Regional and Global Background Values in the Assessment of Heavy Metals Pollution of Water Bodies

From the point of view of technogenic preasure on water bodies, the most dangerous pollutants are trace elements Hg, Cd, Zn, Pb, Cu, Cr, Co, Ni, Fe, Mn, As. Studies of sediments of reservoirs make it possible to identify unfavorable areas and identify sources of pollution. The degree of contamination by microelements is determined based on the excess of their content over their background values. The paper presents an assessment of contamination of bottom sediments with the above–mentioned trace elements in a number of areas of the Upper Volga - from the Upper Volga Lakes to the Ivan’kovo reservoir, based on background values in the sediments of the Upper Volga lakes. The results of studies of the contamination of bottom sediments were evaluated by igeo-classes – by the contamination of the sorbing fraction (less than 0.020 mm). A comparative analysis of the regional background values of the Upper Volga sediments with the accepted global values is given. As a result, it was found that for each large water system and for each geographical area, it is necessary to determine its own regional background values. It is necessary to update the data periodically – according to a single methodology. From the available data, it can be concluded that, despite the significant number of pollution sources, there is currently no need to talk about a dangerous load on the studied object.