scholarly journals Preservation of organic carbon during active fluvial transport and particle abrasion

Geology ◽  
2019 ◽  
Vol 47 (10) ◽  
pp. 958-962 ◽  
Author(s):  
Joel S. Scheingross ◽  
N. Hovius ◽  
M. Dellinger ◽  
R.G. Hilton ◽  
M. Repasch ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Solid Phase ◽  
Global Climate ◽  
Flume Experiments ◽  
Lowland Rivers ◽  
River Transport ◽  
Fluvial Transport ◽  
Static Water ◽  
Transport Particle ◽  
Water Tanks

Abstract Oxidation of particulate organic carbon (POC) during fluvial transit releases CO2 to the atmosphere and can influence global climate. Field data show large POC oxidation fluxes in lowland rivers; however, it is unclear if POC losses occur predominantly during in-river transport, where POC is in continual motion within an aerated environment, or during transient storage in floodplains, which may be anoxic. Determination of the locus of POC oxidation in lowland rivers is needed to develop process-based models to predict POC losses, constrain carbon budgets, and unravel links between climate and erosion. However, sediment exchange between rivers and floodplains makes differentiating POC oxidation during in-river transport from oxidation during floodplain storage difficult. Here, we isolated in-river POC oxidation using flume experiments transporting petrogenic and biospheric POC without floodplain storage. Our experiments showed solid phase POC losses of 0%–10% over ∼103 km of fluvial transport, compared to ∼7% to >50% losses observed in rivers over similar distances. The production of dissolved organic carbon (DOC) and dissolved rhenium (a proxy for petrogenic POC oxidation) was consistent with small POC losses, and replicate experiments in static water tanks gave similar results. Our results show that fluvial sediment transport, particle abrasion, and turbulent mixing have a minimal role on POC oxidation, and they suggest that POC losses may accrue primarily in floodplain storage.

Global climate and river transport simulations of early Mars around the Noachian and Hesperian boundary

Icarus ◽  
2021 ◽  
pp. 114618
Author(s):  
A. Kamada ◽  
T. Kuroda ◽  
Y. Kasaba ◽  
N. Terada ◽  
H. Nakagawa
Keyword(s):  
Global Climate ◽  
River Transport ◽  
Early Mars

Mosquitoes and Static Water Tanks

BMJ ◽  
1943 ◽  
Vol 2 (4317) ◽  
pp. 435-435
Author(s):  
A. G. Newell
Keyword(s):  
Static Water ◽  
Water Tanks

scholarly journals Permafrost-Affected Soils of the Russian Arctic and their Carbon Pools

2014 ◽  
Vol 6 (1) ◽  
pp. 619-655
Author(s):  
S. Zubrzycki ◽  
L. Kutzbach ◽  
E.-M. Pfeiffer
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Sink ◽  
Global Climate ◽  
Fundamental Property ◽  
Climate System ◽  
The Arctic ◽  
Quaternary Period ◽  
Permafrost Regions

Abstract. Permafrost-affected soils have accumulated enormous pools of organic matter during the Quaternary Period. The area occupied by these soils amounts to more than 8.6 million km2, which is about 27% of all land areas north of 50° N. Therefore, permafrost-affected soils are considered to be one of the most important cryosphere elements within the climate system. Due to the cryopedogenic processes that form these particular soils and the overlying vegetation that is adapted to the arctic climate, organic matter has accumulated to the present extent of up to 1024 Pg (1 Pg = 1015 g = 1 Gt) of soil organic carbon stored within the uppermost three meters of ground. Considering the observed progressive climate change and the projected polar amplification, permafrost-affected soils will undergo fundamental property changes. Higher turnover and mineralization rates of the organic matter are consequences of these changes, which are expected to result in an increased release of climate-relevant trace gases into the atmosphere. As a result, permafrost regions with their distinctive soils are likely to trigger an important tipping point within the global climate system, with additional political and social implications. The controversy of whether permafrost regions continue accumulating carbon or already function as a carbon source remains open until today. An increased focus on this subject matter, especially in underrepresented Siberian regions, could contribute to a more robust estimation of the soil organic carbon pool of permafrost regions and at the same time improve the understanding of the carbon sink and source functions of permafrost-affected soils.

scholarly journals Mineral protection regulates the long-term global preservation of natural organic carbon

2021 ◽  
Author(s):  
Jordon Hemingway ◽  
Daniel Rothman ◽  
Katherine Grant ◽  
Sarah Rosengard ◽  
Timothy Eglinton ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Redox State ◽  
Global Climate ◽  
Atmospheric Oxygen ◽  
Atmospheric Composition ◽  
Earth Surface ◽  
Mountain Ranges ◽  
Surface Redox ◽  
Carbon Erosion

<p>The vast majority of organic carbon (OC) produced by life is respired back to carbon dioxide (CO<sub>2</sub>), but roughly 0.1% escapes and is preserved over geologic timescales. By sequestering reduced carbon from Earth’s surface, this “slow OC leak” contributes to CO<sub>2</sub> removal and promotes the accumulation of atmospheric oxygen and oxidized minerals. Countering this, OC contained within sedimentary rocks is oxidized during exhumation and erosion of mountain ranges. By respiring previously sequestered reduced carbon, erosion consumes atmospheric oxygen and produces CO<sub>2</sub>. The balance between these two processes—preservation and respiration—regulates atmospheric composition, Earth-surface redox state, and global climate. Despite this importance, the governing mechanisms remain poorly constrained. To provide new insight, we developed a method that investigates OC composition using bond-strength distributions coupled with radiocarbon ages. Here I highlight a suite of recent results using this approach, and I show that biospheric OC interacts with particles and becomes physiochemically protected during aging, thus promoting preservation. I will discuss how this mechanistic framework can help elucidate why OC preservation—and thus atmospheric composition, Earth-surface redox state, and climate—has varied throughout Earth history.</p>

Physical and chemical characteristics of cryoconites, sampled from glaciers of the Central Caucasus (Russia).

2021 ◽  
Author(s):  
Ivan Kushnov ◽  
Evgeny Abakumov ◽  
Rustam Tembotov ◽  
Viacheslav Polyakov
Keyword(s):  
Particle Size ◽  
Organic Carbon ◽  
Particle Size Distribution ◽  
Solid Phase ◽  
Basal Respiration ◽  
Chemical Characteristics ◽  
Significant Similarity ◽  
Physical And Chemical Characteristics ◽  
Central Caucasus ◽  
Physical And Chemical

<p>Cryoconites are a dark-colored granular sediments found in glacial landscapes. Cryoconites are known as a dark colored accumulation of various origin material in superficial holed of the glaciers which formed in polar and mountain regions of the Earth. They can significantly accelerate glacier retreating by reducing the albedo of the glacier and play a significant role in the colonization of the territory after its retreat, being an "oasis" for development of microorganisms on an uninhabited glacier surface. The understanding of key cryoconites properties is necessary to understand their impact on the mountain glaciers of the Central Caucasus, especially taking into account their recent rapid retreat.</p><p>The aim of this research is to study the physical and chemical characteristics of various cryoconites and cryoconite derived periglacial soils of the Central Caucasus. Eight cryoconite samples and eight soil samples from three soil sections were selected. The following characteristics of the samples were determined in laboratory conditions: total organic carbon (TOC), basal respiration level, pH H<sub>2</sub>O and exchangeable soil acidity, solid phase density and particle size distribution.</p><p>The results of the analyses showed both differences and some similarities in the physical and chemical characteristics of the cryoconites and soils of periglacial zone which were studied. Cryoconites, on average, are characterized by lower values of basal respiration than more developed soils from this region. The total organic carbon content in most samples was relatively low, but its values increase significantly soils investigated due to accumulation of carbon in fine earth under the influence of primary vegetation. The water extractable acidity values showed a significant similarity between the studied cryoconites and soils, they vary from slightly acidic to slightly alkaline in both groups. At the same time, the variation of exchangeable acidity values between cryoconite samples is significantly greater than in developed soils. Moreover, the density of the solid phase of the studied cryoconites varies in a larger range of values than that of the studied soils due to variety of sources of cryoconite materials. However, the analysis of particle size distribution showed a significant similarity of the studied objects: in almost all samples there is a significant dominance of the sand fraction (d=1-0.05 mm). The obtained data indicate both the difference in the physical and chemical properties of the studied cryoconites among themselves, and the probable influence of cryoconites on soil formation in this region.</p><p>This work was supported by Russian Foundation for Basic Research, project No <strong>19-05-50107</strong>  “The role of microparticles of organic carbon in degradation of ice cover of polar regions of the Earths and in the process of soil-like bodies formation”.</p>

Aerobic degradation of organic carbon inferred from dinoflagellate cyst decomposition in Southern Ocean sediments

2012 ◽  
Vol 78 (1) ◽  
pp. 130-138 ◽  
Author(s):  
Monika Kupinska ◽  
Oliver Sachs ◽  
Eberhard J. Sauter ◽  
Karin A.F. Zonneveld
Keyword(s):  
Organic Carbon ◽  
Southern Ocean ◽  
Pore Water ◽  
Global Climate Change ◽  
Global Climate ◽  
Strong Relationship ◽  
Aerobic Degradation ◽  
Important Process ◽  
Degradation Index ◽  
Factors Influencing

AbstractOrganic carbon (OC) burial is an important process influencing atmospheric CO2 concentration and global climate change; therefore it is essential to obtain information on the factors determining its preservation. The Southern Ocean (SO) is believed to play an important role in sequestering CO2 from the atmosphere via burial of OC. Here we investigate the degradation of organic-walled dinoflagellate cysts (dinocysts) in two short cores from the SO to obtain information on the factors influencing OC preservation. On the basis of the calculated degradation index kt, we conclude that both cores are affected by species-selective aerobic degradation of dinocysts. Further, we calculate a degradation constant k using oxygen exposure time derived from the ages of our cores. The constant k displays a strong relationship with pore-water O2, suggesting that decomposition of OC is dependent on both the bottom- and pore-water O2 concentrations.

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