Tracers solute transport

Since transport occurs solely by the exchange of A and A it follows that /a + Ja = 0. The isotope tracer solution is also ideal with /VA + /VA = 1, so Eqn. (5.52) yields... 

Tracer breakthrough profiles within the matrix regime confirmed that the dissolved gases and Br were slowly moving into the bedrock matrix and at different rates. Concentration profiles of the three tracers 6 m from the source and 0.8 m into the matrix relative to the fracture zone are shown in Figure 1.5(a). The movement of He and Ne into and from the matrix was more rapid than Br, which is consistent with the larger molecular diffusion coefficients for the dissolved gases relative to Br. These results support the notion that matrix diffusion contributed to the overall physical nonequilibrium process that controls solute transport in bedrock at this site (Maloszewski and Zuber, 1990, 1993). 

In the bubble column the velocity profile of recirculating liquid is shown in Fig. 27, where the momentum of the mixed gas and liquid phases diffuses radially, controlled by the turbulent kinematic viscosity Pf When I/l = 0 (essentially no liquid feed), there is still an intense recirculation flow inside the column. If a tracer solution is introduced at a given cross section of the column, the solution diffuses radially with the radial diffusion coefficient Er and axially with the axial diffusion coefficient E. At the same time the tracer solution is transported axially Iby the recirculating liquid flow. Thus, the tracer material disperses axially by virtue of both the axial diffusivity and the combined effect of radial diffusion and the radial velocity profile. 

Green, R.E., P.S.C. Rao., and J.C. Corey. 1972. Solute transport in aggregated soils Tracer zone shape in relation to pore-velocity distribution and adsorption. In Proc. 2nd Symp. Transport Phenomena in Porous Media, lAHR and ISSS, Guelph, Canada. 

Wheatcraft et al. (1991) considered flow and solute transport in a medium composed of high and low sat distributed according to a Sierpinski carpet fractal, reminiscent of low permeability pebbles distributed in a high permeability matrix. A multigrid solver was used to compute the flow field (Fig. 3 1B) and a particletracking algorithm was used to determine the tracer motion. No diffusion was considered. They found that dispersion increased with the scale of the simulation faster than could be predicted with other models. 

Laboratory column experiments were used to identify potential rate-controlling mechanisms that could affect transport of molybdate in a natural-gradient tracer test conducted at Cape Cod, Mass. Column-breakthrough curves for molybdate were simulated by using a one-dimensional solute-transport model modified to include four different rate mechanisms equilibrium sorption, rate-controlled sorption, and two side-pore diffusion models. The equilibrium sorption model failed to simulate the experimental data, which indicated the presence of a ratecontrolling mechanism. The rate-controlled sorption model simulated results from one column reasonably well, but could not be applied to five other columns that had different input concentrations of molybdate without changing the reaction-rate constant. One side-pore diffusion model was based on an average side-pore concentration of molybdate (mixed side-pore diffusion) the other on a concentration profile for the overall side-pore depth (profile side-pore diffusion). 

Sayles, F.L. and Martin, W.R., 1995. In Situ tracer studies of solute transport across the sediment - water interface at the Bermuda Time Series site. Deep-Sea Res. I, 42(1), 31-52. 

Neretnieks 1. A stochastic multi-channel model for solute transport- Analysis of tracer transport in fractured rock, J. Contaminant Hydrology, 55, p 175-211,2002. 

Canada solute transport in highly fractured rock, groundwater tracer tests, scale dependence... 

The first online DD-HPLC/FT-IR interface was reported by Lange et al. [42], who interfaced a concentric flow nebulizer to the Bio-Rad Tracer. Solutes were deposited on a continuously moving ZnSe substrate as a trace that was 150 pm in width. In an manner analogous to DD-GC/FT-IR measurements, the solute spots were transported into the beam of a rudimentary microscope, and transmission spectra were measured at intervals of 1 to 2 s. It was not possible to eliminate aqueous solvents at a rate of more than about 50pLmin with the concentric flow nebulizer, so the separations either had to be carried out on a 1-mm-i.d. column or to use a wider-bore column with an output stream splitter. Although Robertson et al. reported the elimination of aqueous mobile phases at flow rates up to 1 mL min using a monodisperse aerosol generator and achieved spot diameters of between 300 and 50 pm [35], it was not possible to direct the IR beam inside the vacuum chamber, and this device was never used online. 

Flury, M. Huehler, H. Brilliant Blue FCF as a dye tracer for solute transport studies— toxicological overview. J. Environ. Qual 1994, 23, 1108-1112. 

The solute transport relationships in each column experiment were evaluated using an analytical solution of the advection-dispersion equation (Ogata Banks 1961). This model was used to estimate the hydraulic parameters (kinematic velocity, dispersivity and porosity) of each column by least-squares fitting to the chloride tracer. The hydraulic parameters were then fixed for the transport simulations and evaluation of experimental solute distribution coefficients (A j). The latter was estimated using the following relationship ... 

Powerful solvents such as dimethyl sulfoxide (common laser dye solvent) and solubilizing substituents (K" and R " = sulfoalkyl in stmcture 32) may enhance the transport of dyes in solution through skin and other membranes. Reference 88 (on laser dye solutions and toxicity) is recommended to researchers working with dye solutions. Other dyes, such as Indocyanine Green, attain useful properties (blood tracer dye) as a result of having solubilizing substituents in their stmcture. 

The skew in the fit of the tracer curve in Example 6.7 occurs because the tails are not modeled well. This is a problem with the reactors-in-series model and most computational models as well. A solution to this curve-fit problem will be discussed in the next section on leaky dead zones. For most applications, in transport modeling. 

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