Department of Chemistry, University of Girona, Campus de Montilivi s/n, 17071 Girona, Spain.
Chemosphere. 2011 Sep;84(11):1664-70. doi: 10.1016/j.chemosphere.2011.05.006. Epub 2011 May 28.
Speciation plays a crucial role in elemental mobility. However, trace level selenium (Se) speciation analyses in aqueous samples from acidic environments are hampered due to adsorption of the analytes (i.e. selenate, selenite) on precipitates. Such solid phases can form during pH adaptation up till now necessary for chromatographic separation. Thermodynamic calculations in this study predicted that a pH<4 is needed to prevent precipitation of Al and Fe phases. Therefore, a speciation method with a low pH eluent that matches the natural sample pH of acid rain-soil interaction samples from Etna volcano was developed. With a mobile phase containing 20mM ammonium citrate at pH 3, selenate and selenite could be separated in different acidic media (spiked water, rain, soil leachates) in <10 min with a LOQ of 0.2 μg L(-1) using (78)Se for detection. Applying this speciation analysis to study acid rain-soil interaction using synthetic rain based on H(2)SO(4) and soil samples collected at the flanks of Etna volcano demonstrated the dominance of selenate over selenite in leachates from samples collected close to the volcanic craters. This suggests that competitive behavior with sulfate present in acid rain might be a key factor in Se mobilization. The developed speciation method can significantly contribute to understand Se cycling in acidic, Al/Fe rich environments.
分异作用在元素迁移中起着至关重要的作用。然而，由于分析物（即硒酸盐、亚硒酸盐）在沉淀物上的吸附，酸性环境下水样中的痕量硒（Se）形态分析受到阻碍。这些固相可以在 pH 适应过程中形成，迄今为止，这对于色谱分离是必要的。本研究中的热力学计算预测，需要 pH<4 以防止 Al 和 Fe 相的沉淀。因此，开发了一种具有低 pH 洗脱液的形态分析方法，该洗脱液与埃特纳火山的酸雨-土壤相互作用样品的自然样品 pH 相匹配。使用含有 20mM 柠檬酸铵的流动相，在 pH 3 下，硒酸盐和亚硒酸盐可以在不同的酸性介质（加标水、雨水、土壤浸出液）中在<10 分钟内分离，LOQ 为 0.2μg L(-1)，使用 (78)Se 进行检测。应用这种形态分析方法研究基于 H(2)SO(4)的合成雨水与埃特纳火山侧翼采集的土壤样品之间的酸雨-土壤相互作用，表明在靠近火山口的样品浸出液中硒酸盐的含量超过亚硒酸盐。这表明与酸雨中原位硫酸盐的竞争行为可能是 Se 迁移的关键因素。开发的形态分析方法可以为了解酸性、富 Al/Fe 环境中的 Se 循环做出重要贡献。
