Diffusion and mass flow of dissolved carbon dioxide, methane, and dissolved organic carbon in a 7-m deep raised peat bog

Clymo, R.S. and Bryant, C.L. (2008) Diffusion and mass flow of dissolved carbon dioxide, methane, and dissolved organic carbon in a 7-m deep raised peat bog. Geochimica et Cosmochimica Acta, 72(8), pp. 2048-2066. (doi: 10.1016/j.gca.2008.01.032)

Abstract

In 65 samples, we got values (unusually replicable and consistent for this type of work) of concentration, 14C/13C (AMS) age, and δ13C for: peat, dissolved organic carbon (DOC), peat fractions, and dissolved CO2 and CH4 at 50-cm intervals down to 700 cm in Ellergower Moss, a rainwater-dependent raised (domed) bog in southwest Scotland. (1) We attribute the consistency of the results to Ellergower Moss being unusually homogeneous, with unusually low hydraulic conductivity, and containing only a few gas spaces; and to the sampling methods including 18-month equilibration of in situ samplers. (2) The dissolved gas concentration depth profiles are convex and very similar to each other, though CO2 is 5–10 times more concentrated than CH4, while the profile of DOC is concave. (3) The age profile of peat is near linearly proportional to depth; that for DOC is about 500–1000 yr younger than the peat at the same depth; the dissolved gases are 500–4300 years younger than the peat. The age of the operational peat fractions humic acid and humin is similar to that of whole peat. (4) The δ13C profile for deep peat is almost constant; δ13C–CO2 is more enriched than the peat (δ13C–CO2 35‰ more); δ13C–CH4 is the same amount more depleted. Nearer the surface both dissolved gases become steadily more depleted, δ13C is about 20‰ less at the surface. (5) A simulation shows that mass flow can account for the concentration and age profiles of DOC, but for the gases diffusion and an additional source near the surface are needed as well, and diffusion accounts for over 99% of the dissolved gas movements. (6) The same processes must operate in other peatlands but the results for Ellergower should not be extrapolated uncritically to them.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Bryant, Dr Charlotte
• Authors: Clymo, R.S., and Bryant, C.L.
• Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Geochimica et Cosmochimica Acta
• ISSN: 0016-7037
• ISSN (Online): 1872-9533
• Published Online: 19 February 2008