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

Abstract

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.

Keywords

• thioarsenate
• hydrothermal synthesis
• liquid chromatography-inductively coupled plasma mass spectrometry
• datong basin
• groundwater