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HERO ID
6109155
Reference Type
Journal Article
Title
BIOGEOCHEMICAL CYCLING IN AN ORGANIC-RICH COASTAL MARINE BASIN .1. METHANE SEDIMENT-WATER EXCHANGE PROCESSES
Author(s)
Martens, CS; Valklump, J
Year
1980
Is Peer Reviewed?
Yes
Journal
Geochimica et Cosmochimica Acta
ISSN:
0016-7037
Volume
44
Issue
3
Page Numbers
471-490
DOI
10.1016/0016-7037(80)90045-9
Web of Science Id
WOS:A1980JH64700007
URL
http://www.sciencedirect.com/science/article/pii/0016703780900459
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Abstract
Methane produced in anoxic organic-rich sediments of Cape Lookout Bight, North Carolina, enters the water column via two seasonally dependent mechanisms: diffusion and bubble ebullition. Diffusive transport measured in situ with benthic chambers averages 49 and 163 μmol · m −2 · hr −1 during November–May and June–October respectively. High summer sediment methane production causes saturation concentrations and formation of bubbles near the sediment-water interface. Subsequent bubble ebullition is triggered by low-tide hydrostatic pressure release. June–October sediment-water gas fluxes at the surface average 411 ml (377 ml STP: 16.8 mmol) · m−2 per low tide. Bubbling maintains open bubble tubes which apparently enhance diffusive transport. When tubes are present, apparent sediment diffusivities are 1.2–3.1-fold higher than theoretical molecular values reaching a peak value of 5.2 × 10−5 cm2 · sec−1. Dissolution of 15% of the rising bubble flux containing 86% methane supplies 170μmol · m−2 · hr−1 of methane to the bight water column during summer months; the remainder is lost to the troposphere. Bottom water methane concentration increases observed during bubbling can be predicted using a 5–15 μm stagnant boundary layer dissolution model. Advective transport to surrounding waters is the major dissolved methane sink: aerobic oxidation and diffusive atmospheric evasion losses are minor within the bight.
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