Geochemical barriers in oligotrophic peat bog (Western Siberia)

Peat bogs play an important role in the functioning of the biogeochemical cycles of the chemical elements that are connected to climatological and environmental changes, at least at the regional level. For several decades, this has made the issue of wetland evolution of particular interest among the scientific community worldwide. A number of authors have studied different aspects of wetland geochemistry and evolution: the chemical composition of bog water and peat, including nutrient dynamics, bog vegetation, hydrological characteristics, and the mineralogical composition of peat. However, some issues remained insufficiently studied, including the distribution of chemical elements in peat deposits and, particularly, the causes of the formation of some minerals in the peat deposits. To research these issues, we estimated the geochemical conditions of the formation of some minerals in the oligotrophic pine-shrub-sphagnum bog and adjacent area (part of the Vasyugan Swamp, Western Siberia) in the winter period of 2017 and 2018. It was revealed that there were no less than two complex geochemical barriers in the peat deposit. These barriers correspond to changes in advective and diffusion flows and result in the accumulation of Fe and some other chemical elements in the peat deposit. The upper complex geochemical barrier of redox, sulfide, and sorption type is located approximately at a depth of 0.40-1.25 m. The bottom barrier, which is the combination of complex geochemical barrier of alkaline and sorption type with mechanical barrier, are located at the bottom layer of the peat deposit, at a depth of 2.25-2.50 m. Accumulation of substances in the upper geochemical barrier is always less significant than in the bottom barrier. Therefore, the probability of detecting high concentrations of various substances is very high in the bottom part of the peat deposit, the organomineral sediments, and the upper part of the underlying mineral ground.