Investigation of the Phosphate Load on the Volga River Basin in the Area of Yaroslavl City

Excessive runoff of biogenic elements into natural watercourses as a result of anthropogenic activities leads to ecological balance violation in aquatic ecosystems, resulting in negative effect on aquatic organism vital activities and worsening the natural water quality due to activity of phytoplankton, especially blue-green algae. Nowadays eutrophication is one of the most serious environmental problems, especially in large rivers such as the Volga River.Since the Volga River flows through many agricultural areas and large cities, the influence of diffuse runoff from horticultural associations, as well as industrial and domestic runoff, on the river is significant. At the same time, the reservoir system built on the river also makes a significant contribution to the stagnation of water masses, which contributes to eutrophication.Currently, phosphates are recognized to be one of the main elements determining the eutrophication degree. Phosphorus for aquatic plants is the dominant component in mineral nutrition, therefore, significant deviations from the established standards of permissible concentrations lead to disastrous consequences for aquatic ecosystems.The purpose of this study was to monitor phosphate ion content in the Volga River and its tributaries in Yaroslavl city for a year and to find the dependence of the riverbed quantitative characteristics on dissolved phosphates content in them using the example of the Kotorosl River.The objects of the study were the Volga, Kotorosl, Tolgobolka, Nora, Dunayka, Uroch rivers, located in four districts of Yaroslavl city.The assessment of the dependence of the river morphometric parameters on the predisposition to phosphate accumulation was carried out on the Kotorosl River, as among of all the rivers represented in the Yaroslavl Region, it has a sufficiently large depth, a winding channel and a weak current, which makes it possible to assess the parameters of the channel at the inflow place to the Volga River.Based on the annual observation results, graphs of seasonal variability of phosphate concentrations in rivers by month of the year were constructed. The presented fluctuations in concentrations are of a wave nature.Correlation and regression analysis has been used to evaluate the relationship between the indicators of the Kotorosl riverbed and the phosphate content in the water column. According to the results of the work, the relationship between water section area and phosphate concentration in the river was revealed.The paper presents graphs of seasonal variability of phosphate ion concentrations in the Volga, Kotorosl, Dunayka, Tolgobolka, Nora, and Uroch rivers in Yaroslavl city. The morphometric parameters of the Kotorosl River at the place of its inflow to the Volga River were measured, and a correlation and regression analysis of the dependence of quantitative indicators of the riverbed and phosphate ions content in the water was carried out.