GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 3.2 457 On two PVC bins, filled with different materials and housing three specimens of each of the two plants respectively, small holes were drilled in the bottom to simulate the presence of the water table and allow water from irrigation or rainfall to flow through and not completely saturate the bin. The micro-ERT apparatus consists of 48 buried metal plugs, inserted on the bin sides in 4 vertical rows, plus other 24 mini-electrodes on the ground surface. We adopted a time-lapse approach, conducting repeated ERT acquisitions over time in order to assess the evolution of the system’s dynamics under changing moisture conditions: a first time-zero measure, six acquisitions every 1.5 hour after the irrigation and a last control measurement after 24 hours from the test beginning. As a basic starting point, we checked the experimental design and the acquisition sequence through synthetic modeling (Fig. 2), with a special focus on sensitivity and coverage. Fig. 2 - Synthetic modeling before the experiment. Data were acquired using the MAE X612EM+ multichannel georesistivimeter, with dipole- dipole skip 0 acquisition sequence, including reciprocal measurements. Before each acquisition the contact resistance check was carefully performed, to ensure a good current injection and the reliability of the experiment. Processing and time-lapse inversion of the datasets (Fig. 3) were conducted through ResIPy (Blanchy et al. , 2020). Fig. 3 - Resistivity and relative differences time-steps sections for the Alnus incana .