Transformation of iron oxides in oscillating redox and sulfidic conditions and its implications for phosphate immobilization in aquatic ecos

Excessive phosphorus (P) in surface water ecosystems is a primary cause of eutrophication, and chemical immobilization using Fe-rich materials is a commonly used approach to mitigate eutrophication due to their high affinity toward P. However, the long-term effect of Fe addition on P dynamics at the sediment-water interface is currently poorly understood, especially in environmentally relevant conditions. The objective of the proposed experiment is to determine Fe speciation of Fe amended lake sediments under fluctuating redox and sulfidic conditions with Fe K-edge bulk XAS. These data will allow us to determine how Fe speciation influences the biogeochemical cycle of P in the long term. This understanding is essential for assessing the effectiveness of Fe amendments as a sustainable strategy for improving water quality in rivers and lakes.