Elemental composition of peat profiles in western Siberia: Effect of the micro-landscape, latitude position and permafrost coverage

Abstract

The concentrations of major and trace elements in the organic layer of peat soils across a 1800-km latitude profile of western Siberia were measured within various dominating ecosystems to evaluate the effect of landscape, latitude position and permafrost coverage on the peat chemical composition. In this study, peat core samples were collected every 10cm along the entire length of the column, down to 3–4m until the mineral horizon was reached. The peat samples were analyzed for major and trace elements using an ICP–MS technique following full acid digestion in a microwave oven. Depending on their concentration pattern along the peat column, several groups of elements were distinguished according to their general physico-chemical properties, mobility in soils, affinity to organic matter and plant biomass. Within similar ecosystems across various climate zones, there was a relatively weak variation in the TE concentration in the upper organic layer (green and brown parts of sphagnum mosses) with the latitude position. Within the intrinsic variability of the TE concentration over the peat column, the effects of climate, latitude position, and landscape location were not significantly pronounced. In different landscapes of the middle taiga, the peat columns collected in the fen zone, the low and mature forest, the ridge and the hollow did not demonstrate a statistically significant difference in most major and trace element concentrations over the full depth of the peat column. In live (green) parts and dead (brown) parts of sphagnum mosses from this climate zone, the concentrations of Mn, P, Ca and Cu decreased significantly with increasing moss net primary production (NPP) at various habitats, whereas the other elements exhibited no link with the NPP trends. The Al- and mineral horizon-normalized peat concentration profiles, allowing removal of the occasional contamination by the underlying mineral substrate and atmospheric dust, demonstrated a homogeneous distribution of TEs along the peat column among various climate zones in the non-permafrost regions but significantly non-conservative behavior in the discontinuous permafrost site. The peat deposits in the northern part of western Siberia potentially have very high release of metals to the surface waters and the riverine systems, depending on the persistence of the ongoing permafrost thaw and the increase in the thickness of the active layer.