Avaliação do nível de radioatividade natural da região da futura APA Municipal Ilha Verde, Muriqui, Mangaratiba - RJ

Abstract

The project for the creation of the Municipal Environmental Protection Area (APA) Ilha Verde in 2024 aims primarily to transform an area that once functioned as a quarry into a space for environmental preservation, sustainability, and recreation for the residents of Muriqui, the 4th district of Mangaratiba, thereby promoting ecotourism in the locality. Considering the presence of rocky outcrops in the region, which are part of the geological context of Granito Serra do Piloto, and that these have been described in the literature as sources of natural radioactivity due to their mineralogical composition, it becomes essential to analyze the natural background radiation of the area and the potential radiation dose to which visitors and workers of this APA may be exposed. In light of the above, given that the consequences of prolonged exposure to ionizing radiation on human health are extremely harmful, this study aims to conduct a radiometric survey to investigate the gamma background radiation levels at distinct and specific points within the area where the APA will be established. The in situ measurement of gamma background radiation levels was carried out using a portable nuclear radiation detector of the Geiger-Müller type, model GQ GMC 500+, properly calibrated, at an elevation of approximately 1 meter above ground level. A Global Positioning System (GPS) was utilized to identify the geographical positions throughout the analyzed region. A total of 17 points were analyzed across the study area for gamma background radiation. The measured values of average absorbed dose rates of gamma background radiation varied from 0.14 ± 0.025 μSv/h to 0.20 ± 0.027 μSv/h, with an overall mean value of 0.17 μSv/h ± 0.021 μSv/h. These values were used to assess the radiological risk arising from radiation at the measurement sites through calculations of annual effective dose equivalent rates, the lifetime excess cancer risk, and the effective dose to various organs of the body. Thus, by comparing the values obtained from measurements at the different points in the region and the calculations described earlier with the limits established by legislation, it was concluded that the region does not pose immediate radiological risks to the health of visitors and workers in the future APA.