Representative impedance spectra. (a) Run A2354 with fluid fraction of 0.19 and salinity of 3 wt.%. (b) Run A2341 with fluid fraction of 0.30 and salinity of 17 wt.%. The straight segments indicate the lines fitted to the data points. The insets show the expected circuit. The low-frequency tail is possibly approximated by Randles circuit (Randles 1947), which includes a double-layer capacitor (Cdl), charge transfer reaction resistance (Rct), and Warburg impedance (Zw).