A multi-level field site was built at the As-affected area of the Datong basin. The one-year monitoring results showed that the three aquifers exhibit different redox conditions and hydrogeochemical behaviors. In the shallow aquifer, groundwater As concentration is up to 220.5 μg/L, which is related to the dissimilatory reduction of poor-crystalline Fe minerals. In the middle aquifer, groundwater sulfate reduction shows two sides effects on As mobilization that the reduced sulfide on the one hand promotes the release of sediment As via abiotic reductive dissolution of Fe minerals and on the other hand immobilizes groundwater As via the adsorption on the newly formed Fe(II)-sulfide minerals. In the deep aquifer, the reductive dissolution of crystalline Fe minerals was the dominant process causing the release of sediment As into groundwater with the highest As concentration up to 341.1 μg/L. Based on the one-year monitored data, a coupled flow and reactive transport model was developed. The model results showed that only considering the groundwater flow underestimated the concentration of groundwater As. When adding the hydro-biogeochemical processes, the good agreement was achieved between the observed and simulated groundwater As. In the shallow and deep aquifers, microbially mediated reduction of poor-crystalline and crystalline Fe minerals contributed approximately 85 % of groundwater As. In the middle aquifer, abiotic reduction of Fe minerals driven is responsible for around 35 % of the release of sediment As, and around 17 % of released As was re-adsorbed or co-precipitated onto the neo-formed Fe(II) minerals. Under different redox conditions, the hydrogeochemical behavior of As was dominantly controlled by the Fe-S-As cycling in the groundwater system.

中文翻译：

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地下水流动和氧化还原条件对大同盆地含水层砷迁移的影响

在大同盆地灾区建立了多层野外现场。一年的监测结果表明，三个含水层表现出不同的氧化还原条件和水文地球化学行为。浅层含水层地下水As浓度高达220.5μg/L，这与贫晶Fe矿物的异化还原有关。在中部含水层中，地下水硫酸盐还原对As的迁移表现出两个副作用，一方面被还原的硫化物通过铁矿物的非生物还原溶解促进沉积物As的释放，另一方面通过新吸附的矿物固定地下水As。形成 Fe(II)-硫化物矿物。在深层含水层中，结晶Fe矿物的还原溶解是导致沉积物As释放到地下水中的主要过程，As浓度最高可达341.1 μg/L。根据一年的监测数据，开发了耦合流和反应性传输模型。模型结果表明，仅考虑地下水流量低估了地下水As浓度。当添加水文生物地球化学过程时，观测到的地下水 As 与模拟的地下水 As 之间取得了良好的一致性。在浅层和深层含水层中，微生物介导的低结晶和结晶铁矿物的还原贡献了大约 85% 的地下水砷。在中部含水层中，由铁矿物驱动的非生物还原导致约 35% 的沉积物砷释放，约 17% 的释放砷被重新吸附或共沉淀到新形成的 Fe(II) 矿物上。在不同的氧化还原条件下，As的水文地球化学行为主要受地下水系统中Fe-S-As循环的控制。