Arsenic (As) contamination in groundwater remains a pressing global challenge. In this study, we evaluated the potential of green rust (GR), a redox-active iron phase frequently occurring in anoxic environments, to treat As contamination at a former wood preservation site. We performed long-term batch experiments by exposing synthetic GR sulfate (GR_SO4) to As-free and As-spiked (6 mg L⁻¹) natural groundwater at both 25 and 4 °C. At 25 °C, GR_SO4 was metastable in As-free groundwater and transformed to GR_CO3, and then fully to magnetite within 120 days; however, GR_SO4 stability increased 7-fold by lowering the temperature to 4 °C, and 8-fold by adding As to the groundwater at 25 °C. Highest GR_SO4 stability was observed when As was added to the groundwater at 4 °C. This stabilizing effect is explained by GR solubility being lowered by adsorbed As and/or lower temperatures, inhibiting partial GR dissolution required for transformation to GR_CO3, and ultimately to magnetite. Despite these mineral transformations, all added As was removed from As-spiked samples within 120 days at 25 °C, while uptake was 2 times slower at 4 °C. Overall, we have successfully documented that GR is an important mineral substrate for As immobilization in anoxic subsurface environments.

地下水中的砷（As）污染仍然是紧迫的全球挑战。在这项研究中，我们评估了绿锈（GR）（一种在缺氧环境中经常发生的氧化还原活性铁相）在以前的木材保存地点处理As污染物的潜力。我们通过在25°C和4°C下将合成的GR硫酸盐（GR _SO4）暴露于无砷和掺As（6 mg L ^-1）的天然地下水中，进行了长期的批量试验。在25°C时，GR _SO4在无砷地下水_中亚稳并转化为GR _CO3，然后在120天内完全转化为磁铁矿。但是，通过将温度降低到4°C ，GR _SO4的稳定性提高了7倍，而在25°C的地下水中添加了As，其稳定性提高了8倍。最高GR _SO4当在4°C下向地下水中添加As时，观察到稳定性。这种稳定作用的解释是，吸附的As和/或较低的温度会降低GR的溶解度，并抑制转化为GR _CO3并最终转变为磁铁矿所需的部分GR溶解。尽管进行了这些矿物转化，但在25°C下120天之内，所有添加的As仍从掺砷样品中去除，而在4°C下，其吸收速度慢了2倍。总体而言，我们已经成功地证明了GR是将As固定在缺氧地下环境中的重要矿物底物。