scholarly journals Morphology, Formation, and Activity of Three Different Pockmark Systems in Peri-Alpine Lake Thun, Switzerland

2021 ◽  
Vol 3 ◽  
Author(s):  
Adeline N. Y. Cojean ◽  
Katrina Kremer ◽  
Maciej Bartosiewicz ◽  
Stefano C. Fabbri ◽  
Moritz F. Lehmann ◽  
...  
Keyword(s):  
Water Depth ◽  
Isotopic Signature ◽  
Karst System ◽  
Swath Bathymetry ◽  
Carbon Isotopic ◽  
Biogenic Carbon ◽  
Mechanisms Of Formation ◽  
Marine Realm ◽  
Variable Morphology ◽  
Exact Origin

Pockmarks are crater-like depressions formed by upward fluid flow (gas and/or liquid) through the unconsolidated sediment column on the floor of oceans and lakes. While pockmarks are well described in the marine realm, they have essentially been overlooked in lacustrine settings, likely due to a lack in economic interest to apply high-resolution hydroacoustic techniques in lakes. A swath-bathymetry survey on Lake Thun, Switzerland, revealed the existence of three pockmark systems. One pockmark (110 m in diameter) was discovered near a big karst system at Beatenberg at a water depth of ~217 m. Its activity is probably associated with episodic groundwater seepage induced by earthquakes, floods and snowmelt. At another site, Daerligen, we detected at ~60 m water depth the presence of multiple smaller pockmarks (~1.5 to 10 m in diameter) that seem to be active, continuously liberating CH4 gas by bubble ebullition. The CH4 displayed a biogenic carbon isotopic signature, however, the exact origin of the gas remains unknown. The third site, Tannmoos (~35 m water depth), comprises two large pockmarks (20–43 m in diameter) connected to a karst system in gypsum-carrying bedrock. One of these pockmarks is constituted of several unit pockmarks (e.g., sub-pockmarks; 0.3 to 0.8 m in diameter). While strong evidence is still lacking, we suggest that groundwater discharge occasionally occurs through these unit pockmarks during periods of intense precipitation. Hence, this study reveals the existence of three pockmark systems of variable morphology and mechanisms of formation within the same lake, reflecting different hydrological and biogeochemical regimes. Moreover, it underscores the potential importance of pockmarks in influencing hydrological and CH4 budgets in lakes. Clearly more work on quantifying seasonal fluxes of groundwater and CH4 release via lacustrine pockmarks is required, and it needs to be seen whether the observations made in Lake Thun are universal and apply also to many other lacustrine environments worldwide.

Seasonal variations in the stable carbon isotopic signature of biogenic methane in a coastal sediment

Science ◽  
1986 ◽  
Vol 233 (4770) ◽  
pp. 1300-1303 ◽  
Author(s):  
C. Martens ◽  
N. Blair ◽  
C. Green ◽  
D. Des Marais
Keyword(s):  
Seasonal Variations ◽  
Isotopic Signature ◽  
Coastal Sediment ◽  
Stable Carbon ◽  
Biogenic Methane ◽  
Carbon Isotopic

UK landfill methane emissions: Use of mobile plume measurements and carbon isotopic characterisation to reassess oxidation rates for open and closed sites 

2021 ◽  
Author(s):  
Semra Bakkaloglu ◽  
Dave Lowry ◽  
Rebecca Fisher ◽  
James France ◽  
Euan Nisbet
Keyword(s):  
Methane Oxidation ◽  
Mole Fraction ◽  
Oxidation Rate ◽  
Methane Emissions ◽  
Isotopic Signature ◽  
Oxidation Rates ◽  
Landfill Cover ◽  
Carbon Isotopic ◽  
Landfill Sites ◽  
The Impact

<p>Biological methane oxidation in landfill cover material can be characterised using stable isotopes. Methane oxidation fraction is calculated from the carbon isotopic signature of emitted CH<sub>4</sub>, with enhanced microbial consumption of methane in the aerobic portion of the landfill cover indicated by a shift to less depleted isotopic values in the residual methane emitted to air. This study was performed at four southwest England landfill sites. Mobile mole fraction measurement at the four sites was coupled with Flexfoil bag sampling of air for high-precision isotope analysis. Gas well samples collected from the pipeline systems and downwind plume air samples were utilized to estimate methane oxidation rate for whole sites. This work was designed to assess the impact on carbon isotopic signature and oxidation rate as UK landfill practice and waste streams have changed in recent years.</p><p>The landfill status such as closed and active, seasonal variation, cap stripping and site closure impact on landfill isotopic signature and oxidation rate were evaluated. The isotopic signature of <sup>13</sup>C-CH<sub>4</sub> values of emissions varied between -60 and -54‰, with an averaged value of -57 +- 2‰ for methane from closed and active landfill sites. Methane emissions from older, closed landfill sites were typically more enriched in <sup>13</sup>C than emissions from active sites. This study found that the isotopic signature of <sup>13</sup>C-CH<sub>4</sub> of fugitive methane did not show a seasonal trend, and there was no plume observed from a partial cap stripping process to assess changes in <sup>13</sup>C-CH<sub>4</sub>  isotopic signatures of emitted methane. Also, the closure of an active landfill cell caused a significant decrease in mole fraction of measured CH<sub>4</sub>, which was less depleted <sup>13</sup>C in the emitted plume due to a higher oxidation rate. Methane oxidation, estimated from the isotope fractionation, ranged from 3 to 27%, with mean values of 7% and 15% for active and closed landfills, respectively. These results indicate that the oxidation rate is highly site specific.</p><p> </p>

Co-Isotopic Signature of Two Mechanisms of Basal-Ice Formation in Arctic Outlet Glaciers

1988 ◽  
Vol 10 ◽  
pp. 163-166 ◽  
Author(s):  
R. Souchez ◽  
R. Lorrain ◽  
J.L. Tison ◽  
J. Jouzel
Keyword(s):  
Water Pressure ◽  
Isotopic Signature ◽  
Ice Formation ◽  
Basal Ice ◽  
Basal Sliding ◽  
Mechanisms Of Formation ◽  
Pressure Melting

Basal ice is formed by regelation as a consequence of both pressure-melting and freezing-on at the glacier sole.A study of D/H and 18O/16O ratios in basal ice from five Arctic outlet glaciers indicates that a co-isotopic signature exists for these two mechanisms of formation.The dispersed and stratified facies of basal ice present in these glaciers are related respectively to the occurrence of regelation and to freezing-on at the glacier base. Their origin is tentatively connected with the onset of basal sliding and the zone of bed decoupling due to basal water pressure in these Arctic outlet glaciers.

Effectiveness of carbon isotopic signature for estimating soil erosion and deposition rates in Sicilian vineyards

2015 ◽  
Vol 152 ◽  
pp. 1-7 ◽  
Author(s):  
Novara Agata ◽  
Cerdà Artemi ◽  
Dazzi Carmelo ◽  
Lo Papa Giuseppe ◽  
Santoro Antonino ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Isotopic Signature ◽  
Erosion And Deposition ◽  
Deposition Rates ◽  
Carbon Isotopic

scholarly journals Physiological controls of the isotopic time lag between leaf assimilation and soil CO2 efflux

2014 ◽  
Vol 41 (8) ◽  
pp. 850 ◽  
Author(s):  
Yann Salmon ◽  
Romain L. Barnard ◽  
Nina Buchmann
Keyword(s):  
Environmental Changes ◽  
Ecosystem Respiration ◽  
Isotopic Signature ◽  
Sink Strength ◽  
Clear Understanding ◽  
Co2 Efflux ◽  
Carbon Isotopic ◽  
Environmental Controls ◽  
Carbon Transfer ◽  
Wide Range

Environmental factors and physiological controls on photosynthesis influence the carbon isotopic signature of ecosystem respiration. Many ecosystem studies have used stable carbon isotopes to investigate environmental controls on plant carbon transfer from above- to belowground. However, a clear understanding of the internal mechanisms underlying time-lagged responses of carbon isotopic signatures in ecosystem respiration to environmental changes is still lacking. This study addressed plant physiological controls on the transfer time of recently assimilated carbon from assimilation to respiration. We produced a set of six wheat plants with varying physiological characteristics, by growing them under a wide range of nitrogen supply and soil water content levels under standardised conditions. The plants were pulse-labelled with 13C-CO2, and the isotopic signature of CO2 respired in the dark by plants and soil was monitored continuously over two days. Stomatal conductance (gs) was strongly related to the rate of transfer of recently assimilated carbon belowground. The higher gs, the faster newly assimilated carbon was allocated belowground and the faster it was respired in the soil. Our results suggest that carbon sink strength of plant tissues may be a major driver of transfer velocity of recently assimilated carbon to plant respiratory tissues and soil respiration.

scholarly journals Combining Geoelectrical Measurements and CO2Analyses to Monitor the Enhanced Bioremediation of Hydrocarbon-Contaminated Soils: A Field Implementation

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Cécile Noel ◽  
Jean-Christophe Gourry ◽  
Jacques Deparis ◽  
Michaela Blessing ◽  
Ioannis Ignatiadis ◽  
...  
Keyword(s):  
Contaminated Soils ◽  
Isotopic Ratio ◽  
Geophysical Methods ◽  
Isotopic Signature ◽  
Geophysical Monitoring ◽  
Carbon Isotopic Ratio ◽  
Carbon Isotopic ◽  
Enhanced Biodegradation ◽  
Enhanced Bioremediation

Hydrocarbon-contaminated aquifers can be successfully remediated through enhanced biodegradation. However,in situmonitoring of the treatment by piezometers is expensive and invasive and might be insufficient as the information provided is restricted to vertical profiles at discrete locations. An alternative method was tested in order to improve the robustness of the monitoring. Geophysical methods, electrical resistivity (ER) and induced polarization (IP), were combined with gas analyses, CO2concentration, and its carbon isotopic ratio, to develop a less invasive methodology for monitoring enhanced biodegradation of hydrocarbons. The field implementation of this monitoring methodology, which lasted from February 2014 until June 2015, was carried out at a BTEX-polluted site under aerobic biotreatment. Geophysical monitoring shows a more conductive and chargeable area which corresponds to the contaminated zone. In this area, high CO2emissions have been measured with an isotopic signature demonstrating that the main source of CO2on this site is the biodegradation of hydrocarbon fuels. Besides, the evolution of geochemical and geophysical data over a year seems to show the seasonal variation of bacterial activity. Combining geophysics with gas analyses is thus promising to provide a new methodology forin situmonitoring.

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