Abstract Understanding the formation of thioarsenate, an important arsenic species, is of great significance with respect to explaining the mobilization of arsenic in fresh groundwater systems. Monothioarsenate (MTA), dithioarsenate (DTA), and trithioarsenate (TriTA) are three main forms of thioarsenate in fresh groundwater. A total of 30 groundwater samples were collected from the Datong basin to conduct hydrochemistry and arsenic speciation analysis. Geochemical simulations were established to verify the occurrence of thioarsenate. The results show thioarsenate was detected in 40% of the groundwater samples at concentrations ranging from 2.36 to 209.9 μg/L; the highest concentration accounted for 68% of total arsenic. Thioarsenate mainly occurs in the discharge area of the Datong basin, where the groundwater was characterized by strongly reducing conditions (Eh up to −175.3 mV) and higher concentrations of arsenic (up to 3450 μg/L) and sulfide (up to 8480 μg/L). A strong positive correlation (r = 0.81, p

中文翻译：

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大同盆地高砷地下水中硫代砷酸盐的分布与形成

摘要 了解硫代砷酸盐这一重要的砷物种的形成，对于解释淡水系统中砷的迁移具有重要意义。单硫代砷酸盐 (MTA)、二硫代砷酸盐 (DTA) 和三硫代砷酸盐 (TriTA) 是淡水中硫代砷酸盐的三种主要形式。共采集大同盆地30个地下水样品进行水化学和砷形态分析。建立地球化学模拟以验证硫代砷酸盐的存在。结果表明，40%的地下水样品中检出硫代砷酸盐，浓度范围为2.36~209.9 μg/L；最高浓度占总砷的68%。硫砷​​酸盐主要产于大同盆地的排泄区，其中地下水的特征是强烈还原条件（Eh 高达 -175.3 mV）和更高浓度的砷（高达 3450 μg/L）和硫化物（高达 8480 μg/L）。强正相关（r = 0.81，p