A spectral induced polarization instrument using square-wave current injection to track critical zone processes: application to long-term monitoring of a wetland (Guidel, France).

Dataset of spectral induced polarization measurements collected in the wetland area at the Ploemeur-Guidel hydrogeological observatory, to monitor reactive processes with high spatial resolution across the top meter of soil. The spectral content of a signal with line spectrum resulting from square-wave current is exploited by injecting successively three square-wave currents with periods of 1, 10 and 100 s, covering the frequency range of 0.01 to 100 Hz in less than 4 minutes. One dataset consists of eight successive current injections at different depths. For each current injection, the electrical potential is simultaneously measured at seven dipoles. The time-series are recorded with a 2 kHz sampling rate, allowing the Fourier transform of the time-series into amplitude and phase spectra for each quadrupole. Details can be found in the corresponding paper.