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Volume XV |

Hydro-ecological trends of the Chepelarska River (Western Rhodope Mountains, Bulgaria)

Abstract: Significant anthropogenic impacts and climate change are putting the hydro-ecological conditions in river systems at risk of deterioration. It is crucial to record long-term trends for both an objective assessment during the planning process and the development of a methodological basis for further scientific investigations. This article analyzes human pressure and changes in the hydro-ecological status of the Chepelarska River (Southern Bulgaria), making recommendations for its improvement. The study relies on long-term hydrological data about registered runoff for 74 years from 1950 to 2023, information regarding hydro-morphological changes (regulated river sections and constructed hydropower plants), and dataset from monitoring of biological (phytobenthos, phytoplankton, fish fauna, macrophytes, and macrozoobenthos), physicochemical (pH, DO2, BOD5, Total N, Total P, NH4, NO3, NO2, and PO4), and specific chemical (Al, Cd, Cu, Pb, Mn, and Zn) water quality elements collected for 14 years between 2010 and 2023. The resulting information show a rising variability of runoff and a statistically significant tendency toward a flow volume decline, increasing morphological pressure from hydropower construction and aquaculture farming, and despite the overall positive hydro-ecological trend – constant deviations in some biological (macrozoobenthos), physicochemical (Total N, Total P, NH4, NO2, PO4), and specific chemical (Cd, Mn, Pb, Zn) water quality elements. The achievement of better hydro-ecological conditions requires the application of a complex of environmental, engineering, and legislative measures.

Volume XXII |

Evaluation of water contamination in a crossborder river catchment affected by mining activities (a case study between Republics of Serbia and Bulgaria)

Abstract: The current article aims to evaluate water contamination in the crossborder section of the Timok River in terms of metalloids and heavy metals. Water pollution comes due to the unregulated discharges of untreated effluents from the Bor mining area (Eastern Serbia) and surrounding ore-smelting plants, dressing and processing factories. Input data includes information concerning the values of eight chemical parameters (As, Cd, Cu, Fe, Mn, Ni, Pb, and Zn), measured at one water sampling site from 2015 until 2020. The analysis follows the Environmental Quality Standards (EQS) for priority substances and some other pollutants recommended in Directive 2013/39/EC and their equivalent criteria transposed into Ordinance H-4/2012. The Heavy Metal Pollution Indеx (HPI) to assess the suitability of water resources for various human needs is calculated. Results obtained show the content of Cd, Cu, Fe, Mn, Ni, and Zn does not fulfill the EQS. The contamination with Cd and Cu is the most severe, the highest concentrations exceeding the normatively determined standards by more than 20 times. The HPI achieves scores ranging from 200.58 (2015) up to 1163.65 (2019), indicating “High pollution” and suggesting the water resources are inappropriate for human consumption. This work complements past studies with findings for a recent period.