HR: 15:40h
AN: H23H-08    [Abstracts]
TI: Stochastic Simulations of Colloid-Facilitated Transport for Long Time and Space Scales
AU: * Painter, S
EM: spainter@swri.org
AF: CNWRA Southwest Research Instituter, 6220 Culebra Rd., San Antonio, TX 78238 United States
AU: Pickett, D
EM: dpickett@swri.org
AF: CNWRA Southwest Research Instituter, 6220 Culebra Rd., San Antonio, TX 78238 United States
AU: Cvetkovic, V
EM: vdc@kth.se
AF: Royal Institute of Technology, Kungl Tekniska H”gskolan, Stockholm, SE-100 44 Sweden
AB: Although it is widely recognized that naturally occurring inorganic colloids can potentially enhance the transport of radionuclides in the subsurface, comparatively few analyses have considered the long times and large travel distances associated with potential nuclear waste repositories. One-dimensional transient simulations in a stochastic Lagrangian framework are used to explore model and parameter sensitivities for colloid-facilitated transport at large scales. The model accounts for (i) advection and dispersion of radionuclides and colloids, (ii) radionuclide decay, (iii) exchange of radionuclides among colloid-bound, dissolved, and fixed substrate phases, and (iv) attachment and detachment of colloids to the fixed substrate. Kinetics of the exchanges between dissolved and colloid-bound states are addressed using linear and non-linear models. Generic sensitivity studies addressing both fractured and granular aquifers are considered, as is an example based on the groundwater transport pathway for the potential repository at Yucca Mountain, Nevada. In the absence of mitigating factors such as permanent filtration of colloids, transport may be enhanced over the situation without colloids, but only for strongly sorbing radionuclides. Mass transfer between solution and immobilized colloids makes colloid retardation relatively ineffective at reducing facilitated transport except when the retardation factor is large. Results are particularly sensitive to the rate of desorption from colloids, a parameter that is difficult to measure with short-duration experiments. This paper is an independent product of the CNWRA and does not necessarily reflect the view or regulatory position of the U.S. Nuclear Regulatory Commission.
DE: 3210 Modeling
DE: 1832 Groundwater transport
DE: 1869 Stochastic processes
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting