scholarly journals Technical Note: Uncovering the influence of methodological variations on the extractability of iron bound organic carbon

2020 ◽  
Author(s):  
Ben J. Fisher ◽  
Johan C. Faust ◽  
Oliver W. Moore ◽  
Caroline L. Peacock ◽  
Christian März
Keyword(s):  
Organic Carbon ◽  
Freeze Drying ◽  
Global Carbon Cycle ◽  
Technical Note ◽  
Preparation Methods ◽  
Reactive Iron ◽  
Concentration Time ◽  
Cbd Method ◽  
Global Carbon ◽  
Insight Into

Abstract. Association of organic carbon (OC) with reactive iron (FeR) represents an important mechanism by which OC is protected against remineralisation in soils and marine sediments. Recent studies indicate that the molecular structure of organic compounds and/or the identity of associated FeR phases exerts a control on the ability of an OC-FeR complex to be extracted by the citrate-bicarbonate-dithionite (CBD) method. While many variations of this method exist in the literature, these are often uncalibrated to each other, rendering comparisons of OC-FeR values extracted by different method iterations impossible. Here, we created a synthetic ferrihdyrite sample coprecipitated with simple organic structures and subjected these to modifications of the most common CBD method. Method parameters (reagent concentration, time of the extraction and sample preparation methods) were altered and FeR recovery measured to determine which (if any) modifications resulted in the greatest release of FeR from the sediment sample. We provide an assessment of the reducing capacity of Na dithionite in the CBD method and find that the concentration of dithionite deployed can limit OC-FeR extractability for sediments with a high FeR content. Additionally, we show that extending the length of any CBD extraction offers no benefit in removing FeR. Finally, we demonstrate that for synthetic OC-FeR samples, the almost universal technique of freeze drying samples can significantly reduce OC-FeR extractability and we offer insight into how this may translate to environmental samples using Arctic Ocean sediments. These results provide a valuable perspective on how the efficiency of this extraction could be improved to provide a more accurate assessment of sediment OC-FeR content. Accurate determinations of OC-FeR in sediments and soils represents an important step in improving our understanding of, and ability to model, the global carbon cycle.

scholarly journals Technical note: Uncovering the influence of methodological variations on the extractability of iron-bound organic carbon

2021 ◽  
Vol 18 (11) ◽  
pp. 3409-3419
Author(s):  
Ben J. Fisher ◽  
Johan C. Faust ◽  
Oliver W. Moore ◽  
Caroline L. Peacock ◽  
Christian März
Keyword(s):  
Organic Carbon ◽  
Marine Sediments ◽  
Freeze Drying ◽  
Method Comparison ◽  
Technical Note ◽  
Synthetic Sample ◽  
Fixed Amount ◽  
Preparation Methods ◽  
Reactive Iron ◽  
Cbd Method

Abstract. Association of organic carbon (OC) with reactive iron (FeR) represents an important mechanism by which OC is protected against remineralisation in soils and marine sediments. Recent studies indicate that the molecular structure of organic compounds and/or the identity of associated FeR phases exert a control on the ability of an OC–FeR complex to be extracted by the citrate–bicarbonate–dithionite (CBD) method. However, many variations of the CBD extraction are used, and these are often uncalibrated to each other, rendering comparisons of OC–FeR values extracted via the different methods impossible. Here, we created synthetic ferrihydrite samples coprecipitated with simple organic structures and subjected these to modifications of the most common CBD method. We altered some of the method parameters (reagent concentration, time of the extraction and sample preparation methods) and measured FeR recovery to determine which (if any) modifications affected the release of FeR from the synthetic sample. We provide an assessment of the reducing capacity of Na dithionite in the CBD method (the amount of Fe reduced by a fixed amount of dithionite) and find that the concentration of dithionite deployed can limit OC–FeR extractability for sediments with a high FeR content. Additionally, we show that extending the length of any CBD extraction offers no benefit in removing FeR. Moreover, we demonstrate that for synthetic OC–FeR samples dominated by ferrihydrite, freeze-drying samples can significantly reduce OC–FeR extractability; this appears to be less of an issue for natural marine sediments where natural ageing mechanisms may mimic the freeze-drying process for more stable Fe phases. While our study is not an all-inclusive method comparison and is not aimed at delivering the “perfect” extraction setup, our findings provide a collected summary of critical factors which influence the efficiency of the CBD extraction for OC–FeR. As such, we provide a platform from which OC–FeR values obtained under different methods can be interpreted and future studies of sediment carbon cycling can build upon.

scholarly journals Hydrogenotrophic methanogenesis in archaeal phylum Verstraetearchaeota reveals the shared ancestry of all methanogens

2019 ◽  
Vol 116 (11) ◽  
pp. 5037-5044 ◽  
Author(s):  
Bojk A. Berghuis ◽  
Feiqiao Brian Yu ◽  
Frederik Schulz ◽  
Paul C. Blainey ◽  
Tanja Woyke ◽  
...  
Keyword(s):  
Paradigm Shift ◽  
Carbon Fixation ◽  
Methanogenic Archaea ◽  
Global Carbon Cycle ◽  
Hydrogenotrophic Methanogenesis ◽  
Shared Ancestry ◽  
Hydrogenotrophic Methanogens ◽  
Methyl Coenzyme M Reductase ◽  
Global Carbon ◽  
Insight Into

Methanogenic archaea are major contributors to the global carbon cycle and were long thought to belong exclusively to the euryarchaeal phylum. Discovery of the methanogenesis gene cluster methyl-coenzyme M reductase (Mcr) in the Bathyarchaeota, and thereafter the Verstraetearchaeota, led to a paradigm shift, pushing back the evolutionary origin of methanogenesis to predate that of the Euryarchaeota. The methylotrophic methanogenesis found in the non-Euryarchaota distinguished itself from the predominantly hydrogenotrophic methanogens found in euryarchaeal orders as the former do not couple methanogenesis to carbon fixation through the reductive acetyl-CoA [Wood–Ljungdahl pathway (WLP)], which was interpreted as evidence for independent evolution of the two methanogenesis pathways. Here, we report the discovery of a complete and divergent hydrogenotrophic methanogenesis pathway in a thermophilic order of the Verstraetearchaeota, which we have named Candidatus Methanohydrogenales, as well as the presence of the WLP in the crenarchaeal order Desulfurococcales. Our findings support the ancient origin of hydrogenotrophic methanogenesis, suggest that methylotrophic methanogenesis might be a later adaptation of specific orders, and provide insight into how the transition from hydrogenotrophic to methylotrophic methanogenesis might have occurred.

scholarly journals Carbon isotope variations in the Upper Carboniferous - Pennian Mallemuk Mountain Group, eastern North Greenland

1989 ◽  
Vol 37 ◽  
pp. 205-211
Author(s):  
Lars Stemmerik ◽  
Mordeckai Magaritz
Keyword(s):  
Organic Carbon ◽  
Sea Level ◽  
Global Carbon Cycle ◽  
Late Permian ◽  
Early Permian ◽  
Isotopic Data ◽  
Upper Carboniferous ◽  
Global Carbon ◽  
Early Late ◽  
North Greenland

Isotope data from Late Palaeozoic limestones of the Wandel Sea Basin in eastern North Greenland show a variation of b13C from 0.0 %o to 5.7 %o vs PDB. Carbonates depleted in 13C occur in the basal part of lower Moscovian, upper Moscovian and middle Gzhelian transgressive sequences. 13C enriched limestones occur later in the cycles. The most 13C enriched limestones occur in the youngest (late Early Permian-early Late Permian) part of the sequence in Amdrup Land. The isotopic data is believed to represent changes in the global carbon cycle. Thus 13C enriched carbonates correlate to periods of burial of organic carbon mostly as coal, while 13C depleted carbonates formed as the result of erosion and oxidation of organic carbon during sea-level low stands.

scholarly journals ABOUT ROLE OF PHOTOSYNTHESIS IN CARBON TURNOVER

2019 ◽  
Vol 47 (4) ◽  
pp. 76-87
Author(s):  
A. A. Ivlev
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Sulfate Reduction ◽  
Subduction Zone ◽  
Global Carbon Cycle ◽  
Carbon Turnover ◽  
Sedimentary Organic Carbon ◽  
Lithospheric Plates ◽  
Global Carbon

The article considers the model of the global carbon cycle, in which photosynthesis is one of the key elements. The model itself is considered as the transition of carbon from the oxidized state to the reduced one and back. This transition is carried out by photosynthesis. The main oxidation of sedimentary organic carbon and its transition to an oxidized form is carried out by means of a natural reaction of thermochemical sulfate reduction, which occurs in the subduction zone (the zone of collision of lithospheric plates). A number of natural facts substantiating some key provisions of the model are given.

scholarly journals Increasing Autochthonous Production in Inland Waters as a Contributor to the Missing Carbon Sink

2021 ◽  
Vol 9 ◽  
Author(s):  
Zaihua Liu ◽  
Hao Yan ◽  
Sibo Zeng
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Carbon Sink ◽  
Global Carbon Cycle ◽  
Inland Waters ◽  
Organic Carbon Burial ◽  
Missing Carbon Sink ◽  
Organic Carbon Storage ◽  
Autochthonous Production ◽  
Global Carbon

Accounting for the residual land sink (or missing carbon sink) has become a major budget focus for global carbon cycle modelers. If we are not able to account for the past and current sources and sinks, we cannot make accurate predictions about future storage of fossil fuel combustion emissions of carbon in the terrestrial biosphere. Here, we show that the autochthonous production (AP) in inland waters appears to have been strengthening in response to changes in climate and land use, as evidenced by decreasing CO2 emissions from and increasing dissolved organic carbon storage and/or organic carbon burial in inland waters during recent decades. The increasing AP may be due chiefly to increasing aquatic photosynthesis caused by global warming and intensifying human activities. We estimate that the missing carbon sink associated with the strengthening AP in inland waters may range from 0.38 to 1.8 Gt C yr-1 with large uncertainties. Our study stresses the potential role that AP may play in the further evolution of the global carbon cycle. Quantitative estimates of future freshwater AP effects on the carbon cycle may also help to guide the action needed to reduce carbon emissions, and increase carbon sinks in terrestrial aquatic ecosystems.

scholarly journals Hydrogenotrophic methanogenesis in archaeal phylum Verstraetearchaeota reveals the shared ancestry of all methanogens

2018 ◽  
Author(s):  
Bojk A. Berghuis ◽  
Feiqiao Brian Yu ◽  
Frederik Schulz ◽  
Paul C. Blainey ◽  
Tanja Woyke ◽  
...  
Keyword(s):  
Paradigm Shift ◽  
Carbon Fixation ◽  
Methanogenic Archaea ◽  
Global Carbon Cycle ◽  
Acetyl Coenzyme A ◽  
Hydrogenotrophic Methanogenesis ◽  
Shared Ancestry ◽  
Methyl Coenzyme M Reductase ◽  
Global Carbon ◽  
Insight Into

AbstractMethanogenic archaea are major contributors to the global carbon cycle and were long thought to belong exclusively to the euryarchaeotal phylum. Discovery of the methanogenesis gene cluster methyl-coenzyme M reductase (Mcr) in the Bathyarchaeota and thereafter the Verstraetearchaeota led to a paradigm shift, pushing back the evolutionary origin of methanogenesis to pre-date that of the Euryarchaeota. The methylotrophic methanogenesis found in the non-Euryarchaota distinguished itself from the predominantly hydrogenotrophic methanogens found in euryarchaeal orders as the former do not couple methanogenesis to carbon fixation through the reductive acetyl-coenzyme A (Wood-Ljungdahl) pathway, which was interpreted as evidence for independent evolution of the two methanogenesis pathways. Here, we report the discovery of a complete and divergent hydrogenotrophic methanogenesis pathway in a novel, thermophilic order of the Verstraetearchaeota which we have named Candidatus Methanohydrogenales, as well as the presence of the Wood-Ljungdahl pathway in the crenarchaeal order Desulfurococcales. Our findings support the ancient origin of hydrogenotrophic methanogenesis, suggest that methylotrophic methanogenesis might be a later adaptation of specific orders, and provide insight into how transition from hydrogenotrophic to methylotrophic methanogenesis might occur.

Mercury evidence from the Sino-Korean block for Emeishan volcanism during the Capitanian mass extinction

2018 ◽  
Vol 156 (06) ◽  
pp. 1105-1110 ◽  
Author(s):  
HYOSANG KWON ◽  
MUN GI KIM ◽  
YONG IL LEE
Keyword(s):  
Organic Carbon ◽  
Mass Extinction ◽  
Volcanic Eruptions ◽  
Global Carbon Cycle ◽  
Upper Permian ◽  
South China Block ◽  
Extinction Event ◽  
Tethys Ocean ◽  
Mass Extinction Event ◽  
Global Carbon

AbstractA prominent large negative δ13Corg excursion and a coeval notable spike in mercury (Hg)/total organic carbon ratio are observed in the middle–upper Permian Gohan Formation in central Korea, located in the eastern Sino-Korean block (SKB), which may represent the Capitanian mass extinction event. The SKB was separated from the South China block by the eastern Palaeo-Tethys Ocean. This finding from the SKB supports the widespread Hg loading to the environment emitted from the Emeishan volcanic eruptions in SW China. This study demonstrates that the Hg cycle was globally perturbed in association with global carbon cycle perturbation that occurred during the Capitanian Extinction.

scholarly journals First pan-Arctic assessment of dissolved organic carbon in lakes of the permafrost region

2021 ◽  
Vol 18 (12) ◽  
pp. 3917-3936
Author(s):  
Lydia Stolpmann ◽  
Caroline Coch ◽  
Anne Morgenstern ◽  
Julia Boike ◽  
Michael Fritz ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Cycle ◽  
Dissolved Organic Carbon ◽  
Significant Relationship ◽  
Global Carbon Cycle ◽  
Doc Concentration ◽  
Global Carbon ◽  
Permafrost Regions

Abstract. Lakes in permafrost regions are dynamic landscape components and play an important role for climate change feedbacks. Lake processes such as mineralization and flocculation of dissolved organic carbon (DOC), one of the main carbon fractions in lakes, contribute to the greenhouse effect and are part of the global carbon cycle. These processes are in the focus of climate research, but studies so far are limited to specific study regions. In our synthesis, we analyzed 2167 water samples from 1833 lakes across the Arctic in permafrost regions of Alaska, Canada, Greenland, and Siberia to provide first pan-Arctic insights for linkages between DOC concentrations and the environment. Using published data and unpublished datasets from the author team, we report regional DOC differences linked to latitude, permafrost zones, ecoregions, geology, near-surface soil organic carbon contents, and ground ice classification of each lake region. The lake DOC concentrations in our dataset range from 0 to 1130 mg L−1 (10.8 mg L−1 median DOC concentration). Regarding the permafrost regions of our synthesis, we found median lake DOC concentrations of 12.4 mg L−1 (Siberia), 12.3 mg L−1 (Alaska), 10.3 mg L−1 (Greenland), and 4.5 mg L−1 (Canada). Our synthesis shows a significant relationship between lake DOC concentration and lake ecoregion. We found higher lake DOC concentrations at boreal permafrost sites compared to tundra sites. We found significantly higher DOC concentrations in lakes in regions with ice-rich syngenetic permafrost deposits (yedoma) compared to non-yedoma lakes and a weak but significant relationship between soil organic carbon content and lake DOC concentration as well as between ground ice content and lake DOC. Our pan-Arctic dataset shows that the DOC concentration of a lake depends on its environmental properties, especially on permafrost extent and ecoregion, as well as vegetation, which is the most important driver of lake DOC in this study. This new dataset will be fundamental to quantify a pan-Arctic lake DOC pool for estimations of the impact of lake DOC on the global carbon cycle and climate change.

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