scholarly journals High organic carbon burial but high potential for methane ebullition in the sediments of an Amazonian reservoir

2019 ◽  
Author(s):  
Gabrielle R. Quadra ◽  
Sebastian Sobek ◽  
José R. Paranaíba ◽  
Anastasija Isidorova ◽  
Fábio Roland ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Pore Water ◽  
Amazon Basin ◽  
Accumulation Rate ◽  
River System ◽  
High Potential ◽  
Sediment Pore Water ◽  
River Inflow ◽  
Burial Rate ◽  
Organic Carbon Burial

Abstract. Reservoir sediments sequester significant amounts of organic carbon (OC), but at the same time, high amounts of methane (CH4) can be produced during the degradation of sediment OC. Hydropower is expanding in the Amazon basin, but the potential effects of river damming on the biogeochemistry of the Amazon river system can at present not be gauged due to a lack of studies. Here we present results from the first investigation of OC burial and CH4 concentrations in the sediments of an Amazonian reservoir. We performed sub-bottom profiling, sediment coring and sediment pore water analysis in the Curuá-Una reservoir (Amazon, Brazil) during rising and falling water periods. A mean sediment accumulation rate of 0.6 cm yr−1 and a mean OC burial rate of 91 g C m−2 yr−1 were found, which is the highest OC burial rate on record for low-latitude reservoirs, probably resulting from high OC deposition onto the sediment compensating for high OC mineralization at 28–30 °C water temperature. Elevated OC burial was found near the dam, and close to major river inflow areas. C : N ratios between 10.3 and 17 (mean ± SD: 12.9 ± 2.1) indicate that both land-derived and aquatic OC accumulate in CUN sediments. About 29 % of the sediment pore water samples had dissolved CH4 close to saturation concentration, a higher share than other hydroelectric reservoirs, indicating a high potential for CH4 ebullition, particularly in river inflow areas.

scholarly journals High organic carbon burial but high potential for methane ebullition in the sediments of an Amazonian hydroelectric reservoir

2020 ◽  
Vol 17 (6) ◽  
pp. 1495-1505 ◽  
Author(s):  
Gabrielle R. Quadra ◽  
Sebastian Sobek ◽  
José R. Paranaíba ◽  
Anastasija Isidorova ◽  
Fábio Roland ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Pore Water ◽  
Greenhouse Gas Emission ◽  
High Potential ◽  
Sediment Pore Water ◽  
Hydroelectric Reservoirs ◽  
River Inflow ◽  
Hydroelectric Reservoir ◽  
Burial Rate ◽  
Organic Carbon Burial

Abstract. Reservoir sediments sequester significant amounts of organic carbon (OC), but at the same time, high amounts of methane (CH4) can be produced and emitted during the degradation of sediment OC. While the greenhouse gas emission of reservoirs has received a lot of attention, there is a lack of studies focusing on OC burial. In particular, there are no studies on reservoir OC burial in the Amazon, even though hydropower is expanding in the basin. Here we present results from the first investigation of OC burial and CH4 concentrations in the sediments of an Amazonian hydroelectric reservoir. We performed sub-bottom profiling, sediment coring and sediment pore water analysis in the Curuá Una (CUN) reservoir (Amazon, Brazil) during rising- and falling-water periods. The spatially resolved average sediment accumulation rate was 0.6 cm yr−1, and the average OC burial rate was 91 g C m−2 yr−1. This is the highest OC burial rate on record for low-latitude hydroelectric reservoirs. Such a high rate probably results from a high OC deposition onto the sediment, which compensates the high OC mineralization at a 28–30 ∘C water temperature. Elevated OC burial was found near the dam and close to major river inflow areas. C:N ratios between 10.3 and 17 (average ± SD: 12.9±2.1) suggest that both land-derived and aquatic OC accumulate in CUN sediments. About 23 % of the sediment pore water samples had dissolved CH4 above the saturation concentration. This represents a higher share than in other hydroelectric reservoirs, indicating a high potential for CH4 ebullition, particularly in river inflow areas.

Enhanced paleo-wildfire occurrences caused by marine organic carbon burial during the Late Devonian Frasnian–Famennian mass extinction

2021 ◽  
Author(s):  
Man Lu ◽  
YueHan Lu ◽  
Takehitio Ikejiri ◽  
Richard Carroll
Keyword(s):  
Organic Carbon ◽  
Mass Extinction ◽  
Atmospheric Oxygen ◽  
Burial Rate ◽  
Carbon Burial ◽  
Chattanooga Shale ◽  
Chemical Index ◽  
Organic Carbon Burial ◽  
Polycyclic Aromatic ◽  
Extinction Events

<p>The Frasnian–Famennian (F–F) boundary is characterized by worldwide depositions of organic-rich strata, a series of marine anoxia events and one of the biggest five mass extinction events of the Phanerozoic. Due to the enhanced burial of organic matter, a coeval positive carbon isotope (δ<sup>13</sup>C) excursion occurred around the F–F boundary, raising questions about carbon cycle feedbacks during the mass extinction. In this study, we test the hypothesis that enhanced burial organic carbon during the F–F mass extinction led to the rise of paleo-wildfire occurrences. Here, we reconstructed paleo-wildfire changes across the F–F boundary via analyzing fossil charcoal (inertinites) and pyrogenic polycyclic aromatic hydrocarbons (PAHs) from an Upper Devonian Chattanooga Shale in the southern Appalachian Basin. Our data show low abundances of inertinites and pyrogenic PAHs before the F–F transition and an increasing trend during the F–F transition, followed by a sustained enhancement through the entire Famennian interval. The changes in paleo-wildfire proxies suggest a rise of wildfires starting from the F–F transition. Furthermore, we quantified the amount of organic carbon burial required to drive the observed δ<sup>13</sup>C excursion using a forward box model. The modeling results show an increased carbon burial rate after the onset of the F–F transition and peaking during its termination. The comparison of the carbon burial rate and wildfire proxies indicates that widespread organic carbon burial during the F–F transition might cause elevated atmospheric oxygen levels and hence increased occurrences of wildfires. In addition, chemical index alteration index and plant biomarkers suggest a drying climate initiated during the F–F transition, implying that the enhanced carbon burial probably result in the climate change and amplify the wildfire occurrences.</p>

scholarly journals Supplementary material to "High organic carbon burial but high potential for methane ebullition in the sediments of an Amazonian reservoir"

2019 ◽  
Author(s):  
Gabrielle R. Quadra ◽  
Sebastian Sobek ◽  
José R. Paranaíba ◽  
Anastasija Isidorova ◽  
Fábio Roland ◽  
...  
Keyword(s):  
Organic Carbon ◽  
High Potential ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Supplementary Material ◽  
Methane Ebullition

scholarly journals Erosion-induced massive organic carbon burial and carbon emission in the Yellow River basin, China

2014 ◽  
Vol 11 (4) ◽  
pp. 945-959 ◽  
Author(s):  
L. Ran ◽  
X. X. Lu ◽  
Z. Xin
Keyword(s):  
Soil Erosion ◽  
Organic Carbon ◽  
River Basin ◽  
Yellow River ◽  
River System ◽  
Yellow River Basin ◽  
Transport Processes ◽  
The Yellow River ◽  
Organic Carbon Burial ◽  
The Yellow River Basin

Abstract. Soil erosion and terrestrial deposition of soil organic carbon (SOC) can potentially play a significant role in global carbon cycling. Assessing the redistribution of SOC during erosion and subsequent transport and burial is of critical importance. Using hydrological records of soil erosion and sediment load, and compiled organic carbon (OC) data, estimates of the eroded soils and OC induced by water in the Yellow River basin during the period 1950–2010 were assembled. The Yellow River basin has experienced intense soil erosion due to combined impact of natural process and human activity. Over the period, 134.2 ± 24.7 Gt of soils and 1.07 ± 0.15 Gt of OC have been eroded from hillslopes based on a soil erosion rate of 1.7–2.5 Gt yr−1. Approximately 63% of the eroded soils were deposited in the river system, while only 37% were discharged into the ocean. For the OC budget, approximately 0.53 ± 0.21 Gt (49.5%) was buried in the river system, 0.25 ± 0.14 Gt (23.5%) was delivered into the ocean, and the remaining 0.289 ± 0.294 Gt (27%) was decomposed during the erosion and transport processes. This validates the commonly held assumption that 20–40% of the eroded OC would be oxidized after erosion. Erosion-induced OC redistribution on the landscape likely represented a carbon source, although a large proportion of OC was buried. In addition, about half of the terrestrially redeposited OC (49.4%) was buried behind dams, revealing the importance of dam trapping in sequestering the eroded OC. Although several uncertainties need to be better constrained, the obtained budgetary results provide a means of assessing the redistribution of the eroded OC within the Yellow River basin. Human activities have significantly altered its redistribution pattern over the past decades.

scholarly journals Organic carbon burial efficiency in a subtropical hydroelectric reservoir

2016 ◽  
Vol 13 (11) ◽  
pp. 3331-3342 ◽  
Author(s):  
Raquel Mendonça ◽  
Sarian Kosten ◽  
Sebastian Sobek ◽  
Simone Jaqueline Cardoso ◽  
Marcos Paulo Figueiredo-Barros ◽  
...  
Keyword(s):  
Organic Carbon ◽  
High Efficiency ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Low Oxygen ◽  
Spatially Resolved ◽  
Natural Lakes ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Burial Efficiency

Abstract. Hydroelectric reservoirs bury significant amounts of organic carbon (OC) in their sediments. Many reservoirs are characterized by high sedimentation rates, low oxygen concentrations in bottom water and a high share of terrestrially derived OC, and all of these factors have been linked to a high efficiency of OC burial. However, investigations of OC burial efficiency (OCBE, i.e., the ratio between buried and deposited OC) in reservoirs are limited to a few studies, none of which include spatially resolved analyses. In this study we determined the spatial variation in OCBE in a large subtropical reservoir and related it to sediment characteristics. Our results show that the sediment accumulation rate explains up to 92 % of the spatial variability in OCBE, outweighing the effect of other variables, such as OC source and oxygen exposure time. OCBE at the pelagic sites varied from 48 to 86 % (mean 67 %) and decreased towards the dam. At the margins, OCBE was lower (9–17 %) due to the low sediment accumulation in shallow areas. Our data show that the variability in OCBE both along the rivers–dam and the margin–pelagic axes must be considered in whole-reservoir assessments. Combining these results with a spatially resolved assessment of sediment accumulation and OC burial in the studied reservoir, we estimated a spatially resolved mean OC burial efficiency of 57 %. Being the first assessment of OCBE with such a high spatial resolution in a reservoir, these results suggest that reservoirs may bury OC more efficiently than natural lakes.

scholarly journals Sediment Organic Carbon Sequestration of Balkhash Lake in Central Asia

2021 ◽  
Vol 13 (17) ◽  
pp. 9958
Author(s):  
Wen Liu ◽  
Long Ma ◽  
Jilili Abuduwaili ◽  
Gulnura Issanova ◽  
Galymzhan Saparov
Keyword(s):  
Carbon Sequestration ◽  
Organic Carbon ◽  
The Past ◽  
Burial Rate ◽  
Carbon Burial ◽  
Sediment Organic Carbon ◽  
Organic Carbon Burial ◽  
Organic Carbon Burial Rate ◽  
Organic Carbon Sequestration ◽  
Global Carbon

As an important part of the global carbon pool, lake carbon is of great significance in the global carbon cycle. Based on a study of the sedimentary proxies of Balkhash Lake, Central Asia’s largest lake, changes in the organic carbon sequestration in the lake sediments and their possible influence over the past 150 years were studied. The results suggested that the organic carbon in the sediments of Lake Balkhash comes mainly from aquatic plants. The organic carbon burial rate fluctuated from 8.16 to 30.04 g·m−2·a−1 and the minimum appeared at the top of the core. The organic carbon burial rate continues to decline as it has over the past 150 years. Global warming, higher hydrodynamic force, and low terrestrial input have not been conducive to the improvement of organic carbon sequestration in Balkhash Lake; the construction of a large reservoir had a greater impact on the sedimentary proxy of total organic carbon content, which could lead to a large deviation for environmental reconstruction. This is the first study to assess the sediment organic carbon sequestration using the modern sediments of Central Asia’s largest lake, which is of great scientific significance. The results contribute to an understanding of organic carbon sequestration in Central Asia and may provide a scientific basis for carbon balance assessment in regional and global scales.

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