PERIODYK NAUKOWY AKADEMII POLONIJNEJ 35 (2019) nr 4 11 SOCIAL SCIENCES LEVELS OF HEAVY METALS IN SEVERAL RIVERS OF THE WESTERN BUG AND DNIESTER BASINS IN THE LVIV REGION (WESTERN UKRAINE) Halyna Antonyak Professor, PhD, DSc, Ivan Franko National University of Lviv, e-mail: halyna_antonyak@yahoo.com, orcid.org/0000-0002-1640-737X, Ukraine Marta Lesiv Post-graduate, Ivan Franko National University of Lviv, e-mail: mlesivmarta@gmail.com, orcid.org/0000-0001-9007-7383, Ukraine Natalia Panas Associate Professor, PhD, Lviv National Agrarian University, e-mail: panas_natali@ukr.net, orcid.org/0000-0003-3737-6338, Ukraine Stepan Yanyshyn Post-graduate, Lviv National Agrarian University, e-mail: kafedra_ekolog@ukr.net, https://orcid.org/0000-0002-9992-6289, Ukraine Abstract. Lviv region, one of the most urbanized and industrialized regions of Western Ukraine, faces environmental problems, including pollution of surface waters. The study was aimed to investigate the levels of heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in the waters of three tributaries of the Western Bug River (Poltva, Rata and Kamyanka), as well as in the Dniester River and its two tributaries (the Zubra and Vivnya rivers) within the Lviv region. The results show that the degree of contamination of the Western Bug tributaries with heavy metals is considerably higher at the mouths of the rivers compared to river sources. In particular, metal concentrations at the mouth of the Rata River were 1.23–3.98 times higher than at its source, while water samples at the mouth of the Kamianka River were characterized by higher levels of Fe, Mn, Zn and Cd (2, 12–6.55 times) compared with the source of the river. Concentrations of several heavy metals, especially Fe, exceeded the maximum allowable levels in the waters of the analyzed rivers. Results of the study suggest a significant anthropogenic load in the catchment areas of the analyzed rivers within the Lviv region. Keywords: heavy metals, surface waters, Lviv region, Western Bug, Dniester. DOI: http://dx.doi.org/10.23856/3501 Introduction Surface water resources can be adversely affected by virtually all types of human activity. Water quality of rivers, lakes and other reservoirs is influenced by pollution from industrial facilities, discharges from sewage treatment plants or seepage from landfills, as well as diffuse pollution from agricultural activities and deposition from the atmosphere due to