title: Assessing methane oxidation under landfill covers and its contribution to the above atmospheric CO₂ levels: the added value of the isotope (δ¹³C and δ¹⁸O CO₂; δ¹³C and δD CH₄) approach.
abstract: We are presenting here a multi-isotope approach (δ¹³C and δ¹⁸O of CO₂; δ¹³C and δD of CH₄) to assess (i) the level(s) of methane oxidation during waste biodegradation and its migration through a landfill cover in Sonzay (France), and (ii) its contribution to the atmospheric CO₂ levels above the surface. The isotope approach is compared to the more conventional mass balance approach. Results from the two techniques are comparable and show that the CH₄ oxidation under the landfill cover is heterogenous, with low oxidation percentages in samples showing high biogas fluxes, which was expected in clay covers presenting fissures, through which CH₄ is rapidly transported. At shallow depth, more immobile biogas pockets show a higher level of CH₄ oxidation by the methanotrophic bacteria. δ¹³C of CO₂ samples taken at different heights (from below the cover up to 8m above the ground level) were also used to identify and assess the relative contributions of its main sources both under the landfill cover and in the surrounding atmosphere.
authors.affiliation: BRGM, 3 ave Claude Guillemin, 45000 Orléans, France. d.widory@brgm.fr
authors.forename: D
authors.initials: D
authors.lastname: Widory
authors.forename: E
authors.initials: E
authors.lastname: Proust
authors.forename: G
authors.initials: G
authors.lastname: Bellenfant
authors.forename: O
authors.initials: O
authors.lastname: Bour
mesh_terms: D000388:Air / Q000032:analysis; D002245:Carbon Dioxide / Q000032:analysis / Q000737:chemistry*; D002247:Carbon Isotopes / Q000032:analysis; D003903:Deuterium / Q000032:analysis; D005602:France; D008697:Methane / Q000737:chemistry*; D010084:Oxidation-Reduction; D018505:Waste Management
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide; D003903:Deuterium; D008697:Methane