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https://doi.org/10.5194/bg-2019-483
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-483
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 28 Jan 2020

Submitted as: research article | 28 Jan 2020

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This preprint is currently under review for the journal BG.

A revised northern soil Hg pool, based on western Siberia permafrost peat Hg and carbon observations

Artem G. Lim1, Martin Jiskra2, Jeroen E. Sonke3, Sergey V. Loiko1, Natalia Kosykh4, and Oleg S. Pokrovsky3,5 Artem G. Lim et al.
  • 1BIO-GEO-CLIM Laboratory, Tomsk State University, Tomsk, Russia
  • 2University of Basel, Environmental Geosciences, Bernoullistrasse 30, 4056 Basel, Switzerland
  • 3Geosciences and Environment Toulouse, UMR 5563 CNRS, 14 Avenue Edouard Belin 31400 Toulouse, France
  • 4Lab Biogeocenol, Inst Soil Science & Agrochem, Russian Acad Sci, Siberian Branch, Novosibirsk, Russia
  • 5N. Laverov Federal Center for Integrated Arctic Research, Russian Academy of Sciences, Arkhangelsk, Russia

Abstract. Natural and anthropogenic mercury (Hg) emissions are sequestered in terrestrial soils over short, annual, to long, millennial time scales, before Hg mobilization and run-off impacts wetland and coastal Ocean ecosystems. Recent studies have used Hg to carbon (C) ratios, RHgC, measured in Alaskan permafrost mineral and peat soils, together with a northern soil carbon inventory, to estimate that these soils contain large amounts, 184 to 755 Gg of Hg in the upper 1 m. However, measurements of RHgC on Siberian permafrost peatlands are largely missing, leaving the size of estimated northern soil Hg budget, and its fate under arctic warming scenarios uncertain. Here we present Hg and carbon data for 6 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 lowlands (WSL). Hg concentrations increase from south to north in all soil horizons, reflecting enhanced net accumulation of atmospheric gaseous Hg by the vegetation Hg pump. The RHgC in 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 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 0.77 Gg Pg−1, and use a soil carbon budget to revise the northern soil Hg pool to be 67 Gg (37–88 Gg, interquartile range (IQR)) in the upper 30 cm, 225 Gg (102–320 Gg) in the upper 1 m, and 557 Gg (371–699 Gg) in the upper 3 m. Using the same RHgC approach, we revise the global upper 30 cm soil Hg pool to contain 1078 Gg of Hg (842–1254 Gg, IQR), of which 6 % (67 Gg) resides in northern permafrost soils. Additional soil and river studies must be performed in Eastern and Northern Siberia to lower the uncertainty on these estimates, and assess the timing of Hg release to atmosphere and rivers.

Artem G. Lim et al.

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Artem G. Lim et al.

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Short summary
Towards better understanding the mercury (Hg) content in northern soils, we measured Hg concentration in peat cores across a 1700-km permafrost gradient in Siberia. We demonstrated a northward increase in Hg concentration in peat and Hg pools in frozen peatlands. We revised the 0–30 cm northern soil Hg pool as of 67 Gg, which is 6 % of global soil Hg pool of 1078 Gg. Results are important for understanding Hg exchange between soil, water and atmosphere under climate change in the Arctic.
Towards better understanding the mercury (Hg) content in northern soils, we measured Hg...
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