Natural radionuclides in bottom sediments of the saline lakes. What factors determine their concentration

Concentrations of ²²⁶Ra, ⁴⁰K, ²¹⁰Pb, ²³⁴Th, ²³⁸U, ²³²Th, and ²¹⁰Po were determined in bottom sediments of 11 Crimean saline lakes. From lake to lake, concentration of all radioisotopes and their total amount varied. The greatest variability was noted for ²²⁶Ra (CV = 1.268), and the smallest for total sum of radionuclides (CV = 0.336). In all lakes, the concentration of studied radionuclides did not exceed the maximum concentrations found in bottom sediments of water bodies in different regions excepting Lake Sasyk-Sivash where ²²⁶Ra concentration was slightly higher than previously found the upper limit. There are the inter-lake differences and temporal changes in radionuclide concentrations in the bottom sediments. Salinity is not main determinant of radioisotope concentrations in the lake bottom sediments, but may modify their concentrations in some ranges. The behavior of ²¹⁰Pb and ²¹⁰Po under anoxic conditions differs from observed in oxic. Authors conclude that there is no any single factor itself controlling concentrations of radionuclides in the upper layer of bottom sediments in the saline lakes; there is multicausal determination. Only coupling of many factors (physical, chemical, and geochemical properties of radioisotopes, and geological, climatic, and biological) determines radionuclide distribution patterns.