АУТОР / AUTHOR(S): Zvezdelina Marcheva 
, Simeon Matev , Kalina Radeva , Ilia Tamburadzhiev
DOI: 10.46793/CSGE5.15ZM
САЖЕТАК / ABSTRACT:
River water quality is one of the current topics of theoretical and applied hydrology, ecological and urban hydrology, and one of the main problems in the planning and management of water resources. The chemical, physical, and biological characteristics of surface water, based on standards for its use, are related to human health, food production, wetland ecosystems, economic development, and social growth in our communities. The question of the quality of surface water in urban areas, where a combination of point and diffuse sources of pollution is registered, is particularly acute. Both organic pollution and heavy metal contamination remain unsolved problems facing the water resources management sector in Bulgaria. Thus, the objective of the current work is to analyse the quality of surface water in urbanized territories by examining the current hydro-ecological condition of river Vladayska through the application of the CCME Water Quality Index and Principal Component Analysis (PCA). The water quality index of the Vladayska River at two points (before and after the city of Sofia) has been calculated based on monthly measurements of 15 physicochemical parameters for the period 2010–2021. The obtained results establish a strong anthropogenic pressure on the river waters and deteriorated water quality, after Sofia city, regardless of the presence of a water treatment facility. The results show that the main indicators affecting the water quality are the increased concentrations of phosphorus and nitrogen compounds. The main source of phosphorus is most often domestic and industrial wastewater, while the source of nitrogen is pollution from leachate from septic systems and urban runoff. Seasonal differences in pollutant concentration were also found depending on hydrological conditions and changes in the intensity of anthropopressure. The results also indicate that fluctuations in the concentrations of dissolved chemical substances in river waters depend on several hydroclimatic factors. Studying these relationships would provide a better understanding of the dynamics of pollutants and the conditions under which the concentrations of specific dissolved substances are expected to exceed the permissible norms.
КЉУЧНЕ РЕЧИ / KEYWORDS:
river pollution; urban territories; water quality assessment; Principal Component Analysis
ПРОЈЕКАТ / ACKNOWLEDGEMENTS:
The work is specifically financed under the state budget of Sofia University for scientific research for 2024 (Agreement № 80-10-54/ 9.4.2024).