Вплив іонної сили розчину на формування підвищеної міграції 90Sr в підземних водах промислового майданчика Чорнобильської АЕС

Abstract

Thermodynamic modeling of 90Sr migration was performed based on data from monitoring studies on well 4-G, which, before its liquidation in 2008, was located on the industrial site of the Chornobyl nuclear power plant. The study of the 90Sr migration forms was carried out using a set of software tools “Geochemist’s Workbench Community Edition”. In order to confirm and understand the migration processes, modeling of the spread of various complex 90Sr compounds such as SrCO3, SrHCO3, SrSO4, SrOH+ and SrNO3 + with groundwater was carried out. With the help of SpecE8, the calculation of various forms of 90Sr was performed, and the ionic strength of the groundwater solution (ISS) was also calculated. In the range of pH 9.5–12.4, there is an increase in the Sr2+ concentration in groundwater by 200–500 times to 550 Bq/l. In the same pH interval, according to thermodynamic modeling, an increase in the concentration of strontium in the form of SrOH+ and a decrease in the form of Sr2+ is observed in groundwater. At the same time, the dominance of strontium concentrations in the form of SrOH+ over Sr2+ does not occur. The reason for the sharp increase in the volume activities of 90Sr in strongly alkaline groundwater was the increase in the ISS > 5 mmol/l. An increase in the ISS of strongly alkaline groundwater leads to a decrease in the sorption properties of soils, and to the remobilization of adsorbed 90Sr back to groundwater through cation exchange. Probably, in the pH range of 9.5–12.4 and the ISS > 5 mmol/l, there is a change in the surface charge of soil particles, usually from negative to positive, in which cations cannot be sorbed, but, on the contrary, must to remobilize from the soil surface to groundwater. At the same time, pH = 9.5 is probably the point of zero charge (pzc). To assess the possibility of a relationship between the concentrations of 90Sr and ISS, a correlation analysis using the geochemical statistics method was carried out. At the same time, the correlation coefficient K = 0.87, which proves the existence of a close relationship.