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@PHDTHESIS{Sun:890450,
      author       = {Sun, Yajie},
      title        = {{U}ranium accumulation in agricultural soilsas derived from
                      long-term phosphorus fertilizer applications},
      volume       = {527},
      school       = {Universität Bonn},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2021-00966},
      isbn         = {978-3-95806-521-5},
      series       = {Schriften des Forschungszentrums Jülich. Reihe Energie
                      $\&$ Umwelt / Energy $\&$ Environment},
      pages        = {XII, 136 S.},
      year         = {2020},
      note         = {Universität Bonn, Diss., 2020},
      abstract     = {It is well known that uranium (U) in mineral phosphorus (P)
                      fertilizers may accumulate in agricultural soils; yet, this
                      U accumulation occurs at different rates, likely depending
                      on the type of fertilizer used. To substantiate this
                      assumption, the aims of my thesis were: i) to quantify the
                      accumulation rates of fertilizer-derived U in different
                      long-term agricultural field experiments with P fertilized
                      soils of central Europe, and ii) to contrast this with data
                      from longterm experimental sites on volcanic soils that
                      require higher amounts of P fertilizers for optimal crop
                      production, and iii) finally to explain the variations of U
                      accumulation rates by an assessment of the formation
                      mechanisms and stocks of U in major phosphate rocks (PRs)
                      deposits of the world. Soil samples were taken from the
                      surface soils and selected depth profiles of seven long-term
                      experiment sites, i.e. at the grassland fertilization trials
                      in Rengen (Germany), Park Grass (Rothamsted, UK), as well as
                      in Geitasandur and Sámstaðir (Iceland), and the
                      agricultural field experimental sites in Thyrow (Germany),
                      Askov (Denmark), Broadbalk (Rothamsted, UK), Uranium
                      concentrations were analyzed after microwave-assisted acid
                      digestion by nitric acidor/and a complete digestion by
                      lithium meta/tetraborate. In addition, I assessed U
                      concentrations and the natural stable oxygen isotope
                      compositions of phosphate (δ$^{18}$OP) in PRs as potential
                      indicators for the genesis of the U in PRs from different
                      deposits all over the world. My results revealed a wide
                      range of U accumulation rates in soils, ranging from 0-310
                      μg U kg$^{-1}$ yr$^{-1}$ in the monitored fields. Uranium
                      accumulation was small when the P fertilizers were derived
                      from igneous PRs from Finland and Kola Peninsula, as used
                      for sites in Askov (< 0.4 μg U kg$^{-1}$ yr$^{-1}$; <1.2 g
                      ha$^{-1}$ yr$^{-1}$ (20 cm)) and Thyrow (0.6 μg U kg$^{-1}$
                      yr$^{-1}$; 2.3 g ha$^{-1}$ yr$^{-1}$ (24 cm)), respectively,
                      or when basic slag was applied as used for the Rengen (1.2
                      μg U kg$^{-1}$ yr$^{-1}$; 1.3 g ha$^{-1}$ yr$^{-1}$ (10
                      cm)) site. Higher U accumulation rates (3.4, 7.8 μg U
                      kg$^{-1}$ yr$^{-1}$; 11.7, 21.9 g ha$^{-1}$ yr$^{-1}$ (23
                      cm)) were found at Rothemsted experiment stations
                      (Broadbalk; Parkgrass), where P fertilizers used had been
                      predominantly produced from PRs from North Africa. The most
                      serious case of fertilizer-derived U accumulation (up to 310
                      μg U kg$^{-1}$ yr$^{-1}$; 33.2 g ha$^{-1}$ yr$^{-1}$ (5
                      cm)) was found in Icelandic agricultural soil as a
                      consequence of both high U concentrations in the applied P
                      fertilizers (from an unknown PR source) and of large amounts
                      of P fertilizer application. Overall, soil U concentrations
                      will increase by 0.5 μg U kg$^{-1}$ (0-5.1 μg U kg$^{-1}$)
                      soil for 1 kg P applied per hectare and there will be 2.7-11
                      g U ha$^{-1}$ yr$^{-1}$ input to the EU’s agricultural
                      soil with 21.2 kg P (as P$_{2}$O$_{5}$) per hectare
                      fertilization. To explain these variations of U
                      concentrations in the world’s PRs, U concentrations in the
                      PRs were discussed corresponding to their δ$^{18}$OP
                      values. I found that there was a ‘coevolutionary’
                      relationship between the U (U/P$_{2}$O$_{5}$ ratio) and the
                      δ$^{18}$OP value: the lower the δ$^{18}$Op value of the PR
                      was, the lower its U concentration was. In igneous PRs, low
                      U concentration can be explained by the lack of secondary U
                      enrichment processes after rock formation, whereas the low
                      δ$^{18}$Op values was resulted from limited isotope
                      fractionation at high temperatures in the magma. In
                      sedimentary PRs, on the other hand, the variations of U
                      concentrations and δ$^{18}$Op values were related to the
                      geologic age at which PRs were formed. Generally, older
                      sedimentary PRs (formed in Precambrian-Cambrian) exhibited
                      lower U concentrations and lower δ$^{18}$Op values than the
                      younger ones (formed in Ordovician-Neogene), which were
                      influenced by paleoclimate and paleographic features. In
                      summary, the accumulation rates of fertilizer-derived U in
                      agricultural soils were regionspecific, depending on the
                      source and the amount of P fertilizer applied. My data show
                      that when applying P fertilizers with low U content, soil U
                      concentration will remain at a non-critical level even at
                      multi-centennial scale. However, fertilizer-derived U
                      accumulation may pose an environmental issue at the places
                      where large amounts of P fertilizers are needed for
                      maximizing crop production (such as in Andosols). Selecting
                      igneous PRs or ancient sedimentary PRs (formed in Paleozoic
                      and Precambrian) as precursor materials for P fertilizer
                      production is therefore crucial for minimizing potential U
                      contamination risks and thus for sustainable agricultural
                      management.},
      cin          = {IBG-3},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/890450},
}