ИСТИНА

Moscow city is the largest metropolitan area in Europe. Due to inefficient infrastructure of water supply and treatment systems, it pose a huge impact on the downstream reaches of Moskva-Oka-Volga river system. Rather limited availability of sediment and water quality information impedes detection of specific pollution sources and control over them: low spatial coverage, scarcity and poor accessibility of its environmental monitoring data hinders comprehensive research. Since 2019, integrated study on the Moskva River and its tributaries was conducted, complete with determination of the with a focus on sediment and water quality regime and pollutants spreading. The study is based on the network of autonomous monitoring station which capture water discharges and suspended load on regular basis (each 30 minutes) and are used as a proxy of urban (artificial) regime of the area. Water and sediment sampling at 38 locations on the main river and at 17 of its tributaries is done on monthly basis. The ADCP discharge measurements are linked to water sampling along depth profiles to assess metals variability with depth in suspended and dissolved modes. For each sample analyses were made for trace metals (68 elements), nutrients and dissolved and suspended organic carbon matter content both in dissolved and particulate (suspended and bed loads) forms. These samples can determine annual and seasonal distribution to 70% of the chemical elements and substances. Additionally RUSLE-based erosion model was developed for case study catchments to assess impact of catchment processes on sediment and pollutants spreading over metropolitan area. The results revealed a formation of specific anthropogenic sediment and chemical regime over river system which is characterized by frequent extreme loads of organic sediments. Manifold increase in sediment transport and nutrients as the river crosses the Moscow metropolitan area, which can be attributed to both direct discharge of poorly treated sewage and nonpoint urban pollution. Within the city borders, organic matter concentration increased by a factor of 1.5 due to an inflow from the Volga River via the Moskva-Volga Canal, whereas the release of treated sewage from the Moscow City wastewater treatment facilities did not have a significant effect. Below the city, the nutrients content grew increased again by a factor of 1.5 due to the inflow of urban and industrial wastewater and polluted tributaries. Even at the Moskva’s lower reaches, where the anthropogenic pressure on the river and its tributaries is less pronounced, the inorganic nitrogen and phosphorus content remains consistently high and exceeds the environmental guidelines by up to almost 10 times. This indicates increased vulnerability of the Moskva River ecosystem during periods of low flow, which can be a major factor of eutrophication in the entire Moskva-Oka-Volga system. Comparison of our data with some archive records shows no significant improve in the nutrient pollution of the river since the 1990s, which raises further concern about the effectiveness of water quality management in Moscow urban region.