Organic carbon sorbed to reactive iron minerals released during permafrost collapse

The release of vast amounts of organic carbon during thawing of high-latitude permafrost is an urgent issue of global concern, yet it is unclear what controls how much carbon will be released and how fast it will be subsequently metabolized and emitted as greenhouse gases. Binding of organic carbon by iron(III) oxyhydroxide minerals can prevent carbon mobilization and degradation. This &#8220;rusty carbon sink&#8221; has already been suggested to protect organic carbon in soils overlying intact permafrost. However, the extent to which iron-bound carbon will be mobilized during permafrost thaw is entirely unknown. We have followed the dynamic interactions between iron and carbon across a thaw gradient in Abisko (Sweden), where wetlands are expanding rapidly due to permafrost retreat. Using both bulk (selective extractions, EXAFS) and nanoscale analysis (correlative SEM and nanoSIMS), we found that up to 19.4&#177;0.7% of total organic carbon is associated with reactive iron minerals in palsa underlain by intact permafrost. However, during permafrost collapse, the rusty carbon sink is lost due to more reduced conditions which favour microbial Fe(III) mineral dissolution. This leads to high dissolved Fe(II) (2.93&#177;0.42 mM) and organic carbon concentrations (480.06&#177;34.10 mg/L) in the porewater at the transition of desiccating palsa to waterlogged bog. Additionally, by combining FT-ICR-MS and greenhouse gas analysis both in the field and in laboratory microcosm experiments, we are currently determining the fate of the mobilized organic carbon directly after permafrost collapse. Our findings will improve our understanding of the processes controlling organic carbon turnover in thawing permafrost soils and help to better predict future greenhouse gas emissions.&#160;

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Iron mineral dissolution releases iron and associated organic carbon during permafrost thaw

Nature Communications ◽

10.1038/s41467-020-20102-6 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Monique S. Patzner ◽

Carsten W. Mueller ◽

Miroslava Malusova ◽

Moritz Baur ◽

Verena Nikeleit ◽

...

Keyword(s):

Organic Carbon ◽

Carbon Sink ◽

Mineral Dissolution ◽

Dynamic Interactions ◽

Terminal Electron Acceptor ◽

Iron Mineral ◽

Permafrost Thaw ◽

Reducing Conditions ◽

Carbon Release ◽

Reducing Bacteria

AbstractIt has been shown that reactive soil minerals, specifically iron(III) (oxyhydr)oxides, can trap organic carbon in soils overlying intact permafrost, and may limit carbon mobilization and degradation as it is observed in other environments. However, the use of iron(III)-bearing minerals as terminal electron acceptors in permafrost environments, and thus their stability and capacity to prevent carbon mobilization during permafrost thaw, is poorly understood. We have followed the dynamic interactions between iron and carbon using a space-for-time approach across a thaw gradient in Abisko (Sweden), where wetlands are expanding rapidly due to permafrost thaw. We show through bulk (selective extractions, EXAFS) and nanoscale analysis (correlative SEM and nanoSIMS) that organic carbon is bound to reactive Fe primarily in the transition between organic and mineral horizons in palsa underlain by intact permafrost (41.8 ± 10.8 mg carbon per g soil, 9.9 to 14.8% of total soil organic carbon). During permafrost thaw, water-logging and O2 limitation lead to reducing conditions and an increase in abundance of Fe(III)-reducing bacteria which favor mineral dissolution and drive mobilization of both iron and carbon along the thaw gradient. By providing a terminal electron acceptor, this rusty carbon sink is effectively destroyed along the thaw gradient and cannot prevent carbon release with thaw.

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Organic carbon remobilized from thawing permafrost is resequestered by reactive iron on the Eurasian Arctic Shelf

Geophysical Research Letters ◽

10.1002/2015gl066058 ◽

2015 ◽

Vol 42 (19) ◽

pp. 8122-8130 ◽

Cited By ~ 18

Author(s):

Joan A. Salvadó ◽

Tommaso Tesi ◽

August Andersson ◽

Johan Ingri ◽

Oleg V. Dudarev ◽

...

Keyword(s):

Organic Carbon ◽

Arctic Shelf ◽

Reactive Iron ◽

Thawing Permafrost

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Technical advances in measuring greenhouse gas emissions from thawing permafrost soils in the laboratory

Polar Science ◽

10.1016/j.polar.2019.01.003 ◽

2019 ◽

Vol 19 ◽

pp. 137-145 ◽

Cited By ~ 2

Author(s):

Seiichiro Yonemura ◽

Masao Uchida ◽

Go Iwahana ◽

Yongwon Kim ◽

Kenji Yoshikawa

Keyword(s):

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Gas Emissions ◽

Permafrost Soils ◽

Technical Advances ◽

Thawing Permafrost

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7. The Arctic carbon vault

10.1093/actrade/9780198819288.003.0007 ◽

2021 ◽

pp. 125-136

Author(s):

Klaus Dodds ◽

Jamie Woodward

Keyword(s):

Organic Carbon ◽

Carbon Sink ◽

Ice Age ◽

The Arctic ◽

Yamal Peninsula ◽

Frozen Ground ◽

Global Soil ◽

Shelf Sea ◽

Thawing Permafrost ◽

Bodies Of Water

‘The Arctic carbon vault’ describes the large share of Earth's organic carbon sequestered in the frozen ground and within the shelf sea sediments of the Arctic Ocean. The organic carbon stock of the permafrost is roughly equivalent to half of total global soil carbon. A cold Arctic with extensive permafrost is an effective long-term carbon sink as carbon is safely locked away as long as permafrost is maintained. Giant craters appeared on the Yamal peninsula. The thawing permafrost leads to the formation of thermokarst lakes, which are frozen bodies of water held in subsidence depressions created by the thawing of ground ice. Well-preserved carcasses of extinct ice age beasts, including woolly mammoths and cave bears, have been recovered from the thawing permafrost.

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Low soil organic carbon storage in a subarctic alpine permafrost environment

The Cryosphere Discussions ◽

10.5194/tcd-8-3493-2014 ◽

2014 ◽

Vol 8 (4) ◽

pp. 3493-3524 ◽

Cited By ~ 2

Author(s):

M. Fuchs ◽

P. Kuhry ◽

G. Hugelius

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Land Cover ◽

Carbon Sink ◽

Vegetation Zones ◽

Permafrost Environment ◽

Recent Origin ◽

Thawing Permafrost ◽

Organic Carbon Storage ◽

Net Carbon Sink

Abstract. This study investigates the soil organic carbon (SOC) storage in Tarfala Valley, Northern Sweden. Field inventories upscaled based on land cover show that this alpine permafrost environment does not store large amounts of SOC, with an estimate mean of 0.9 ± 0.2 kg C m−2 for the upper meter of soil. This is one to two orders of magnitude lower than what has been reported for lowland permafrost terrain. The SOC storage varies for different land cover classes and ranges from 0.05 kg C m−2 for stone-dominated to 8.4 kg C m−2 for grass-dominated areas. No signs of organic matter burial through cryoturbation or slope processes were found and radiocarbon dated SOC is generally of recent origin (<2000 cal yr BP). An inventory of permafrost distribution in Tarfala Valley, based on bottom temperature of snow measurements and a ogistic regression model, showed that at an altitude where permafrost is probable, the SOC storage is very low. In the high altitude permafrost zones (above 1500 m), soils store only ca 0.1 kg C m−2. Under future climate warming an upward shift of vegetation zones may lead to a net ecosystem C uptake from increased biomass and soil development. As a consequence, alpine permafrost environments could act as a net carbon sink in the future, as there is no loss of older or deeper SOC from thawing permafrost.

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Siberian Arctic inland waters emit mostly contemporary carbon

10.5194/egusphere-egu2020-17416 ◽

2020 ◽

Author(s):

Joshua Dean ◽

Ove Meisel ◽

Melanie Martyn Roscoe ◽

Luca Belelli Marchesini ◽

Mark Garnett ◽

...

Keyword(s):

Organic Carbon ◽

Particulate Organic Carbon ◽

Carbon Emissions ◽

Carbon Sink ◽

Inland Waters ◽

Terrestrial Carbon ◽

Study Region ◽

Inland Water ◽

Radiocarbon Age ◽

Thawing Permafrost

Inland waters (rivers, lakes and ponds) are important conduits for the emission of terrestrial carbon in Arctic permafrost landscapes. These emissions are driven by turnover of contemporary terrestrial carbon and additional &#8220;pre-aged&#8221; (Holocene and late-Pleistocene) carbon released from thawing permafrost soils, but the magnitude of these source contributions to total inland water carbon fluxes remains unknown. Here we present unique simultaneous radiocarbon age measurements of inland water CO2, CH4 and dissolved and particulate organic carbon in northeast Siberia during summer. We show that >80% of total inland water carbon emissions were contemporary in age, but that pre-aged carbon contributed >50% at sites strongly affected by permafrost thaw. CO2 and CH4 were younger than dissolved and particulate organic carbon, suggesting emissions were primarily fuelled by contemporary carbon decomposition. The study region was a net carbon sink (-876.9 &#177; 136.4 Mg C for 25 July to 17 August), but inland waters were a source of contemporary (16.8 Mg C) and pre-aged (3.7 Mg C) emissions that respectively offset 1.9 &#177; 1.2% and 0.4 &#177; 0.3% of CO2 uptake by tundra (&#8209;897 &#177; 115 Mg C). Our findings reveal that inland water carbon emissions from permafrost landscapes may be more sensitive to changes in contemporary carbon turnover than the release of pre-aged carbon from thawing permafrost.

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Low below-ground organic carbon storage in a subarctic Alpine permafrost environment

The Cryosphere ◽

10.5194/tc-9-427-2015 ◽

2015 ◽

Vol 9 (2) ◽

pp. 427-438 ◽

Cited By ~ 11

Author(s):

M. Fuchs ◽

P. Kuhry ◽

G. Hugelius

Keyword(s):

Organic Carbon ◽

Land Cover ◽

Carbon Sink ◽

Vegetation Zones ◽

Permafrost Environment ◽

Below Ground ◽

Recent Origin ◽

Thawing Permafrost ◽

Organic Carbon Storage ◽

Net Carbon Sink

Abstract. This study investigates the soil organic carbon (SOC) storage in Tarfala Valley, northern Sweden. Field inventories, upscaled based on land cover, show that this alpine permafrost environment does not store large amounts of SOC, with an estimate mean of 0.9 ± 0.2 kg C m−2 for the upper meter of soil. This is 1 to 2 orders of magnitude lower than what has been reported for lowland permafrost terrain. The SOC storage varies for different land cover classes and ranges from 0.05 kg C m−2 for stone-dominated to 8.4 kg C m−2 for grass-dominated areas. No signs of organic matter burial through cryoturbation or slope processes were found, and radiocarbon-dated SOC is generally of recent origin (<2000 cal yr BP). An inventory of permafrost distribution in Tarfala Valley, based on the bottom temperature of snow measurements and a logistic regression model, showed that at an altitude where permafrost is probable the SOC storage is very low. In the high-altitude permafrost zones (above 1500 m), soils store only ca. 0.1 kg C m−2. Under future climate warming, an upward shift of vegetation zones may lead to a net ecosystem C uptake from increased biomass and soil development. As a consequence, alpine permafrost environments could act as a net carbon sink in the future, as there is no loss of older or deeper SOC from thawing permafrost.

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Microbial iron(III) reduction during palsa collapse promotes greenhouse gas emissions before complete permafrost thaw

10.21203/rs.3.rs-691992/v1 ◽

2021 ◽

Author(s):

Monique Patzner ◽

Merritt Logan ◽

Amy McKenna ◽

Robert Young ◽

Zhe Zhou ◽

...

Keyword(s):

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

High Resolution Mass Spectrometry ◽

Carbon Sink ◽

Mineral Dissolution ◽

Co2 Production ◽

Gas Emissions ◽

Microbial Decomposition ◽

Iron Mineral ◽

Permafrost Thaw

Abstract Reactive iron (Fe) minerals can preserve organic carbon (OC) in soils overlying intact permafrost. With permafrost thaw, reductive dissolution of iron minerals releases Fe and OC into the porewater, potentially increasing the bioavailability of OC for microbial decomposition. However, the stability of this so-called rusty carbon sink, the microbial community driving mineral dissolution, the identity of the iron-associated carbon and the resulting impact on greenhouse gas emissions are unknown. We examined palsa hillslopes, gradients from intact permafrost-supported palsa to semi-wet partially-thawed bog in a permafrost peatland in Abisko (Sweden). Using high-resolution mass spectrometry, we found that Fe-bound OC in intact palsa is comprised of loosely bound more aliphatic and strongly-bound more aromatic species. Iron mineral dissolution by both fermentative and dissimilatory Fe(III) reduction releases Fe-bound OC along the palsa hillslopes, before complete permafrost thaw. The increasing bioavailability of dissolved OC (DOC) leads to its further decomposition, demonstrated by an increasing nominal oxidation state of carbon (NOSC) and a peak in bioavailable acetate (61.7±42.6 mg C/L) at the collapsing palsa front. The aqueous Fe2+ released is partially re-oxidized by Fe(II)-oxidizing bacteria but cannot prevent the overall loss of the rusty carbon sink with palsa collapse. The increasing relative abundance and activity of Fe(III)-reducers is accompanied by an increasing abundance of methanogens and a peak in methane (CH4) emissions at the collapsing front. Our data suggest that the loss of the rusty carbon sink directly contributes to carbon dioxide (CO2) production by Fe(III) reduction coupled to OC oxidation and indirectly to CH4 emission by promoting methanogenesis even before complete permafrost thaw.

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Microbial iron(III) reduction during palsa collapse promotes greenhouse gas emissions before complete permafrost thaw

10.31223/x5v908 ◽

2021 ◽

Author(s):

Monique Patzner ◽

Merritt Logan ◽

Amy McKenna ◽

Robert Young ◽

Zhe Zhou ◽

...

Keyword(s):

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

High Resolution Mass Spectrometry ◽

Carbon Sink ◽

Mineral Dissolution ◽

Co2 Production ◽

Gas Emissions ◽

Microbial Decomposition ◽

Iron Mineral ◽

Permafrost Thaw

Reactive iron (Fe) minerals can preserve organic carbon (OC) in soils overlying intact permafrost. With permafrost thaw, reductive dissolution of iron minerals releases Fe and OC into the porewater, potentially increasing the bioavailability of OC for microbial decomposition. However, the stability of this so-called rusty carbon sink, the microbial community driving mineral dissolution, the identity of the iron-associated carbon and the resulting impact on greenhouse gas emissions are unknown. We examined palsa hillslopes, gradients from intact permafrost-supported palsa to semi-wet partially-thawed bog in a permafrost peatland in Abisko (Sweden). Using high-resolution mass spectrometry, we found that Fe-bound OC in intact palsa is comprised of loosely bound more aliphatic and strongly-bound more aromatic species. Iron mineral dissolution by both fermentative and dissimilatory Fe(III) reduction releases Fe-bound OC along the palsa hillslopes, before complete permafrost thaw. The increasing bioavailability of dissolved OC (DOC) leads to its further decomposition, demonstrated by an increasing nominal oxidation state of carbon (NOSC) and a peak in bioavailable acetate (61.7±42.6 mg C/L) at the collapsing palsa front. The aqueous Fe2+ released is partially re-oxidized by Fe(II)-oxidizing bacteria but cannot prevent the overall loss of the rusty carbon sink with palsa collapse. The increasing relative abundance and activity of Fe(III)-reducers is accompanied by an increasing abundance of methanogens and a peak in methane (CH4) emissions at the collapsing front. Our data suggest that the loss of the rusty carbon sink directly contributes to carbon dioxide (CO2) production by Fe(III) reduction coupled to OC oxidation and indirectly to CH4 emission by promoting methanogenesis even before complete permafrost thaw.

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The Potential of Photoelectrochemical Carbon Sinks

10.26434/chemrxiv.6231140.v2 ◽

2018 ◽

Author(s):

Matthias May ◽

Kira Rehfeld

Keyword(s):

Global Warming ◽

High Temperature ◽

Greenhouse Gas ◽

Large Scale ◽

High Efficiency ◽

Carbon Sink ◽

Solar Fuels ◽

Negative Emissions ◽

Viable Approach ◽

Low Sensitivity

Greenhouse gas emissions must be cut to limit global warming to 1.5-2C above preindustrial levels. Yet the rate of decarbonisation is currently too low to achieve this. Policy-relevant scenarios therefore rely on the permanent removal of CO2 from the atmosphere. However, none of the envisaged technologies has demonstrated scalability to the decarbonization targets for the year 2050. In this analysis, we show that artificial photosynthesis for CO2 reduction may deliver an efficient large-scale carbon sink. This technology is mainly developed towards solar fuels and its potential for negative emissions has been largely overlooked. With high efficiency and low sensitivity to high temperature and illumination conditions, it could, if developed towards a mature technology, present a viable approach to fill the gap in the negative emissions budget.

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