HYDROCHEMICAL ASSESSMENT OF THE WATER OF THE OKKEVIL RIVER

Okkervil is one of the small rivers of St. Petersburg, which, like many other small rivers on the territory of cities, is subject to diverse anthropogenic pressure, which worsens the quality of its waters. Thus, the water of the Okkervil River may not be of adequate quality for recreational and other uses. The main objective of this work is to determine the chemical composition of the waters of the river and to establish its suitability for various types of water use. Sampling was carried out during the open water period at three points with different levels of anthropogenic load: outside the city, near the village of Novosergievka; at the entrance to the city; and in the residential area near the metro station. At each point, the main hydrochemical indicators were determined: the concentrations of iron, copper, ammonium ions, phosphates, nitrates and nitrites, heavy metals, as well as the concentration of dissolved oxygen and BOD5. At all points of sampling during the period of research in water, the normative indicators for the content of nitrites, phosphates, iron and copper were exceeded. The highest level of water pollution was noted at a point located in a residential area. The water here corresponds to the V class of quality (dirty). In two other sections, the water of the river corresponded to III-IV quality classes (moderately polluted - polluted). The deterioration of the water quality of the Okkervil River is caused by an increase in the anthropogenic load on the river in the direction from the source to the mouth, which makes the sections of the river within the city unsuitable for various types of water use.