Radionuclide composition of natural waters of the Crimean Peninsula

Abstract

This study presents new data on uranium and thorium concentrations in various hydrogeological structures of Crimea. Relevance of the study: under conditions of climate change and increasing anthropogenic pressure, assessment of the state of water resources is becoming increasingly important, particularly with regard to the water resources of the Crimean Peninsula. The region has considerable tourism and recreational potential, which highlights the importance of preserving and ensuring the rational use of natural waters utilized for drinking purposes, health-resort treatment, and agriculture. Objective: to summarize the authors’ data on the distribution of uranium and thorium in different types of natural waters of the Crimean Peninsula. Materials and methods: rapidly changing physicochemical parameters of groundwater samples were measured in situ at the sampling sites. Laboratory analyses of the ionic composition and trace-element content were performed using titrimetry, ion chromatography, inductively coupled plasma mass spectrometry, and other analytical methods at the Problem Research Laboratory of Hydrogeochemistry, School of Earth Sciences and Engineering, National Research Tomsk Polytechnic University. Results: the waters are predominantly of the HCO₃–Ca type, with total dissolved solids ranging from 40 to 330,519 mg/dm³. Neutral and alkaline waters predominate, with pH values ranging from 6 to 10 (mean 8). Redox conditions vary from reducing, with Eh = −183 mV, to oxidizing, with Eh = +507 mV. Dissolved oxygen concentrations reach 27.7 mg/dm³, with a mean value of 6.6 mg/dm³. Radionuclide concentrations in the natural waters of the Crimean Peninsula vary within the following ranges:²³⁸U from 3.10 ×10⁻⁷to 0.12 mg/dm³and ²³²Th from 1.92 ×10⁻⁷to 1.20 ×10⁻³mg/dm³. The ²³²Th/²³⁸U ratio ranges from 5.26 × 10⁻⁵ to 9.51.