[1] River-aquifer exchange is considered within a transition probability framework along the Rio Grande in Albuquerque, New Mexico, to provide a stochastic estimate of aquifer heterogeneity and river loss. Six plausible hydrofacies configurations were determined using categorized drill core and wetland survey data processed through the TPROGS geostatistical package. A base case homogeneous model was also constructed for comparison. River loss was simulated for low, moderate, and high Rio Grande stages and several different riverside drain stage configurations. Heterogeneity effects were quantified by determining the mean and variance of the K field for each realization compared to the root-mean-square (RMS) error of the observed groundwater head data. Simulation results showed that the heterogeneous models produced smaller estimates of loss than the homogeneous approximation. Differences between heterogeneous and homogeneous model results indicate that the use of a homogeneous K in a regional-scale model may result in an overestimation of loss but comparable RMS error. We find that the simulated river loss is dependent on the aquifer structure and is most sensitive to the volumetric proportion of fines within the river channel.Citation: Engdahl, N. B., E. T. Vogler, and G. S. Weissmann (2010), Evaluation of aquifer heterogeneity effects on river flow loss using a transition probability framework, Water Resour. Res., 46, W01506,
[1] The effect of acoustic waves on the transport of a conservative tracer in a water saturated column packed with glass beads was investigated. It was observed from the experimental data that the addition of acoustic waves, in the frequency range between 60 to 245 Hz, to a steady background pressure gradient, enhances solute transport compared to the base case consisting of only a background pressure gradient. Furthermore, it was found that the effective velocity of the solute is approximately inversely proportional to the frequency of the acoustic wave.
A pore network consisting of a monolayer of glass beads was constructed for experimental investigation of the effects of acoustic waves on the dissolution and mobilization of perchloroethylene (PCE) ganglia. Dissolution experiments were conducted with acoustic wave frequencies ranging from 75 to 225 Hz at a constant pressure amplitude of 3.68 kPa applied to the inlet of the monolayer. Ganglia mobilization experiments were conducted with a constant acoustic wave frequency of 125 Hz and acoustic pressure amplitudes ranging from 0 to 39.07 kPa. Effluent dissolved PCE concentrations were observed to increase in the presence of acoustic waves with the greatest increase (over 300%) occurring at the lowest frequency employed (75 Hz). Acoustic waves were also observed to mobilize otherwise immobile PCE ganglia, break them apart, and further enhance dissolution.
A methodology is developed for estimating temporally variable virus inactivation rate coefficients from experimental virus inactivation data. The methodology consists of a technique for slope estimation of normalized virus inactivation data in conjunction with a resampling parameter estimation procedure. The slope estimation technique is based on a relatively flexible geostatistical method known as universal kriging. Drift coefficients are obtained by nonlinear fitting of bootstrap samples and the corresponding confidence intervals are obtained by bootstrap percentiles. The proposed methodology yields more accurate time dependent virus inactivation rate coefficients than those estimated by fitting virus inactivation data to a firstorder inactivation model. The methodology is successfully applied to a set of poliovirus batch inactivation data. Furthermore, the importance of accurate inactivation rate coefficient determination on virus transport in water saturated porous media is demonstrated with model simulations.
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