Spatial and temporal variations in mire surface water chemistry as a function of geology, atmospheric circulation and zonal features in the south-eastern part of Western Siberia

Abstract

This study analysed the chemistry of water samples collected from mires in the south-eastern part of Western Siberia. The aim was to determine spatial and temporal patterns in the hydrochemistry of mires in relation to the environmental conditions and geological history of the region. The results show that concentrations of Fetotal, Са2+, Mg2+, Na+, and HCO3– ions are higher than those obtained in other regions of Russia and Europe, which is consistent with the geological conditions of Western Siberia. High Fetotal concentrations are associated with the distribution of sedimentary ore in the region's largest iron ore basin, the Bakchar deposit, which is represented by strata of various Cretaceous sedimentsary rock at depths of 150–200 m. The Fe-rich rocks contribute to the high Fe concentrations in deep groundwater that feeds into the fens. The increase in Са2+, Mg2+, Na+, Cl−, and HCO3– in the water resulted from a xerothermic period that occurred in the southern part of Western Siberia (4500–2500 years ago) that increased the carbonation and salinity of the rocks. A feature characteristic of the hydrochemical regime in raised bogs is the transformation of the chemical composition during the year, with a change in dominant anions from HCO3– to Cl− or SO42−. The water in transitional mires and rich fens were characterised by the predominance of HCO3– and Са2+. Studies have shown that the size and stage of development play leading roles in the formation of the water chemistry in the mires. Small bogs and transitional mires were characterised by a rich mineral nutrition; while, the chemical composition of fens was mainly determined by their geomorphologic position and proximity to large river systems. The results of this study provide a better understanding of the functions of peatland ecosystems in Western Siberia and improve water sampling strategies for future research.