Biogenic pollution of the Unava River waterbody

Biogenic pollution of Ukraine’s waterbodies is a systemic issue requiring continuous monitoring due to its impact on water quality and its role in driving anthropogenic eutrophication. This study aimed to assess the Unava River waterbody to determine the level of biogenic pollution and identify the predominant contamination type (nitrogen- or phosphorus-based). The findings indicate that the concentration of biogenic substances in the Unava River affects water quality, depending on its intended use and the functioning of the aquatic biota (aquatic ecosystem). Specifically, nitrite nitrogen concentrations (0.006-0.306 mgN/dm3 in 2022; 0.006-0.051 mgN/dm3 in 2024) are critical for the aquatic ecosystem. Ammonium nitrogen levels impact recreational and domestic uses (1.21-1.83 mgNH4+/dm3 in 2022; 1.16-5.88 mgNH4+/dm3 in 2024) as well as drinking water supply and the aquatic ecosystem as a whole (0.814-6.84 mgN/dm3 in 2022; 0.364‑4.56 mgN/dm3 in 2024). Phosphorus concentrations also influence the aquatic ecosystem (0.062-0.196 mgP/dm3 in 2022; 0.333-0.597 mgP/dm3 in 2024). Calculations of the degree of correlation between the variables revealed a negative (inverse) correlation between air temperature and phosphate levels (r = -0.07), nitrate nitrogen (r = -0.69), and nitrite nitrogen (r = -0.10). Conversely, a positive correlation was observed between water temperature and mineral nitrogen (rNH4+ = 0.38; rNO3– = 0.79; rNO2– = 0.46) as well as phosphorus (rPO43– = 0.52). Calculations based on the Redfield Ratio (RR) demonstrated that in 2022 (RR = 29.42-108.64), mineral phosphorus ions were the limiting biogenic substance, while mineral nitrogen ions were in excess, leading to predominant nitrogen pollution, potentially promoting the growth of green algae. In 2024 (RR = 6.32-18.71), mineral nitrogen ions became the limiting factor, whereas phosphorus ions were in excess under these conditions, resulting in predominant phosphorus pollution, which could facilitate the proliferation of cyanobacteria