Relationships between natural radionuclides activity concentration in soils of the State of Alagoas, Brazil and WRB/FAO soil classification, types of parental rocks and rainfall variability.

Climate, soil type and geology that can influence the activity concentrations of natural radionuclides in soils. For this, 41 samples were collected in the first 25 cm of soil from the state of Alagoas, Northeast Brazil. This sample collection represents the mains soils classifications, parental rocks, and rainfall variability in this locality. The samples of soils were processed and analyzed by means of gamma-ray spectrometry for the K, Ra and Ra. The non-parametric Mann-Whitney U test was applied to perform the statistical inference on the differences in activity concentration for each soil class studied. There was a significant difference in the K activity distributions between the combination for most soil types. The results for Ra show no significant difference. However, Planosols differ significantly from Yellow Acrisols and Regosols for Ra. The strong relationship of the K concentration with the rock classes was shown. On the other hand, an association of the activity concentration of Ra and Ra with the rock type was not evidenced. There was a negative correlation between the K activity concentration and the rainfall index. Ra concentrations showed no correlation with the rainfall index.