Microelement composition of bottom sediments of water bodies in urban conditions

Under the urbanization conditions there is an increase in the technogenic impact on water bodies, which is most clearly manifested in water bodies located on the territory of residential development. The value of reservoirs in cities lies in the possibility of using them as recreation places. Pollutants enter such water bodies with organized wastewater from industrial production and urban storm water. However, in a significant part of urban areas, the system of surface runoff is not organized. In this case, rain and snowmelt runoff enters water bodies disorderly (diffusely). Pollutants decrease the quality of natural waters, disrupt the functioning of aquatic ecosystems and reduce the self-purification ability. As a result, there is an intensification of the processes of eutrophication of water bodies, swamping and disturbance of local biocenoses. Pollutants entering surface water bodies accumulate in bottom sediments and create secondary pollution of rivers. Bottom sediments of reservoirs are accumulators of heavy metals. Due to sorption processes, water is purified from heavy metals, but under certain conditions the desorption of metals and their transition, when in the dissolved state, into the water column are observed, thus, secondary pollution occurs. In this study, the influence of the state of the catchment area on water quality in a reservoir, the content of pollutants in water and bottom sediments have been investigated. It is shown that the quality of water and bottom sediments in terms of content of chemical elements is determined by the type of anthropogenic load. For the river sections, not subject to technogenic load, the main influence is the state of the atmosphere and catchment area, from which the diffuse flow of rain and melt water occurs. The composition of heavy metals in water and bottom sediments mainly characterizes the natural geochemical background. The discharge of industrial wastewater leads to an increase of elements of anthropogenic origin in the composition of water and bottom sediments.