Radiological risk assessment and spatial distribution of naturally occurring radionuclides within riverbed sediments near uranium deposits: Tulgheș-Grințieș, Eastern Carpathians (Romania)

Abstract

ABSTRACT The concentration and spatial distribution of three naturally occurring radionuclides, 238U, 232Th and 40K, has been determined in stream sediments from six left side tributaries of Bistricioara river (Bistriței Mountains, Eastern Carpathians, Romania). Historically, several mining works were undertaken in the area, with a view of exploring its’ potential regarding mineral resources. The aim of this study is to serve as a reference point for future environmental monitoring, in the event of resuming the mining activities in this area, which accommodates a major uranium deposit. Stream sediment samples were collected from the riverbed and the concentration of naturally occurring radionuclides was determined using gamma-ray spectrometry with a high purity germanium (HPGe) detector. The average activity concentration of 238U, 232Th and 40K was found to be 27.84, 41.08 and 511.27 Bq·kg−1. Based on radionuclides’ activity concentrations, radiological hazard parameters were estimated in order to assess any radiation risk which may be associated with the riverbed sediments. The radiological hazard parameters, such as radium equivalent activity (Raeq.), absorbed gamma dose rates in air (DR), annual gonadal dose equivalent (AGDE), representative level index (RLI), annual effective dose equivalent (AEDE), external hazard index (Hex) and internal hazard index (Hin), were all calculated and later compared with international safety limits. Generally, all radiological hazard parameters have values lower than world average excepting AGDE and RLI values that exceed the UNSCEAR thresholds.