Deriving reference activity concentrations in Spanish terrestrial ecosystems to protect the public and the...

This study adapts the methodology developed by the OSPAR Convention to protect the marine environment of the North-East Atlantic to Spanish terrestrial ecosystems to derive Reference Activity Concentrations (C_ref) ensuring adequate radiological protection of humans and wildlife. For each radionuclide, the activity concentration in air (C_DL), corresponding to a dose of 0.1 mSv·y^-1 to the representative person (dose-limit criterion accepted by the Spanish Regulatory Body), was calculated using the SRS-19 dispersion models. These C_DL values were used to estimate dose rates to reference organisms using the ERICA Tool. The estimated dose rates were compared with the lower bound of the ICRP Derived Consideration Reference Levels (DCRL) for each organism group. When the concentration associated with the human dose results in a biota dose rate exceeding the relevant DCRL, a correction factor was applied to derive the corresponding C_ref. These C_ref, ensure that radiological impact to humans and wildlife remains negligible at or below these concentrations, while exceedances of monitored or modelled environmental activity concentrations require a more detailed assessment. The integrated Risk Quotient (∑RQ) framework applied to derive C_ref values provides a practical, tiered screening approach aligned with international regulatory practice. A ∑RQ < 1 confirms simultaneous compliance with the 0.1 mSv·y^-1 dose constraint established by the Spanish Regulatory Body for nuclear power plants and with the ICRP ecological reference levels. These results are intended solely for screening purposes and do not replace a detailed radiological assessment when evaluating total doses in specific scenarios or when considering radionuclides not included in this approach.