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1. Closing the Winter Gap—Year‐Round Measurements of Soil CO ₂ Emission Sources in Arctic Tundra

   https://doi.org/10.1029/2021GL097347  

   Pedron, Shawn A.; Welker, J. M.; Euskirchen, E. S.; Klein, E. S.; Walker, J. C.; Xu, X.; Czimczik, C. I. (March 2022, Geophysical Research Letters)

   Abstract Non‐growing season CO₂emissions from Arctic tundra remain a major uncertainty in forecasting climate change consequences of permafrost thaw. We present the first time series of soil and microbial CO₂emissions from a graminoid tundra based on year‐round in situ measurements of the radiocarbon content of soil CO₂(Δ¹⁴CO₂) and of bulk soil C (Δ¹⁴C), microbial activity, and temperature. Combining these data with land‐atmosphere CO₂exchange allows estimates of the proportion and mean age of microbial CO₂emissions year‐round. We observe a seasonal shift in emission sources from fresh carbon during the growing season (August Δ¹⁴CO₂ = 74 ± 4.7‰, 37% ± 3.4% microbial, mean ± se) to increasingly older soil carbon in fall and winter (March Δ¹⁴CO₂ = 22 ± 1.3‰, 47% ± 8% microbial). Thus, rising soil temperatures and emissions during fall and winter are depleting aged soil carbon pools in the active layer and thawing permafrost and further accelerating climate change. 

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2. Ecosystem Scale Implication of Soil CO ₂ Concentration Dynamics During Soil Freezing in Alaskan Arctic Tundra Ecosystems

   https://doi.org/10.1029/2020JG005724  

   Wilkman, Eric; Zona, Donatella; Arndt, Kyle; Gioli, Beniamino; Nakamoto, Kyoko; Lipson, David A.; Oechel, Walter C. (May 2021, Journal of Geophysical Research: Biogeosciences)

   null (Ed.)
3. Response of CO ₂ and CH ₄ emissions from Arctic tundra soils to a multifactorial manipulation of water table, temperature and thaw depth

   https://doi.org/10.1088/2752-664X/ad089d  

   Best, K.; Zona, D.; Briant, E.; Lai, Chun-Ta; Lipson, D. A.; McEwing, K. R.; Davidson, S. J.; Oechel, W. C. (November 2023, Environmental Research: Ecology)

   Abstract Significant uncertainties persist concerning how Arctic soil tundra carbon emission responds to environmental changes. In this study, 24 cores were sampled from drier (high centre polygons and rims) and wetter (low centre polygons and troughs) permafrost tundra ecosystems. We examined how soil CO₂and CH₄fluxes responded to laboratory-based manipulations of soil temperature (and associated thaw depth) and water table depth, representing current and projected conditions in the Arctic. Similar soil CO₂respiration rates occurred in both the drier and the wetter sites, suggesting that a significant proportion of soil CO₂emission occurs via anaerobic respiration under water-saturated conditions in these Arctic tundra ecosystems. In the absence of vegetation, soil CO₂respiration rates decreased sharply within the first 7 weeks of the experiment, while CH₄emissions remained stable for the entire 26 weeks of the experiment. These patterns suggest that soil CO₂emission is more related to plant input than CH₄production and emission. The stable and substantial CH₄emission observed over the entire course of the experiment suggests that temperature limitations, rather than labile carbon limitations, play a predominant role in CH₄production in deeper soil layers. This is likely due to the presence of a substantial source of labile carbon in these carbon-rich soils. The small soil temperature difference (a median difference of 1 °C) and a more substantial thaw depth difference (a median difference of 6 cm) between the high and low temperature treatments resulted in a non-significant difference between soil CO₂and CH₄emissions. Although hydrology continued to be the primary factor influencing CH₄emissions, these emissions remained low in the drier ecosystem, even with a water table at the surface. This result suggests the potential absence of a methanogenic microbial community in high-centre polygon and rim ecosystems. Overall, our results suggest that the temperature increases reported for these Arctic regions are not responsible for increases in carbon losses. Instead, it is the changes in hydrology that exert significant control over soil CO₂and CH₄emissions. 

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4. Formation of CO ₂ Hydrates within Single-Walled Carbon Nanotubes at Ambient Pressure: CO ₂ Capture and Selective Separation of a CO ₂ /H ₂ Mixture in Water

   https://doi.org/10.1021/acs.jpcc.7b12700  

   Zhao, Wenhui; Bai, Jaeil; Francisco, Joseph S.; Zeng, Xiao Cheng (April 2018, The Journal of Physical Chemistry C)
5. The Prototypical Transition Metal Carbenes, (CO) ₅ Cr=CH ₂ , (CO) ₄ Fe=CH ₂ , (CO) ₃ Ni=CH ₂ , (CO) ₅ Mo=CH ₂ , (CO) ₄ Ru=CH ₂ , (CO) ₃ Pd=CH ₂ , (CO) ₅ W=CH ₂ , (CO) ₄ Os=CH ₂ , and (CO) ₃ Pt=CH ₂ : Challenge to Experiment

   https://doi.org/10.1021/acs.jpca.8b05394  

   Weidman, Jared D.; Estep, Marissa L.; Schaefer, Henry F. (July 2018, The Journal of Physical Chemistry A)