Europium binding to humic substances extracted from deep underground sedimentary groundwater studied by time-resolved laser fluorescence spectroscopy
Europium binding to humic substances extracted from deep underground sedimentary groundwater studied by time-resolved laser fluorescence spectroscopy
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DOI：
10.1080/00223131.2016.1274688
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发表时间：
2017-01
影响因子：
1.2
通讯作者：
Takumi Saito;N. Aoyagi;M. Terashima
中科院分区：
文献类型：
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作者：
Takumi Saito;N. Aoyagi;M. Terashima
摘要腐殖物质广泛存在于包括地下深处在内的各种环境中，对放射性核素的形成和迁移起着重要作用。通过时间分辨激光荧光光谱结合平行因子分析（PARAFAC）研究了Eu 3+（三价锕系离子的化学同系物）与从地表以下−250 m的沉积地下水中分离出的HS的结合，作为pH值和盐浓度的函数。PARAFAC模型揭示了对应于不同Eu 3+物种的多个因素的存在。这些因素类似于从地表环境中观察到的Eu 3+结合到HS，然而，详细的比较表明，有一些特殊性，在Eu 3+结合到深层地下水HS。由PARAFAC模型计算的Eu ~（3+）与HS结合的分配系数（Kd）显示出较强的盐效应。在0.01 M NaClO 4时，Kd值相对较大，与表面HS的Kd值相当;在0.1 M NaClO 4时，Kd值降低了一个数量级以上。在本研究中，在整个pH和盐浓度范围内，深地下HS的腐殖酸组分的Kd值大于富里酸组分。
ABSTRACT Humic substances (HSs) are ubiquitous in various environments including deep underground and play an important role in the speciation and mobility of radionuclides. The binding of Eu3+, a chemical homologue of trivalent actinide ions, to HSs isolated from sedimentary groundwater at −250 m below the surface was studied by time-resolved laser fluorescence spectroscopy combined with parallel factor analysis (PARAFAC) as a function of pH and salt concentration. PARAFAC modeling reveals the presence of multiple factors that correspond to different Eu3+ species. These factors resemble those observed for Eu3+ binding to HSs from surface environments; however, detailed comparison shows that there are some particularities in Eu3+ binding to the deep groundwater HSs. The distribution coefficients (Kd) of Eu3+ binding to the HSs calculated from the PARAFAC modeling exhibits a rather strong salt effect. At 0.01 M NaClO4, the Kd values are relatively large and comparable to those to the surface HSs; they are decreaed at 0.1 M NaClO4 by more than an order of the magnitude. The Kd values are larger for the humic acid fraction of the deep underground HSs than the fulvic acid fraction over the entire range of pH and salt concentration investigated in this study.