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  • 1995-1999  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 18 (1998), S. 0 
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The low bioavailability of hydrophobic organic compounds (HOCs) is one of the key sources of uncertainty in the implementation of in situ bioremediation. Bioavailability of HOCs in the subsurface is affected by sorption/desorption processes in two important ways. First, sorption causes high organic concentrations in microporous regions and impermeable zones to which bacterial access is obstructed. Second, because desorption and immobile zone diffusion must occur before biodegradation can proceed, the overall rate of bioremediation can be limited or even controlled by these mass transfer processes, not by the activity of the degrading microorganisms. Rate models that couple sorption/desorption—related mass transfer processes and biodegradation have been successfully applied to laboratory results and are beginning to offer some insight into the problem. Specifically, the influence of sorption on biodegradation is quantified here by defining a bioavailability factor, Bf. However, many questions remain and predictive modeling is elusive, especially in the context of complicated heterogeneous natural systems. Challenges facing environmental engineers are to develop a better understanding of these processes at both laboratory and field scales and ultimately to use such understanding toward the development of more effective and economical remediation technologies.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-1634
    Keywords: solute transport ; multi-layer porous media ; analytical solution ; integral transform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An analytical solution to the one-dimensional solute advection-dispersion equation in multi-layer porous media is derived using a generalized integral transform method. The solution was derived under conditions of steady-state flow and arbitrary initial and inlet boundary conditions. The results obtained by this solution agree well with the results obtained by numerically inverting Laplace transform-generated solutions previously published in the literature. The analytical solution presented in this paper provides more flexibility with regard to the inlet conditions. The numerical evaluation of eigenvalues and matrix exponentials required in this solution technique can be accurately and efficiently computed using the sign-count method and eigenvalue evaluation methods commonly available. The illustrative calculations presented herein have shown how an analytical solution can provide insight into contaminant distribution and breakthrough in transport through well defined layered column systems. We also note that the method described here is readily adaptable to two and three-dimensional transport problems.
    Type of Medium: Electronic Resource
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