The river–groundwater interface as a hotspot for arsenic release
The river–groundwater interface as a hotspot for arsenic release
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DOI：
10.1038/s41561-020-0557-6
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发表时间：
2020-04
影响因子：
18.3
通讯作者：
Ilka Wallis;H. Prommer;M. Berg;A. Siade;Jing Sun;R. Kipfer
中科院分区：
文献类型：
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作者：
Ilka Wallis;H. Prommer;M. Berg;A. Siade;Jing Sun;R. Kipfer
在南亚和东南亚的许多含水层中，地质地下水砷（As）污染是普遍存在的。人们担心，最近地下水抽取量的增加可能会导致高砷地下水迁移到以前的安全含水层。在这里，我们研究了受污染的含水层在货车，越南，位于约10公里的河内东南部的银行的红河，这是受大规模地下水抽取。我们使用数值模型模拟集成的地下水流和地下水地球化学反应过程中的含水层规模，详细的水力，环境示踪剂，水化学和矿物学数据的约束。我们的模拟提供了一个机械重建的地下水流和地球化学动力学的时空变化，并确定了几十年来的迁移率和质量平衡的演变。我们发现，河床-含水层界面构成了一个地球化学反应热点，作为As浓度升高的主要来源。我们表明，持续的释放依赖于定期补充河流淤泥丰富的不稳定的有机物和活性氧化铁和抽水引起的地下水流可能会促进迁移到邻近的含水层的距离为几公里。
Geogenic groundwater arsenic (As) contamination is pervasive in many aquifers in south and southeast Asia. It is feared that recent increases in groundwater abstractions could induce the migration of high-As groundwaters into previously As-safe aquifers. Here we study an As-contaminated aquifer in Van Phuc, Vietnam, located ~10 km southeast of Hanoi on the banks of the Red River, which is affected by large-scale groundwater abstraction. We used numerical model simulations to integrate the groundwater flow and biogeochemical reaction processes at the aquifer scale, constrained by detailed hydraulic, environmental tracer, hydrochemical and mineralogical data. Our simulations provide a mechanistic reconstruction of the anthropogenically induced spatiotemporal variations in groundwater flow and biogeochemical dynamics and determine the evolution of the migration rate and mass balance of As over several decades. We found that the riverbed–aquifer interface constitutes a biogeochemical reaction hotspot that acts as the main source of elevated As concentrations. We show that a sustained As release relies on regular replenishment of river muds rich in labile organic matter and reactive iron oxides and that pumping-induced groundwater flow may facilitate As migration over distances of several kilometres into adjacent aquifers.