Noninvasive Quantitative Measurement of Colloid Transport in Mesoscale Porous Media Using Time Lapse Fluorescence Imaging

Abstract

We demonstrate noninvasive quantitative imaging of colloid and solute transport at millimeter to decimeter (meso-) scale. Ultraviolet (UV) excited fluorescent solute and colloid tracers were independently measured simultaneously during co-advection through saturated quartz sand. Pulse-input experiments were conducted at constant flow rates and ionic strengths 10(-3), 10(-2) and 10(-1) M NaCl. Tracers were 1.9 microm carboxylate latex microspheres and disodium fluorescein. Spatial moments analysis was used to quantify relative changes in mass distribution of the colloid and solute tracers over time. The solute advected through the sand at a constant velocity proportional to flow rate and was described well by a conservative transport model (CXTFIT). In unfavorable deposition conditions increasing ionic strength produced significant reduction in colloid center of mass transport velocity over time. Velocity trends correlated with the increasing fraction of colloid mass retained along the flowpath. Attachment efficiencies (defined by colloid filtration theory) calculated from nondestructive retained mass data were 0.013 +/- 0.03, 0.09 +/- 0.02, and 0.22 +/- 0.05 at 10(-3), 10(-2), and 10(-1) M ionic strength, respectively, which compared well with previously published data from breakthrough curves and destructive sampling. Mesoscale imaging of colloid mass dynamics can quantify key deposition and transport parameters based on noninvasive, nondestructive, spatially high-resolution data.

Real-Time Gamma Imaging of Technetium Transport through Natural and Engineered Porous Materials for Radioactive Waste Disposal

“…Imaging techniques include visible light transmission and fluorescence imaging, 12,13 nuclear magnetic resonance (NMR), and X-ray computed tomography (see ref (14) for a recent review). Gamma attenuation techniques with external americium-241 or cesium-137 sources have been used to determine fluid transported within a column.…”

A review of non-invasive imaging methods and applications in contaminant hydrogeology research

“…A common approach is to image the spatial distribution of an aqueous phase colored- or fluorescent-dye as it flows through a model pore structure. This approach has been used to capture images of conservative tracers flowing through 2D pore networks etched into glass (Corapcioglu et al, 1997) or silicon (Nambi et al, 2003; Willingham et al, 2008), or fabricated from quartz sand or glass beads held between two glass or acrylic plates (Corapcioglu and Fedirchuk, 1999; Zinn et al, 2004; Jones and Smith, 2005; Bridge et al, 2006), or through a polymethylmethacrylate (PMMA) column packed with beads from the same material and refractive index matched fluid (Rashidi et al, 1996). When calibrated against standards of known dye concentration, image intensity can be correlated to dye concentration and breakthrough can be quantified.…”

“…Abiotic particles have been imaged in 2D pore structures etched into glass (Wan and Wilson, 1994) (Figure 4c) or silicon (Baumann and Werth, 2004; Sirivithayapakorn and Keller, 2003a, b), imprinted on polydimethylsiloxane (PDMS) (Auset and Keller, 2004, 2006), or created by sandwiching a thin layer of sand or glass beads between glass or acrylic plates (Crist et al, 2004; Bradford et al, 2005; Bridge et al, 2006, 2007; Zhang and Wang, 2006). Fluorescent particles were also imaged flowing through a PMMA column packed with beads from the same material and refractive index matched fluid (Northrup et al., 1993; Peurrung et al, 1995; Rashidi et al, 1996).…”

“…Individual colloid particles were resolved in most imaging experiments performed with 2D model porous media. However, in two studies (Bridge et al, 2006; Zhang and Wang, 2006), a coarser resolution was used and total fluorescence intensity was related to particle concentration.…”

Characterization of nanoparticle transport through quartz and dolomite gravels by magnetic resonance imaging

“…To overcome these issues, novel techniques have been developed which enable transport to be spatially resolved, including the use of fluorescent imaging protocols that visualize the transport of fluorescent particulates in translucent quartz matrices (Bridge et al 2006). This, however, relies on sufficient photon penetration and thus uses translucent quartz and thin columns (\1 cm).…”