Eurasian river spring flood observations support net Arctic Ocean mercury export to the atmosphere and Atlantic Ocean

Sonke, Jeroen E.; Teisserenc, Roman; Heimbürger‐Boavida, Lars‐Eric; Petrova, Mariia V.; Marusczak, Nicolas; Dantec, Théo Le; Chupakov, Artem V.; Li, Chuxian; Thackray, Colin P.; Sunderland, Elsie M.; Tananaev, Nikita; Pokrovsky, Oleg S.

doi:10.1073/pnas.1811957115

Cited by 82 publications

(110 citation statements)

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“…With an ongoing warming and greening trend associated with climate change, an amplification of the Arctic tundra Hg(0) vegetation pump can be expected. Contrarily, higher soil temperatures, leading to permafrost thaw and degradation and development of thermokarsts, increase the risk of the re-mobilisation of large amounts of Hg that is currently stored in Arctic tundra soils (St. Pierre et al, 2018;Olson et al, 2018;Schuster et al, 2018). The net effect of these complex alterations in Arctic Hg cycling driven by climate change is currently poorly understood and the risk needs to be assessed.…”

Section: Discussionmentioning

confidence: 99%

Insights from mercury stable isotopes on terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra

et al. 2019

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Abstract. The tundra plays a pivotal role in the Arctic mercury (Hg) cycle by storing atmospheric Hg deposition and shuttling it to the Arctic Ocean. A recent study revealed that 70 % of the atmospheric Hg deposition to the tundra occurs through gaseous elemental mercury (GEM or Hg(0)) uptake by vegetation and soils. Processes controlling land–atmosphere exchange of Hg(0) in the Arctic tundra are central, but remain understudied. Here, we combine Hg stable isotope analysis of Hg(0) in the atmosphere, interstitial snow air, and soil pore air, with Hg(0) flux measurements in a tundra ecosystem at Toolik Field Station in northern Alaska (USA). In the dark winter months, planetary boundary layer (PBL) conditions and Hg(0) concentrations were generally stable throughout the day and small Hg(0) net deposition occurred. In spring, halogen-induced atmospheric mercury depletion events (AMDEs) occurred, with the fast re-emission of Hg(0) after AMDEs resulting in net emission fluxes of Hg(0). During the short snow-free growing season in summer, vegetation uptake of atmospheric Hg(0) enhanced atmospheric Hg(0) net deposition to the Arctic tundra. At night, when PBL conditions were stable, ecosystem uptake of atmospheric Hg(0) led to a depletion of atmospheric Hg(0). The night-time decline of atmospheric Hg(0) was concomitant with a depletion of lighter Hg(0) isotopes in the atmospheric Hg pool. The enrichment factor, ε202Hgvegetationuptake=-4.2 ‰ (±1.0 ‰) was consistent with the preferential uptake of light Hg(0) isotopes by vegetation. Hg(0) flux measurements indicated a partial re-emission of Hg(0) during daytime, when solar radiation was strongest. Hg(0) concentrations in soil pore air were depleted relative to atmospheric Hg(0) concentrations, concomitant with an enrichment of lighter Hg(0) isotopes in the soil pore air, ε202Hgsoilair-atmosphere=-1.00 ‰ (±0.25 ‰) and E199Hgsoilair-atmosphere=0.07 ‰ (±0.04 ‰). These first Hg stable isotope measurements of Hg(0) in soil pore air are consistent with the fractionation previously observed during Hg(0) oxidation by natural humic acids, suggesting abiotic oxidation as a cause for observed soil Hg(0) uptake. The combination of Hg stable isotope fingerprints with Hg(0) flux measurements and PBL stability assessment confirmed a dominant role of Hg(0) uptake by vegetation in the terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra.

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Section: Discussionmentioning

confidence: 99%

Insights from mercury stable isotopes on terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra

et al. 2019

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“…Tundra soils play a central role in the Arctic Hg cycling by storing atmospheric Hg deposition from where it can be mobilized and transported to the Arctic Ocean (Obrist et al, 2017;Sonke and Heimburger, 2012;Sonke et al, 2018). Over millennia, 40…”

Section: Introductionmentioning

confidence: 99%

Insights from mercury stable isotopes on terrestrial – atmosphere exchange of Hg(0) in the Arctic tundra

Jiskra¹,

Sonke²,

Agnan³

et al. 2019

Preprint

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Abstract. The tundra plays a pivotal role in the Arctic mercury (Hg) cycling by storing atmospheric Hg deposition and shuttling it to the Arctic Ocean. A recent study revealed that 70&#8201;% of the atmospheric Hg deposition to the tundra occurs by gaseous elemental mercury (GEM or Hg(0)) uptake by vegetation and soils. Processes controlling land &#8211; atmosphere exchange of Hg(0) in the Arctic tundra are therefore central, but remain understudied. Here, we combine Hg stable isotope analysis of Hg(0) in the atmosphere, interstitial snow and soil pore air, with Hg(0) flux measurements in a tundra ecosystem at Toolik field station in northern Alaska (USA). In dark winter months, planetary boundary layer (PBL) conditions and Hg(0) concentrations were generally stable throughout the day and small Hg(0) net deposition occurred. In spring, halogen-induced atmospheric mercury depletion events (AMDE's) occurred, with fast re-emission of Hg(0) after AMDE's resulting in net emission fluxes of Hg(0). During the short snow-free growing season in summer, vegetation uptake of atmospheric Hg(0) enhanced atmospheric Hg(0) net deposition to the Arctic tundra. At night, when PBL conditions were stable, ecosystem uptake of atmospheric Hg(0) led to a depletion of atmospheric Hg(0). The night time decline of atmospheric Hg(0) was concomitant with a depletion of lighter Hg(0) isotopes in the atmospheric Hg pool. The enrichment factor, &#949;202Hg&#8201;=&#8201;&#8722;4.2&#8201;&#8240;&#8201;&#177;&#8201;1.0&#8201;&#8240; was consistent with the preferential uptake of light Hg(0) isotopes by vegetation. Hg(0) flux measurements indicated a partial re-emission of Hg(0) during daytime, when solar radiation was strongest. Hg(0) concentrations in soil pore air were depleted relative to atmospheric Hg(0) concentrations, concomitant with an enrichment of lighter Hg(0) isotopes in the soil pore air (&#949;202Hgsoilair-atmosphere&#8201;=&#8201;&#8722;1.00&#8201;&#8240; (&#177;0.25&#8201;&#8240;) and E199Hgsoilair-atmosphere&#8201;=&#8201;0.07&#8201;&#8240; (&#177;0.04&#8201;&#8240;)). These first Hg stable isotope measurements of Hg(0) in soil pore air are consistent with the fractionation previously observed during Hg(0) oxidation by natural humic acids suggesting abiotic oxidation as a cause for observed soil Hg(0) uptake.

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“…Soil core analyses in Alaska indicate that large amounts of carbon and Hg have accumulated since the last glacial maximum, and two upscaling approaches to Hg stocks in pan-Arctic permafrost soils resulted in differing estimates of 184 Gg and 755 Gg for the upper 1 m (Schuster et al, 2018;Olson et al, 2018). Despite the overall net atmospheric Hg deposition to soils, research has found that Arctic rivers export 44 Mg y -1 of soil Hg, bound to particulate and dissolved organic matter, to the Arctic Ocean (Fisher et al, 2012;Dastoor et al, 2014;Zhang et al, 2015;Sonke et al, 2018). Together with coastal erosion of soils (30 Mg y -1 ), river Hg inputs constitute a terrestrial Hg flux of 74 Mg y -1 to the Arctic Ocean that is of similar magnitude to gross atmospheric deposition over the Arctic Ocean (80 Mg y -1 , Sonke et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Despite the overall net atmospheric Hg deposition to soils, research has found that Arctic rivers export 44 Mg y -1 of soil Hg, bound to particulate and dissolved organic matter, to the Arctic Ocean (Fisher et al, 2012;Dastoor et al, 2014;Zhang et al, 2015;Sonke et al, 2018). Together with coastal erosion of soils (30 Mg y -1 ), river Hg inputs constitute a terrestrial Hg flux of 74 Mg y -1 to the Arctic Ocean that is of similar magnitude to gross atmospheric deposition over the Arctic Ocean (80 Mg y -1 , Sonke et al, 2018). Permafrost thawing has been shown to enhance river Hg export from soils to rivers https://doi.org/10.5194/bg-2019-483 Preprint.…”

Section: Introductionmentioning

confidence: 99%

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

Lim

Jiskra

Sonke

et al. 2020

Preprint

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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.

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Eurasian river spring flood observations support net Arctic Ocean mercury export to the atmosphere and Atlantic Ocean

Cited by 82 publications

References 35 publications

Insights from mercury stable isotopes on terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra

Insights from mercury stable isotopes on terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra

Insights from mercury stable isotopes on terrestrial – atmosphere exchange of Hg(0) in the Arctic tundra

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

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