40 results on '"DelSontro T"'
Search Results
2. Sediment dynamics in the subaquatic channel of the Rhone delta (Lake Geneva, France/Switzerland)
- Author
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Corella, J. P., Arantegui, A., Loizeau, J. L., DelSontro, T., le Dantec, N., Stark, N., Anselmetti, F. S., and Girardclos, S.
- Published
- 2014
- Full Text
- View/download PDF
3. Spatial heterogeneity of benthic methane dynamics in the subaquatic canyons of the Rhone River Delta (Lake Geneva)
- Author
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Sollberger, S., Corella, J. P., Girardclos, S., Randlett, M.-E., Schubert, C. J., Senn, D. B., Wehrli, B., and DelSontro, T.
- Published
- 2014
- Full Text
- View/download PDF
4. Spatial heterogeneity of benthic methane dynamics in the subaquatic canyons of the Rhone River Delta (Lake Geneva)
- Author
-
Sollberger, S., Corella, J., Girardclos, S., Randlett, M.-E, Schubert, C., Senn, D., Wehrli, B., DelSontro, T., Sollberger, S., Corella, J., Girardclos, S., Randlett, M.-E, Schubert, C., Senn, D., Wehrli, B., and DelSontro, T.
- Abstract
Heterogeneous benthic methane (CH4) dynamics from river deltas with important organic matter accumulation have been recently reported in various aquatic and marine environments. The spatial heterogeneity of dissolved CH4 concentrations and associated production and diffusion rates were investigated in the Rhone River Delta of Lake Geneva (Switzerland/France) using sediment cores taken as part of the éLEMO Project. Benthic CH4 dynamics within the complex subaquatic canyon structure of the Rhone Delta were compared (1) between three canyons of different sedimentation regimes, (2) along a longitudinal transect of the ‘active' canyon most influenced by the Rhone River, and (3) laterally across a canyon. Results indicated higher CH4 diffusion and production rates in the ‘active' compared to the other canyons, explained by more allochthonous carbon deposition. Within the active canyon, the highest diffusion and production rates were found at intermediate sites further along the canyon. Stronger resuspension of sediments directly in front of the river inflow was likely the cause for the variable emission rates found there. Evidence also suggests more CH4 production occurs on the levees (shoulders) of canyons due to preferred sedimentation in those locations. Our results from the heterogeneous Rhone delta in Lake Geneva further support the concept that high sedimentary CH4 concentrations should be expected in depositional environments with high inputs of allochthonous organic carbon.
- Published
- 2019
5. Sediment dynamics in the subaquatic channel of the Rhone delta (Lake Geneva, France/Switzerland)
- Author
-
Corella, J., Arantegui, A., Loizeau, J., DelSontro, T., le Dantec, N., Stark, N., Anselmetti, F., Girardclos, S., Corella, J., Arantegui, A., Loizeau, J., DelSontro, T., le Dantec, N., Stark, N., Anselmetti, F., and Girardclos, S.
- Abstract
With its smaller size, well-known boundary conditions, and the availability of detailed bathymetric data, Lake Geneva's subaquatic canyon in the Rhone Delta is an excellent analogue to understand sedimentary processes in deep-water submarine channels. A multidisciplinary research effort was undertaken to unravel the sediment dynamics in the active canyon. This approach included innovative coring using the Russian MIR submersibles, in situ geotechnical tests, and geophysical, sedimentological, geochemical and radiometric analysis techniques. The canyon floor/levee complex is characterized by a classic turbiditic system with frequent spillover events. Sedimentary evolution in the active canyon is controlled by a complex interplay between erosion and sedimentation processes. In situ profiling of sediment strength in the upper layer was tested using a dynamic penetrometer and suggests that erosion is the governing mechanism in the proximal canyon floor while sedimentation dominates in the levee structure. Sedimentation rates progressively decrease down-channel along the levee structure, with accumulation exceeding 2.6cm/year in the proximal levee. A decrease in the frequency of turbidites upwards along the canyon wall suggests a progressive confinement of the flow through time. The multi-proxy methodology has also enabled a qualitative slope-stability assessment in the levee structure. The rapid sediment loading, slope undercutting and over-steepening, and increased pore pressure due to high methane concentrations hint at a potential instability of the proximal levees. Furthermore, discrete sandy intervals show very high methane concentrations and low shear strength and thus could correspond to potentially weak layers prone to scarp failures.
- Published
- 2019
6. Size Does Matter: Importance of Large Bubbles and Small-Scale Hot Spots for Methane Transport
- Author
-
DelSontro, T., McGinnis, Daniel, Wehrli, B., Ostrovsky, I., DelSontro, T., McGinnis, Daniel, Wehrli, B., and Ostrovsky, I.
- Abstract
Ebullition (bubbling) is an important mechanism for the transfer of methane (CH4) from shallow waters to the atmosphere. Because of their stochastic nature, however, ebullition fluxes are difficult to accurately resolve. Hydroacoustic surveys have the potential to significantly improve the spatiotemporal observation of emission fluxes, but knowledge of bubble size distribution is also necessary to accurately assess local, regional, and global water body CH4 emission estimates. Therefore, we explore the importance of bubble size and small-scale flux variability on CH4 transport in and emissions from a reservoir with a bubble-size-calibrated echosounder that can efficiently and economically survey greater areas while still resolving individual bubbles. Using a postprocessing method that resolves bubble density, we found that the largest 10% of the >6700 observed bubbles were responsible for more than 65% of the total CH4 transport. Furthermore, the asymmetry of CH4 ebullition flux distribution and the high spatial heterogeneity of those fluxes suggests that inadvertently omitting emission hot spots (i.e., areas of high flux) could lead to significant underestimations of CH4 emissions from localized areas and potentially from entire water bodies. While the bubble sizes resolved by the hydroacoustic method may provide insight into the factors controlling ebullition (e.g., sediment type, carbon sedimentation), the better resolution of small-scale CH4 emission hot spots afforded by hydroacoustics will bring us closer to the true CH4 emission estimates from all shallow waters, be them lakes, reservoirs, or coastal oceans and seas.
- Published
- 2015
- Full Text
- View/download PDF
7. Preface: Towards a full greenhouse gas balance of the biosphere
- Author
-
Merbold, L., Wohlfahrt, G., Butterbach-Bahl, K., Pilegaard, Kim, DelSontro, T., Stoy, P., Zona, D., Merbold, L., Wohlfahrt, G., Butterbach-Bahl, K., Pilegaard, Kim, DelSontro, T., Stoy, P., and Zona, D.
- Abstract
Ecosystem greenhouse gas (GHG) emissions (CO2, CH4, and N2O) represent a major driver of global environmental change (IPCC, 2014). While there exists an emerging understanding on the net exchange of CO2 across terrestrial and aquatic ecosystems due in part to the existence of large measurement and modeling networks (Baldocchi et al., 2001; Friend et al., 2007; Raymond et al., 2013; Tranvik et al., 2009), similar information on the biosphere–atmosphere exchange of non-CO2 greenhouse gases (i.e., CH4 and N2O) is sparsely available in comparison. To date, a strong focus has been given to so-called high-emission ecosystems, such as wetlands, rivers and lakes, rice cultivations and ruminants for CH4 (Nisbet et al., 2014) and agricultural ecosystems for N2O emissions (Butterbach-Bahl et al., 2013; Sutton et al., 2007). Even though CO2, CH4, and N2O emissions have been increasing during the last century, a combined quantification of the exchange of these three major greenhouse gases from a wide range of terrestrial and aquatic ecosystems is still missing. Therefore, approaches to develop full greenhouse gas monitoring networks, as currently undertaken in larger environmental research infrastructures such as ICOS (Integrated Carbon Observation System) and NEON (National Ecological Observation Network), are highly valuable.
- Published
- 2015
8. Influence of river inflow and organic matter loads on benthic methane fluxes in the Rhone Delta (Lake Geneva)
- Author
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Sollberger, S., Corella, J.P., Girardclos, S., Randlett, M.-E., Schubert, C.J., Senn, D., Wehrli, B., Delsontro, T., Spanish National Research Council (CSIC), University of Geneva [Switzerland], ANR-11-LABX-0010,DRIIHM / IRDHEI,Dispositif de recherche interdisciplinaire sur les Interactions Hommes-Milieux(2011), Pardo, Corinne, and Dispositif de recherche interdisciplinaire sur les Interactions Hommes-Milieux - - DRIIHM / IRDHEI2011 - ANR-11-LABX-0010 - LABX - VALID
- Subjects
[SDE.ES] Environmental Sciences/Environmental and Society ,[SDE.ES]Environmental Sciences/Environmental and Society ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2013
9. Preface: Towards a full greenhouse gas balance of the biosphere
- Author
-
Merbold, L., primary, Wohlfahrt, G., additional, Butterbach-Bahl, K., additional, Pilegaard, K., additional, DelSontro, T., additional, Stoy, P., additional, and Zona, D., additional
- Published
- 2015
- Full Text
- View/download PDF
10. Size Does Matter: Importance of Large Bubbles and Small-Scale Hot Spots for Methane Transport
- Author
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DelSontro, T., primary, McGinnis, D. F., additional, Wehrli, B., additional, and Ostrovsky, I., additional
- Published
- 2015
- Full Text
- View/download PDF
11. Anthropogenic and natural methane fluxes in Switzerland synthesized within a spatially explicit inventory
- Author
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Hiller, R V, Bretscher, D, DelSontro, T, Diem, T, Eugster, W, Henneberger, R, Hobi, S, Hodson, E, Imer, D, Kreuzer, M, Künzle, T, Merbold, L, Niklaus, P A, Rihm, B, Schellenberger, A, Schroth, M H, Schubert, C J, Siegrist, H, Stieger, J, Buchmann, N, Brunner, D, Hiller, R V, Bretscher, D, DelSontro, T, Diem, T, Eugster, W, Henneberger, R, Hobi, S, Hodson, E, Imer, D, Kreuzer, M, Künzle, T, Merbold, L, Niklaus, P A, Rihm, B, Schellenberger, A, Schroth, M H, Schubert, C J, Siegrist, H, Stieger, J, Buchmann, N, and Brunner, D
- Abstract
We present the first high-resolution (500 m × 500 m) gridded methane (CH4) emission inventory for Switzerland, which integrates 90 % of the national emission totals reported to the United Nations Framework Convention on Climate Change (UNFCCC) and recent CH4 flux studies conducted by research groups across Switzerland. In addition to anthropogenic emissions, we also include natural and semi-natural CH4 fluxes, i.e., emissions from lakes and reservoirs, wetlands, wild animals as well as uptake by forest soils. National CH4 emissions were disaggregated using detailed geostatistical information on source locations and their spatial extent and process- or area-specific emission factors. In Switzerland, the highest CH4 emissions in 2011 originated from the agricultural sector (150 Gg CH4 yr−1), mainly produced by ruminants and manure management, followed by emissions from waste management (15 Gg CH4 yr−1) mainly from landfills and the energy sector (12 Gg CH4 yr−1), which was dominated by emissions from natural gas distribution. Compared with the anthropogenic sources, emissions from natural and semi-natural sources were relatively small (6 Gg CH4 yr−1), making up only 3% of the total emissions in Switzerland. CH4 fluxes from agricultural soils were estimated to be not significantly different from zero (between −1.5 and 0 Gg CH4 yr−1), while forest soils are a CH4 sink (approx. −2.8 Gg CH4 yr−1), partially offsetting other natural emissions. Estimates of uncertainties are provided for the different sources, including an estimate of spatial disaggregation errors deduced from a comparison with a global (EDGAR v4.2) and an European (TNO/MACC) CH4 inventory. This new spatially explicit emission inventory for Switzerland will provide valuable input for regional-scale atmospheric modeling and inverse source estimation.
- Published
- 2014
12. Anthropogenic and natural methane fluxes in Switzerland synthesized within a spatially explicit inventory
- Author
-
Hiller, R. V., primary, Bretscher, D., additional, DelSontro, T., additional, Diem, T., additional, Eugster, W., additional, Henneberger, R., additional, Hobi, S., additional, Hodson, E., additional, Imer, D., additional, Kreuzer, M., additional, Künzle, T., additional, Merbold, L., additional, Niklaus, P. A., additional, Rihm, B., additional, Schellenberger, A., additional, Schroth, M. H., additional, Schubert, C. J., additional, Siegrist, H., additional, Stieger, J., additional, Buchmann, N., additional, and Brunner, D., additional
- Published
- 2014
- Full Text
- View/download PDF
13. Anthropogenic and natural methane fluxes in Switzerland synthesized within a spatially-explicit inventory
- Author
-
Hiller, R V, Bretscher, D, DelSontro, T, Diem, T, Eugster, W, Henneberger, R, Hobi, S, Hodson, E, Imer, D, Kreuzer, M, Künzle, T, Merbold, L, Niklaus, P A, Rihm, B, Schellenberger, A, Schroth, M H, Schubert, C J, Siegrist, H, Stieger, J, Buchmann, N, Brunner, D, Hiller, R V, Bretscher, D, DelSontro, T, Diem, T, Eugster, W, Henneberger, R, Hobi, S, Hodson, E, Imer, D, Kreuzer, M, Künzle, T, Merbold, L, Niklaus, P A, Rihm, B, Schellenberger, A, Schroth, M H, Schubert, C J, Siegrist, H, Stieger, J, Buchmann, N, and Brunner, D
- Abstract
We present the first high-resolution (500 m × 500 m) gridded methane (CH4) emission inventory for Switzerland, which integrates the national emission totals reported to the United Nations Framework Convention on Climate Change (UNFCCC) and recent CH4 flux studies conducted by research groups across Switzerland. In addition to anthropogenic emissions, we also include natural and semi-natural CH4 fluxes, i.e., emissions from lakes and reservoirs, wetlands, wild animals as well as uptake by forest soils. National CH4 emissions were disaggregated using detailed geostatistical information on source locations and their spatial extent and process- or area-specific emission factors. In Switzerland, the highest CH4 emissions in 2011 originated from the agricultural sector (150 Gg CH4 yr−1), mainly produced by ruminants and manure management, followed by emissions from waste management (15 Gg CH4 yr−1) mainly from landfills and the energy sector (12 Gg CH4 yr−1), which was dominated by emissions from natural gas distribution. Compared to the anthropogenic sources, emissions from natural and semi-natural sources were relatively small (6 Gg CH4 yr−1), making up only 3 % of the total emissions in Switzerland. CH4 fluxes from agricultural soils were estimated to be not significantly different from zero (between −1.5 and 0 Gg CH4 yr−1), while forest soils are a CH4 sink (approx. −2.8 Gg CH4 yr−1), partially offsetting other natural emissions. Estimates of uncertainties are provided for the different sources, including an estimate of spatial disaggregation errors deduced from a comparison with a global (EDGAR v4.2) and a European CH4 inventory (TNO/MACC). This new spatially-explicit emission inventory for Switzerland will provide valuable input for regional scale atmospheric modeling and inverse source estimation.
- Published
- 2013
14. Identifying hot-spot methane emission sites in an impounded river
- Author
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Maeck, A., Flury, S., DelSontro, T., Schmidt, Mark, McGinnis, Daniel, Fischer, H., Fietzek, Peer, Lorke, A., Maeck, A., Flury, S., DelSontro, T., Schmidt, Mark, McGinnis, Daniel, Fischer, H., Fietzek, Peer, and Lorke, A.
- Published
- 2012
15. Eddy covariance flux measurements confirm extreme CH(4) emissions from a Swiss hydropower reservoir and resolve their short-term variability
- Author
-
Eugster, W., DelSontro, T., Sobek, Sebastian, Eugster, W., DelSontro, T., and Sobek, Sebastian
- Abstract
Greenhouse gas budgets quantified via land-surface eddy covariance (EC) flux sites differ significantly from those obtained via inverse modeling. A possible reason for the discrepancy between methods may be our gap in quantitative knowledge of methane (CH(4)) fluxes. In this study we carried out EC flux measurements during two intensive campaigns in summer 2008 to quantify methane flux from a hydropower reservoir and link its temporal variability to environmental driving forces: water temperature and pressure changes (atmospheric and due to changes in lake level). Methane fluxes were extremely high and highly variable, but consistently showed gas efflux from the lake when the wind was approaching the EC sensors across the open water, as confirmed by floating chamber flux measurements. The average flux was 3.8 +/- 0.4 mu g C m(-2) s(-1) (mean +/- SE) with a median of 1.4 mu g C m(-2) s(-1), which is quite high even compared to tropical reservoirs. Floating chamber fluxes from four selected days confirmed such high fluxes with 7.4 +/- 1.3 mu g C m(-2) s(-1). Fluxes increased exponentially with increasing temperatures, but were decreasing exponentially with increasing atmospheric and/or lake level pressure. A multiple regression using lake surface temperatures (0.1 m depth), temperature at depth (10 m deep in front of the dam), atmospheric pressure, and lake level was able to explain 35.4% of the overall variance. This best fit included each variable averaged over a 9-h moving window, plus the respective short-term residuals thereof. We estimate that an annual average of 3% of the particulate organic matter (POM) input via the river is sufficient to sustain these large CH(4) fluxes. To compensate the global warming potential associated with the CH(4) effluxes from this hydropower reservoir a 1.3 to 3.7 times larger terrestrial area with net carbon dioxide uptake is needed if a European-scale compilation of grass-lands, croplands and forests is taken as reference. This
- Published
- 2011
- Full Text
- View/download PDF
16. Methane emissions from rivers – Results from sampling a 93-km longitudinal transect of river Saar, Germany
- Author
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Maeck, A., Flury, S., DelSontro, T., Schmidt, Mark, McGinnis, Daniel, Fischer, H., Lorke, A., Maeck, A., Flury, S., DelSontro, T., Schmidt, Mark, McGinnis, Daniel, Fischer, H., and Lorke, A.
- Published
- 2011
17. Methane bubble release - Oceans to Lakes
- Author
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McGinnis, Daniel, Delsontro, T. S., McGinnis, Daniel, and Delsontro, T. S.
- Published
- 2009
18. Spatial heterogeneity of benthic methane dynamics in the subaquatic canyons of the Rhone River Delta (Lake Geneva)
- Author
-
Sollberger, S., primary, Corella, J. P., additional, Girardclos, S., additional, Randlett, M.-E., additional, Schubert, C. J., additional, Senn, D. B., additional, Wehrli, B., additional, and DelSontro, T., additional
- Published
- 2013
- Full Text
- View/download PDF
19. Sediment dynamics in the subaquatic channel of the Rhone delta (Lake Geneva, France/Switzerland)
- Author
-
Corella, J. P., primary, Arantegui, A., additional, Loizeau, J. L., additional, DelSontro, T., additional, le Dantec, N., additional, Stark, N., additional, Anselmetti, F. S., additional, and Girardclos, S., additional
- Published
- 2013
- Full Text
- View/download PDF
20. Supplementary material to "Anthropogenic and natural methane fluxes in Switzerland synthesized within a spatially-explicit inventory"
- Author
-
Hiller, R. V., primary, Bretscher, D., additional, DelSontro, T., additional, Diem, T., additional, Eugster, W., additional, Henneberger, R., additional, Hobi, S., additional, Hodson, E., additional, Imer, D., additional, Kreuzer, M., additional, Künzle, T., additional, Merbold, L., additional, Niklaus, P. A., additional, Rihm, B., additional, Schellenberger, A., additional, Schroth, M. H., additional, Schubert, C. J., additional, Siegrist, H., additional, Stieger, J., additional, Buchmann, N., additional, and Brunner, D., additional
- Published
- 2013
- Full Text
- View/download PDF
21. Anthropogenic and natural methane fluxes in Switzerland synthesized within a spatially-explicit inventory
- Author
-
Hiller, R. V., primary, Bretscher, D., additional, DelSontro, T., additional, Diem, T., additional, Eugster, W., additional, Henneberger, R., additional, Hobi, S., additional, Hodson, E., additional, Imer, D., additional, Kreuzer, M., additional, Künzle, T., additional, Merbold, L., additional, Niklaus, P. A., additional, Rihm, B., additional, Schellenberger, A., additional, Schroth, M. H., additional, Schubert, C. J., additional, Siegrist, H., additional, Stieger, J., additional, Buchmann, N., additional, and Brunner, D., additional
- Published
- 2013
- Full Text
- View/download PDF
22. Eddy covariance flux measurements confirm extreme CH<sub>4</sub> emissions from a Swiss hydropower reservoir and resolve their short-term variability
- Author
-
Eugster, W., primary, DelSontro, T., additional, and Sobek, S., additional
- Published
- 2011
- Full Text
- View/download PDF
23. Anthropogenic and natural methane fluxes in Switzerland synthesized within a spatially-explicit inventory.
- Author
-
Hiller, R. V., Bretscher, D., DelSontro, T., Diem, T., Eugster, W., Henneberger, R., Hobi, S., Hodson, E., Imer, D., Kreuzer, M., Künzle, T., Merbold, L., Niklaus, P. A., Rihm, B., Schellenberger, A., Schroth, M. H., Schubert, C. J., Siegrist, H., Stieger, J., and Buchmann, N.
- Subjects
EMISSION inventories ,ATMOSPHERIC methane ,ANTHROPOGENIC effects on nature ,GEOGRAPHIC spatial analysis ,EMISSIONS (Air pollution) ,METHANE & the environment ,ATMOSPHERIC models ,GEOLOGICAL statistics - Abstract
We present the first high-resolution (500 m x 500 m) gridded methane (CH
4 ) emission inventory for Switzerland, which integrates the national emission totals reported to the United Nations Framework Convention on Climate Change (UNFCCC) and recent CH4 flux studies conducted by research groups across Switzerland. In addition to anthropogenic emissions, we also include natural and semi-natural CH4 fluxes, i. e., emissions from lakes and reservoirs, wetlands, wild animals as well as uptake by forest soils. National CH4 emissions were disaggregated using detailed geostatistical information on source locations and their spatial extent and process- or area-specific emission factors. In Switzerland, the highest CH4 emissions in 2011 originated from the agricultural sector (150 GgCH4 yr-1 ), mainly produced by ruminants and manure management, followed by emissions from waste management (15 GgCH4 yr-1 ) mainly from landfills and the energy sector (12 GgCH4 yr-1 ), which was dominated by emissions from natural gas distribution. Compared to the anthropogenic sources, emissions from natural and semi-natural sources were relatively small (6 GgCH4 yr-1 ), making up only 3% of the total emissions in Switzerland. CH4 fluxes from agricultural soils were estimated to be not significantly different from zero (between -1. 5 and 0 GgCH4 yr-1 ), while forest soils are a CH4 sink (approx. -2. 8 GgCH4 yr-1 ), partially offsetting other natural emissions. Estimates of uncertainties are provided for the different sources, including an estimate of spatial disaggregation errors deduced from a comparison with a global (EDGAR v4. 2) and a European CH4 inventory (TNO/MACC). This new spatially-explicit emission inventory for Switzerland will provide valuable input for regional scale atmospheric modeling and inverse source estimation. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
24. Eddy covariance flux measurements confirm extreme CH4 emissions from a Swiss hydropower reservoir and resolve their short-term variability.
- Author
-
Eugster, W., DelSontro, T., Sobek, S., and Wang, X.
- Subjects
WATER power ,METHANE ,RESERVOIRS ,EDDY flux ,MULTIPLE regression analysis ,ORGANIC compounds ,GLOBAL warming ,QUANTITATIVE research - Abstract
Greenhouse gas budgets quantified via land-surface eddy covariance (EC) flux sites differ significantly from those obtained via inverse modeling. A possible reason for the discrepancy between methods may be our gap in quantitative knowledge of methane (CH
4 ) fluxes. In this study we carried out EC flux measurements during two intensive campaigns in summer 2008 to quantify methane flux from a hydropower reservoir and link its temporal variability to environmental driving forces: water temperature and pressure changes (atmospheric and due to changes in lake level). Methane fluxes were extremely high and highly variable, but consistently showed gas efflux from the lake when the wind was approaching the EC sensors across the open water, as confirmed by floating chamber flux measurements. The average flux was 3.8±0.4 µg C m-2 s-1 (mean ± SE) with a median of 1.4 µg C m-2 s-1 , which is quite high even compared to tropical reservoirs. Floating chamber fluxes from four selected days confirmed such high fluxes with 7.4 ± 1.3 µg C m-2 s-1 . Fluxes increased exponentially with increasing temperatures, but were decreasing exponentially with increasing atmospheric and/or lake level pressure. A multiple regression using lake surface temperatures (0.1m depth), temperature at depth (10m deep in front of the dam), atmospheric pressure, and lake level was able to explain 35.4% of the overall variance. This best fit included each variable averaged over a 9-h moving window, plus the respective short-term residuals thereof. We estimate that an annual average of 3% of the particulate organic matter (POM) input via the river is sufficient to sustain these large CH4 fluxes. To compensate the global warming potential associated with the CH4 effluxes from this hydropower reservoir a 1.3 to 3.7 times larger terrestrial area with net carbon dioxide uptake is needed if a European-scale compilation of grass-lands, croplands and forests is taken as reference. This indicates the potential relevance of temperate reservoirs and lakes in local and regional greenhouse gas budgets. [ABSTRACT FROM AUTHOR]- Published
- 2011
- Full Text
- View/download PDF
25. Searching the Rhone delta channel in Lake Geneva since François Alphonse FOREL
- Author
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Girardclos, S., Hilbe, M., Corella, J. P., Loizeau, J. -L, Katrina Kremer, Delsontro, T., Arantegui, A., Moscariello, A., Arlaud, F., Akhtman, Y., Anselmetti, F. S., and Lemmin, U.
- Subjects
ddc:333.7-333.9 ,Submersible ,Underflow ,Rhone delta ,ddc:550 ,Canyon ,Lake Geneva ,Multibeam bathymetry ,Léman ,Channel - Abstract
In the late 19th century, F.A. FOREL led investigations of the Rhone River delta area of Lake Geneva that resulted in the discovery of a textbook example of a river-fed delta system containing impressive subaquatic channels. Well ahead of the marine counterparts, scientific observations and interpretations of water currents shaping the delta edifice for the first time documented how underflow currents carry cold, suspension-laden waters from the river mouth all the way to the deep basin. These early investigations of the Rhone delta laid the basis for follow-up studies in the 20th and 21th centuries. Sediment coring, water-column measurements, manned submersible diving, seismic reflection profiling and bathymetric surveying eventually provided a rich database to unravel the key erosional and depositional processes, further documenting the impact of human-induced changes in the catchment. With the merging of old and new scientific knowledge, today a comprehensive understanding prevails of how a delta changes through time, how its channels are formed, and what potential natural hazards may be related to its evolution. New and efficient bathymetric techniques, paired with novel coring operations, provided a time-series of morphologic evolution showing and quantifying the high dynamics of the delta/channel evolution in an unprecedented temporal and spatial resolution. Future investigations will continue to further quantify these dynamic processes and to link the evolution of the subaquatic domain with changes and processes in the catchment and with natural hazards. Its size, easy access, and large variety of states and processes will continue to make the Rhone delta area a perfect ‘laboratory' in which general processes can be studied that could be upscaled or downscaled to other marine and lacustrine deltas.
26. Anthropogenic and natural methane fluxes in Switzerland synthesized within a spatially explicit inventory
- Author
-
Hiller, R. V., Bretscher, D., Delsontro, T., Diem, T., Eugster, W., Henneberger, R., Hobi, S., Hodson, E., Imer, D., Kreuzer, M., Kuenzle, T., Lutz Merbold, Niklaus, P. A., Rihm, B., Schellenberger, A., Schroth, M. H., Schubert, C. J., Siegrist, H., Stieger, J., Buchmann, N., Brunner, D., University of Zurich, and Hiller, R V
- Subjects
Ecology ,Evolution ,lcsh:QE1-996.5 ,lcsh:Life ,1904 Earth-Surface Processes ,Earth ,lcsh:Geology ,lcsh:QH501-531 ,10127 Institute of Evolutionary Biology and Environmental Studies ,1105 Ecology, Evolution, Behavior and Systematics ,Surface Processes ,Behavior and Systematics ,lcsh:QH540-549.5 ,570 Life sciences ,biology ,590 Animals (Zoology) ,lcsh:Ecology - Abstract
We present the first high-resolution (500 m × 500 m) gridded methane (CH4) emission inventory for Switzerland, which integrates 90 % of the national emission totals reported to the United Nations Framework Convention on Climate Change (UNFCCC) and recent CH4 flux studies conducted by research groups across Switzerland. In addition to anthropogenic emissions, we also include natural and semi-natural CH4 fluxes, i.e., emissions from lakes and reservoirs, wetlands, wild animals as well as uptake by forest soils. National CH4 emissions were disaggregated using detailed geostatistical information on source locations and their spatial extent and process- or area-specific emission factors. In Switzerland, the highest CH4 emissions in 2011 originated from the agricultural sector (150 Gg CH4 yr−1), mainly produced by ruminants and manure management, followed by emissions from waste management (15 Gg CH4 yr−1) mainly from landfills and the energy sector (12 Gg CH4 yr−1), which was dominated by emissions from natural gas distribution. Compared with the anthropogenic sources, emissions from natural and semi-natural sources were relatively small (6 Gg CH4 yr−1), making up only 3% of the total emissions in Switzerland. CH4 fluxes from agricultural soils were estimated to be not significantly different from zero (between −1.5 and 0 Gg CH4 yr−1), while forest soils are a CH4 sink (approx. −2.8 Gg CH4 yr−1), partially offsetting other natural emissions. Estimates of uncertainties are provided for the different sources, including an estimate of spatial disaggregation errors deduced from a comparison with a global (EDGAR v4.2) and an European (TNO/MACC) CH4 inventory. This new spatially explicit emission inventory for Switzerland will provide valuable input for regional-scale atmospheric modeling and inverse source estimation.
27. Spatial heterogeneity of benthic methane dynamics in the subaquatic canyons of the Rhone River Delta (Lake Geneva)
- Author
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Sollberger, S., Corella, J., Girardclos, S., Randlett, M.-E, Schubert, C., Senn, D., Wehrli, B., DelSontro, T., Sollberger, S., Corella, J., Girardclos, S., Randlett, M.-E, Schubert, C., Senn, D., Wehrli, B., and DelSontro, T.
- Abstract
Heterogeneous benthic methane (CH4) dynamics from river deltas with important organic matter accumulation have been recently reported in various aquatic and marine environments. The spatial heterogeneity of dissolved CH4 concentrations and associated production and diffusion rates were investigated in the Rhone River Delta of Lake Geneva (Switzerland/France) using sediment cores taken as part of the éLEMO Project. Benthic CH4 dynamics within the complex subaquatic canyon structure of the Rhone Delta were compared (1) between three canyons of different sedimentation regimes, (2) along a longitudinal transect of the ‘active' canyon most influenced by the Rhone River, and (3) laterally across a canyon. Results indicated higher CH4 diffusion and production rates in the ‘active' compared to the other canyons, explained by more allochthonous carbon deposition. Within the active canyon, the highest diffusion and production rates were found at intermediate sites further along the canyon. Stronger resuspension of sediments directly in front of the river inflow was likely the cause for the variable emission rates found there. Evidence also suggests more CH4 production occurs on the levees (shoulders) of canyons due to preferred sedimentation in those locations. Our results from the heterogeneous Rhone delta in Lake Geneva further support the concept that high sedimentary CH4 concentrations should be expected in depositional environments with high inputs of allochthonous organic carbon.
28. Sediment dynamics in the subaquatic channel of the Rhone delta (Lake Geneva, France/Switzerland)
- Author
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Corella, J., Arantegui, A., Loizeau, J., DelSontro, T., le Dantec, N., Stark, N., Anselmetti, F., Girardclos, S., Corella, J., Arantegui, A., Loizeau, J., DelSontro, T., le Dantec, N., Stark, N., Anselmetti, F., and Girardclos, S.
- Abstract
With its smaller size, well-known boundary conditions, and the availability of detailed bathymetric data, Lake Geneva's subaquatic canyon in the Rhone Delta is an excellent analogue to understand sedimentary processes in deep-water submarine channels. A multidisciplinary research effort was undertaken to unravel the sediment dynamics in the active canyon. This approach included innovative coring using the Russian MIR submersibles, in situ geotechnical tests, and geophysical, sedimentological, geochemical and radiometric analysis techniques. The canyon floor/levee complex is characterized by a classic turbiditic system with frequent spillover events. Sedimentary evolution in the active canyon is controlled by a complex interplay between erosion and sedimentation processes. In situ profiling of sediment strength in the upper layer was tested using a dynamic penetrometer and suggests that erosion is the governing mechanism in the proximal canyon floor while sedimentation dominates in the levee structure. Sedimentation rates progressively decrease down-channel along the levee structure, with accumulation exceeding 2.6cm/year in the proximal levee. A decrease in the frequency of turbidites upwards along the canyon wall suggests a progressive confinement of the flow through time. The multi-proxy methodology has also enabled a qualitative slope-stability assessment in the levee structure. The rapid sediment loading, slope undercutting and over-steepening, and increased pore pressure due to high methane concentrations hint at a potential instability of the proximal levees. Furthermore, discrete sandy intervals show very high methane concentrations and low shear strength and thus could correspond to potentially weak layers prone to scarp failures.
29. Evaluation of the methane paradox in four adjacent pre-alpine lakes across a trophic gradient.
- Author
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Ordóñez C, DelSontro T, Langenegger T, Donis D, Suarez EL, and McGinnis DF
- Abstract
Contrasting the paradigm that methane is only produced in anoxic conditions, recent discoveries show that oxic methane production (OMP, aka the methane paradox) occurs in oxygenated surface waters worldwide. OMP drivers and their contribution to global methane emissions, however, are not well constrained. In four adjacent pre-alpine lakes, we determine the net methane production rates in oxic surface waters using two mass balance approaches, accounting for methane sources and sinks. We find that OMP occurs in three out of four studied lakes, often as the dominant source of diffusive methane emissions. Correlations of net methane production versus chlorophyll-a, Secchi and surface mixed layer depths suggest a link with photosynthesis and provides an empirical upscaling approach. As OMP is a methane source in direct contact with the atmosphere, a better understanding of its extent and drivers is necessary to constrain the atmospheric methane contribution by inland waters., (© 2023. The Author(s).)
- Published
- 2023
- Full Text
- View/download PDF
30. Practical Guide to Measuring Wetland Carbon Pools and Fluxes.
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Bansal S, Creed IF, Tangen BA, Bridgham SD, Desai AR, Krauss KW, Neubauer SC, Noe GB, Rosenberry DO, Trettin C, Wickland KP, Allen ST, Arias-Ortiz A, Armitage AR, Baldocchi D, Banerjee K, Bastviken D, Berg P, Bogard MJ, Chow AT, Conner WH, Craft C, Creamer C, DelSontro T, Duberstein JA, Eagle M, Fennessy MS, Finkelstein SA, Göckede M, Grunwald S, Halabisky M, Herbert E, Jahangir MMR, Johnson OF, Jones MC, Kelleway JJ, Knox S, Kroeger KD, Kuehn KA, Lobb D, Loder AL, Ma S, Maher DT, McNicol G, Meier J, Middleton BA, Mills C, Mistry P, Mitra A, Mobilian C, Nahlik AM, Newman S, O'Connell JL, Oikawa P, van der Burg MP, Schutte CA, Song C, Stagg CL, Turner J, Vargas R, Waldrop MP, Wallin MB, Wang ZA, Ward EJ, Willard DA, Yarwood S, and Zhu X
- Abstract
Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions., Supplementary Information: The online version contains supplementary material available at 10.1007/s13157-023-01722-2., Competing Interests: Competing InterestsThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© The Author(s) 2023.)
- Published
- 2023
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31. Interannual, summer, and diel variability of CH 4 and CO 2 effluxes from Toolik Lake, Alaska, during the ice-free periods 2010-2015.
- Author
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Eugster W, DelSontro T, Shaver GR, and Kling GW
- Subjects
- Alaska, Arctic Regions, Methane, Seasons, Carbon Dioxide analysis, Lakes
- Abstract
Accelerated warming in the Arctic has led to concern regarding the amount of carbon emission potential from Arctic water bodies. Yet, aquatic carbon dioxide (CO
2 ) and methane (CH4 ) flux measurements remain scarce, particularly at high resolution and over long periods of time. Effluxes of methane (CH4 ) and carbon dioxide (CO2 ) from Toolik Lake, a deep glacial lake in northern Alaska, were measured for the first time with the direct eddy covariance (EC) flux technique during six ice-free lake periods (2010-2015). CO2 flux estimates from the lake (daily average efflux of 16.7 ± 5.3 mmol m-2 d-1 ) were in good agreement with earlier estimates from 1975-1989 using different methods. CH4 effluxes in 2010-2015 (averaging 0.13 ± 0.06 mmol m-2 d-1 ) showed an interannual variation that was 4.1 times greater than median diel variations, but mean fluxes were almost one order of magnitude lower than earlier estimates obtained from single water samples in 1990 and 2011-2012. The overall global warming potential (GWP) of Toolik Lake is thus governed mostly by CO2 effluxes, contributing 86-93% of the ice-free period GWP of 26-90 g CO2,eq m-2 . Diel variation in fluxes was also important, with up to a 2-fold (CH4 ) to 4-fold (CO2 ) difference between the highest nighttime and lowest daytime effluxes. Within the summer ice-free period, on average, CH4 fluxes increased 2-fold during the first half of the summer, then remained almost constant, whereas CO2 effluxes remained almost constant over the entire summer, ending with a linear increase during the last 1-2 weeks of measurements. Due to the cold bottom temperatures of this 26 m deep lake, and the absence of ebullition and episodic flux events, Toolik Lake and other deep glacial lakes are likely not hot spots for greenhouse gas emissions, but they still contribute to the overall GWP of the Arctic.- Published
- 2020
- Full Text
- View/download PDF
32. Eutrophication will increase methane emissions from lakes and impoundments during the 21st century.
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Beaulieu JJ, DelSontro T, and Downing JA
- Abstract
Lakes and impoundments are an important source of methane (CH
4 ), a potent greenhouse gas, to the atmosphere. A recent analysis shows aquatic productivity (i.e., eutrophication) is an important driver of CH4 emissions from lentic waters. Considering that aquatic productivity will increase over the next century due to climate change and a growing human population, a concomitant increase in aquatic CH4 emissions may occur. We simulate the eutrophication of lentic waters under scenarios of future nutrient loading to inland waters and show that enhanced eutrophication of lakes and impoundments will substantially increase CH4 emissions from these systems (+30-90%) over the next century. This increased CH4 emission has an atmospheric impact of 1.7-2.6 Pg C-CO2 -eq y-1 , which is equivalent to 18-33% of annual CO2 emissions from burning fossil fuels. Thus, it is not only important to limit eutrophication to preserve fragile water supplies, but also to avoid acceleration of climate change.- Published
- 2019
- Full Text
- View/download PDF
33. Greenhouse gas emissions from lakes and impoundments: upscaling in the face of global change.
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DelSontro T, Beaulieu JJ, and Downing JA
- Abstract
Lakes and impoundments are important sources of greenhouse gases (GHG: i.e., CO
2 , CH4 , N2 O), yet global emission estimates are based on regionally-biased averages and elementary upscaling. We assembled the largest global dataset to date on emission rates of all three GHGs and found they covary with lake size and trophic state. Fitted models were upscaled to estimate global emission using global lake size inventories and a remotely-sensed global lake productivity distribution. Traditional upscaling approaches overestimated CO2 and N2 O emission but underestimated CH4 by half. Our upscaled size-productivity weighted estimates (1.25-2.30 Pg of CO2 -equivalents annually) are nearly 20% of global CO2 fossil fuel emission with ~75% of the climate impact due to CH4 . Moderate global increases in eutrophication could translate to 5-40% increases in the GHG effects in the atmosphere, adding the equivalent effect of another 13% of fossil fuel combustion or an effect equal to GHG emissions from current land use change.- Published
- 2019
- Full Text
- View/download PDF
34. Greenhouse Gas Emissions from Freshwater Reservoirs: What Does the Atmosphere See?
- Author
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Prairie YT, Alm J, Beaulieu J, Barros N, Battin T, Cole J, Del Giorgio P, DelSontro T, Guérin F, Harby A, Harrison J, Mercier-Blais S, Serça D, Sobek S, and Vachon D
- Abstract
Freshwater reservoirs are a known source of greenhouse gas (GHG) to the atmosphere, but their quantitative significance is still only loosely con- strained. Although part of this uncertainty can be attributed to the difficulties in measuring highly variable fluxes, it is also the result of a lack of a clear accounting methodology, particularly about what constitutes new emissions and potential new sinks. In this paper, we review the main processes involved in the generation of GHG in reservoir systems and propose a simple approach to quantify the reservoir GHG footprint in terms of the net changes in GHG fluxes to the atmosphere induced by damming, that is, 'what the atmosphere sees.' The approach takes into account the pre-impoundment GHG balance of the landscape, the temporal evolution of reservoir GHG emission profile as well as the natural emissions that are displaced to or away from the reservoir site resulting from hydrological and other changes. It also clarifies the portion of the reservoir carbon burial that can potentially be considered an offset to GHG emissions.
- Published
- 2018
- Full Text
- View/download PDF
35. Cross continental increase in methane ebullition under climate change.
- Author
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Aben RCH, Barros N, van Donk E, Frenken T, Hilt S, Kazanjian G, Lamers LPM, Peeters ETHM, Roelofs JGM, de Senerpont Domis LN, Stephan S, Velthuis M, Van de Waal DB, Wik M, Thornton BF, Wilkinson J, DelSontro T, and Kosten S
- Abstract
Methane (CH
4 ) strongly contributes to observed global warming. As natural CH4 emissions mainly originate from wet ecosystems, it is important to unravel how climate change may affect these emissions. This is especially true for ebullition (bubble flux from sediments), a pathway that has long been underestimated but generally dominates emissions. Here we show a remarkably strong relationship between CH4 ebullition and temperature across a wide range of freshwater ecosystems on different continents using multi-seasonal CH4 ebullition data from the literature. As these temperature-ebullition relationships may have been affected by seasonal variation in organic matter availability, we also conducted a controlled year-round mesocosm experiment. Here 4 °C warming led to 51% higher total annual CH4 ebullition, while diffusion was not affected. Our combined findings suggest that global warming will strongly enhance freshwater CH4 emissions through a disproportional increase in ebullition (6-20% per 1 °C increase), contributing to global warming.- Published
- 2017
- Full Text
- View/download PDF
36. Minor methane emissions from an Alpine hydropower reservoir based on monitoring of diel and seasonal variability.
- Author
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Sollberger S, Wehrli B, Schubert CJ, DelSontro T, and Eugster W
- Subjects
- Altitude, Carbon Dioxide analysis, Climate, Switzerland, Wind, Environmental Monitoring methods, Greenhouse Gases analysis, Methane analysis, Power Plants, Seasons
- Abstract
We monitored CH
4 emissions during the ice-free period of an Alpine hydropower reservoir in the Swiss Alps, Lake Klöntal, to investigate mechanisms responsible for CH4 variability and to estimate overall emissions to the atmosphere. A floating eddy-covariance platform yielded total CH4 and CO2 emission rates at high temporal resolution, while hydroacoustic surveys provided no indication of CH4 ebullition. Higher CH4 fluxes (2.9 ± 0.1 mg CH4 per m2 per day) occurred during the day when surface water temperatures were warmer and wind speeds higher than at night. Piston velocity estimates (k600 ) showed an upper limit at high wind speeds that may be more generally valid also for other lakes and reservoirs with limited CH4 dissolved in the water body: above 2.0 m s-1 a further increase in wind speed did not lead to higher CH4 fluxes, because under such conditions it is not the turbulent mixing and transport that limits effluxes, but the resupply of CH4 to the lake surface. Increasing CH4 fluxes during the warm season showed a clear spatial gradient once the reservoir started to fill up and flood additional surface area. The warm period contributed 27% of the total CH4 emissions (2.6 t CH4 per year) estimated for the full year and CH4 accounted for 63% of carbonic greenhouse gas emissions. Overall, the average CH4 emissions (1.7 to 2.2 mg CH4 per m2 per day determined independently from surface water samplings and eddy covariance, respectively) were small compared to most tropical and some temperate reservoirs. The resulting greenhouse gas (GHG) emissions in CO2 -equivalents revealed that electricity produced in the Lake Klöntal power plant was relatively climate-friendly with a low GHG-to-power output ratio of 1.24 kg CO2,eq per MW h compared to 6.5 and 8.1 kg CO2,eq per MW h associated with the operation of solar photovoltaics and wind energy, respectively, or about 980 kg CO2,eq per MW h for coal-fired power plants.- Published
- 2017
- Full Text
- View/download PDF
37. Greenhouse Gas Emissions from Reservoir Water Surfaces: A New Global Synthesis.
- Author
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Deemer BR, Harrison JA, Li S, Beaulieu JJ, DelSontro T, Barros N, Bezerra-Neto JF, Powers SM, Dos Santos MA, and Vonk JA
- Abstract
Collectively, reservoirs created by dams are thought to be an important source of greenhouse gases (GHGs) to the atmosphere. So far, efforts to quantify, model, and manage these emissions have been limited by data availability and inconsistencies in methodological approach. Here, we synthesize reservoir CH
4 , CO2 , and N2 O emission data with three main objectives: (1) to generate a global estimate of GHG emissions from reservoirs, (2) to identify the best predictors of these emissions, and (3) to consider the effect of methodology on emission estimates. We estimate that GHG emissions from reservoir water surfaces account for 0.8 (0.5-1.2) Pg CO2 equivalents per year, with the majority of this forcing due to CH4 . We then discuss the potential for several alternative pathways such as dam degassing and downstream emissions to contribute significantly to overall emissions. Although prior studies have linked reservoir GHG emissions to reservoir age and latitude, we find that factors related to reservoir productivity are better predictors of emission.- Published
- 2016
- Full Text
- View/download PDF
38. Sediment trapping by dams creates methane emission hot spots.
- Author
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Maeck A, Delsontro T, McGinnis DF, Fischer H, Flury S, Schmidt M, Fietzek P, and Lorke A
- Subjects
- Europe, Fresh Water, Rivers, Seasons, Geologic Sediments, Methane analysis, Water Pollutants, Chemical analysis
- Abstract
Inland waters transport and transform substantial amounts of carbon and account for ∼18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (∼0.23 mmol CH4 m(-2) d(-1) vs ∼19.7 mmol CH4 m(-2) d(-1), respectively) and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%.
- Published
- 2013
- Full Text
- View/download PDF
39. Spatial heterogeneity of methane ebullition in a large tropical reservoir.
- Author
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DelSontro T, Kunz MJ, Kempter T, Wüest A, Wehrli B, and Senn DB
- Subjects
- Bays, Environmental Monitoring, Lakes, Rivers, Tropical Climate, Methane analysis
- Abstract
Tropical reservoirs have been identified as important methane (CH(4)) sources to the atmosphere, primarily through turbine and downstream degassing. However, the importance of ebullition (gas bubbling) remains unclear. We hypothesized that ebullition is a disproportionately large CH(4) source from reservoirs with dendritic littoral zones because of ebullition hot spots occurring where rivers supply allochthonous organic material. We explored this hypothesis in Lake Kariba (Zambia/Zimbabwe; surface area >5000 km(2)) by surveying ebullition in bays with and without river inputs using an echosounder and traditional surface chambers. The two techniques yielded similar results, and revealed substantially higher fluxes in river deltas (∼10(3) mg CH(4) m(-2) d(-1)) compared to nonriver bays (<100 mg CH(4) m(-2) d(-1)). Hydroacoustic measurements resolved at 5 m intervals showed that flux events varied over several orders of magnitude (up to 10(5) mg CH(4) m(-2) d(-1)), and also identified strong differences in ebullition frequency. Both factors contributed to emission differences between all sites. A CH(4) mass balance for the deepest basin of Lake Kariba indicated that hot spot ebullition was the largest atmospheric emission pathway, suggesting that future greenhouse gas budgets for tropical reservoirs should include a spatially well-resolved analysis of ebullition hot spots.
- Published
- 2011
- Full Text
- View/download PDF
40. Extreme methane emissions from a Swiss hydropower reservoir: contribution from bubbling sediments.
- Author
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Delsontro T, McGinnis DF, Sobek S, Ostrovsky I, and Wehrli B
- Subjects
- Atmosphere chemistry, Oxidation-Reduction, Solubility, Surface Properties, Switzerland, Temperature, Time Factors, Fresh Water chemistry, Geologic Sediments chemistry, Methane analysis, Power Plants, Water Pollutants, Chemical analysis
- Abstract
Methane emission pathways and their importance were quantified during a yearlong survey of a temperate hydropower reservoir. Measurements using gas traps indicated very high ebullition rates, but due to the stochastic nature of ebullition a mass balance approach was crucial to deduce system-wide methane sources and losses. Methane diffusion from the sediment was generally low and seasonally stable and did not account for the high concentration of dissolved methane measured in the reservoir discharge. A strong positive correlation between water temperature and the observed dissolved methane concentration enabled us to quantify the dissolved methane addition from bubble dissolution using a system-wide mass balance. Finally, knowing the contribution due to bubble dissolution, we used a bubble model to estimate bubble emission directly to the atmosphere. Our results indicated that the total methane emission from Lake Wohlen was on average >150 mg CH(4) m(-2) d(-1), which is the highest ever documented for a midlatitude reservoir. The substantial temperature-dependent methane emissions discovered in this 90-year-old reservoir indicate that temperate water bodies can be an important but overlooked methane source.
- Published
- 2010
- Full Text
- View/download PDF
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