硫代砷化合物的合成及其在地下水中的赋存特征:以大同盆地为例

硫代砷酸盐作为富硫地下水中砷的重要赋存形态,在其迁移转化过程中起着十分重要的作用,但现有硫代砷酸盐的标准合成方法流程复杂、操作繁琐,限制了对地下水中硫代砷酸盐赋存规律的研究。为此,首先改进了硫代砷酸盐标准物质的合成方法,采用操作简便的水热法合成了硫代砷化合物标准物质,建立了基于HPLC-ICPMS的硫代砷化合物分析方法,该方法检出限为0.01μg/L;探讨了不同保存条件对硫代砷化合物稳定性的影响,发现干冰速冻-20℃是地下水硫代砷酸盐样品的最佳保存条件。应用上述方法对大同盆地地下水中的硫代砷酸盐进行了取样分析,结果表明40%的水样中均检出硫代砷酸盐,最高质量浓度可达209.90μg/L;弱碱性还原条件有利于硫代砷酸盐的赋存,且硫化物质量浓度对硫代砷酸盐的生成有重要控制作用。对地下水中硫代砷酸盐的深入研究有助于揭示富硫地下水中砷的迁移转化规律,丰富和完善高砷地下水成因理论。

Synthesis of thioarsenate compounds and their occurrence characteristics in groundwater: A case study of Datong Basin

As an important occurrence form of arsenic in sulfur-rich groundwater, thioarsenate plays a very important role in its migration and transformation. However, the standard synthesis method of thioarsenate is complex and the occurrence characteristics and influencing factors in low temperature groundwater are rarely reported. In this paper, firstly, the synthesis method of thioarsenate reference material was improved, the standard reference material of thioarsenate was synthesized by hydrothermal method, and the analytical method of thioarsenate based on HPLC-ICPMS was established. The detection limit of this method was 0.01 μg/L. The effects of different preservation conditions on the stability of thioarsenate compounds were discussed. It was found that quick freezing of dry ice at -20℃ was the best way to keep the stability of thioarsenate samples in groundwater. The above method was used to analyze thioarsenate in groundwater in Datong Basin. The results showed that thioarsenate was detected in 40% of the water samples, and the highest concentrate was 209.90 μg/L. The weak alkaline reduction condition is beneficial to the occurrence of thioarsenate, and the sulfide concentration plays an important role in controlling the formation of thioarsenate. The in-depth study of thioarsenate in groundwater is helpful to reveal the law of migration and transformation of arsenic in sulfur-rich groundwater and is of great significance to enrich the genetic theory of high-arsenic groundwater.