DISTRIBUTION OF 40K IN FRESHWATER FISH TISSUES AS AN INDICATOR OF RADIOECOLOGICAL STATUS OF THE ZDVYZH RIVER

Abstract

This study presents the results of a radioecological investigation focused on assessing the anatomical distribution of the natural radionuclide potassium-40 (⁴⁰K) in tissues of freshwater fish from the Zdvyzh River (Zhytomyr Region, Ukraine) as a potential indicator of the ecological condition of aquatic ecosystems under post-Chernobyl environmental conditions. The study involved four fish species representing different trophic levels: Hypophthalmichthys molitrix (Valenciennes, 1844), Cyprinus carpio (Linnaeus, 1758), Carassius gibelio (Bloch, 1782), and Esox lucius (Linnaeus, 1758). For each species, two key anatomical compartments were examined–muscle tissue and the head with internal organs. The specific activity of ⁴⁰K was determined using gamma spectrometry with certified scintillation-based equipment (MKS-AT1315) following national metrological standards (DSTU ISO 10012:2005). The results demonstrated a pronounced anatomical specificity in ⁴⁰K accumulation: in all fish species, muscle tissue exhibited significantly higher levels of ⁴⁰K compared to internal organs. The highest value of ⁴⁰K specific activity was recorded in pike (156.00 Bq/kg in muscle), a top-level predatory species, suggesting potential biological magnification of potassium-40 along the trophic chain. In contrast, the herbivorous silver carp showed notably lower concentrations (85.80 Bq/kg), highlighting interspecies variation. Statistical analysis confirmed the robustness of the results, with standard deviation not exceeding 12% across all tissue types, indicating stable physiological patterns of radionuclide distribution and reliable measurement reproducibility. This research provides the first detailed comparative assessment of ⁴⁰K anatomical distribution in fish from this particular freshwater system. The findings offer new insights into the radioecological structure of aquatic ecosystems in the Polissya region and validate the potential of using ⁴⁰K tissue profiling as an ecological indicator. From an applied perspective, all detected values remained within established regional background levels, indicating no significant radiological impact on the ecosystem. The results may be used in developing long-term monitoring protocols and recommendations for the sustainable exploitation of aquatic bioresources in post-accident environments. Additionally, the study offers a foundational model for future integrative research on radionuclide biokinetics and ecosystem health assessment in contaminated or post-contamination scenarios.