Controlling Arsenic Mobilization during Managed Aquifer Recharge: The Role of Sediment Heterogeneity
Controlling Arsenic Mobilization during Managed Aquifer Recharge: The Role of Sediment Heterogeneity
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DOI：
10.1021/acs.est.0c00794
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发表时间：
2020-07-21
影响因子：
11.4
通讯作者：
Fendorf, Scott
中科院分区：
文献类型：
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作者：
Fakhreddine, Sarah;Prommer, Henning;Fendorf, Scott
有管理的含水层补给可加强淡水安全并增加当地地下水供应。然而，在海洋和海洋研究期间，地球化学和水文变化可能会将有毒的地质污染物从沉积物释放到地下水中，威胁到海洋和海洋研究作为水管理战略的可行性。利用反应输运模型，再加上含水层分析和水化学测量，我们调查的因果机制，砷释放MAR通过注入橙子县地下水流域。在这里，注入水是通过高级水处理产生的充氧、高度净化的循环水。注入是通过在160-365米之间的几个深度间隔处筛选的井进行的，允许向含水层系统的多个承压层（区）进行补给。然而，这些地区的特点是不同程度的事先氧化，由于历史，长期渗透从上覆含水层。由此产生的沉积物地球化学异质性提供了一个关键的控制释放（或保留）的砷。在区域与前氧化，作为动员发生通过砷酸盐解吸从Fe-（氢）氧化物，主要与pH值的变化;在区域内，保持减少注入前，作为释放是由于氧化溶解的含砷黄铁矿。我们发现，由于整个含水层系统的地球化学不均匀性，As释放可以归因于单个注入井内的各种地球化学机制。
Managed aquifer recharge (MAR) enhances freshwater security and augments local groundwater supplies. However, geochemical and hydrological shifts during MAR can release toxic, geogenic contaminants from sediments to groundwater, threatening the viability of MAR as a water management strategy. Using reactive transport modeling coupled with aquifer analyses and measured water chemistry, we investigate the causal mechanisms of arsenic release during MAR via injection in the Orange County Groundwater Basin. Here, injection water is oxygenated, highly purified recycled water produced by advanced water treatment. Injection occurs via a well screened at several depth intervals ranging from 160-365 m, allowing recharge into multiple confined horizons (zones) of the aquifer system. However, these zones are characterized by varying degrees of prior oxidation due to historic, long-term infiltration from the overlying aquifer. The resulting sediment geochemical heterogeneity provides a critical control on the release (or retention) of arsenic. In zones with prior oxidation, As mobilization occurs via arsenate desorption from Fe-(hydr)oxides, primarily associated with shifts in pH; within zones that remain reduced prior to injection, As release is attributed to the oxidative dissolution of As-bearing pyrite. We find that As release can be attributed to various geochemical mechanisms within a single injection well owing to geochemical heterogeneity across the aquifer system.