Publication Details

Category Text Publication
Reference Category Journals
DOI 10.1029/2021GB007056
Licence creative commons licence
Title (Primary) Iron exports from catchments are constrained by redox status and topography
Author Tittel, J.; Büttner, O.; Friese, K. ORCID logo ; Lechtenfeld, O.J. ORCID logo ; Schuth, S.; von Tümpling, W. ORCID logo ; Musolff, A.
Source Titel Global Biogeochemical Cycles
Year 2022
Volume 36
Issue 1
Page From e2021GB007056
Language englisch
Topic T5 Future Landscapes
T9 Healthy Planet
Data and Software links
Keywords river; mineral phosphorus; carbon; soil; watershed; metal; groundwater; NOSC
Abstract Fe(III) hydroxides stabilize organic carbon (OC) and P in soils. Observations of rising stream Fe concentrations are controversially posited to result from a flushing of iron-rich deeper soil layers or a decrease of competing electron acceptors inhibiting Fe reduction (urn:x-wiley:08866236:media:gbc21222:gbc21222-math-0001 and urn:x-wiley:08866236:media:gbc21222:gbc21222-math-0002). Here, we argue that catchment topography constrains the release of Fe, OC, and P to streams. We therefore incubated organic topsoil and mineral subsoil and modified the availability of urn:x-wiley:08866236:media:gbc21222:gbc21222-math-0003. We found that Fe leaching was highest in topsoil. Fe, OC, and P released at quantities proportional to their ratios in the source soil. Supply of urn:x-wiley:08866236:media:gbc21222:gbc21222-math-0004 reduced Fe leaching to 18% and increased pore water OC:Fe and P:Fe ratios. Subsoil, however, was an insignificant Fe source (<0.5%). Here, the leached quantities of Fe, OC and P were highly disproportionate to the soil source with an excess of released OC and P. We tested if experimental findings scale up using data from 88 German catchments representing gradients in urn:x-wiley:08866236:media:gbc21222:gbc21222-math-0005 concentration and topography. Average stream Fe concentrations increased with decreasing urn:x-wiley:08866236:media:gbc21222:gbc21222-math-0006 and were high in catchments with shallow topography where high groundwater levels support reductive processes and topsoils are hydrologically connected to streams; but Fe concentrations were low in catchments with steep topography where flow occurs primarily through subsoils. OC:Fe and P:Fe ratios in the streams similarly varied by urn:x-wiley:08866236:media:gbc21222:gbc21222-math-0007 and topography. This corroborates the findings from the laboratory experiment and suggests that catchment topography and competing electron acceptors constrain the formation of Fe-reducing conditions and control the release of Fe, OC, and P to streams.
Persistent UFZ Identifier
Tittel, J., Büttner, O., Friese, K., Lechtenfeld, O.J., Schuth, S., von Tümpling, W., Musolff, A. (2022):
Iron exports from catchments are constrained by redox status and topography
Glob. Biogeochem. Cycles 36 (1), e2021GB007056 10.1029/2021GB007056