Major and trace elements in suspended matter of western Siberian rivers: First assessment across permafrost zones and landscape parameters of watersheds

In contrast to good understanding of chemical composition of the river suspended matter (RSM) of large rivers, small rivers remain strongly understudied, despite the fact that they can provide valuable information on mechanisms of RSM generation and transport depending on key environmental parameter...
Ausführliche Beschreibung

In contrast to good understanding of chemical composition of the river suspended matter (RSM) of large rivers, small rivers remain strongly understudied, despite the fact that they can provide valuable information on mechanisms of RSM generation and transport depending on key environmental parameters of the watershed. This is especially true for permafrost-affected boreal and subarctic territories, subjected to strong modification due to permafrost thaw and landscape changes under climate warming. We selected Earth’s largest frozen peatland zone, the western Siberia Lowland (WSL) in order to test an impact of climate warming, permafrost thaw and landscape zone changes on riverine transport of particulate material from mainland to the Arctic Ocean. We sampled 33 small and medium size WSL rivers during spring flood, summer baseflow and autumn flood over a 1700 km gradient of climate and permafrost. Major and trace elements in particulate (>0.45 µm) and dissolved (<0.45 µm) fraction were analyzed. We hypothesize that future increase in active layer thickness and the change of dominant landscape from bogs and lakes to forest can be predicted via analyzing the actual pattern of RSM chemical composition across various permafrost zones and landscape parameters of WSL river watershed. We observed a minimum concentration of Li, Mg, Na, K, Rb, V, Cr, Zn, Cu, Co, Ni, Al, Ga, Y, REEs, Nb, W, Ti, Zr, Hf, Th and U in RSM collected from isolated and sporadic permafrost zones. Considering all seasons together, the presence of forest in the permafrost-bearing zone increased particulate concentrations of all alkalis and alkaline-earth elements, B, As, Nb, Mn, Co, Al, Ga, REEs, Ti, Zr, Hf, Th. This is consistent with element mobilization from mineral horizons that become available for interacting with soil fluids under forested regions. Lakes retained particulate alkaline-earths, Fe, Mn, Co, trivalent and tetravalent hydrolysates (TE3+, TE4+). The concentration of lithogenic low-soluble elements (TE3+, TE4+) in the RSM strongly increased with the river size (watershed area). Ausführliche Beschreibung