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@PHDTHESIS{Weihermller:46201,
      author       = {Weihermüller, Lutz},
      title        = {{C}omparison of different soil water extraction systems for
                      the prognoses of solute transport at the field scale using
                      numerical simulations, field and lysimeter experiments},
      volume       = {55},
      school       = {Universität Bonn},
      type         = {Dr. (Univ.)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-46201},
      isbn         = {3-89336-402-1},
      series       = {Schriften des Forschungszentrums Jülich. Reihe Umwelt /
                      Environment},
      pages        = {XXII, 145 S.},
      year         = {2005},
      note         = {Record converted from VDB: 12.11.2012; Universität Bonn,
                      Diss., 2005},
      abstract     = {Sampling of water and solutes in soils is of major
                      importance to understand water movement and solute transport
                      in soils and to validate mathematical models. Porous cups
                      are widely used to extract soil water for monitoring solute
                      transport. However, it is not yet clear how the suction cup
                      influences the matrix potential in the surrounding soil and
                      which part of the soil is sampled. This research was
                      designed to numerically evaluate the activity domain, the
                      extraction domain and sampling area of a suction cup under
                      constant infiltration. A finite element model (HYDRUS-2D)
                      was used to simulate the effect of various applied suctions
                      at two infiltration rates on the water status in three soils
                      (clay loam, sandy clay and sandy soil). Particle tracking
                      was used to track the streamlines which define the sampling
                      area and extraction domain of the suction cup. In general,
                      the activity domain, the extraction domain and sampling area
                      of the suction cup depend primarily on the soil hydraulic
                      parameters and the upper boundary, and secondarily on the
                      applied suction. The results showed that the activity
                      domain, the extraction domain and the sampling area are
                      largest for highest ambient hydraulic conductivities. The
                      activity domain and the sampling area also decrease with
                      increasing infiltration rates. Further, the extraction
                      domain of the suction cup depends strongly on the duration
                      of water extraction. Soil heterogeneity seems to play a
                      minor role with respect to the activity domain and sampling
                      area of the cup, but a major role in the amount of extracted
                      water and solute breakthrough. In a second step, a lysimeter
                      and field experiment equipped with porous ceramic plates,
                      tensiometers, TDR-probes and suction cups was conducted over
                      a 427 day period to evaluate differences in soil water
                      sampling and solute transport for a conservative tracer and
                      the test compounds Methabenzthiazuron (MBT) and Ethidimuron
                      (ETD). In general, the two lysimeters at the lysimeter
                      station at the $\textit{Forschungszentrum Jülich}$ showed
                      comparable leaching behaviour over time, reflected by the
                      tensiometer, TDR and drainage measurements. In comparison to
                      the lysimeters the sampling pits at the test site
                      Merzenhausen indicate lower water contents and amounts of
                      extracted water over the whole sampling period. These
                      differences can be traced back to variability in the
                      climatic data (e.g. precipitation and evaporation) caused by
                      microclimatic distinctions at the two locations. The results
                      of the field and lysimeter experiments show that no complete
                      tracer breakthrough could be determined at a depth of 120 cm
                      for the sampling pits and the lysimeters as a consequence of
                      the short sampling time and the dry summer in 2003. As a
                      result of retardation the breakthrough of the test
                      substances MBT and ETD is not complete even for the samplers
                      at 40 cm depth. Therefore, bromide breakthrough at 120 cm
                      depth and MBT/ETD breakthrough for 40 and 120 cm depth were
                      just described in qualitative terms. The variability in
                      bromide tracer breakthrough at 40 cm depth for the different
                      samplers at the two locations is reflected in the
                      variability of the mean pore water velocity, $\nu$, and
                      dispersivity, $\lambda$. On the other hand, no transport
                      parameters could be determined for the pesticide
                      breakthrough at all locations. In general, larger ETD
                      recoveries were measured compared to the MBT for all
                      samplers, whereby high peak concentrations in the samplers
                      can be traced back to single events. The differences in the
                      amount of extracted water, bromide masses, and as a result
                      variability in transport [...]},
      cin          = {ICG-IV},
      ddc          = {333.7},
      cid          = {I:(DE-Juel1)VDB50},
      pnm          = {Chemie und Dynamik der Geo-Biosphäre},
      pid          = {G:(DE-Juel1)FUEK257},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/46201},
}