Effects of Redox Oscillations on Soil Clay Mineralogy and Colloid Dynamics

• Applicants: Dr. Reiner Dohrmann; Professor Dr. Christian Mikutta
• Subject Area: Soil Sciences
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 418449917

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.

• DFG Programme: Research Grants