The results of the assessment of the current state of the Kizhi skerries of Lake Onego by the water chemical parameters compering to the background area of the open central part of Lake Onego were presented. The following parameters were considered: ionic composition, nutrients, organic matter, gas composition (CO2, O2), Fe, Mn, pollutants (heavy metals, oils, synthetic surface-active substance). It was found that the water of the Kizhi skerries area is weakly mineralized, mesotrophic with a low content of organic substances. A systematic excess of the maximum permissible concentration for oils (1.2–4.0 times), as well as for Fe (1.1–3.6 times) and Cu (1.1–5.8 times) was fixed. The first one was caused by intensive navigation in this part of the lake, while the second and third ones – by regional water characteristics of the humid zone, and not by anthropogenic influence. Currently, water in this part of the lake is of good quality. Using archival data, an assessment of water chemical composition changes of the Kizhi skerries for the last three decades has been conducted. The ionic composition was changed in the area of the Kizhi skerries and the central part of the lake, which was confirmed by the Pearson’s test. The concentration of all nitrogen forms and the values of Nmin/TP ratio were decreased, but at the same time, the color values and concentrations of oils and CO2 were increased. Apparently, intensive navigation due to the growing tourist flow has led to increasing of oil concentrations in the area of the Kizhi skerries. Other changes of chemical parameters were not caused by local anthropogenic influence and require further study. They may probably be associated with global processes, such as reducing industrial emissions of contaminants into the atmosphere or climate change.
Mariya Zobkova (Mon,) studied this question.