Radial solute transport in highly heterogeneous aquifers: Modeling and experimental comparison

Abstract

We analyze solute transport in a radially converging 3‐D flow field in a porous medium with spatially heterogeneous hydraulic conductivity (K). The aim of the paper is to analyze the impact of heterogeneity and the mode of injection on BreakThrough Curves (BTCs) detected at a well pumping a contaminated aquifer. The aquifer is conceptualized as an ensemble of blocks of uniform but contrasting K and the analysis makes use of the travel time approach. Despite the approximations introduced, the model reproduces a laboratory experiment without calibration of transport parameters. Our results also show excellent agreement with numerical simulations for different levels of heterogeneity. We focus on the impact on the BTC of both heterogeneity in K and solute release conditions. It is shown that the injection mode matters, and the differences in the BTCs between uniform and flux‐proportional injection increase with the heterogeneity of the K‐field. Furthermore, we study the effect of heterogeneity and mode of injection on early and late arrivals at the well.

Well‐Type Steady Flow in Strongly Heterogeneous Porous Media: An Experimental Study

“…In this case, the K eff is not anymore a function of the position, and therefore, one can claim that in the far field it is a medium's property. A similar result was found to be valid also for transport (Di Dato et al, 2017).…”

“…Given the geometrical configuration of the packed aquifer, we have taken for granted the requirement of ergodicity, that is the ratio between the aquifer's thickness and the vertical integral scale is much larger than one. In the present study, this ratio is 35/5 that is not large enough to regard the flow as fully ergodic [an extended treatment on this requirement can be found in Sanchez-Vila and Tartakovsky ( 2007) and Di Dato et al (2017)]. This leaves a certain degree of uncertainty upon the mean values of the hydraulic heads; 4.…”

“…In the present study, this ratio is 35/5 that is not large enough to regard the flow as fully ergodic [an extended treatment on this requirement can be found in Sanchez‐Vila and Tartakovsky (2007) and Di Dato et al. (2017)]. This leaves a certain degree of uncertainty upon the mean values of the hydraulic heads; We have dealt with a zero correlated joint probability distribution (8).…”

“…While the above example shows straightforwardly how findings of our study can be readily applied to solve practical problems, there are numerous aspects which require further investigations. Among these, we believe that the priority should be given to the impact of the aquifer's boundaries, and to the attainment of the ergodicity requirement (along the lines traced in Di Dato et al., 2017). Another central topic is the extension of the self‐consistent solution to 3 D .…”

On the Bimodal Radial Solute Transport in Dual‐Permeability Porous Media

“…To test the practical application of the proposed model in dealing with formation heterogeneity, the MM model is applied to a DFTT conducted by Fernàndez-Garcia et al (2004) in a tank where a heterogeneous K-field was constructed. Although the test porous media was artificially packed in a laboratory, it exhibits a heterogeneous structure of K resembling those in some natural fields (Dato et al, 2017). Description of experimental setup and procedures can be found in Text S7 in Supporting Information S1.…”