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Fig. 6. Results of the NaCl diffusion experiment (no flow, salt added to the upstream reservoir). (a) Room temperature; (b) Conductivity in the upstream reservoir, exponentially decreasing with time due to diffusion of salt to the sand; (c) electric potential differences between the electrodes located at 5 cm from the upstream reservoir and the reference (see Fig. 3). The fact that results depend on the depth suggests a density effect. (d, e, f) same as (c) for the electrodes located at 12, 19, and 26 cm from the upstream reservoir, respectively.
