Assessment of regional background values of bottom deposits at water bodies as their monitoring basis

Microelements Hg, Cd, Zn, Pb, Cu, Cr, Co, Ni, Fe, Mn, As are the most hazardous contaminants for water bodies. The study of bottom deposits in water reservoirs permits the authors us to reveal the endangered sites and determine the contamination sources. The estimation of the bottom sediment contamination by the above-listed microelements is given for a number of the Upper Volga regions, from the Upper Volga lakes to the Ivan’kovskoe water reservoir on the basis of comparing them with the background values for the deposits in the Upper Volga lakes. The results of bottom deposit contamination study have been assessed according to igeo-classes, i. e., the sorbing fraction (<0.020 mm) contamination. The comparative analysis of the background microelement values is performed for the Upper Volga water bodies and the values adopted in Europe. The changes of these background values for the latest 20 years are assessed. As a result, it has been found out that for each major water system and for each geographical region, it is necessary to determine the regional background values of their own and to update data recurrently according to a common procedure. The results obtained permit the authors to conclude that despite numerous contamination sources, the technogenic load at the studied objects cannot be considered hazardous.