ФОРМИРОВАНИЕ ИЗМЕНЧИВОСТИ КАЧЕСТВА СТОКА В ВЕРХОВЬЯХ РЕКИ ЛУГИ В МЕЖГОДОВОМ И КРАТКОСРОЧНОМ МАСШТАБАХ ВРЕМЕНИ. ЧАСТЬ 2. ГЕОХИМИЧЕСКИЕ ФОНОВЫЕ КОНЦЕНТРАЦИИ И ВКЛАД КРАТКОСРОЧНЫХ АНОМАЛИЙ В ЗАГРЯЗНЁННОСТЬ ВОДЫ

The objective of this work was a modern assessment at geochemical background concentrations of the twenty chemical components and the contribution of their short-term anomalies to water pollution in the Luga River section at Tolmachevo Urban Village from 2000 to 2017. For the calculations, the data of hydrochemical observations of the North-West Department of Hydrometeorology and Environmental Monitoring and the methodology developed at FSBI «Caspian Marine Research Center» were used. It has been shown that the values of the long-term geochemical background are higher for components such as COD, Fe_total, Mn²⁺ and Cu²⁺ and lower the maximum permissible concentrations for fisheries use for saturation of water with oxygen. The long-term formation of the geochemical background in this part of the river basin is based on regional features: the flow of the river and its main tributary, the Oredej River, through bogs, the influence of the river’s recharge with groundwater and the high degree of development of the territory. The contribution of short-term anomalies to water pollution at all times of the year for Cu²⁺, NH₄⁺, NO₂^–, Cd²⁺ and petroleum products was high. The work showed that the methodology, developed at the «Caspian Marine Research Center», is informative and can be used for assessing the state of a water body at a certain time. It can be used to estimate the pollution of the watercourse, both by the background geochemical concentrations of the components and by the contribution of short-term anomalies to the water pollution by each chemical component.