Surface sediments of Karelian lakes: their formation peculiarities and chemical composition

Abstract

The territory of Karelia is a unique geographical region, where currently more than 62,000 lakes function in a humid climate, being at different stages of the evolution of their ecosystems. In this study, we analyzed the data on the chemical composition of the bottom sediments of Karelian lakes collected during the period 1965-2020. The patterns of the formation of the chemical composition of the bottom sediments of lakes are discussed. It is shown that in the lakes of the southeastern part of the Fennoscandian Crystal Shield, the bottom sediments of a mixed type are currently being formed: iron-humus-silicon, iron-silicon-humus, or humus-iron-silicon. There are small lakes where the bottom sediments accumulate either silicon (diatomite), iron (lake ore), or organic matter.