Evaluation of the sedimentation rate in a sediment profile of Bortolan Dam, MG, Brazil

Volcanic extrusion is one of the main causes for the high levels of environmental radioactivity in the region of Poços de Caldas (MG, Brazil). Uranium mining during the 80's further increased the background radiation in the region, especially in the Ribeirao das Antas watershed, where Bortolan Dam is located. Besides the uranium mining facility operating in the region, other activities, such as agriculture, were also responsible for the enhancement of the levels of radioactivity. The dam sediment profile provides an appropriate compartment for the study of the temporal variation of these radionuclides and for the evaluation of anthropogenic contamination. The main aim of this study is to evaluate the sedimentation rate and the dating of a profile collected in Bortolan Dam, by using the geochronology method. The activity concentration of ²²⁶Ra and ²¹⁰Pb were measured in the sediment profile by gamma spectrometry. The concentration of ²²⁶Ra and ²¹⁰Pb varied from (217 ± 9) Bq kg^-1 to (286 ± 12) Bq kg^-1 and from (262 ± 11) Bq kg^-1 to (322 ± 34) Bq·kg^-1 respectively; and the sedimentation rates varied from 0.021 to 0.144 g cm^-2y^-1. (author)