Abstract：
Aquifer storage and recovery (ASR) is a promising water management technique in terms of quantity and quality. During ASR, iron (Fe) (hydr)oxides contained in the aquifer play a crucial role as electron acceptors in attenuating dissolved organic carbon (DOC) in recharging water through dissimilatory iron reduction (DIR). Considering the preference of electron acceptors, nitrate (NO3⁻), possibly coexisting with DOC as the prior electron acceptor to Fe (hydr)oxides, might influence DIR by interrupting electron transfer. However, this phenomenon is yet to be clarified. In this study, we systematically investigated the potential effect of NO3⁻ on DOC attenuation during ASR using a series of sediment columns representing typical aquifer conditions. The results suggest that DOC attenuation could be enhanced by the presence of NO3⁻. Specifically, total DOC attenuation was notably higher than that from the stoichiometric calculation simply employing NO3⁻ as the additional electron acceptor to Fe (hydr)oxides, implying a synergetic effect of NO3⁻ in the overall reactions. X-ray photoelectron spectroscopy analyzes revealed that the Fe(II) ions released from DIR transformed the Fe (hydr)oxides into a less bioavailable form, inhibiting further DIR. In the presence of NO3⁻, however, no aqueous Fe(II) was detected, and another form of Fe (hydr)oxide appeared on the sediment surface. This may be attributed to nitrate-dependent Fe(II) oxidation (NDFO), in which Fe(II) is (re)oxidized into Fe (hydr)oxide, which is available for the subsequent DOC attenuation. These mechanisms were supported by the dominance of DIR-relevant bacteria and the growth of NDFO-related bacteria in the presence of NO3⁻.
摘要：
就数量和质量而言，含水层的储存和回收（ASR）是一种有前途的水管理技术。在ASR期间，含水层中含有的铁（Fe）（hydr）氧化物在通过异化铁还原（DIR）减弱补给水中的溶解有机碳（DOC）方面起着至关重要的作用。考虑到电子受体的偏好，硝酸盐（NO3），可能与DOC共存，作为Fe（氢）氧化物的优先电子受体，可能会通过中断电子转移来影响DIR。然而,这种现象还有待澄清。在这项研究中,我们使用一系列代表典型含水层条件的沉积物柱，系统地研究了在ASR过程中NO3对DOC衰减的潜在影响。结果表明，NO3的存在可以增强DOC的衰减。具体来说,总DOC衰减明显高于化学计量计算，简单地采用NO3作为Fe（hydr）氧化物的附加电子受体，暗示NO3-在整体反应中的协同作用。X射线光电子能谱分析表明，从DIR释放的Fe（II）离子将Fe（氢）氧化物转化为生物利用度较低的形式，进一步抑制DIR。在NO3的存在下，然而,未检测到Fe(II)水溶液，沉积物表面出现了另一种形式的Fe（氢）氧化物。这可能归因于硝酸盐依赖性Fe（II）氧化（NDFO），其中Fe(II)(再)氧化成Fe(氢)氧化物，这可用于随后的DOC衰减。这些机制得到了DIR相关细菌的优势和NDFO相关细菌在NO3-存在下的生长的支持。
