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@PHDTHESIS{Wang:902271,
      author       = {Wang, Jihuan},
      title        = {{C}haracterisation of the effect of redox potential on the
                      emission of greenhouse gases using wireless sensing
                      techniques},
      volume       = {554},
      school       = {Universität Bonn},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2021-04134},
      isbn         = {978-3-95806-581-9},
      series       = {Schriften des Forschungszentrums Jülich. Reihe Energie
                      $\&$ Umwelt / Energy $\&$ Environment},
      pages        = {XIV, 104 S.},
      year         = {2021},
      note         = {Universität Bonn, Diss., 2021},
      abstract     = {Soils act as both a source and sink of greenhouse gases
                      (GHGs) and are widely considered to contribute to global
                      warming. Soil N$_{2}$O emissions originate from microbial
                      nitrification and denitrification processes. Reducing
                      conditions in soils alter the biogeochemical processes and
                      result in large emissions of N$_{2}$O and CH$_{4}$. Soil
                      redox potential (Eh) measurements are a promising way to
                      differentiate the major source mechanism in soil N$_{2}$O
                      production and evaluate their functions within the N cycle
                      and may contribute to the development of N$_{2}$O emission
                      mitigation strategies. While soil GHG emissions have been
                      studied in the recent past, the relationship between GHG
                      productionand Eh has not been systematically studied in
                      detail. Eh monitoring can improve the assessment of soil
                      chemical potential variations and GHG emissions, especially
                      for CH$_{4}$ emissions, which mainly occur when soil is in
                      highly reduced conditions as a result of the soil submerged
                      below the water table (WT) continually, and for N$_{2}$O
                      emissions, that have two distinct source processes at
                      different Eh, i.e. nitrification at high Eh, and
                      denitrification at intermediate Eh values. The change
                      between oxidizing and reducing conditions insoil can be
                      monitored and quantified by soil platinum (Pt) electrodes in
                      combination with a reference electrode and a datalogger
                      system with high temporal resolution (less than 1 min). The
                      objectives of this thesis were to systematically investigate
                      soil surface GHG emissions and their relationship with the
                      spatial distribution and temporal variation of Eh. Because
                      it is challenging to establish controlled conditions in
                      natural soils, this study is based on a series of
                      step-by-step laboratory experiments, exploring the effects
                      of soil water content, N fertilization, and Eh on GHG
                      emissions, followed by longterm measurements of Eh and GHG
                      emissions in the field. In laboratory experiments, soil was
                      exposed to varying WT levels to evaluate the utility of Eh
                      monitoring for interpretating soil GHG emissions. To
                      quantify soil GHG emissions, the static chamber method was
                      used, in which gas samples were collected manually and
                      analyzed by gas chromatography (GC). These measurements
                      opened the possibility to interpret the long-term monitoring
                      Eh data and to evaluate their influence on soil GHG emission
                      under controlled soil moisture conditions. The Eh decreased
                      steadily after the soil was submerged under water. It was
                      found that CO$_{2}$ emissions had no clear relationship with
                      Eh variations, but were closely related to soil water
                      potential. In addition, soil Eh variations showed different
                      ranges of values at different depths. N$_{2}$O emission
                      peaks occurred at different Eh ranges and were influenced by
                      WT level changes or fertilization events. In order to obtain
                      more accurate information on N$_{2}$O emission sources in
                      cropland, we used an irrigation system in combination with
                      the stable isotope labeling technique using a
                      $^{15}$N-labeled fertilizer. This isotope tracer method
                      provided better insight into N$_{2}$O source partitioning
                      and provided an independent validation of the Eh-based
                      N$_{2}$O source partitioning. It was found that the changes
                      in soil Eh and N$_{2}$O emissions were induced by irrigation
                      and fertilization events, and were also related to the
                      vertical distribution of dissolved NO$_{3}^{-}$ and
                      NH$_{4}^{+}$ in the soil profile. Soil Eh values proved to
                      be a suitable basis for identifying the two dominant
                      N$_{2}$O sources, i.e. hydroxylamine oxidation (during
                      nitrification) and nitrite reduction (during
                      denitrification). It can be concluded from the laboratory
                      experiments that measurements of Eh with high spatial and
                      temporal resolution can make an important contribution to
                      the study and interpretation of the temporally and spatially
                      diverse N turnover processes in soils. [...]},
      cin          = {IBG-3},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {2173 - Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2173},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2021111009},
      url          = {https://juser.fz-juelich.de/record/902271},
}