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@PHDTHESIS{Liang:153727,
      author       = {Liang, Yan},
      title        = {{T}ransport and {R}etention of {S}tabilized {S}ilver
                      {N}anoparticles in {P}orous {M}edia},
      volume       = {212},
      school       = {RWTH Aachen},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2014-03223},
      isbn         = {978-3-89336-957-7},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {IV, 109 S.},
      year         = {2014},
      note         = {Dissertation, RWTH Aachen, 2014},
      abstract     = {Due to the widespread application of silver nanoparticles
                      (AgNPs) and the resulting potential exposure in the
                      environment, information about their environmental transport
                      and fate is essential for risk assessment. AgNPs are
                      commonly modified with functional groups, surfactants, or
                      polymers to increase their stability in liquids and the
                      surface modification greatly influences the environmental
                      behavior of AgNPs. The aim of this study is therefore to
                      investigate the transport and retention of
                      surfactant-stabilized AgNPs under environmentally relevant
                      conditions. Experiments were conducted with water-saturated
                      columns packed with quartz sand, around $90\%$
                      water-saturated columns filled with undisturbed loamy sand
                      soil, and a lysimeter. Inductively coupled plasma-mass
                      spectrometry/optical emission spectrometry (ICP-MS/OES) was
                      used to analyze the concentrations of AgNPs, Ca$^{2+}$ , K+,
                      Fe, and Al. The experimental breakthrough curves (BTCs) and
                      retention profiles (RPs) from column experiments were
                      described using a numerical model that considers time- and
                      depth-dependent retention. Column experiments with quartz
                      sand packing were also conducted in the presence of
                      surfactant to deduce the influence of surfactant on AgNP
                      transport, especially on the spatial distribution of
                      retained AgNPs that determines the long-term transport
                      potential. In addition, to better understand the
                      interactions of AgNPs and the matrix in the environment,
                      remobilization of retained AgNPs from undisturbed soil was
                      studied by changing the solution chemistry such as change of
                      cation types and ionic strength reduction. Experimental
                      results showed that the normalized concentration in BTCs for
                      AgNPs obtained from water-saturated columns increased with a
                      decrease in solution ionic strength (IS), and an increase in
                      flow velocity ($\textit{q}$), sand grain size, and input
                      concentration (C$_{o}$). In contrast to the conventional
                      filtration theory, RPs in sand exhibited uniform,
                      nonmonotonic, or hyperexponential shapes that were sensitive
                      to physicochemical conditions. The simulated retention rate
                      coefficient (k$_{1}$) and maximum retained concentration on
                      the solid phase (S$_{max}$) increased with IS and as the
                      grain size and/or C$_{o}$ decreased. The RPs were more
                      hyperexponential in finer textured sand and at lower C$_{o}$
                      because of their higher values of S$_{max}$, which indicated
                      a larger retention capacity of the porous media. Conversely,
                      RPs were nonmonotonic or uniform at higher C$_{o}$ and in
                      coarser sand that had lower values of S$_{max}$, and tended
                      to exhibit higher peak concentrations in the RPs at lower
                      flow velocities and at higher solution IS. These
                      observations indicate that uniform and nonmonotonic RPs
                      occurred under conditions when S$_{max}$ was filled. The
                      sensitivity of the nonmonotonic RPs to IS and flow velocity
                      in coarser textured sand indicates that AgNPs were partially
                      interacting in a secondary energy minimum according to the
                      Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. However,
                      elimination of the secondary minimum only produced recovery
                      of a small portion (<10\%) of the retained AgNPs. These
                      results imply that AgNPs were largely irreversibly
                      interacting in a primary minimum associated with microscopic
                      heterogeneity of the porous [...]},
      keywords     = {Dissertation (GND)},
      cin          = {IBG-3},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {246 - Modelling and Monitoring Terrestrial Systems: Methods
                      and Technologies (POF2-246) / 255 - Terrestrial Systems:
                      From Observation to Prediction (POF3-255)},
      pid          = {G:(DE-HGF)POF2-246 / G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/153727},
}