Distribution of Metals in the Coastal Zone of Lake Onega Depending on the Shore Type

This article presents the results of a study performed in the coastal zone of Lake Onega and is devoted to the effect of coastal (abrasion in particular) processes and inflowing rivers on the quality of surface lake waters. We took 47 water samples from the surface and bottom horizons, 26 samples of bottom sediments, and 16 samples of shore-forming sediments to further determine metal concentrations in the east of the lake in the area of abrasive (the Andoma Mountain test site) and delta (Shal'skoe Onego test site) coasts in October 2019. The content of the following metals was analyzed: iron (total), manganese, aluminum, zinc, copper, nickel, chromium, lead, cobalt, and cadmium. Special attention was focused on determining dissolved forms of metals in the water and mobile forms in coastal and bottom sediments. The results showed that the concentrations of metals in the natural environment of the lake in general reflected the hydrochemical regularities typical for this area, with Mn, Fe, Cu, Pb, and Al exceeding the maximal permissible concentration up to 20 times. The collected array of geochemical data enabled us to perform a correlation analysis of the effect of coastal processes on the quality of near-shore waters of Lake Onega with respect to the metal content. The results showed different types of relationships between the content of metals in bottom sediments and water (from very weak to strong), which were statistically insignificant. There is a close correlation between the Al, Cu, and Pb contents in bottom sediments and in water in the area of Mount Andoma test site.