Assessment of background dose rate on non-human biota in a Mediterranean terrestrial ecosystem.

Abstract

The assessment of radiological impact to the environment is usually carried out by the dose rate estimation to hypothetical entities named Reference Animals and Plants (RAPs). There are many codes to carry out this assessment, which requires the definition of a scenario and using site-specific transfer parameters when possible. Transfer parameters present a geographical bias, as they are mostly derived from temperate and arctic climate datasets, but there is a scarcity of data for Mediterranean climates. In this study, a terrestrial Mediterranean scenario was defined using the distribution of activity concentrations of anthropogenic (⁹⁰Sr, ¹³⁷Cs) and naturally occurring radionuclides (⁴⁰ K, ²¹⁰Pb, ²¹⁰Po, ^226,228Ra, ^235,238U, ²³²Th) in Cáceres province (Spain). Site-specific transfer factors, CR_wo-media, defined as the ratio between the concentration in the whole organism and the medium (soil in this case) were considered. Dose rate assessments for terrestrial RAPs were carried out using Tier 3 in ERICA Tool, ranging 0.23-3.73 µGy/h which is below the screening level of 10 µGy/h. Therefore, no harmful effects are expected to occur. Internal dose rate predominates over external one because the main contributors are naturally occurring radionuclides (in most cases ⁴⁰ K, ^226,228Ra, ²¹⁰Pb, ²¹⁰Po), which are mostly α-emitting radionuclides. These results can be used for the evaluation of other radiological and nuclear installations in Mediterranean climates, as they set the background dose rate.