Soil Manganese: Speciation, Transformation, and Reactivity

尽管锰是植物必需的微量营养素，在溶液浓度升高时可能会引起植物毒性效应，锰（III，IV）-（羟基）氧化物是土壤中痕量金属（类）的重要清除剂和氧化剂，但对锰在土壤中的固相形态和转化知之甚少。因此，拟议的研究土壤锰的形态，转化和反应性将探讨不同的锰池在土壤中的相对丰度和变异性，验证现有的连续提取程序用于目标土壤锰，并探讨亚/缺氧土壤环境中的锰氧化物的还原转化及其对重金属溶解度的影响。为了实现这些目标，我们将使用同步辐射X射线吸收光谱研究锰在欧洲主要土壤类型的形态，并验证顺序提取程序作为简单和具有成本效益的手段来调查土壤锰循环。此外，我们将进行批量实验结合详细的X-射线衍射，红外光谱，和拉曼光谱分析，探讨溶解的锰（II）的还原转化的重金属负载的锰氧化物在水溶液中的存在下，铁（II），这是一个假设的过程，强烈影响的流动性的重金属在土壤中进行定期水浸的影响。总之，计划中的项目将提供基本的见解土壤锰的形态，可靠的量化土壤锰池使用顺序提取，和重要的地球化学控制土壤锰循环。

Despite that manganese is an essential micronutrient for plants which may cause phytotoxic effects at elevated solution concentrations and manganese(III,IV)-(oxyhydr)oxides are important scavengers and oxidants for trace metal(loid)s in soils, the solid-phase speciation and transformation of manganese in soils are poorly understood. Therefore, the proposed research on the speciation, transformation, and reactivity of soil manganese will explore the relative abundance and variability of different manganese pools in soils, validate existing sequential extraction procedures used to target soil manganese, and explore the reductive transformation of manganese oxides in sub-/anoxic soil environments and its effect on heavy metal solubility. To reach these objectives, we will use synchrotron-based X-ray absorption spectroscopy to study the speciation of manganese in major soil types of Europe and validate sequential extraction procedures as simple and cost-effective means to investigate the soil manganese cycle. Additionally, we will conduct batch experiments in combination with detailed X-ray diffraction, IR-, and Raman spectroscopy analyses to explore the effect of dissolved manganese(II) on the reductive transformation of heavy metal-loaded manganese oxides in the presence of aqueous iron(II), a process which is hypothesized to strongly impact the mobility of heavy metals in soils subjected to periodic water logging. In summary, the planned project will provide fundamental insights into the speciation of soil manganese, the reliable quantification of soil manganese pools using sequential extractions, and important geochemical controls of the soil manganese cycle.