Department of Geological Sciences, University of Florida, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611, USA.
Department of Geological Sciences, University of Florida, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611, USA.
Sci Total Environ. 2016 May 1;551-552:238-45. doi: 10.1016/j.scitotenv.2016.02.028. Epub 2016 Feb 12.
While aquifer storage and recovery (ASR) is becoming widely accepted as a way to address water supply shortages, there are concerns that it may lead to release of harmful trace elements such as arsenic (As). Thus, mechanisms of As release from limestone during ASR operations were investigated using 110-day laboratory incubations of core material collected from the Floridan Aquifer, with treatment additions of labile or refractory dissolved organic matter (DOM) or microbes. During the first experimental phase, core materials were equilibrated with native groundwater lacking in DO to simulate initial non-perturbed anaerobic aquifer conditions. Then, ASR was simulated by replacing the native groundwater in the incubations vessels with DO-rich ASR source water, with DOM or microbes added to some treatments. Finally, the vessels were opened to the atmosphere to mimic oxidizing conditions during later stages of ASR. Arsenic was released from aquifer materials, mainly during transitional periods at the beginning of each incubation stage. Most As released was during the initial anaerobic experimental phase via reductive dissolution of Fe oxides in the core materials, some or all of which may have formed during the core storage or sample preparation period. Oxidation of As-bearing Fe sulfides released smaller amounts of As during the start of later aerobic experimental phases. Additions of labile DOM fueled microbially-mediated reactions that mobilized As, while the addition of refractory DOM did not, probably due to mineral sorption of DOM that made it unavailable for microbial utilization or metal chelation. The results suggest that oscillations of groundwater redox conditions, such as might be expected to occur during an ASR operation, are the underlying cause of enhanced As release in these systems. Further, ASR operations using DOM-rich surface waters may not necessarily lead to additional As releases.
尽管含水层储存和恢复（ASR）作为解决供水短缺的方法正被广泛接受，但人们担心它可能会导致有害物质如砷（As）的释放。因此，通过使用从佛罗里达含水层采集的岩心材料进行为期 110 天的实验室孵育实验，研究了 ASR 操作过程中砷从石灰岩中释放的机制，并添加了可溶或难溶的溶解有机质（DOM）或微生物。在第一个实验阶段，将岩心材料与缺乏 DO 的天然地下水平衡，以模拟初始未受干扰的厌氧含水层条件。然后，通过用富含 DO 的 ASR 源水替代孵育容器中的天然地下水来模拟 ASR，在一些处理中添加 DOM 或微生物。最后，将容器暴露在大气中，以模拟 ASR 后期的氧化条件。砷从含水层物质中释放出来，主要是在每个孵育阶段开始的过渡时期。在初始厌氧实验阶段，通过核心材料中 Fe 氧化物的还原溶解释放了大部分 As，其中一些或全部可能是在核心储存或样品制备期间形成的。在随后的好氧实验阶段开始时，含 As 的 Fe 硫化物的氧化释放出较少的 As。可溶 DOM 的添加促进了微生物介导的反应，从而使 As 发生迁移，而难溶 DOM 的添加则没有，这可能是由于 DOM 被矿物吸附，使其无法被微生物利用或金属螯合。结果表明，地下水氧化还原条件的波动，如在 ASR 操作中可能发生的那样，是这些系统中增强 As 释放的根本原因。此外，使用富含 DOM 的地表水进行 ASR 操作不一定会导致额外的 As 释放。
