| 1. |
- Almeida, Nazare da Silva, et al.
(författare)
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Incubation experiments to constrain the production of methane and carbon dioxide in organic-rich shales of the Permian Irati Formation, Parana Basin
- 2020
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Ingår i: Marine and Petroleum Geology. - : Elsevier. - 0264-8172 .- 1873-4073. ; 112
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Tidskriftsartikel (refereegranskat)abstract
- The Permian Irati Formation in Brazil hosts organic-rich shales and heavy hydrocarbons suitable for biogenic production of methane (CH4) and carbon dioxide (CO2). In this study, shale samples from the irati Formation were used in laboratory incubation experiments performed under different temperatures (22 degrees C, 50 degrees C, 70 degrees C and 80 degrees C) to evaluate the generation of CH4 and CO2 under thermal conditions compatible with biodegradation in shallow gas systems (< 80 degrees C). Despite our laboratory experiments do not represent natural subsurface temperature conditions, it is observed that the concentrations of CH4 and CO2 increase when shale samples are incubated under temperature higher than 22 degrees C. Samples incubated at 80 degrees C presented a maximum CH4 yield of 2.45 ml/t.d (milliliter per ton of shale per day) compared to 0,49 ml/t.d at 22 degrees C, 1.75 ml/t.d at 50 degrees C and 2.09 ml/t.d at 70 degrees C. The same trend of increasing production rates with higher temperatures was observed for CO2, with maximum potential production observed under a laboratory temperature of 80 degrees C, reaching 23.47 ml/t.d. Stable carbon isotopes (delta C-13) on CH4 and CO2 suggest a mixture of thermogenic and secondary microbial gas. However, the measured CH4 and CO2 can be generated through methanogenic degradation of heavy hydrocarbons present in the studied shales, difficulting the use of carbon isotope composition to discriminate between biogenic and thermogenic gases. The studied shale samples showed significant differences in CH4 and CO2 production rates, which are possibly related to the major elements composition of the mineral matrix. Higher CH4 and CO2 production rates occurred in samples with higher amount of sulfur. Besides sulfur, we highlight that others soluble elements in the mineral matrix, such as Ca and Mg, can play an important role for the generation of biogenic CH4 and CO2. The present work intends to alert for the importance of thermal conditions as well as the geochemical composition of the mineral matrix to build conceptual models about shallow gas systems, acting on organic-rich shales in sedimentary basins.
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| 2. |
- Bertassoli, Dailson J. Jr., et al.
(författare)
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How green can Amazon hydropower be? : Net carbon emission from the largest hydropower plant in Amazonia
- 2021
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Ingår i: Science Advances. - : American Association for the Advancement of Science. - 2375-2548. ; 7:26
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Tidskriftsartikel (refereegranskat)abstract
- The current resurgence of hydropower expansion toward tropical areas has been largely based on run-of-the-river (ROR) dams, which are claimed to have lower environmental impacts due to their smaller reservoirs. The Belo Monte dam was built in Eastern Amazonia and holds the largest installed capacity among ROR power plants worldwide. Here, we show that postdamming greenhouse gas (GHG) emissions in the Belo Monte area are up to three times higher than preimpoundment fluxes and equivalent to about 15 to 55 kg CO(2)eq MWh(-1). Since per-area emissions in Amazonian reservoirs are significantly higher than global averages, reducing flooded areas and prioritizing the power density of hydropower plants seem to effectively reduce their carbon footprints. Nevertheless, total GHG emissions are substantial even from this leading-edge ROR power plant. This argues in favor of avoiding hydropower expansion in Amazonia regardless of the reservoir type.
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| 3. |
- Covey, Kristofer, et al.
(författare)
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Carbon and Beyond : The Biogeochemistry of Climate in a Rapidly Changing Amazon
- 2021
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Ingår i: Frontiers in Forests and Gobal Change. - : Frontiers Media S.A.. - 2624-893X. ; 4
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Forskningsöversikt (refereegranskat)abstract
- The Amazon Basin is at the center of an intensifying discourse about deforestation, land-use, and global change. To date, climate research in the Basin has overwhelmingly focused on the cycling and storage of carbon (C) and its implications for global climate. Missing, however, is a more comprehensive consideration of other significant biophysical climate feedbacks [i.e., CH4, N2O, black carbon, biogenic volatile organic compounds (BV0Cs), aerosols, evapotranspiration, and albedo] and their dynamic responses to both localized (fire, land-use change, infrastructure development, and storms) and global (warming, drying, and some related to El Nino or to warming in the tropical Atlantic) changes. Here, we synthesize the current understanding of (1) sources and fluxes of all major forcing agents, (2) the demonstrated or expected impact of global and local changes on each agent, and (3) the nature, extent, and drivers of anthropogenic change in the Basin. We highlight the large uncertainty in flux magnitude and responses, and their corresponding direct and indirect effects on the regional and global climate system. Despite uncertainty in their responses to change, we conclude that current warming from non-CO2 agents (especially CH4 and N2O) in the Amazon Basin largely offsets- and most likely exceeds-the climate service provided by atmospheric CO2 uptake. We also find that the majority of anthropogenic impacts act to increase the radiative forcing potential of the Basin. Given the large contribution of less-recognized agents (e.g., Amazonian trees alone emit similar to 3.5% of all global CH4), a continuing focus on a single metric (i.e., C uptake and storage) is incompatible with genuine efforts to understand and manage the biogeochemistry of climate in a rapidly changing Amazon Basin.
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| 4. |
- de Araujo, Kleiton R., et al.
(författare)
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Carbon dioxide (CO2) concentrations and emission in the newly constructed Belo Monte hydropower complex in the Xingu River, Amazonia
- 2019
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Ingår i: Biogeosciences. - Gottingen : Copernicus Gesellschaft MBH. - 1726-4170 .- 1726-4189. ; 16:18, s. 3527-3542
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Tidskriftsartikel (refereegranskat)abstract
- The Belo Monte hydropower complex located in the Xingu River is the largest run-of-the-river (ROR) hydroelectric system in the world and has one of the highest energy production capacities among dams. Its construction received significant media attention due to its potential social and environmental impacts. It is composed of two ROR reservoirs: the Xingu Reservoir (XR) in the Xingu's main branch and the Intermediate Reservoir (IR), an artificial reservoir fed by waters diverted from the Xingu River with longer water residence time compared to XR. We aimed to evaluate spatiotemporal variations in CO2 partial pressure (pCO(2)) and CO2 fluxes (FCO2) during the first 2 years after the Xingu River impoundment under the hypothesis that each reservoir has contrasting FCO2 and pCO(2) as vegetation clearing reduces flooded area emissions. Time of the year had a significant influence on pCO(2) with the highest average values observed during the high-water season. Spatial heterogeneity throughout the entire study area was observed for pCO(2) during both low-and high-water seasons. FCO2, on the other hand, only showed significant spatial heterogeneity during the high-water period. FCO2 (0.90 +/- 0.47 and 1.08 +/- 0.62 mu mol m(2) d(-1) for XR and IR, respectively) and pCO(2) (1647 +/- 698 and 1676 +/- 323 mu atm for XR and IR, respectively) measured during the high-water season were on the same order of magnitude as previous observations in other Amazonian clearwater rivers unaffected by impoundment during the same season. In contrast, during the low-water season FCO2 (0.69 +/- 0.28 and 7.32 +/- 4.07 mu mol m(2) d(-1) for XR and IR, respectively) and pCO(2) (839 +/- 646 and 1797 +/- 354 mu atm for XR and IR, respectively) in IR were an order of magnitude higher than literature FCO2 observations in clearwater rivers with naturally flowing waters. When CO2 emissions are compared between reservoirs, IR emissions were 90% higher than values from the XR during low-water season, reinforcing the clear influence of reservoir characteristics on CO2 emissions. Based on our observations in the Belo Monte hydropower complex, CO2 emissions from ROR reservoirs to the atmosphere are in the range of natural Amazonian rivers. However, the associated reservoir (IR) may exceed natural river emission rates due to the preimpounding vegetation influence. Since many reservoirs are still planned to be constructed in the Amazon and throughout the world, it is critical to evaluate the implications of reservoir traits on FCO2 over their entire life cycle in order to improve estimates of CO2 emissions per kilowatt for hydropower projects planned for tropical rivers.
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| 5. |
- Häggi, C., et al.
(författare)
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Negligible Quantities of Particulate Low-Temperature Pyrogenic Carbon Reach the Atlantic Ocean via the Amazon River
- 2021
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Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 35:9
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Tidskriftsartikel (refereegranskat)abstract
- Particulate pyrogenic carbon (PyC) transported by rivers and aerosols, and deposited in marine sediments, is an important part of the carbon cycle. The chemical composition of PyC is temperature dependent and levoglucosan is a source-specific burning marker used to trace low-temperature PyC. Levoglucosan associated to particulate material has been shown to be preserved during riverine transport and marine deposition in high- and mid-latitudes, but it is yet unknown if this is also the case for (sub)tropical areas, where 90% of global PyC is produced. Here, we investigate transport and deposition of levoglucosan in suspended and riverbed sediments from the Amazon River system and adjacent marine deposition areas. We show that the Amazon River exports negligible amounts of levoglucosan and that concentrations in sediments from the main Amazon tributaries are not related to long-term mean catchment-wide fire activity. Levoglucosan concentrations in marine sediments offshore the Amazon Estuary are positively correlated to total organic content regardless of terrestrial or marine origin, supporting the notion that association of suspended or dissolved PyC to biogenic particles is critical in the preservation of PyC. We estimate that 0.5-10 x 10(6) g yr(-1) of levoglucosan is exported by the Amazon River. This represents only 0.5-10 ppm of the total exported PyC and thereby an insignificant fraction, indicating that riverine derived levoglucosan and low-temperature PyC in the tropics are almost completely degraded before deposition. Hence, we suggest caution in using levoglucosan as tracer for past fire activity in tropical settings near rivers.
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| 6. |
- Pelissari, Maria Rogieri, et al.
(författare)
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Water influence on CH4 and CO2 generation from tar sandstones: Insights from incubation experiments in the Piramboia Formation, Parana Basin
- 2021
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Ingår i: Journal of South American Earth Sciences. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0895-9811 .- 1873-0647. ; 106
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Tidskriftsartikel (refereegranskat)abstract
- Processes controlling the biogenic production of CH4 and CO2 are relevant not only to environmental issues related to greenhouse gases emissions, but also in the energy scenario, since the biogenic generation of CH4 can be associated with the formation of natural gas reserves over time. This work aimed to evaluate the influence of water and calcium sulfate in the production of CH4 and CO2 from petroleum biodegradation in tar sandstones. Water saturation and sulfate concentration are taken to be important factors of influence in the oil biodegradation process. Long-term incubation experiments (up to 363 days) were carried out with samples of sandstone impregnated with high-viscosity hydrocarbons. The rocks used in this study were collected from outcrops of the Piramboia Formation, a known heavy-oil reservoir of the Parana Basin, Brazil. The net accumulation of both CH4 and CO2 was crescent during all the experiments performed, but with decreasing production rates through time. Average potential production rates obtained were 18 mL CH4/t.y (milliliter per ton of sandstone per year) and 54,000 mL CO2/t.y. The addition of water resulted in an average increase of 11% and 10% in the CH4 and CO2 cumulative production, respectively, in comparison with the dry incubation experiments. The water influence was stronger in the first 30 days of incubations when average production was around 70% higher in wet samples. Once the pH remained constant in the presence of calcium sulfate, the experiments indicate that calcium sulfate may function as buffer for pH, limiting acidification, which has a known negative influence on CH4 and CO2 production. Thus, the present work aims to alert for the potential of CO2 and CH4 production from tar sands in Brazil and for the importance of water as a positive influence on CH4 and CO2 generation from tar sandstones. This helps to evaluate the influence of environmental conditions on biogenic gas systems as well as on green-house gases emissions from geological sources, which are taken to be important sources of carbon to the atmosphere in a context of climate change.
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| 7. |
- Sawakuchi, A. O., et al.
(författare)
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Luminescence of quartz and feldspar fingerprints provenance and correlates with the source area denudation in the Amazon River basin
- 2018
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Ingår i: Earth and Planetary Science Letters. - : Elsevier. - 0012-821X .- 1385-013X. ; 492, s. 152-162
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Tidskriftsartikel (refereegranskat)abstract
- The Amazon region hosts the world's largest watershed spanning from high elevation Andean terrains to lowland cratonic shield areas in tropical South America. This study explores variations in optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) signals in suspended silt and riverbed sands retrieved from major Amazon rivers. These rivers drain Pre-Cambrian to Cenozoic source rocks in areas with contrasting denudation rates. In contrast to the previous studies, we do not observe an increase in the OSL sensitivity of quartz with transport distance; for example, Tapajos and Xingu Rivers show more sensitive quartz than Solimbes and Madeira Rivers, even though the latter have a significantly larger catchment area and longer sediment transport distance. Interestingly, high sensitivity quartz is observed in rivers draining relatively stable Central Brazil and Guiana shield areas (denudation rate xi = 0.04 mm yr(-1)), while low sensitivity quartz occurs in less stable Andean terrains (xi = 0.24 mm yr(-1)). An apparent linear correlation between quartz OSL sensitivity and denudation rate suggests that OSL sensitivity may be used as a proxy for erosion rates in the Amazon basin. Furthermore, luminescence sensitivity measured in sand or silt arises from the same mineral components (quartz and feldspar) and clearly discriminates between Andean and shield sediments, avoiding the grain size bias in provenance analysis. These results have implications for using luminescence sensitivity as a proxy for Andean and shield contributions in the stratigraphic record, providing a new tool to reconstruct past drainage configurations within the Amazon basin.
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| 8. |
- Sawakuchi, Henrique O., et al.
(författare)
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Methane emissions from Amazonian Rivers and their contribution to the global methane budget
- 2014
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Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 20:9, s. 2829-2840
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Tidskriftsartikel (refereegranskat)abstract
- Methane (CH4) fluxes from world rivers are still poorly constrained, with measurements restricted mainly to temperate climates. Additional river flux measurements, including spatio-temporal studies, are important to refine extrapolations. Here we assess the spatio-temporal variability of CH4 fluxes from the Amazon and its main tributaries, the Negro, Solimoes, Madeira, Tapajos, Xingu, and Para Rivers, based on direct measurements using floating chambers. Sixteen of 34 sites were measured during low and high water seasons. Significant differences were observed within sites in the same river and among different rivers, types of rivers, and seasons. Ebullition contributed to more than 50% of total emissions for some rivers. Considering only river channels, our data indicate that large rivers in the Amazon Basin release between 0.40 and 0.58 Tg CH4 yr(-1). Thus, our estimates of CH4 flux from all tropical rivers and rivers globally were, respectively, 19-51% to 31-84% higher than previous estimates, with large rivers of the Amazon accounting for 22-28% of global river CH4 emissions.
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| 9. |
- Sawakuchi, Henrique O., et al.
(författare)
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Oxidative mitigation of aquatic methane emissions in large Amazonian rivers
- 2016
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Ingår i: Global Change Biology. - : WILEY-BLACKWELL. - 1354-1013 .- 1365-2486. ; 22:3, s. 1075-1085
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Tidskriftsartikel (refereegranskat)abstract
- The flux of methane (CH4) from inland waters to the atmosphere has a profound impact on global atmospheric greenhouse gas (GHG) levels, and yet, strikingly little is known about the dynamics controlling sources and sinks of CH4 in the aquatic setting. Here, we examine the cycling and flux of CH4 in six large rivers in the Amazon basin, including the Amazon River. Based on stable isotopic mass balances of CH4, inputs and outputs to the water column were estimated. We determined that ecosystem methane oxidation (MOX) reduced the diffusive flux of CH4 by approximately 28-96% and varied depending on hydrologic regime and general geochemical characteristics of tributaries of the Amazon River. For example, the relative amount of MOX was maximal during high water in black and white water rivers and minimal in clear water rivers during low water. The abundance of genetic markers for methane-oxidizing bacteria (pmoA) was positively correlated with enhanced signals of oxidation, providing independent support for the detected MOX patterns. The results indicate that MOX in large Amazonian rivers can consume from 0.45 to 2.07 Tg CH4 yr(-1), representing up to 7% of the estimated global soil sink. Nevertheless, climate change and changes in hydrology, for example, due to construction of dams, can alter this balance, influencing CH4 emissions to atmosphere.
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| 10. |
- Bastviken, David, et al.
(författare)
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The importance of plants for methane emission at the ecosystem scale
- 2023
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Ingår i: Aquatic Botany. - : ELSEVIER. - 0304-3770 .- 1879-1522. ; 184
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Tidskriftsartikel (refereegranskat)abstract
- Methane (CH4), one of the key long-lived atmospheric greenhouse gases, is primarily produced from organic matter. Accordingly, net primary production of organic matter sets the boundaries for CH4 emissions. Plants, being dominant primary producers, are thereby indirectly sustaining most global CH4 emissions, albeit with delays in time and with spatial offsets between plant primary production and subsequent CH4 emission. In addition, plant communities can enhance or hamper ecosystem production, oxidation, and transport of CH4 in multiple ways, e.g., by shaping carbon, nutrient, and redox gradients, and by representing a physical link be-tween zones with extensive CH4 production in anoxic sediments or soils and the atmosphere. This review focuses on how plants and other primary producers influence CH4 emissions with the consequences at ecosystem scales. We outline mechanisms of interactions and discuss flux regulation, quantification, and knowledge gaps across multiple ecosystem examples. Some recently proposed plant-related ecosystem CH4 fluxes are difficult to reconcile with the global atmospheric CH4 budget and the enigmas related to these fluxes are highlighted. Overall, ecosystem CH4 emissions are strongly linked to primary producer communities, directly or indirectly, and properly quantifying magnitudes and regulation of these links are key to predicting future CH4 emissions in a rapidly changing world.
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