Characterization of salt crystals in soil using electrochemical measurements

Soil salinization is considered among the most serious problems that affect irrigated lands and, thus, food security in the world. It is interesting to develop methods to test soil salinization. In this paper, the electric properties of sand-salt crystals (NaCl) mixtures (SSM) are investigated using electrical impedance spectroscopy. Seven samples were considered by mixing dry sand and salt crystals with different salt mass percentages (SMP) from 0% to 100%. The electrical responses are explored by measuring the electrical impedance and the global conductance for different SSM filling a small capacitive cell. The influence of frequency and SMP on the electrical conductance and the complex impedance are investigated. It was found that the conductance shows high dispersion with SMP at the whole frequency range and a high dispersion with frequency at low and high frequencies (≤103Hz and ≥105Hz). Impedance diagrams show a frequency dispersion at high and low frequencies that is modeled by an equivalent circuit constituted of three dipoles in series, each one formed by a pure resistance and a constant phase element in parallel. Findings characteristics are directly related to the rate of salt crystals in the samples. Then, the method developed in this work constitutes a non-destructive technique for detecting salt crystals in soils in arid regions and can be used to develop devices for in situ measurements.