Radiometric evaluation of Ouratea miersii (Planch.) Engl. From the Municipal Natural Park of Niterói, Brazilian Atlantic Rainforest remnant

Concern about radiation exposure to non-human biota and the environment has increased since the 1990s, resulting in several publications by UNSCEAR, IAEA, ICRP, among other agencies, which highlighted significant gaps in knowledge regarding non-human biota and resulted in the establishment of Reference Animals and Plants (RAPs). In Brazil, the Atlantic Forest biome has vast biodiversity, but there is a lack of information on the radiometric profile of plant species growing there. Thus, the objective of this study was to evaluate the radiometric profile of Ouratea miersii (Malpighiales), endemic to the Atlantic Rainforest, collected in the State of Rio de Janeiro, city of Niterói, at the Municipal Natural Park (PARNIT), which covers a region of protected Atlantic Rainforest. The specimen was completely collected (root, stem, leaf and soil including organic matter around the root), and each sample analyzed individually by gamma spectrometry using a HPGe detector (Canberra). The calculated activity concentrations (AC) indicated the presence of ⁴⁰K, ²²⁶Ra and ²²⁸Ra, with significant AC of ⁴⁰K in the soil (3901 Bq·kg⁻¹). The ⁴⁰K soil-plant transfer was 11.6%, being limited by some physiological mechanism and/or osmotic saturation, while the transfer factor for ²²⁶Ra was 45.3%. The dose rate in non-human biota due to AC's of ²²⁶Ra and ²²⁸Ra in soil was estimated by modeling with the ERICA Tool, which indicated the absence of adverse effect on non-human biota due to exposure. The radiological hazard index values (Raeq, ADR, AEDR, and ELCR) obtained from the soil AC collected at PARNIT were significantly higher than those from other locations in Brazil, and about three times the value reported by UNSCEAR (2000) due to a ⁴⁰K anomaly in the soil. For this reason, a more extensive environmental monitoring was necessary in the PARNIT region.