Determining Water Resource Formation at the “Delegen” Nuclear Test Site Using Stable Isotope Analysis

Despite the closure of the Semipalatinsk nuclear test site (STS) more than 30 years ago, water continues to transport radioactive contamination beyond the boundaries of the “Degelen” test site. Therefore, assessing the formation of water resources at this test site is highly relevant, particularly in terms of forecasting the development of radioactive contamination at the STS. In this case, isotope hydrology is the most promising method for understanding these processes. The aquatic environment at the “Degelen” test site consists of radioactively contaminated tunnel water, streams, and groundwater. This paper presents the research results regarding the determination of stable isotopes of hydrogen and oxygen for the aquatic environment of the “Degelen” test site. 3H concentrations and the chemical composition of water at the site were also determined. Analysis of the water’s isotopic composition (δ2H and δ18O) showed that the tunnel and stream water are formed by precipitation (snowmelt and rain). In summer, when precipitation is low, atmospheric condensation contributes significantly to recharge at the “Degelen” test site. The high radionuclide content of tunnel water leads to the contamination of stream water, and, to a lesser extent, groundwater. The 3H content of tunnel water can reach 260 kBq/L, and that of stream water can reach 58 kBq/L, both of which exceed the established standards in the Republic of Kazakhstan.