Environmental Research Institute, School of Science, Faculty of Science and Engineering, University of Waikato , Hamilton, New Zealand.
School of Geography, Planning and Environmental Management, The University of Queensland , Brisbane, Australia.
Environ Sci Technol. 2015 Dec 15;49(24):14101-9. doi: 10.1021/acs.est.5b03506. Epub 2015 Nov 23.
The microbial oxidation of organic matter coupled to reductive iron oxide dissolution is widely recognized as the dominant mechanism driving elevated arsenic (As) concentrations in aquifers. This paper considers the potential of nanoparticles to increase the mobility of As in aquifers, thereby accounting for discrepancies between predicted and observed As transport reported elsewhere. Arsenic, phosphorus, and iron size distributions and natural organic matter association were examined along a flow path from surface water via the hyporheic zone to shallow groundwater. Our analysis demonstrates that the colloidal Fe concentration (>1 kDa) correlates with both colloidal P and colloidal As concentrations. Importantly, increases in the concentration of colloidal P (>1 kDa) were positively correlated with increases in the concentration of nominally dissolved As (<1 kDa), but no correlation was observed between colloidal As and nominally dissolved P. This suggests that P actively competes for adsorption sites on Fe nanoparticles, displacing adsorbed As, thus mirroring their interaction with Fe oxides in the aquifer matrix. Dynamic redox fronts at the interface between streams and aquifers may therefore provide globally widespread conditions for the generation of Fe nanoparticles, a mobile phase for As adsorption currently not a part of reactive transport models.
微生物氧化有机质与还原氧化铁溶解的耦合作用被广泛认为是驱动含水层中砷（As）浓度升高的主要机制。本文考虑了纳米颗粒增加含水层中 As 迁移性的潜力，从而解释了其他地方报道的预测和观察到的 As 迁移之间的差异。本文沿地表水-地下水过渡带-浅层地下水的水流路径，对砷、磷和铁的粒径分布以及天然有机物的结合情况进行了研究。我们的分析表明，胶体 Fe 浓度（>1 kDa）与胶体 P 和胶体 As 浓度均相关。重要的是，胶体 P 浓度（>1 kDa）的增加与名义溶解 As 浓度（<1 kDa）的增加呈正相关，但胶体 As 与名义溶解 P 之间没有相关性。这表明 P 积极地与 Fe 纳米颗粒上的吸附位点竞争，从而取代吸附的 As，反映了它们与含水层基质中氧化铁的相互作用。因此，溪流和含水层界面处的动态氧化还原前缘可能为生成 Fe 纳米颗粒提供了全球广泛的条件，这是目前尚未纳入反应性迁移模型的 As 吸附的一个移动相。
