Technical note: In situ measurement of flux and isotopic composition of CO<sub>2</sub> released during oxidative weathering of sedimentary rocks
-
Published:2018-07-04
Issue:13
Volume:15
Page:4087-4102
-
ISSN:1726-4189
-
Container-title:Biogeosciences
-
language:en
-
Short-container-title:Biogeosciences
Author:
Soulet Guillaume,Hilton Robert G.,Garnett Mark H.,Dellinger Mathieu,Croissant Thomas,Ogrič Mateja,Klotz Sébastien
Abstract
Abstract. Oxidative weathering of sedimentary rocks can release carbon dioxide
(CO2) to the atmosphere and is an important natural CO2
emission. Two mechanisms operate – the oxidation of sedimentary organic
matter and the dissolution of carbonate minerals by sulfuric acid. It has
proved difficult to directly measure the rates at which CO2 is
emitted in response to these weathering processes in the field, with previous
work generally using methods which track the dissolved products of these
reactions in rivers. Here we design a chamber method to measure CO2
production during the oxidative weathering of shale bedrock, which can be
applied in erosive environments where rocks are exposed frequently to the
atmosphere. The chamber is drilled directly into the rock face and has a high
surface-area-to-volume ratio which benefits measurement of CO2
fluxes. It is a relatively low-cost method and provides a long-lived chamber
(several months or more). To partition the measured CO2 fluxes and
the source of CO2, we use zeolite molecular sieves to trap
CO2 “actively” (over several hours) or “passively” (over a
period of months). The approaches produce comparable results, with the
trapped CO2 having a radiocarbon activity (fraction modern, Fm)
ranging from Fm = 0.05 to Fm = 0.06 and demonstrating relatively
little contamination from local atmospheric CO2 (Fm = 1.01). We
use stable carbon isotopes of the trapped
CO2 to partition between an organic and inorganic carbon source.
The measured fluxes of rock-derived organic matter oxidation
(171 ± 5 mgC m−2 day−1) and carbonate dissolution by
sulfuric acid (534±16 mgC m−2 day−1) from a single chamber
were high when compared to the annual flux estimates derived from using
dissolved river chemistry in rivers around the world. The high oxidative
weathering fluxes are consistent with the high erosion rate of the study
region. We propose that our in situ
method has the potential to be more widely deployed to directly measure
CO2 fluxes during the oxidative weathering of sedimentary rocks,
allowing for the spatial and temporal variability in these fluxes to be
determined.
Funder
European Research Council
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
Reference50 articles.
1. Bardgett, R. D., Richter, A., Bol, R., Garnett, M. H., Bäumler, R., Xu,
X., Lopez-Capel, E., Manning, D. A. C., Hobbs, P. J., Hartley, I. R., and
Wanek, W.: Heterotrophic microbial communities use ancient carbon following
glacial retreat, Biol. Lett., 3, 487–490, https://doi.org/10.1098/rsbl.2007.0242, 2007. 2. Berner, E. K. and Berner, R. A.: Global environment: Water, air, and
geochemical cycles, Princeton University Press, 488 pp., 2012. 3. Berner, R. A. and Canfield, D. E.: A new model for atmospheric oxygen over
Phanerozoic time, Am. J. Sci., 289, 333–361, https://doi.org/10.2475/ajs.289.4.333,
1989. 4. Bertoni, G., Ciuchini, C., and Tappa, R.: Measurement of long-term average
carbon dioxide concentrations using passive diffusion sampling, Atmos.
Environ., 38, 1625–1630, https://doi.org/10.1016/j.atmosenv.2003.12.010, 2004. 5. Billett, M. F., Garnett, M. H., and Hardie, S. M. L.: A Direct Method to
Measure 14CO2 Lost by Evasion from Surface Waters, Radiocarbon,
48, 61–68, https://doi.org/10.1017/S0033822200035396, 2006.
Cited by
19 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献
|
|