Measurement of labile arsenic speciation in water and soil using diffusive gradients in thin films (DGT) and X-ray absorption near edge spectroscopy (XANES)
Measurement of labile arsenic speciation in water and soil using diffusive gradients in thin films (DGT) and X-ray absorption near edge spectroscopy (XANES)
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DOI：
10.1071/en14047
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发表时间：
2015-02
影响因子：
4.3
通讯作者：
Trang T. X. Huynh;H. Harris;Hao Zhang;B. Noller
中科院分区：
文献类型：
--
作者：
Trang T. X. Huynh;H. Harris;Hao Zhang;B. Noller
The Diffusive Gradients in Thin Films technique is an in-situ sampling technique that can concentrate labile arsenic species from solution. This technique has provided a way to measure the total concentration of labile arsenic, which may be toxic in the environment. A previous study measured arsenic speciation in the solution extracted from the FB-DGT gel deployed in water using coupled high-performance liquid chromatography and hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS). However, the extent of change in arsenic speciation during the extraction process is unknown. By identifying the arsenic species in the FB-DGT gel directly, using X-ray absorption near edge spectroscopy (XANES) fitting with model arsenic compounds, we obtain a better understanding of the ability of FB-DGT to measure labile arsenic species in solution. The results presented herein confirm that FB-DGT accumulated labile inorganic and methylated arsenic species. Arsenic species bound to the FB-DGT gel were stable for up to two weeks following deployment. However, caution should be applied when interpreting the proportion of As species measured by HPLC-HG-AFS in solution extracted from FB-DGT because the distribution of arsenic species in extracted solutions was found to be modified by the extraction process. Some (~ 20 %) of arsenate was converted to arsenite, and a significant amount (~ 25 %) of dimethylarsinic acid (DMAsV) was converted to monomethylarsonic acid (MMAsV) or arsenate (AsV). Only inorganic arsenite (iAsIII) was stable during the extraction process. These findings suggested that, based on the XANES measurement, although As species were quantitatively accumulated in the FB-DGT gel, the FB-DGT technique was still unsuitable for studying As speciation. This is because the XANES technique is not suitable for routine measurement and changes in arsenic speciation were observed to occur during gel extraction, prior HPLC-HG-AFS measurement.
