge/Si ratios
Tracing mechanisms controlling the release of dissolved silicon in forest soil solutions using Si isotopes and Ge/Si ratios
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DOI：
10.1016/j.gca.2010.04.056
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发表时间：
2010-07-15
影响因子：
5
通讯作者：
Opfergelt, S.
中科院分区：
文献类型：
--
作者：
Cornelis, J. -T.;Delvaux, B.;Opfergelt, S.
土壤植物系统中的陆源硅（BSi）库普遍存在且数量巨大，可能影响溶解态硅（DSi）的海陆迁移。在这里，我们认为在温带花岗岩生态系统，将不同于以往的作品主要集中在热带环境中的森林土壤中的DSi控制机制。本研究的目的是追踪来源的DSi在森林地面渗滤液和土壤溶液中的各种树种在均匀的土壤和气候条件下，使用稳定的Si同位素和Ge/Si比。相对于花岗质基岩，粘土矿物富含Si-28，具有较高的Ge/Si比值，植硅体中的BSi也富含Si-28，但Ge/Si比值较低。这样的对比是有用的，以推断相对贡献的硅酸盐风化和BSi溶解在浅层土壤中的森林地面渗滤液中的DSi的释放。森林地面淋溶物中的δ Si-30值（-1.38 ‰至-2.05 ‰）是天然沃茨中发现的最轻的，并且相对于土壤溶液，森林地面淋溶物中的Ge/Si比更高。这些结果表明溶解的Si-28和Ge富集的次生粘土矿物结合生物扰动在有机丰富的视野中，在此溶解过程中释放优先轻Si同位素的同位素分馏。土壤溶液中Ge/Si比值受原生矿物的不一致风化和次生粘土矿物的新生作用的控制。树种的影响Si同位素组成和Ge/Si比值在森林地面渗滤液通过不同的矿物掺入有机层的生物扰动，并在较小程度上，通过不同的Si回收。(C)2010爱思唯尔有限公司保留所有权利。
The terrestrial biogenic Si (BSi) pool in the soil plant system is ubiquitous and substantial, likely impacting the land-ocean transfer of dissolved Si (DSi). Here, we consider the mechanisms controlling DSi in forest soil in a temperate granitic ecosystem that would differ from previous works mostly focused on tropical environments. This study aims at tracing the source of DSi in forest floor leachates and in soil solutions under various tree species at homogeneous soil and climate conditions, using stable Si isotopes and Ge/Si ratios. Relative to granitic bedrock, clays minerals were enriched in Si-28 and had high Ge/Si ratios, while BSi from phytoliths was also enriched in Si-28, but had a low Ge/Si ratio. Such a contrast is useful to infer the relative contribution of silicate weathering and BSi dissolution in the shallow soil on the release of DSi in forest floor leachate solutions. The delta Si-30 values in forest floor leachates (-1.38 parts per thousand to -2.05 parts per thousand) are the lightest ever found in natural waters, and Ge/Si ratios are higher in forest floor leachates relative to soil solution. These results suggest dissolution of Si-28 and Ge-enriched secondary clay minerals incorporated by bioturbation in organic-rich horizons in combination with an isotopic fractionation releasing preferentially light Si isotopes during this dissolution process. Ge/Si ratios in soil solutions are governed by incongruent weathering of primary minerals and neoformation of secondary clays minerals. Tree species influence Si-isotopic compositions and Ge/Si ratios in forest floor leachates through differing incorporation of minerals in organic horizons by bioturbation and, to a lesser extent, through differing Si recycling. (C) 2010 Elsevier Ltd. All rights reserved.