Geochemical alkaline barriers determining radioecological conditions in the Sochi river valley of the Black Sea Coast of Russia

Abstract

Radioecological features of natural environments of the Sochi River valley, one of the largest rivers of the Main Caucasian Range and the Black Sea coast of Russia were studied. Alluvial soils, mosses, and river waters were the subject of investigations. Peculiarities of Th and U behavior (their contents were determined by quantitative ICP method) in conditions of existence of alkaline geochemical barriers — calcium barrier formed at the junction of neutral argillites and alkaline marl, and sodium barrier in the river mouth at the contact of river water with sea water were established. The calcium barrier results in lower Th and U concentrations in river waters and higher concentrations of radioactive elements in soils and mosses. Alkaline sodium barrier causes increase of Th and U concentration in river waters, decrease of Th and U concentration in soils and active sorption of elements by mosses. On the whole, the radioecological state of the Sochi River valley is favorable. The level of gamma-radiation exposure dose rate near the surface is lower than the natural level of this parameter for the open mountain territories of the middle belt of Russia. Bottom sediments of the river are notable for low values of specific activity of natural radionuclides 226Ra, 228Ra, 224Ra, 232Th and 40K.

Keywords

• radioecology
• soils
• river water
• plants
• thorium
• uranium