Spatially Resolved Measurements in Tropical Reservoirs Reveal Elevated Methane Ebullition at River Inflows and at High Productivity

Linkhorst, Annika; Paranaíba, José R.; Mendonça, Raquel; Rudberg, David; DelSontro, Tonya; Barros, Nathan; Sobek, Sebastian

doi:10.1029/2020gb006717

Cited by 21 publications

(10 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The hotspot of gas content acoustically detected at the upstream region of Passaúna Reservoir indicates a higher potential for methane ebullition, which is confirmed by the highest ebullition flux recorded at the location P1. This is in accordance with numerous other studies, reporting high CH 4 fluxes in regions near to the main inflow river with high sedimentation rates (DelSontro et al, 2011;Grinham et al, 2018;Hilgert et al, 2019a;Linkhorst et al, 2021). Whereas in the deeper locations of the reservoir (monitoring sites P2 and P3), higher methane partial pressure is required for bubble formation, Figure 3B, which combined with the deposition of finer sediment particles may increase sediment cohesivity and capacity to hold the produced gas in the sediment, and thus, would explain the observed dynamics of cumulative ebullition fluxes (Figure 3C) at locations P2 and P3 with longer periods (days) of no ebullition.…”

Section: Methane Production Concentration and Ebullitionsupporting

confidence: 94%

“…Whereas, spatial variability of ebullition in lakes and reservoirs results from variations of methane production rates in the sediment, which depend on sediment temperature (Wilkinson et al, 2015), sediment thickness (Maeck et al, 2013) and organic matter content (Grasset et al, 2018). Shallow areas with high deposition rates of organic matter, such as river inflow regions, have been identified as ebullition hot spots (Beaulieu et al, 2016;Linkhorst et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Acoustic Mapping of Gas Stored in Sediments of Shallow Aquatic Systems Linked to Methane Production and Ebullition Patterns

Marcon

Sotiri

Bleninger

et al. 2022

Front. Environ. Sci.

View full text Add to dashboard Cite

Bubble-mediated transport is the predominant pathway of methane emissions from inland waters, which are a globally significant sources of the potent greenhouse gas to the atmosphere. High uncertainties exist in emission estimates due to high spatial and temporal variability. Acoustic methods have been applied for the spatial mapping of ebullition rates by quantification of rising gas bubbles in the water column. However, the high temporal variability of ebullition fluxes can influence estimates of mean emission rates if they are based on reduced surveys. On the other hand, echo sounding has been successfully applied to detect free gas stored in the sediment, which provide insights into the spatial variability of methane production and release. In this study, a subtropical, midsize, mesotrophic drinking water reservoir in Brazil was investigated to address the spatial and temporal variability of free gas stored in the sediment matrix. High spatial resolution maps of gas content in the sediment were estimated from echo-sounding surveys. The gas content was analyzed in relation to water depth, sediment deposition, and organic matter content (OMC) available from previous studies, to investigate its spatial variability. The analysis was further supported by measurements of potential methane production rates, porewater methane concentration, and ebullition flux. The largest gas content (above average) was found at locations with high sediment deposition, and its magnitude depended on the water depth. At shallow water depth (<10 m), high methane production rates support gas-rich sediment, and ebullition is observed to occur rather continuously. At larger water depth (>12 m), the gas stored in the sediment is released episodically during short events. An artificial neural network model was successfully trained to predict the gas content in the sediment as a function of water depth, OMC, and sediment thickness (R2 = 0.89). Largest discrepancies were observed in the regions with steep slopes and for low areal gas content (<4 L m−2). Although further improvements are proposed, we demonstrate the potential of echo-sounding for gas detection in the sediment, which combined with sediment and water body characteristics provides insights into the processes that regulate methane emissions from inland waters.

show abstract

Section: Methane Production Concentration and Ebullitionsupporting

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Acoustic Mapping of Gas Stored in Sediments of Shallow Aquatic Systems Linked to Methane Production and Ebullition Patterns

Marcon

Sotiri

Bleninger

et al. 2022

Front. Environ. Sci.

View full text Add to dashboard Cite

show abstract

“…(2019a) had on average 3 times higher sedimentation rates than the eutrophic Swedish lakes in the present study, and a transition age of only around 10 years (6.4–11.9 years corresponding to 9–23 cm depth). The overall lower transition age in the tropical reservoirs could also be explained by the high bottom water temperature (18–29°C) (Linkhorst et al., 2021; Quadra et al., 2020) triggering OM mineralization processes, particularly methanogenesis. The labile fraction of OM is therefore consumed more rapidly and the burial of OM that is recalcitrant to degradation occurs earlier.…”

Section: Discussionmentioning

confidence: 99%

Predicting Methane Formation Rates of Freshwater Sediments in Different Biogeographic Regions

Moras,

Zellmer,

Hiltunen

et al. 2024

JGR Biogeosciences

Self Cite

View full text Add to dashboard Cite

Freshwater lakes and reservoirs cover a small fraction of the Earth, however their emission of the greenhouse gas methane (CH4) from the sediment to the atmosphere is disproportionately high. Currently, there is still a limited understanding of the links between sediment characteristics and CH4 formation. Earlier studies have indicated that sediment age and nitrogen content are related to sediment CH4 formation rates, but it is uncertain such relationships are valid across gradients of sediment characteristics. We therefore measured potential CH4 formation rates in multiple layers of sediment sampled from nine lakes situated in the temperate, boreal and alpine biogeographic regions of Sweden, thus differing in productivity, catchment and climate properties. Potential CH4 formation varied over 3 orders of magnitude, and was broadly related to the quantity and reactivity of organic matter, and generally decreased with sediment depth. Sediment age and total nitrogen content were found to be the key controlling factors of potential CH4 formation rates, together explaining 62% of its variability. Moreover, the model developed from the Swedish lake sediment data was able to successfully predict the potential CH4 formation rates in reservoirs situated in different biogeographic regions of Brazil (R2 = 0.62). Therefore, potential CH4 formation rates in sediments of highly contrasting lakes and reservoirs, from Amazonia to alpine tundra, could be accurately predicted using one common model (RMSE = 1.6 in ln‐units). Our model provides a valuable tool to improve estimates of CH4 emission from lakes and reservoirs, and illustrates the fundamental regulation of microbial CH4 formation by organic matter characteristics.

show abstract

“…Longitudinal variations in PMP were mainly linked to sediment deposition patterns, as in our shallow system the sediment temperature was nearly homogenous across the monitoring sites. Reservoir geomorphology and sedimentation dynamics are key aspects for methane emission hot‐spots in reservoirs (DelSontro et al., 2011; Linkhorst et al., 2021). The narrow‐elongated shape of the reservoir with one main inflow led to sediment accumulation in the upstream regions near the inflow and in the regions outside the former river Talweg (mostly in the inner parts of the reservoir bends), which explains the slightly lower PMP at monitoring sites in the old riverbed (L01, L04 left, and L05).…”

Section: Discussionmentioning

confidence: 99%

Linking Sediment Gas Storage to the Methane Dynamics in a Shallow Freshwater Reservoir

Marcon,

Schwarz,

Backes

et al. 2023

JGR Biogeosciences

View full text Add to dashboard Cite

Freshwater reservoirs are globally relevant sources of the greenhouse gas methane. Organic matter rich sediments are hot spots of methane production and can store large amounts of methane dissolved in porewater and as free gas. Yet, in‐situ data on the gas storage as free gas (bubbles) in freshwater sediments are scarce. Here, an acoustic approach was tested and used to map the gas content in the sediment of a shallow temperate reservoir. The sediment gas storage was linked to the methane budget obtained from almost two years of in‐situ monitoring. The emission fluxes were dominated by ebullition and degassing at the reservoir outlet, which combined accounted for 93% of the total methane emissions. 66 % of the ebullition variability was explained by a combination of environmental parameters. Mappings of sediment gas content using echo sounder surveys revealed the accumulation of free gas in regions of elevated sediment deposition. Temporally, the gas storage in the sediment was related to methane emissions, in which a period of intensified emissions resulted in a reduction of sediment gas storage. The sediment could store an equivalent of four to thirteen days of accumulated potential methane production, which could supply the mean ebullition flux for more than two months. We suggest that sediment gas storage plays an important role in buffering and modulating methane emissions in aquatic systems and need to be accounted for in process‐based models.

show abstract

Spatially Resolved Measurements in Tropical Reservoirs Reveal Elevated Methane Ebullition at River Inflows and at High Productivity

Cited by 21 publications

References 43 publications

Acoustic Mapping of Gas Stored in Sediments of Shallow Aquatic Systems Linked to Methane Production and Ebullition Patterns

Acoustic Mapping of Gas Stored in Sediments of Shallow Aquatic Systems Linked to Methane Production and Ebullition Patterns

Predicting Methane Formation Rates of Freshwater Sediments in Different Biogeographic Regions

Linking Sediment Gas Storage to the Methane Dynamics in a Shallow Freshwater Reservoir

Contact Info

Product

Resources

About