Gamma-rays and X-rays spectrometries applied to evaluate soil redistribution

This work responds to the growing global demand for food, which requires improvements in agricultural production and sustainable management of natural resources. The focus is on soil erosion as a critical element in preserving agricultural productivity. From this perspective, the levels of radionuclides and chemical elements present in the soil, quantified through Gamma-Rays Spectrometry (GRS) and Energy Dispersive X-ray Fluorescence (EDXRF), were used to investigate soil redistribution over time. 27 soil samples ranging from 0 to 30 cm in depth were collected in an agricultural plot located in southern Brazil. Quantitative analysis indicated high mean concentrations of Fe (161 +/- 7 g kg-1), Al (110 +/- 17 g kg-1), Ca (2.6 +/- 0.5 g kg-1), Mn (2.4 +/- 0.3 g kg-1) and K (543 +/- 165 mg kg-1) in comparison with the other detected elements. The quantification of 137Cs provided a mean inventory of 27 +/- 17 Bq m-2. Using the proportional model, an estimated gross erosion rate of 28.2 ton ha-1 year-1 and a net soil deposition of 6.6 ton ha-1 year-1 were calculated. Therefore, a net soil loss of 21.6 ton ha-1 year-1 was experienced within the agricultural plot studied. The data set combination of both techniques with Principal Component Analysis (PCA) revealed correlations between the variables studied and the soil erosion dynamics. The PCA showed a tendency to separate the samples according to their sampling depth. Moreover, 137Cs behavior in soil proved to be similar to the behavior of elements found in fertilizers, like K. On the other hand, the individual influence of 137Cs was not enough to cause significant changes in the samples distribution in the scores plot, highlighting EDXRF as a promising technique to complement soil erosion studies.