Exposure of biota in the cooling pond of Ignalina NPP: hydrophytes

The radiological assessment of non-human biota is now accepted by a number of international bodies. In this connection the scientific basis to assess and evaluate biota internal and external radiation exposure is required. This paper presents the comparison of freshwater biota (hydrophyte species) exposure due to discharged anthropogenic radionuclides with that due to natural background radiation. The radionuclides from Ignalina Nuclear Power Plant (Lithuania) are discharged into cooling pond – Druksiai Lake. Submerged hydrophytes were selected as biota exposure indicators because they represent the largest biomass in this lake and have comparatively high radionuclide activity concentrations. The detailed methodology evaluation of the submerged hydrophyte dose rate is presented. The ionizing radiation exposure dose rates to submerged hydrophyte roots and above sediment parts due to the major radionuclides (54Mn, 60Co, 137Cs, 90Sr) discharged into the INPP cooling pond – Druksiai Lake were 0.044 μGy h−1 and 0.004 μGy h−1, respectively. The internal exposure dose rate due to natural background α-emitters (210Po,238U, 226Ra) was estimated to be 1.24 μGy h−1, as compared with that of anthropogenic α-emitter 240Pu – 0.04 μGy h−1, whereas the external exposure was 0.069 μGy h−1. The presented data deeper the knowledge about the concentration of radionuclides and submerged hydrophytesʹ exposure dose rates in European freshwater ecosystems.