Resumen
- In-situ geophysical techniques based on electrical resistivity tomography were performed to determine the spatial and temporal distribution of heavy metals. This paper aimed to pursue a novel methodology consisting in combining electrical resistivity tomography measurements, soil chemical data, and statistical analysis to predict As and Cd distribution in paddy soils. The resistivity surveys were performed at 2 m depth in nine locations of Tolima district in Colombia. Chemical concentrations of both As and Cd were introduced in a standardization procedure to estimate their electrical resistivity values. Soil and fertilizers information were acquired to determine As and Cd input in the studied area. The laboratory standardization showed a direct linear regression for Cd and an inverse one for As. A high positive Spearman correlation between electrical resistivity and As / Cd content was determined, with 0.98 and 0.99 values, respectively. Results showed that As-like compounds were distributed mainly in shallower soil layers (0.45 m) and were characterized by lower electrical resistivity values (181–2318 Ω.m). On the contrary, Cd-like compounds were observed in a deeper profile (0.80 m) with higher electrical resistivity values (559–4879 Ω.m). This work underlies the utility of the combined geophysical techniques, soil chemical parameters and statistical analysis to improve the understanding of As and Cd dynamics and origin in topsoil, supporting the need of an agricultural management of paddy soils.