Isotope (¹⁴C and ¹³C) analysis of deep peat CO₂ using a passive sampling technique

Garnett, M.H. and Hardie, S.M.L. (2009) Isotope (¹⁴C and ¹³C) analysis of deep peat CO₂ using a passive sampling technique. Soil Biology and Biochemistry, 41(12), pp. 2477-2483. (doi: 10.1016/j.soilbio.2009.09.004)

Abstract

We developed and tested a new method to collect CO₂ from the surface to deep layers of a peatland for radiocarbon analysis. The method comprises two components: i) a probe equipped with a hydrophobic filter that allows entry of peat gases by diffusion, whilst simultaneously excluding water, and, ii) a cartridge containing zeolite molecular sieve that traps CO₂ passively. We field tested the method by sampling at depths of between 0.25 and 4 m at duplicate sites within a temperate raised peat bog. CO₂ was trapped at a depth-dependent rate of between ∼0.2 and 0.8 ml d⁻¹, enabling sufficient CO₂ for routine ¹⁴C analysis to be collected when left in place for several weeks. The age of peatland CO₂ increased with depth from modern to not, vert, similar170 BP for samples collected from 0.25 m, to ∼4000 BP at 4 m. The CO₂ was younger, but followed a similar trend to the age profile of bulk peat previously reported for the site (Langdon and Barber, 2005). δ¹³C values of recovered CO₂ increased with depth. CO₂ collected from the deepest sampling probes was considerably ¹³C-enriched (up to not, vert, similar+9‰) and agreed well with results reported for other peatlands where this phenomenon has been attributed to fermentation processes. CO₂ collected from plant-free static chambers at the surface of the mire was slightly ¹⁴C-enriched compared to the contemporary atmosphere, suggesting that surface CO₂ emissions were predominantly derived from carbon fixed during the post-bomb era. However, consistent trends of enriched 13C and depleted ¹⁴C in chamber CO₂ between autumn and winter samples were most likely explained by an increased contribution of deep peat CO₂ to the surface efflux in winter. The passive sampling technique is readily portable, easy to install and operate, causes minimal site disturbance, and can be reliably used to collect peatland CO₂ from a wide range of depths.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Garnett, Dr Mark
• Authors: Garnett, M.H., and Hardie, S.M.L.
• Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences; Q Science > QH Natural history > QH345 Biochemistry
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Soil Biology and Biochemistry
• Journal Abbr.: Soil biol. biochem.
• Publisher: Elsevier
• ISSN: 0038-0717
• ISSN (Online): 1879-3428
• Published Online: 18 September 2009
• Copyright Holders: Copyright © 2009 Elsevier
• First Published: First published in Soil Biology and Biochemistry 41(12):2477-2483
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher