Geochemistry and Radioecology of Waters and Bottom Sediments of the Mzymta River, the Black Sea Coast

The geochemical composition of waters of the Mzymta River is subjected to sharp seasonal changes. In summer, the waters are enriched in 34 elements (mainly REE, Fe, Mn, Cs, Al, and Cd) relative to their average contents in river waters. REEs in the waters show steady relations MREE > HREE > LREE with a general positive trend to the mouth. In spring, they are enriched only in 14 elements. They have the poorer REE composition and less fractionated REE patterns. In summer, their contamination significantly increase relative to MPC, with growth from the upper reaches to the river mouth. A general geochemical specialization of bottom sediments is determined by 27 elements, contents of which insignificantly exceed their average contents in rocks exposed in the basin for the upper continental crust. Disagreement between the high level of water contamination in summer and a weak contamination of the bottom sediments of the river is related to the low contents of finely dispersed mineral and organic matter in the latters. It was determined that chemical elements are supplied in water from three main sources: natural, natural-technogenic, and anthropogenic-technogenic. The maximum contribution to the water contamination over the entire river extent is provided by natural sources: rocks that compose the basin. The anomalous increase of concentrations of chemical elements, including Th and Y, in the middle and lower reaches of the river is related to the natural-technogenic sources at the adjacent slopes of the valley. These are technogenic areas and talus, as well as highway and railway roads, and sometimes building embankments, which are made up of disintegrated rocks devoid of soil-vegetation layer. The anthropogenic-technogenic factors make only a limited contribution to the contamination of water and bottom sediments of the river. The radioecological state of waters and bottom sediments of the Mzymta River is safe.