Assessing the Reactive Surface Area of Soils and the Association of Soil Organic Carbon with Natural Oxide Nanoparticles Using Ferrihydrite as Proxy.,Environmental Science & Technology

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Assessing the Reactive Surface Area of Soils and the Association of Soil Organic Carbon with Natural Oxide Nanoparticles Using Ferrihydrite as Proxy.
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-09-09 , DOI: 10.1021/acs.est.0c02163
Juan C Mendez ₁ , Tjisse Hiemstra ₁ , Gerwin F Koopmans ₁

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Assessment of the surface reactivity of natural metal-(hydr)oxide nanoparticles is necessary for predicting ion adsorption phenomena in soils using surface complexation modeling. Here, we describe how the equilibrium concentrations of PO₄, obtained with 0.5 M NaHCO₃ extractions at different solution-to-soil ratios, can be interpreted with a state-of-the-art ion adsorption model for ferrihydrite to assess the reactive surface area (RSA) of agricultural top soils. Simultaneously, the method reveals the fraction of reversibly adsorbed soil PO₄ (R-PO₄). The applied ion-probing methodology shows that ferrihydrite is a better proxy than goethite for consistently assessing RSA and R-PO₄. The R-PO₄ pool agrees well with ammonium oxalate (AO)-extractable phosphorus, but only if measured as orthophosphate. The RSA varied between ∼2 and 20 m²/g soil. The corresponding specific surface area (SSA) of the natural metal-(hydr)oxide fraction is ∼350–1400 m²/g, illustrating that this property is highly variable and cannot be represented by a single value based on the AO-extractable oxide content. The soil organic carbon (SOC) content of our top soils increases linearly not only with the increase in RSA but remarkably also with the increase in mean particle size (1.5–5 nm). To explain these observations, we present a structural model for organo-mineral associations based on the coordination of SOC particles to metal-(hydr)oxide cores.

中文翻译：

以水铁矿为代表的土壤活性表面积估算及土壤有机碳与天然氧化物纳米粒子的缔合。

评估天然金属氢氧化物纳米粒子的表面反应性对于使用表面络合模型预测土壤中的离子吸附现象是必要的。在这里，我们描述了如何使用最新的离子吸附模型（用于水铁矿来评估反应性表面）来解释以0.5 M NaHCO ₃萃取物在不同溶液/土壤比率下获得的PO ₄平衡浓度。农业表层土壤面积（RSA）。同时，该方法揭示了可逆吸附的土壤PO ₄（R-PO ₄）的比例。所应用的离子探测方法表明，对于一致地评估RSA和R-PO ₄，亚铁水合物优于针铁矿。R-PO ₄该池与草酸铵（AO）可提取的磷非常吻合，但仅当以正磷酸盐测量时才适用。RSA在约2至20 m ² / g土壤之间变化。天然金属-（氢）氧化物馏分的相应比表面积（SSA）为〜350-1400 m ² / g，这说明该性质是高度可变的，不能通过基于AO可萃取氧化物的单一值来表示内容。我们表层土壤的有机碳含量不仅随着RSA的增加呈线性增加，而且随着平均粒径（1.5-5 nm）的增加也显着增加。为了解释这些发现，我们提出了一种基于SOC颗粒与金属-（氢）氧化物核的配位的有机-矿物结合的结构模型。

更新日期：2020-10-06

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