Xia Lichao, Schellenger Alexandra E P, Onnis-Hayden Annalisa, Jaisi Deb, Larese-Casanova Philip
Department of Civil & Environmental Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.
Department of Civil & Environmental Engineering, Northeastern University, Boston, MA, USA.
Isotopes Environ Health Stud. 2020 Jun;56(3):297-313. doi: 10.1080/10256016.2020.1733552. Epub 2020 Mar 5.
Selenium and oxygen isotope systematics can be useful tools for tracing sources and fate of Se oxyanions in water. In order to measure δO values of selenate, SeO must first be sequestered from water by precipitation as BaSeO. However, other dissolved oxyanions insoluble with Ba require removal. Dissolved selenate was separated from dissolved selenite, carbonate, phosphate, and arsenate by addition of Ce cations that quantitatively removed these oxyanions by precipitation as insoluble Ce(SeO), Ce(CO), CePO, and CeAsO, respectively. δO-selenate (-8.19 ± 0.17 ‰) did not change after four replicates of selenite removal by Ce(SeO) precipitation and Ce removal by cation exchange (-8.20 ± 0.14, -8.32 ± 0.09, -8.17 ± 0.13, and -8.29 ± 0.13 ‰). δO-selenate values (-10.86 ± 0.45 ‰) were preserved also when selenate was pre-concentrated on anion exchange resin, quantitatively retrieved by elution, and processed with Ce to remove interfering oxyanions (-10.77 ± 0.07 ‰). The extraction and purification steps developed here successfully isolated dissolved selenate from interfering oxyanions while preserving δO-selenate values. This method should be useful for characterizing δO-selenate when present with the co-occurring oxyanions above in laboratory experiments and field sites with high Se concentrations, although further research is required for methods to eliminate any co-occurring sulphate.
硒和氧同位素体系可作为追踪水中硒酸盐来源和归宿的有用工具。为了测量硒酸盐的δO值，必须首先通过沉淀为BaSeO4将SeO4从水中分离出来。然而，其他与Ba不溶的溶解含氧阴离子需要去除。通过添加Ce阳离子，将溶解的硒酸盐与溶解的亚硒酸盐、碳酸盐、磷酸盐和砷酸盐分离，Ce阳离子分别通过沉淀为不溶性的Ce(SeO4)、Ce(CO3)、CePO4和CeAsO4来定量去除这些含氧阴离子。通过Ce(SeO4)沉淀去除亚硒酸盐和通过阳离子交换去除Ce进行四次重复后，δO-硒酸盐（-8.19±0.17‰）没有变化（-8.20±0.14、-8.32±0.09、-8.17±0.13和-8.29±0.13‰）。当硒酸盐在阴离子交换树脂上预浓缩、通过洗脱定量回收并用Ce处理以去除干扰性含氧阴离子时，δO-硒酸盐值（-10.86±0.45‰）也得以保留（-10.77±0.07‰）。此处开发的提取和纯化步骤成功地从干扰性含氧阴离子中分离出溶解的硒酸盐，同时保留了δO-硒酸盐值。该方法对于在实验室实验和高硒浓度现场中与上述共存含氧阴离子一起存在时表征δO-硒酸盐应该是有用的，尽管对于消除任何共存硫酸盐的方法还需要进一步研究。
