Origin of the difference in the distribution behavior of tellurium and selenium in a soil-water system
Origin of the difference in the distribution behavior of tellurium and selenium in a soil-water system
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DOI：
10.1016/j.gca.2007.12.008
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发表时间：
2008-03-01
影响因子：
5
通讯作者：
Takahashi, Yoshio
中科院分区：
文献类型：
--
作者：
Harada, Teppei;Takahashi, Yoshio
采用x射线吸收精细结构（XAFS）光谱和高效液相色谱联用ICP-MS （HPLC-ICP-MS）技术，研究了土壤-水体系中碲（Te）在土壤和水相中的分布行为以及Te在土壤和水相中的形态。结果与本研究同时获得的Se的类似数据集进行了比较。土壤样品中Te和Se的氧化态和宿主相采用XAFS法测定，水中Te和Se的氧化态采用HPLC-ICP-MS法测定。结果表明，在氧化条件下，土壤中的Te和Se主要与Fe（III）氢氧化物伴生。从EXAFS分析来看，外球配合物对土壤中Fe（III）氢氧化物吸附的Se（VI）很重要，而Se(IV), Te（IV）和Te（VI）形成内球配合物。在还原条件下，发现形成了Te(0)和Se(0)两种物质，并且Se比Te更容易被还原为Se(0)，从它们的Eh-pH图可以预测。Se和Te从六价物种到零价物种的还原过程不同，即Se直接从Se（VI）还原为Se(0)，而Te则通过Te（IV）逐步从Te（VI）还原为Te(0)。在土壤和水之间的分布上，在广泛氧化还原条件下，Se对水的分布远高于Te。由于硒（VI）的溶解度远高于硒（IV），硒酸盐在水中的优势形态为硒酸盐。此外，Te在水中的分布要小得多，主要是由于Te（IV）和Te（VI）对Fe（III）氢氧化物的亲和力比Se（VI）大，这源于Te（IV）和Te（VI）对Fe（III）氢氧化物的球内配合物的形成。(c) 2008 Elsevier Ltd.版权所有。
The distribution behavior of tellurium (Te) between soil and water in a synthetic soil-water system was studied coupled with the speciation of Te both in soil and water phases by using X-ray absorption fine structure (XAFS) spectroscopy and a high-performance liquid chromatography connected to an ICP-MS (HPLC-ICP-MS), respectively. The results were compared with a similar data set for Se, which was simultaneously obtained in this study. The oxidation states and host phases of Te and Se in the soil samples were given by XAFS, while the oxidation states in water were given by HPLC-ICP-MS. It was found that both Te and Se in soil are mainly associated with Fe(III) hydroxides under oxic conditions. From the EXAFS analyses, the outersphere complex is important for the Se(VI) sorbed on Fe(III) hydroxides in soils, while Se(IV), Te(IV), and Te(VI) form inner-sphere complexes. Under reducing condition, it was found that Te(0) and Se(0) species were formed and that Se was more readily reduced to Se(0) than Te, as is predicted from their Eh-pH diagrams. The reduction process from hexavalent to zero-valent species was different between Se and Te, that is, the direct reduction from Se(VI) to Se(0) was observed for Se, while Te was reduced stepwise from Te(VI) to Te(0) via Te(IV). In terms of the distribution between soil and water, Se distribution to water was much higher than that of Te under wide redox conditions. For Se, selenate is the predominant species in water even tinder reducing condition due to the much higher solubility of Se(VI) than Se(IV). Furthermore, a much smaller distribution of Te in water was primarily due to the larger affinities of Te(IV) and Te(VI) to I e(111) hydroxides than Se(VI), which originates from the formation of the inner-sphere complexes of Te(IV) and Te(VI) to Fe(III) hydroxides. (c) 2008 Elsevier Ltd. All rights reserved.