The Relationship between the Oxidation-Reduction State and Toxicity of the Aquatic Environment of the Dubna River

Abstract Data on the integrated characteristics of the Dubna River water near the village of Yurkino (9 km upstream of the inflow into the Volga River) were used to show a relationship between the redox state and the toxicity of the aquatic environment. Using the method of titrating water samples with hydrogen peroxide additives, the dynamics of changes in the concentration of reducing equivalents were determined, and the spectral characteristics of the Dubna River water were studied in the period from 2020 to 2021. The concentrations of nutrients and hydrogen peroxide, as well as water pH and TDS were determined by hydrochemical analyses. At the same time, the toxicity of water samples was determined by bioassay method using a culture of infusoria Tetrahymena pyriphormis (Tetrahymena p.). The toxicity of natural water in the Dubna River was found to depend on the concentration of reducing substances, the maximum concentration of which at the beginning of the summer period was 2.5 × 10–6 M, against a background of increasing water temperature and nutrient content. Based on the results of titration of water samples with hydrogen peroxide, the dependences of the ratio of the slopes of the titration line of the control to the Dubna River water samples were obtained; their ratios ranged from 1 to 1.72.