Biogeochemical Assessment of Toxicity and Radioecological Danger of the Transboundary Kara-Balta River

Abstract—The paper presents the results of researches of the concentration of chemical elements and natural radionuclide in the environmental objects of the Kara-Balta transboundary river basin (adjacent territories of Kyrgyzstan and Kazakhstan). The level of contamination of floodplain soils and bottom sediments of the Kara-Balta River with such chemical elements as U, Sb, As, Th, Pb, Sc, Co, Cu, Mo, Zn, V, Sr, Ba, Cs was established. Based on the calculated indicators of the contamination factor (CF), enrichment factor (EF), and index of geoaccumulation (Igeo), it was found that Sb, As and Br make the largest contribution to soil and bottom sediment pollution in the Kara-Balta water basin. At three checkpoints, an increased concentrations of U, B, Li, Sr, Mo were found in the water samples of the region’s reservoirs, which is related to the influence of the tailings of the Kara-Balta mining plant. The elevated concentrations of As, B, Ba, Co, Mn, Sb, V, and Zn were also established around the mouth of the Kara-Balta River, which flows into the Tasotkel reservoir (Kazakhstan). The results of the research can be explained by the fact that a significant part of the Kara-Balta transboundary river basin is located in the zone of a uranium natural–technogenic province.