Spatiotemporal Variation Evaluation of Biochemical Oxygen Demand (Bod) in Dnipro River

Abstract

The study focused on assessing biochemical oxygen demand (BOD) as an indicator of pollution dynamics in the Dnipro River. It was found that the ecological and hydrochemical conditions of the Kremenchuk, Kamyanske, and Dnipro reservoirs and the water quality of drinking water intakes within them had deteriorated due to increasing BOD. In terms of temporal analysis, 2019 marked the year of the most significant changes in BOD concentrations, resulting in a reversal of long-term trends in biochemical oxygen demand distribution from decreasing to increasing for the territory from Vyshhorod to Horishni Plavni. The most significant increase in BOD was observed at the Cherkasy water intake, likely due to increased ammonium input into the water. The area between Vlasivka and Horishni Plavni, situated at the boundary of the low-flow Kremenchuk reservoir and the flowing Kamyanske reservoir, exhibited the highest BOD concentrations among the entire study area, exceeding the maximum permissible concentration in approximately 80% of cases. BOD levels in the water intakes of Kamyanske and Dnipro showed a steady rise from 2015 to 2023, with peak values in August and September. Positive correlations with phosphates and ammonium, and a negative correlation with dissolved oxygen, suggested anthropogenic influences. These findings indicate the accumulation of biogenic elements and increased oxygen demand, particularly during eutrophication events.