BG Biogeosciences BG Biogeosciences 1726-4189 Copernicus Publications Göttingen, Germany 10.5194/bg-11-1077-2014 Technical Note: Mesocosm approach to quantify dissolved inorganic carbon percolation fluxes Thaysen E. M. 1 Jessen S. 2 Ambus P. 1 Beier C. 3 Postma D. 4 Jakobsen I. 1 Department of Chemical and Biochemical Engineering, Center for Ecosystems and Environmental Sustainability, Technical University of Denmark, 2800, Kongens Lyngby, Denmark Department of Geosciences and Natural Resource Management, Copenhagen University, 1350, Copenhagen, Denmark Center for Catchments and Urban Water Research, Norwegian Institute for Water Research, Oslo, Norway Department of Hydrology, Geological Survey of Denmark and Greenland, 1350, Copenhagen, Denmark 25 02 2014 11 4 1077 1084 Copyright: © 2014 E. M. Thaysen et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://bg.copernicus.org/articles/11/1077/2014/bg-11-1077-2014.html The full text article is available as a PDF file from https://bg.copernicus.org/articles/11/1077/2014/bg-11-1077-2014.pdf

Dissolved inorganic carbon (DIC) fluxes across the vadose zone are influenced by a complex interplay of biological, chemical and physical factors. A novel soil mesocosm system was evaluated as a tool for providing information on the mechanisms behind DIC percolation to the groundwater from unplanted soil. Carbon dioxide partial pressure (<i>p</i>CO<sub>2</sub>), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The <i>p</i>CO<sub>2</sub> varied between 0.2 and 1.1%, and the alkalinity was 0.1–0.6 meq L<sup>−1</sup>. The measured cumulative effluent DIC flux over the 78-day experimental period was 185–196 mg L<sup>−1</sup> m<sup>−2</sup> and in the same range as estimates derived from <i>p</i>CO<sub>2</sub> and alkalinity in samples extracted from the side of the mesocosm column and the drainage flux. Our results indicate that the mesocosm system is a promising tool for studying DIC percolation fluxes and other biogeochemical transport processes in unsaturated environments.

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