Effects of Redox Oscillations on Soil Clay Mineralogy and Colloid Dynamics

动态氧化还原条件是土壤中微生物活性和矿物活性的主要决定因素，但污染物、养分和碳动态的生物地球化学模型描述得很差。在湿地和旱地系统中，由于含水率和地下水位的变化以及相关的生物氧生产和需求，氧化还原条件可能每天、每周或季节性地迅速变化；经常导致明显的氧化还原不平衡。水文水流条件的时间动态可以产生显著的土壤氧化还原梯度，影响矿物(反式)的形成和反应，从而影响主要和微量元素的循环。然而，交替氧化还原条件对土壤矿物学变化的影响以及胶体物质作为“元素穿梭”在土壤中的动力学仍然知之甚少。因此，这项研究的目的是评估(1)土壤对波动氧化还原条件的矿物学响应，重点是Fe(III)氧化物和层状硅酸盐矿物学，以及(2)在多次氧化还原振荡过程中胶体形成和组成的动力学。这项全面的研究将增进我们对与氧化还原诱导的矿物形成、转化和溶解反应有关的基本土壤形成过程的了解，以及在土壤饱和重现期控制土壤-地下水中常量和微量元素迁移的过程。因此，它将有助于更好地了解土壤对气候变化导致的几个中欧地区预期出现的更不同的土壤干湿时期的反应。

Dynamic redox conditions are a major determinant of microbial activity and mineral reactivity in soils, but are poorly described by biogeochemical models of contaminant, nutrient, and carbon dynamics. In wetland and upland systems, redox conditions may change rapidly on a daily, weekly or seasonal basis due to changing moisture contents and water-table levels and associated biological oxygen production and demand; frequently resulting in distinct redox disequilibria. The temporal dynamics of hydrologic flow conditions can create pronounced soil redox gradients influencing mineral (trans)formation and reactivity and thus major and trace element cycling. However, the effect of alternating redox conditions on mineralogical changes and the dynamics of colloidal matter acting as "element shuttle" in soil are still poorly understood. Therefore, the aim of this research proposal is to assess (1) mineralogical responses to fluctuating redox conditions in soils, focusing on Fe(III)-oxide and phyllosilicate mineralogy, and (2) the dynamics of colloid formation and composition during multiple redox oscillations. The panned research will improve our knowledge on basic soil-forming processes linked to redox-induced mineral formation, transformation, and dissolution reactions, as well as processes controlling the soil-groundwater transfer of major and trace elements during recurring periods of soil saturation. It will thus contribute to a better understanding of soil responses to more distinct periods of soil wetting and drying expected in several Central European regions as a consequence of climate change.