Revisiting the Cape Cod Bacteria Injection Experiment Using a Stochastic Modeling Approach

Abstract

Bromide and resting-cell bacteria tracer tests carried out in a sand and gravel aquifer at the USGS Cape Cod site in 1987 were reinterpreted using a three-dimensional stochastic approach and Lagrangian particle tracking numerical methods. Bacteria transport was strongly coupled to colloid filtration through functional dependence of local-scale colloid transport parameters on hydraulic conductivity and seepage velocity in a stochastic advection-dispersion/attachment-detachment model. Information on geostatistical characterization of the hydraulic conductivity (K) field from a nearby plot was utilized as input that was unavailable when the original analysis was carried out. A finite difference model for groundwater flow and a particle-tracking model of conservative solute transport was calibrated to the bromide-tracer breakthrough data using the aforementioned geostatistical parameters. An optimization routine was utilized to adjust the mean and variance of the lnK field over 100 realizations such that a best fit of a simulated, average bromide breakthrough curve is achieved. Once the optimal bromide fit was accomplished (based on adjusting the lnK statistical parameters in unconditional simulations), a stochastic particle-tracking model for the bacteria was run without adjustments to the local-scale colloid transport parameters. Good predictions of the mean bacteria breakthrough data were achieved using several approaches for modeling components of the system. Simulations incorporating the recent Tufenkji and Elimelech

Simulation of the subsurface mobility of carbon nanoparticles at the field scale

“…However, numerical models have been used to investigate colloid transport in larger two-and three-dimensional systems (e.g. [34,41,4,25,27,2,3,28,36]). These studies suggest that field scale heterogeneities are important in determining the mobility of viruses and colloids in the subsurface.…”

“…Other studies have investigated the transport of colloids at the field scale in more complex 3D numerical simulations and found that coupling the colloid removal rate to spatially varying aquifer permeability improved modeling results (e.g. [34,27,28,36]). These studies, however, assumed an infinite number of sites for colloid retention on the soil surface.…”

Comparison of Fickian and temporally nonlocal transport theories over many scales in an exhaustively sampled sandstone slab

“…SLIM-FAST has been applied to a range of problems including stochastic risk assessment Siirila et al, 2010], microbial and bacterial transport [Maxwell et al, 2003[Maxwell et al, , 2007, and age distributions of water and isotopic tracers [Tompson et al, 1999;Maxwell et al, 2003;Kollet and Maxwell, 2008;Maxwell et al, 2009]. Within SLIM-FAST, particles may transfer between a mobile and an immobile state by single-rate Markov chains.…”

Development of RWHet to Simulate Contaminant Transport in Fractured Porous Media

“…It was first applied to tracer transport in saturated alluvial formations [Ahlstrom et al, 1977;Prickett et al, 1981], and then porous media of all types [Uffink, 1985;Kinzelbach, 1988;Cordes et al, 1991;Mahinthakumar and Valocchi, 1992;Tompson, 1993;Semra et al, 1993;LaBolle et al, 1996LaBolle et al, , 1998LaBolle et al, , 2000LaBolle and Fogg, 2001;Weissmann et al, 2002;Maxwell et al, 2007;Green, 2010] and extended to fractured rocks with matrix diffusion [Yamashita and Kimura, 1990;Wels et al, 1997;Liu et al, 2000;Tsang and Tsang, 2001;Roubinet et al, 2009Roubinet et al, , 2012.…”