Dimethylmonothioarsinic acid (DMMTA(V)) and dimethyldithioarsinic acid (DMDTA(V)), which are commonly found in landfill leachate and pore water of rice paddy soil, have attracted considerable attention for their high toxicity. This study aims to evaluate the behavior and potential risks of DMMTA(V) and DMDTA(V) in the environment by conducting an equilibrium sorption test using 2-line ferrihydrite and acute toxicity (immobilization) test using Daphnia magna. The overall maximum sorption capacity (q_m) derived by the Langmuir isotherm model showed an increase in the order of inorganic arsenate (As(V)) > dimethylarsinic acid (DMA(V)) > DMMTA(V) > DMDTA(V), which was likely due to steric hindrance due to the presence of methyl and thiol groups. Moreover, DMMTA(V) and DMDTA(V) showed no or negligible change in q_m with pH change, while q_m decreased rapidly with increasing pH in As(V) and DMA(V). The 50% inhibition concentrations (IC50) for As(V), DMA(V), DMMTA(V), and DMDTA(V), which were measured after 48 h exposure to D. magna, were 9.5, > 30, 1.7, and 6.5 mg/L, respectively. Overall, the results demonstrated that DMMTA(V) and DMDTA(V) have high mobility and eco-toxicity in the environment and that methylated thioarsenicals should be accurately monitored and controlled.

二甲基单硫代胂酸(DMMTA(V))和二甲基二硫代胂酸(DMDTA(V))常见于垃圾渗滤液和稻田土壤孔隙水中，因其高毒性而备受关注。本研究旨在评估 DMMTA(V) 和 DMDTA(V) 在环境中的行为和潜在风险，通过使用 2 线水铁矿进行平衡吸附试验和使用Daphnia magna进行急性毒性（固定化）试验。总最大吸附容量（q _m) 由 Langmuir 等温线模型得出的结果显示无机砷酸盐 (As(V)) > 二甲基胂酸 (DMA(V)) > DMMTA(V) > DMDTA(V) 的顺序增加，这可能是由于空间位阻所致甲基和硫醇基团的存在。此外，DMMTA(V) 和 DMDTA(V) 的 q _m随 pH 值的变化没有变化或变化可忽略不计，而As(V) 和 DMA(V)的 q _{m随着 pH 值的增加而迅速下降。}As(V)、DMA(V)、DMMTA(V) 和 DMDTA(V) 的 50% 抑制浓度 (IC50)，在暴露于D. magna 48 小时后测量，分别为 9.5、> 30、1.7 和 6.5 mg/L。总体而言，结果表明DMMTA（V）和DMDTA（V）在环境中具有高迁移率和生态毒性，应准确监测和控制甲基化硫砷化合物。