What question did this study set out to answer?

This study aims to assess the impact of the Ulba River on the water quality of the Irtysh River due to industrial pollution.

June 8, 2026Open Access

Tributary-induced heavy metal pollution and water quality dynamics in river systems

GMG. MamyrbekovaKazakh National Agrarian Research University YKY. KalybekovaManash Kozybayev North Kazakhstan University YYY. YeremeyevaD. Serikbayev East Kazakhstan State Technical University

Key Points

This study aims to assess the impact of the Ulba River on the water quality of the Irtysh River due to industrial pollution.
Seasonal water sampling was conducted at four monitoring sites along the Ulba and Irtysh Rivers.
Analysis included heavy metals, nutrients, and biological assessment using macrozoobenthos.
Data were collected before and after the confluence of the rivers.
Mineralization in the Ulba River ranged from 75 to 205 mg/L, and in the Irtysh River from 136 to 211 mg/L.
Increased heavy metal concentrations were detected near the Ulba Bridge and downstream, with manganese at 0.037 mg/L and zinc at 0.045 mg/L.
Heavy metal levels in sediments exceeded permissible limits, notably with cadmium at 6-9 mg/kg and zinc at 511 mg/kg.

Abstract

BACKGROUND AND OBJECTIVES: Rivers flowing through large industrial cities experience significant anthropogenic pressure that can alter their ecological condition. Tributaries receiving industrial and municipal wastewater often act as carriers of pollutants and influence the water quality of larger rivers after their confluence. The objectives of this study were to evaluate the influence of the Ulba River on the ecological state of the Irtysh River within the city of Ust-Kamenogorsk using hydrochemical parameters, biological indicators, and the composition of bottom sediments.METHODS: Seasonal water sampling was conducted during 2025 at 4 monitoring sites located along the Ulba River and the Irtysh River before and after their confluence. The investigation included analysis of salt composition, major anions, heavy metals, nutrients, and indicators of organic pollution. Biological assessment of water quality was performed using biotesting with aquatic organisms and bioindication based on macrozoobenthos communities. FINDINGS: The waters of both rivers were characterized as low-mineralized hydrocarbonate waters dominated by calcium. Mineralization in the Ulba River varied from 75 milligrams per liter to 205 milligrams per liter, while in the Irtysh River it ranged from 136 milligrams per liter to 211 milligrams per liter. The hydrogen index ranged from 7.2 to 8.3, indicating weakly alkaline conditions. Increased concentrations of heavy metals were recorded near the Ulba Bridge and downstream from the confluence. Manganese in the Ulba River reached 0.037 milligrams per liter, while zinc reached 0.045 milligrams per liter. After the confluence, manganese in the Irtysh River reached 0.014 milligrams per liter and copper up to 0.0046 milligrams per liter. Nitrate concentrations varied from 0.33 milligrams per liter to 3.59 milligrams per liter. Bottom sediments showed significant accumulation of metals, where cadmium ranged from 6 milligrams per kilogram to 9 milligrams per kilogram and zinc reached 511 milligrams per kilogram, exceeding permissible levels by about 5 times. CONCLUSION: The results demonstrate that the Ulba River acts as a source of transit pollution affecting the Irtysh River within the urban territory. Industrial activity within the Ulba basin drives downstream transport of manganese, zinc, and copper and their accumulation in water and bottom sediments, with post-confluence increases in concentrations and sediment enrichment exceeding Kazakhstani permissible levels.

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