Rapid post-mortem incorporation of aluminum in diatom frustules: Evidence from chemical and structural analyses
Rapid post-mortem incorporation of aluminum in diatom frustules: Evidence from chemical and structural analyses
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DOI：
10.1016/j.marchem.2006.06.009
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发表时间：
2007-07-01
期刊：
影响因子：
3
通讯作者：
Epping, E.
中科院分区：
文献类型：
--
作者：
Koning, E.;Gehlen, M.;Epping, E.
通过一系列实验研究了铝对硅藻硅藻细胞壳的早期影响。灰硅藻Thalassiosira punctigera的硅藻壳暴露于天然海水中，在不同的溶解铝（Al）浓度（没有添加，100 nM和500 nM铝）的时间长达6个月，无论是在批量培养和流通室。这些铝浓度代表了海洋环境中孔隙沃茨中常见的水平。一般而言，硅藻壳的铝含量随暴露时间而增加。在500 nM Al下孵育14天后，观察到铝与硅的摩尔比从1.23 x 10（-3）（第0天）增加到3.14 x 10（-3）。在100 nM Al下孵育时间从1天到21天的时间序列证实，铝与硅藻硅藻壳迅速结合。在孵化过程中的Al的吸收去沿着在孔结构向更小的孔的转变。利用X射线吸收光谱研究了生物硅中铝和硅的结构关联。铝-K-边缘X-射线吸附近边缘光谱（XANES）的孵化硅藻硅藻壳表明，大多数铝是存在于四面体协调，无论铝浓度的海水和曝光的持续时间。Al-K边EXAFS谱表明铝结构并入到Si框架中。从X-射线吸收光谱的结果在铝-K-边缘，硅藻硅藻壳在孵化过程中的纹理变化和湿化学数据都与硅藻硅藻壳表面上的铝硅酸盐相的形成是一致的。在模拟沉积物-水界面处盛行的那些实验条件下，这种表面相发生沉淀。我们建议，记录的反应途径有助于快速死后铝富集硅藻硅藻壳在沉积物-水界面。(C)2006 Elsevier B. V.保留所有权利。
We studied the aluminum-induced early alteration of cultured diatom frustules in a series of laboratory experiments. Ashed frustules of the diatom Thalassiosira punctigera were exposed to natural seawater at varying dissolved aluminum (Al) concentrations (without addition, 100 nM and 500 nM Al) for periods of up to 6 months both in batch incubations and in flowthrough chambers. These Al concentrations are representative of levels commonly found in pore waters in the marine environment. In general, the aluminum content of the frustules increased with time of exposure. A maximum increase of the aluminum to silicon mole ratio from 1.23 x 10(-3) (day 0) to 3.14 x 10(-3) Was observed after 14 days of incubation at 500 nM Al. Time series with incubation times from I to 21 days at 100 nM Al confirm that the aluminum is rapidly associated with the diatom frustule. The uptake of Al during incubation goes along with a shift in pore structure towards smaller pores. The structural association of aluminum and silicon in biogenic silica was investigated using X-ray absorption spectroscopy at the Al-K-edge. Al-K-edge X-ray adsorbtion near edge spectra (XANES) of incubated diatom frustules demonstrate that most aluminum is present in tetrahedral coordination regardless of the Al concentration of the seawater and the duration of exposure. Al-K-edge EXAFS spectroscopy indicates the structural incorporation of aluminum into the Si framework. The results from X-ray absorption spectroscopy at the Al-K-edge, the textural changes of diatom frustules during incubation and wet chemical data are all consistent with the formation of an aluminosilicate phase on the surface of the diatom frustules. The precipitation this surface phase occurred under experimental conditions mimicking those prevailing at the sediment-water interface. We propose that the documented reaction pathway contributes to the rapid post-mortem aluminum enrichment of diatom frustules at the sediment-water interface. (C) 2006 Elsevier B.V. All rights reserved.