Interaction between water ecosystems and the catchment surface by the example of the Ob'-Irtysh catchment area

The interaction of water basins and watercourses with the catchment surface in the Ob'-Irtysh catchment area is considered. The results of long-term observation of water, suspended matter, and bottom sediments in different segments of the watercourse are summarized and compared. The interaction of major and minor tributaries, natural and artificial water reservoirs with the catchment area is discussed in the context of industrial discharge of heavy metals. The areal distribution of metals along the Ob' River is heterogeneous. The chemical composition of water in the upper reaches of Ob' is determined by mercury and complex ore shows; in the middle and lower reaches, by catchments, of major tributaries: Tom, Chulym, and, particularly, Irtysh. The Novosibirsk Reservoir purifies the water from coarse suspensions. Wetlands of the catchment enrich the main watercourse in metals and organic matter. Anthropogenic pollution from large cities (Novosibirsk, Tomsk, Surgut, and Nizhnevartovsk) additionally contaminate the watercourse. With abundance of organic matter, heavy metals are accumulated in bottom sediments and, as a consequence, in tissues of predatory fish. The results of long-term studies indicate that oil products and phenols are the main hazard for the middle and lower Ob' River, especially at elevated water temperatures.