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Towards a Better Knowledge of Natural Methane Releases in the French Alps: A Field Approach
Joint Authors
Gal, Frédérick
Proust, Eric
Kloppmann, Wolfram
Source
Issue
Vol. 2019, Issue 2019 (31 Dec. 2019), pp.1-16, 16 p.
Publisher
Hindawi Publishing Corporation
Publication Date
2019-06-10
Country of Publication
Egypt
No. of Pages
16
Main Subjects
Abstract EN
We report investigations performed at some hydrocarbon gas seeps located in the French Subalpine Chains in zones of outcropping Jurassic black shales, increasing the reported number of such occurrences in this part of the Alps.
We present the characteristics of each of the seeps, based on soil flux measurements and soil gas measurements.
Gases emitted are CH4-rich (87–94%) with the exception of one site (78.5% CH4 + 8.2% CO2) where an active landslide may induce dilution by atmospheric air.
CO2 is generally measured at low levels (<1.6%).
Concentrations in C2H6 are more variable, from less than 1% to more than 2.3%.
Gas is emitted over areas of various sizes.
The smallest gas emission area measures only 60×20 cm, characterized by a strong hydrocarbon flux (release of about 100 kg of CH4 per year).
At a second site, hydrocarbon emissions are measured over a surface of 12 m2.
For this site, methane emission is evaluated at 235 kg per year and CO2 emission is 600 kg per year, 210 kg being related to gas seepage.
At the third site, hydrocarbons are released over a 60 m2 area but strong gas venting is restricted to localized seeps.
Methane emission is evaluated at 5.1 tons per year and CO2 emission at 1.58 tons per year, out of which 0.53 tons are attributed to gas seepage.
Several historical locations remain uninvestigated at present, and numerous others may still be unknown.
We outline strategies to search for such unrecorded sites.
Considering the topography of the potential alpine and perialpine emission areas, the possibilities to detect gas emissions appear of the size recorded so far seem to be restricted to ground-based methods or to methods offering the possibility to point orthogonally to the soil towards the seep maximum.
If such sites are to be investigated in the future in the frame of Environmental Baseline Assessment (EBA), even establishing appropriate monitoring protocols will be challenging.
American Psychological Association (APA)
Gal, Frédérick& Proust, Eric& Kloppmann, Wolfram. 2019. Towards a Better Knowledge of Natural Methane Releases in the French Alps: A Field Approach. Geofluids،Vol. 2019, no. 2019, pp.1-16.
https://search.emarefa.net/detail/BIM-1154130
Modern Language Association (MLA)
Gal, Frédérick…[et al.]. Towards a Better Knowledge of Natural Methane Releases in the French Alps: A Field Approach. Geofluids No. 2019 (2019), pp.1-16.
https://search.emarefa.net/detail/BIM-1154130
American Medical Association (AMA)
Gal, Frédérick& Proust, Eric& Kloppmann, Wolfram. Towards a Better Knowledge of Natural Methane Releases in the French Alps: A Field Approach. Geofluids. 2019. Vol. 2019, no. 2019, pp.1-16.
https://search.emarefa.net/detail/BIM-1154130
Data Type
Journal Articles
Language
English
Notes
Includes bibliographical references
Record ID
BIM-1154130