Doktorarbeit
Phosphorus Mobilization and Transport Across Scales: From Geogenic Sources to Catchment-Scale Dynamics
Betreuer: Stefan Peiffer, Luisa Hopp
Excessive nutrient inputs to surface waters represent a global environmental challenge. Despite extensive efforts to mitigate phosphorus (P) export from anthropogenic sources, water quality improvements remain limited in many catchments. This likely stems from incomplete understanding of P sources and transport pathways, particularly those of geological origin and in complex, redox-dynamic environments. Understanding phosphorus dynamics across various geological settings and catchment scales is therefore crucial for effective management strategies.
Study 1 examines geogenic P dynamics in groundwater at a small (~1 ha) study site within a drained riparian wetland in southeastern Germany. The site's apatite-rich geological background and extensive drainage network provide optimal conditions for investigating P mobilization and export processes. The presence of preferential channels and drainage networks likely facilitates geogenic P transport to surface waters.
Phosphorus exhibits high affinity for iron (Fe) oxides, and the geochemical behavior of P is strongly influenced by Fe oxide transformation reactions. In suboxic and anoxic conditions, elevated aqueous Fe(II) catalyzes the transformation of poorly crystalline ferrihydrite into more crystalline Fe oxides (lepidocrocite, goethite) with reduced sorption capacities. Study 2 examines the combined effects of oscillating oxic-reducing conditions on Fe(II)-catalyzed ferrihydrite transformation and its impact on P sorption.
Study 3 addresses P source complexity at larger catchment scales, where individual assessment of P sources, land use, hydrology, and topography becomes challenging. Using high-frequency concentration and discharge data from the Altmühl River catchment (provided by the Water Management Authority Ansbach), this study investigates high P load sources and transport dynamics during storm events in streams and rivers.