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@ARTICLE{OConnell:281810,
      author       = {O'Connell, David W. and Mark Jensen, Marlene and Jakobsen,
                      Rasmus and Thamdrup, Bo and Joest Andersen, Thorbjørn and
                      Kovacs, Andras and Bruun Hansen, Hans Christian},
      title        = {{V}ivianite formation and its role in phosphorus retention
                      in {L}ake Ørn, {D}enmark},
      journal      = {Chemical geology},
      volume       = {409},
      issn         = {0009-2541},
      address      = {New York, NY [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2016-01477},
      pages        = {42 - 53},
      year         = {2015},
      abstract     = {Vivianite [(Fe3(PO4)2·8H2O)] may precipitate in anoxic
                      lake sediments affecting the porewater orthophosphate
                      concentration, and thereby the trophic status of lakes. We
                      have investigated changes in lake diagenesis of Fe and P
                      (1969–2009), with particular attention focused on
                      vivianite formation with sediment depth (0–20 cm) in an
                      iron–silica–carbon rich lake sediment (Ørnsø,
                      Denmark). Porewaters were supersaturated for vivianite by
                      two to five orders of magnitude (upper 10 cm) with porewater
                      phosphate concentrations ranging between 0.69 and 10 μmol
                      l− 1, in winter, and summer concentrations ranging between
                      9.8 and 40 μmol l− 1. Significant formation of vivianite
                      was confirmed by X-ray diffraction while scanning electron
                      microscopy and electron dispersive X-ray spectroscopy
                      indicated an increase in vivianite crystal size with depth
                      (~ 20 to ~ 70 μm across). Variations in elemental
                      composition of vivianite crystals in relation to $at.\%$ P
                      and Fe were especially seen going from 9.5 cm to 24.5 cm.
                      The total sediment Fe pool was very large ~ 3000 μmol g−
                      1 and total P increased from 200 μmol g− 1 to 400 μmol
                      g− 1 descending down the sediment profile. Differential
                      extraction experiments of P release at pH 3 estimated that
                      vivianite amounts to between 3 and $5\%$ of the total Fe
                      pool. The total P burial fluxes estimate that ~ 38 μmol
                      cm− 2 yr− 1 or ~ $26\%$ of sedimentary P in the lower
                      sediments is sequestered as vivianite. There are seasonal
                      variations in the porewater composition with lower Fe,
                      orthophosphate and higher sulfate concentrations during
                      winter (5 °C), than during summer (15 °C). This suggests
                      that temperature modulates the rate of organic matter
                      degradation which in turns affects the rate of Fe(III) phase
                      reduction, release of phosphate, and thereby the porewater
                      Fe2 + and orthophosphate concentrations and hence vivianite
                      formation. This work highlights the role vivianite can play
                      for P retention in a Si–Fe–C rich lake sediment.},
      cin          = {PGI-5},
      ddc          = {550},
      cid          = {I:(DE-Juel1)PGI-5-20110106},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000358525500005},
      doi          = {10.1016/j.chemgeo.2015.05.002},
      url          = {https://juser.fz-juelich.de/record/281810},
}