TIME-INTEGRATED COLLECTION OF CO2 FOR 14C ANALYSIS FROM SOILS

We developed a passive sampler for time-integrated collection and radiocarbon (14C) analysis of soil respiration, a major flux in the global C cycle. It consists of a permanent access well that controls the CO2 uptake rate and an exchangeable molecular sieve CO2 trap. We tested how access well dimen...

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Bibliographic Details
Published in:Radiocarbon
Main Authors: Pedron, Shawn, Xu, X, Walker, JC, Ferguson, JC, Jespersen, RG, Welker, JM, Klein, ES, Czimczik, CI
Format: Article in Journal/Newspaper
Language:unknown
Published: eScholarship, University of California 2021
Subjects:
carbon
mineral soil
molecular sieve
soil respiration
Geochemistry
Physical Geography and Environmental Geoscience
Archaeology
Paleontology
Tundra
Online Access:https://escholarship.org/uc/item/11x2t2tt
https://escholarship.org/content/qt11x2t2tt/qt11x2t2tt.pdf
https://doi.org/10.1017/rdc.2021.42
Description
Summary:We developed a passive sampler for time-integrated collection and radiocarbon (14C) analysis of soil respiration, a major flux in the global C cycle. It consists of a permanent access well that controls the CO2 uptake rate and an exchangeable molecular sieve CO2 trap. We tested how access well dimensions and environmental conditions affect collected CO2, and optimized cleaning procedures to minimize 14CO2 memory. We also deployed two generations of the sampler in Arctic tundra for up to two years, collecting CO2 over periods of 3 days-2 months, while monitoring soil temperature, volumetric water content, and CO2 concentration. The sampler collects CO2 at a rate proportional to the length of a silicone tubing inlet (7-26 g CO2-C day-1·m Si-1). With constant sampler dimensions in the field, CO2 recovery is best explained by soil temperature. We retrieved 0.1-5.3 mg C from the 1st and 0.6-13 mg C from the 2nd generation samplers, equivalent to uptake rates of 2-215 (n=17) and 10-247 g CO2-C day-1 (n=20), respectively. The method blank is 8 ± 6 g C (mean ± sd, n=8), with a radiocarbon content (fraction modern) ranging from 0.5875-0.6013 (n=2). The sampler enables more continuous investigations of soil C emission sources and is suitable for Arctic environments.

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