INTEGRATED HYDROCHEMICAL AND BIOCHEMICAL EVALUATION OF ENVIRONMENTAL POLLUTION IN LAKE BALKHASH

Abstract

Lake Balkhash is one of the largest inland water bodies in Central Asia. The regional water supply plays an important role in fisheries and biodiversity conservation. In recent decades, the lake has been subjected to intense anthropogenic impact due to industrial activities, agricultural runoff, and hydrological changes. This has led to an increase in pollution by pollutants. This study presents a comprehensive assessment of heavy metal contamination in surface waters, bottom sediments, and commercial fish species in the northern part of Lake Balkhash (Karaganda region), combining chemical analysis with biochemical biomarkers of oxidative stress from fish liver. Surface water and sediment samples were collected in the Torangalyk Bay near the Balkhash mining and metallurgical complex and in the Bertys Bay near the city of Balkhash. The results revealed significant excess of permissible concentrations of Cu, Co, Pb, Ni, Cr and Zn in surface waters, with the highest levels recorded near the Balkhash mining and metallurgical complex and Bertys Bay. At all study sites, the concentration of heavy metals in bottom sediments exceeded the permissible limits, indicating long-term accumulation. Elevated levels of Cu, Co, Pb and Ni were found in fish tissue, especially in the gills and liver. Biochemical analysis revealed increased lipid peroxidation and decreased activity of antioxidant enzymes in fish taken from contaminated areas, indicating severe oxidative stress. The results of the research confirm that industrial pollution poses a significant threat to the ecological health of Lake Balkhash and its ichthyofauna.

Key words: Lake Balkhash, heavy metals, fish, oxidative stress, malondialdehyde, superoxide dismutase, catalase.