Physicochemical and ion-binding properties of highly aliphatic humic substances extracted from deep sedimentary groundwater.
Physicochemical and ion-binding properties of highly aliphatic humic substances extracted from deep sedimentary groundwater.
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从深层沉积地下水中提取的高脂肪族腐殖质的物理化学和离子结合特性。
DOI：
10.1039/c5em00176e
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
T.
中科院分区：
文献类型：
--
作者：
Saito;T.;Terashima;M.;Aoyagi;N.;Nagao;S. Fujitake;N. and Ohnuki;T.
腐殖质普遍存在于各种水生系统中，在许多地球化学过程中起着重要作用。越来越多的证据表明，深层地下水中存在高HSs；然而，它们的离子结合特性在很大程度上是未知的。本文研究了从深层沉积地下水中提取的腐植酸和黄腐酸的理化性质和离子结合特性。用电位法测定了质子（H+）和铜（Cu2+）的结合等温线，拟合了NICA-Donnan模型，并将所得参数与模型的一般参数进行了比较，所得参数是表面环境中HSs的平均参数。深层地下水hs不同于地表hs，具有高脂肪族、高含硫量、小分子尺寸等特点。其酸性官能团的数量与表面hs相当或略大于表面hs；而深层地下水hs中Cu2+的结合幅度较小。NICA-Donnan模型将此归因于Cu2+与化学上均匀的低亲和力位点的结合，这些位点可能由羧基组成，在较高的ph下，Cu2+的结合模式倾向于与羧基和更多相的醇/酚基进行多齿配位。x射线吸收光谱也显示Cu2+与含O/N的官能团结合，并在较小程度上与含S的官能团结合。本研究表明，与地表hs相比，深层地下水hs在理化性质和离子结合性质上具有特殊性。
Humic substances (HSs) are ubiquitous in various aquatic systems and play important roles in many geochemical processes. There is increasing evidence of the presence of HSs in deep groundwater; nevertheless, their ion binding properties are largely unknown. In this study we investigated the physicochemical and ion-binding properties of humic and fulvic acids extracted from deep sedimentary groundwater. The binding isotherms of protons (H+) and copper (Cu2+) were measured by potentiometry and fitted to the NICA-Donnan model, and the obtained parameters were compared with the generic parameters of the model, which are the average parameters for HSs from surface environments. The deep groundwater HSs were different from surface HSs, having high aliphaticities, high sulfur contents, and small molecular sizes. Their amounts of acidic functional groups were comparable to or slightly larger than those of surface HSs; however, the magnitude of Cu2+ binding to the deep groundwater HSs was smaller. The NICA-Donnan model attributed this to the binding of Cu2+ to chemically homogeneous low affinity sites, which presumably consist of carboxylic groups, via mono-dentate coordination at relatively low pH. The binding mode tended to shift to multi-dentate coordination with carboxylic groups and more heterogeneous alcoholic/phenolic groups at higher pH. X-ray absorption spectroscopy also revealed that Cu2+ binds to O/N containing functional groups and to a lesser extent S containing functional groups as its divalent from. This study shows the particularity of the deep groundwater HSs in terms of their physicochemical and ion-binding properties, compared with surface HSs.