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| Titel |
Evidence of authigenic vivianite formation in a recent lake sediment due to an iron amendment |
| VerfasserIn |
Matthias Rothe, Thomas Frederichs, Michaela Eder, Andreas Kleeberg, Michael Hupfer |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091842
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| Publikation (Nr.) |
 EGU/EGU2014-6155.pdf |
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| Zusammenfassung |
| Pore water chemistry and equilibrium calculations indicated supersaturation of the ferrous
iron phosphate mineral vivianite throughout the upper 30 cm of the iron-rich lake sediments
of dimictic lake Groß-Glienicker See, Berlin (Germany). Phosphorus (P) bound in the crystal
lattice of the mineral is supposed to be immobilized since vivianite is stable under anoxic,
reducing sedimentary conditions. Thus, vivianite formation can be an important process
contributing to P retention during early diagenesis. Application of a heavy-liquid separation
enabled to identify vivianite by means of X-ray diffraction. Electron micrographs showed
spherical nodules consisting of platy- and needle-shaped crystal aggregates with diameters
between 50 and 120 μm. Inclusions of diatom shells and other organic debris confirmed
the authigenic origin of the dark blue coloured nodules. Vivianite deposits were
restricted to the upper 22 cm of the sediment although supersaturation even increased in
subjacent pore waters. The high enrichment of vivianite aggregates after sediment
preparation combined with magnetic hysteresis measurements allowed to assess the
significance of vivianite formation for P burial in aquatic systems. From our results we
conclude that vivianite formation was triggered by an artificial iron amendment more
than 20 years ago that aimed at reducing the P content of the lake’s water body.
Furthermore, our results indicate that vivianite formation is located closely beneath the
sediment-water interface and that equilibrium calculations, i.e. supersaturated pore
water, alone cannot serve as a reliable predictor for the in situ formation of vivianite. |
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