title: Mercury exports from a High-Arctic river basin in Northeast Greenland (74°N) largely controlled by glacial lake outburst floods.
abstract: Riverine mercury (Hg) export dynamics from the Zackenberg River Basin (ZRB) in Northeast Greenland were studied for the period 2009-2013. Dissolved and sediment-bound Hg was measured regularly in the Zackenberg River throughout the periods with running water (June-October) and coupled to water discharge measurements. Also, a few samples of snow, soil, and permafrost were analysed for Hg. Mean concentrations of dissolved and sediment-bound Hg in the river water (±SD) were 0.39 ± 0.13 and 5.5 ± 1.4 ngL(-1), respectively, and mean concentrations of Hg in the river sediment were 0.033 ± 0.025 mg kg(-1). Temporal variations in river Hg were mainly associated with snowmelt, sudden erosion events, and outburst floods from a glacier-dammed lake in the upper part of the ZRB. Annual Hg exports from the 514 km(2) ZRB varied from 0.71 to >1.57 kg and the majority (86-96%) was associated with sediment-bound Hg. Hg yields from the ZRB varied from 1.4-3.1 gH gk m(-2)yr(-1) and were among the highest yields reported from Arctic river basins. River exports of Hg from ZRB were found to be largely controlled by the frequency, magnitude and timing of the glacial lake outburst floods, which occurred in four of the five years in July-August. Floods accounted for 5 to >10% of the annual water discharge, and up to >31% of the annual Hg export. Also, the winter snowfall and the summer temperatures were found to be important indirect controls on the annual Hg export. The occurrence and timing of glacial lake outburst floods in the ZRB in late summer at the time of maximum soil thaw depth, the location of the glacier in the upper ZRB, and increased thawing of the permafrost in Zackenberg in recent years leading to destabilisation of river banks are considered central factors explaining the high fraction of flood-controlled Hg export in this area.
authors: Arctic Research Centre, Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark. Electronic address: jens@bios.au.dk.
authors: Jens
authors: J
authors: Søndergaard
authors: Arctic Research Centre, Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
authors: Mikkel
authors: M
authors: Tamstorf
authors: Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
authors: Bo
authors: B
authors: Elberling
authors: Arctic Research Centre, Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
authors: Martin M
authors: MM
authors: Larsen
authors: Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
authors: Maria Rask
authors: MR
authors: Mylius
authors: Arctic Research Centre, Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
authors: Magnus
authors: M
authors: Lund
authors: Asiaq-Greenland Survey, P.O. Box 1003, Qatserisut 8, 3900 Nuuk, Greenland.
authors: Jakob
authors: J
authors: Abermann
authors: Arctic Research Centre, Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
authors: Frank
authors: F
authors: Rigét
mesh_terms: D001110:Arctic Regions; D004784:Environmental Monitoring; D006116:Greenland; D046448:Ice Cover / Q000737:chemistry; D060106:Lakes / Q000737:chemistry; D008628:Mercury / Q000032:analysis*; D045483:Rivers / Q000737:chemistry; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Arctic; Hg; Permafrost; River export; Snow; Soil