Assessment of the water quality of Lake Baikal and its tributaries in areas affected by local pollution based on microbiological and hydrochemical data

Abstract

The water quality of Lake Baikal and its tributaries, influenced by seven different local pollution sources, was assessed in the areas of wastewater discharge from wastewater treatment plants (WWTPs) of the towns of Slyudyanka, Baikalsk, and Severobaikalsk, as well as domestic wastewater discharge from tourist resorts and Maksimikha settlement, runoff of hot springs from thermal baths in Zmeinaya Bay, Baikal seal rookeries, and the tourist center on Tonky Island of the Ushkanyi Islands archipelago in September 2022. The waters of the lake and the Rivers Pokhabikha, Maksimikha, and Tyya using microbiological and hydrochemical analysis methods are assessed as clean II class quality (GOST 17.1.3.07-82), except for the coastal water zone opposite the mouth of the Pokhabikha River, where the water is defined as moderately polluted. The unequal distribution of the values of the self-purification coefficient indicates a high abundance of microflora of allochthonous origin and a low activity of autochthonous microorganisms involved in self-purification processes in the studied areas of the lake. It was found that wastewater discharged by treatment facilities; water at the mouth and surface water of the Baikal in the estuary of the Pohabikha River, water in thermal baths of hot springs in Zmeinaya Bay do not meet the requirements of SanPiN 1.2.3685-21 for the maximum permissible amount of generalized coliform bacteria, Escherichia coli and Enterococcus. At all control stations in the pelagic zone of Lake Baikal, remote from the studied local polluted sites, water quality indicators did not exceed the safety water standards for surface water bodies in terms of microbiological and hydrochemical parameters.