DYNAMICS OF WATER POLLUTION INDICATORS OF THE LUGA RIVER
According to long-term monitoring data (1999-2019), the results of a comprehensive assessment of the degree of pollution of the Luga River based on the analysis of hydrochemical indicators of water quality and the specific combinatorial index of water pollution are presented. The dynamics of water pollution in ecological and water management areas and the trend of spatio-temporal changes in the water quality in the river are considered. The linear trends of changes in the concentrations of pollutants for 1999-2019, indicating changes in concentrations during the period under review, are analyzed. As a result of the study, increased concentrations of COD, iron compounds, copper were revealed, according to which characteristic pollution is observed in all sections of the river. In some years, manganese and nitrite nitrogen made a significant contribution to the overall degree of water pollution. The maximum values of the average annual concentrations of COD were 4.2 MPC (Luga, site N 4), and total iron was 8.5 MPC (Luga, site N1), copper 14 MPC (Kingisepp, site N1). The average annual concentrations of nitrite nitrogen during the period under review reached 11.5 MPC (Luga, site N 1), and manganese - 16 MPC (Luga, site N 1). The value of the specific combinatorial index of water pollution showed that the ecological state of the watercourse in recent years has been stable throughout the entire length of the river, the quality of the water belongs to class 3a “polluted”. It is shown that along the length of the river from the upper to lower reaches, the concentrations of suspended substances in the water decrease, and the concentrations of iron compounds increase. In the long-term dynamics, all sections of the river are characterized by a tendency to decrease the concentrations of petroleum products and lead in the water.