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Nano scale visualization of enhanced adsorption and distribution of humic acid on hematite: Effect of Pb(II) ions
Chemical Geology ( IF 3.9 ) Pub Date : 2020-05-01 , DOI: 10.1016/j.chemgeo.2020.119573
Yang Lu , Yuzhen Liang , Fu Liu , Zimeng Wang , Zhenqing Shi

Abstract The interactions between soil organic matter (SOM) and minerals are key processes controlling the organic carbon (OC) stability in the environment, but the underlying mechanisms responsible for OC distribution on minerals are still not clear. In this study, a common crystalline iron oxide, hematite, and a typical SOM component, humic acid (HA), were chosen to explore, at the nano and even sub-nano scales, HA adsorption and distribution on hematite under the impact of Pb(II) ions. Adsorption experiments and spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) coupled with energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) demonstrated that Pb(II) enhanced the adsorption of HA on hematite, but the nano scale distributions of HA varied between experimental conditions. The Cs-STEM, EDS, and the EELS analyses clearly unveiled that, with the presence of Pb(II), the hematite aggregates became more dispersed, and HA was not only adsorbed on the edges hematite nanoparticles, but also was localized in the extended areas away from the hematite particles/aggregates, which resulted in a heterogeneous distribution of OC in hematite-HA systems. Our imaging methods provided direct visualization of the mineral-SOM-metal interactions at nano scales, which shed lights on the underlying mechanisms for OC stabilization in natural environments and can enable more robust constraints in the models of organic matter-mineral interactions.

中文翻译:

腐植酸在赤铁矿上的增强吸附和分布的纳米级可视化:Pb(II) 离子的影响

摘要 土壤有机质(SOM)与矿物质之间的相互作用是控制环境中有机碳(OC)稳定性的关键过程,但其在矿物质上分布的潜在机制尚不清楚。在这项研究中,选择了一种常见的结晶氧化铁赤铁矿和典型的 SOM 成分腐植酸 (HA),在纳米甚至亚纳米尺度上探索了铅作用下 HA 在赤铁矿上的吸附和分布(二)离子。吸附实验和球差校正扫描透射电子显微镜 (Cs-STEM) 结合能量色散 X 射线光谱 (EDS) 和电子能量损失光谱 (EELS) 表明 Pb(II) 增强了 HA 在赤铁矿上的吸附,但HA 的纳米级分布因实验条件而异。Cs-STEM、EDS 和 EELS 分析清楚地表明,随着 Pb(II) 的存在,赤铁矿聚集体变得更加分散,HA 不仅吸附在边缘的赤铁矿纳米颗粒上,而且还定位在扩展的远离赤铁矿颗粒/聚集体的区域,这导致 OC 在赤铁矿-HA 系统中的不均匀分布。我们的成像方法在纳米尺度上提供了矿物-SOM-金属相互作用的直接可视化,这揭示了自然环境中 OC 稳定的潜在机制,并可以在有机物质-矿物相互作用模型中实现更强大的约束。但也位于远离赤铁矿颗粒/聚集体的扩展区域,这导致 OC 在赤铁矿-HA 系统中的不均匀分布。我们的成像方法在纳米尺度上提供了矿物-SOM-金属相互作用的直接可视化,这揭示了自然环境中 OC 稳定的潜在机制,并可以在有机物质-矿物相互作用模型中实现更强大的约束。但也位于远离赤铁矿颗粒/聚集体的扩展区域,这导致 OC 在赤铁矿-HA 系统中的不均匀分布。我们的成像方法在纳米尺度上提供了矿物-SOM-金属相互作用的直接可视化,这揭示了自然环境中 OC 稳定的潜在机制,并可以在有机物质-矿物相互作用模型中实现更强大的约束。
更新日期:2020-05-01
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