Hydrochemical Characteristics and Water Quality Assessment of Irkutsk Reservoir (Baikal Region, Russia)

The Irkutsk Reservoir, belonging to the largest unified freshwater Baikal–Angara system, is an important source of drinking water in the region. Therefore, studies of its hydrochemical characteristics are of prime importance in deciding on the role of anthropogenic activity in water quality. The water samples were collected across the reservoir in 2007, 2012, and 2021 and then were analyzed for major ions and trace elements. The data revealed that the distribution of HCO₃⁻, SO₄²⁻, Cl⁻, Ca²⁺, Mg²⁺, Na⁺ and K⁺ is stable across the reservoir. Trace element concentrations varied from 1.13 to 15.39 µg L⁻¹ for Al, from <DL to 0.39 µg L⁻¹ for Cr, from 0.39 to 23.12 µg L⁻¹ for Mn, from 1.25 to 53.22 µg L⁻¹ for Fe, from 0.005 to 0.100 µg L⁻¹ for Co, from 0.20 to 1.98 µg L⁻¹ for Cu, from <DL to 13.40 µg L⁻¹ for Zn, from 0.25 to 0.48 µg L⁻¹ for As, from 0.004 to 0.127 µg L⁻¹ for Cd, from <DL to 0.195 µg L⁻¹ for Sn, from <DL to 0.0277 µg L⁻¹ for Cs, from <DL to 1.13 µg L⁻¹ for Pb, from <DL to 0.0202 µg L⁻¹ for Th, and from 0.27 to 0.75 µg L⁻¹ for U. The concentrations of all major ions and trace elements in water were below the drinking water standards. CF values showed considerable and high contamination of samples with Al, Mn, Fe, Co, Cu, Cd, Sn, Pb, and Th. PLI values classified the majority of water samples as water with baseline levels of pollutants, and part of the samples was classified as either polluted or highly polluted.