A revised pan-Arctic permafrost soil Hg pool based on Western Siberian peat Hg and carbon observations
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Published:2020-06-18
Issue:12
Volume:17
Page:3083-3097
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ISSN:1726-4189
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Container-title:Biogeosciences
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language:en
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Short-container-title:Biogeosciences
Author:
Lim Artem G., Jiskra MartinORCID, Sonke Jeroen E., Loiko Sergey V., Kosykh Natalia, Pokrovsky Oleg S.ORCID
Abstract
Abstract. Natural and anthropogenic mercury (Hg) emissions are sequestered in
terrestrial soils over short, annual to long, millennial timescales
before Hg mobilization and run-off impact wetland and coastal ocean
ecosystems. Recent studies have used Hg-to-carbon (C) ratios
(RHgC's) measured in Alaskan permafrost mineral and peat
soils together with a northern circumpolar permafrost soil carbon
inventory to estimate that these soils contain large amounts of Hg (between 184 and
755 Gg) in the upper 1 m. However, measurements
of RHgC on Siberian permafrost peatlands are largely
missing, leaving the size of the estimated northern soil Hg budget and
its fate under Arctic warming scenarios uncertain. Here we present Hg
and carbon data for six peat cores down to mineral horizons at
1.5–4 m depth, across a 1700 km latitudinal (56 to
67∘ N) permafrost gradient in the Western Siberian Lowland
(WSL). Mercury concentrations increase from south to north in all soil
horizons, reflecting a higher stability of sequestered Hg with respect
to re-emission. The RHgC in the WSL peat horizons
decreases with depth, from 0.38 Gg Pg−1 in the active layer
to 0.23 Gg Pg−1 in continuously frozen peat of the WSL. We
estimate the Hg pool (0–1 m) in the permafrost-affected part
of the WSL peatlands to be 9.3±2.7 Gg. We review and
estimate pan-Arctic organic and mineral soil RHgC to be
0.19 and 0.63 Gg Pg−1, respectively, and use a soil carbon budget to
revise the pan-Arctic permafrost soil Hg pool to be 72 Gg
(39–91 Gg; interquartile range, IQR) in the upper
30 cm, 240 Gg (110–336 Gg) in the upper
1 m, and 597 Gg (384–750 Gg) in the upper
3 m. Using the same RHgC approach, we revise the
upper 30 cm of the global soil Hg pool to contain 1086 Gg of
Hg (852–1265 Gg, IQR), of which 7 % (72 Gg)
resides in northern permafrost soils. Additional soil and river
studies in eastern and northern Siberia are needed to lower the
uncertainty on these estimates and assess the timing of Hg release to
the atmosphere and rivers.
Funder
Russian Science Foundation European Commission
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
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