Mercury exports from a High-Arctic river basin in Northeast Greenland (74°N) largely controlled by glacial lake outburst floods

TY - JOUR

T1 - Mercury exports from a High-Arctic river basin in Northeast Greenland (74°N) largely controlled by glacial lake outburst floods

AU - Sondergaard, Jens

AU - Tamstorf, Mikkel

AU - Elberling, Bo

AU - Larsen, Martin M.

AU - Mylius, Maria Rask

AU - Lund, Magnus

AU - Abermann, Jakob

AU - Riget, Frank

N1 - CENPERM[2015]

PY - 2015/5/1

Y1 - 2015/5/1

N2 - 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±1.4ngL-1, respectively, and mean concentrations of Hg in the river sediment were 0.033±0.025mgkg-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 514km2 ZRB varied from 0.71 to >1.57kg and the majority (86-96%) was associated with sediment-bound Hg. Hg yields from the ZRB varied from 1.4-3.1gHgkm-2yr-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.

AB - 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±1.4ngL-1, respectively, and mean concentrations of Hg in the river sediment were 0.033±0.025mgkg-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 514km2 ZRB varied from 0.71 to >1.57kg and the majority (86-96%) was associated with sediment-bound Hg. Hg yields from the ZRB varied from 1.4-3.1gHgkm-2yr-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.

KW - Hg

KW - River export

KW - Arctic

KW - Snow

KW - Soil

KW - Permafrost

U2 - 10.1016/j.scitotenv.2015.01.097

DO - 10.1016/j.scitotenv.2015.01.097

M3 - Journal article

C2 - 25666278

SN - 0048-9697

VL - 514

SP - 83

EP - 91

JO - Science of the Total Environment

JF - Science of the Total Environment

ER -