The influence of methane oxidation on the stable isotopic composition of methane emitted from Florida swamp forests

Journal Article · Sat Oct 01 04:00:00 EDT 1994 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(94)90341-7· OSTI ID:6487850

Happell, J D; Chanton, J P ^[1]; Showers, W S ^[2]

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1. Florida State Univ., Tallahassee, FL (United States)
2. North Carolina State Univ., Raleigh, NC (United States)

This study reports the first measurements of the [delta][sup 13]C of CH[sub 4] emitted from seasonally flooded swamp forests in the southeastern United States. The seasonally averaged [delta][sup 13]C of CH[sub 4] emitted from a north Florida swamp forest located in the St. Marks National Wildlife Refuge was -52.7 [+-] 6.11[per thousand] (error is [+-] one standard deviation throughout, n = 28), a value [sup 13]C-enriched, relative to typical wetland emissions. In an Everglades cypress dome, the average [delta][sup 13]C of emitted CH[sub 4] was -52.5 [+-] 6.7 [per thousand] (n = 3). Consistent with attenuation of CH[sub 4] emission by CH[sub 4] oxidation in these environments, CH[sub 4] emitted via diffusion from the St. Marks swamp forest was enriched in [sup 13]C by 6.4 [+-] 5.8 [per thousand] (n = 28) and D by 57 [+-] 36 [per thousand] (n = 6) relative to sedimentary CH[sub 4]. Emission experiments, performed in situ with inhibitors of aerobic CH[sub 4] oxidizing bacteria, were used to calculate the fractionation factors ([alpha]) for stable carbon and hydrogen isotopes of CH[sub 4] undergoing transport and oxidation. Values ranged from 1.003 to 1.021 and 1.050 to 1.129, respectively. The best estimates for carbon and hydrogen [alpha] values were 1.020 and 1.068, respectively. The [delta] values of produced (sedimentary) CH[sub 4] were relatively constant in the St. Marks subtropical swamp forest. Additionally, because the transport of CH[sub 4] to the atmosphere was dominated by molecular diffusion, variations in the magnitude of CH[sub 4] oxidation appeared to be the primary factor controlling the [delta] values of emitted CH[sub 4]. This contrasts with systems dominated by bubble ebullition, where variations in CH[sub 4] production mechanisms have been hypothesized to be the primary factor controlling the [delta] values of emitted CH[sub 4].

• OSTI ID: 6487850
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 58:20; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540120* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
ALKANES
ATMOSPHERIC CHEMISTRY
CARBON 13
CARBON ISOTOPES
CHEMICAL REACTIONS
CHEMISTRY
EARTH ATMOSPHERE
ECOLOGICAL CONCENTRATION
EVEN-ODD NUCLEI
HYDROCARBONS
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
METHANE
NUCLEI
ORGANIC COMPOUNDS
OXIDATION
STABLE ISOTOPES