Hydrology and geochemistry of river-borne material in a high arctic drainage system, Zackenberg, Northeast Greenland

The roles of chemical and mechanical weathering in permafrost regions were assessed, by measuring stream discharge and major, trace, and rare earth elements (REE) of suspended matter (SPM), river-bed sediments (RBS), and water in two lithologically different catchments in the High Arctic at Zackenberg, Northeast Greenland. The drainage basin contains sedimentary and crystalline rocks. In streams draining the sedimentary rock area, SPM and total dissolved solutes (TDS) are high with maximum values of 2500 mg L-1 and 105 mu S cm(-1), respectively. Variation of both relates to changes in vegetation and morphology. Mineral fractionation during transport and soil-forming processes in the sedimentary portion of the study area lead to characteristic chemical profiles for the SPM and RES. Streams draining the crystalline rock area have low SPM (18 mg L-1) and TDS (14 mu S cm(-1)) as a result of poor soil development and a lack of vegetation. Mechanical denudation exceeds chemical denudation by an order of magnitude for the entire catchment. Because the REE distributions of the crystalline differ from those in the sedimentary SPM differ, it is possible to quantify source rock contributions to the main outflow using a mixing calculation. A mass balance comparing the SPM in the main outflow with the tributaries, using the REEs as fingerprints, indicates that about 90% of the sedimentary basin suspended matter is redeposited before reaching the outflow, at least over the period of observation. Taking this redeposition into account, the rate of chemical denudation (100 kg km(-2) d(-1)) exceeds mechanical denudation (70 kg km(-2) d(-1)) in the sedimentary drainage basin.