Soil radioactivity in the highest volcanic region of Northern Andes

摘要

? 2023 Elsevier LtdThis work studied the spatial pattern of four natural radionuclides (226Ra, 228Ra, 228Th and 40K) as well as one artificial one (137Cs) in soils in the Chimborazo province (Ecuador), which belongs to the North Andes of South America. Soil samples were collected considering the Ecuador geological map. Statistical analyses showed that activity concentrations of 226Ra, 228Ra, 228Th do not exceed the worldwide average, while one geological unit exceeds the worldwide average for 40K. These high activity concentrations are attributed to radionuclide accumulation in plutonic and metamorphic rocks and also in ash resulting from eruptions of the Sangay volcano. The inverse distance weighted interpolation method was used to develop corresponding radioactivity maps where the highest activity concentrations are in the central-east of the studied area. In addition, a distribution pattern of 226Ra and 40K is observed in the geologies influenced by the presence of Chimborazo, Igualata, Tungurahua and Altar volcanoes. Spearman's nonparametric test shows positive correlations suggesting the presence of very homogeneous lithologies and that volcanic activities can influence the distribution of radionuclides in our environment. In seven of the samples, 137Cs was detected.