Articles | Volume 10, issue 6
https://doi.org/10.5194/amt-10-2377-2017
https://doi.org/10.5194/amt-10-2377-2017
Research article
 | 
30 Jun 2017
Research article |  | 30 Jun 2017

A closed-chamber method to measure greenhouse gas fluxes from dry aquatic sediments

Lukas Lesmeister and Matthias Koschorreck

Abstract. Recent research indicates that greenhouse gas (GHG) emissions from dry aquatic sediments are a relevant process in the freshwater carbon cycle. However, fluxes are difficult to measure because of the often rocky substrate and the dynamic nature of the habitat. Here we tested the performance of different materials to seal a closed chamber to stony ground both in laboratory and field experiments. Using on-site material consistently resulted in elevated fluxes. The artefact was caused both by outgassing of the material and production of gas. The magnitude of the artefact was site dependent – the measured CO2 flux increased between 10 and 208 %. Errors due to incomplete sealing proved to be more severe than errors due to non-inert sealing material.

Pottery clay as sealing material provided a tight seal between the chamber and the ground and no production of gases was detected. With this approach it is possible to get reliable gas fluxes from hard-substrate sites without using a permanent collar. Our test experiments confirmed that CO2 fluxes from dry aquatic sediments are similar to CO2 fluxes from terrestrial soils.

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Short summary
Greenhouse gas emissions from dry aquatic sediments are probably globally relevant. However, they are difficult to measure because of the often rocky substrate. We tested the performance of different materials to seal a closed chamber to stony ground both in laboratory and field experiments. Pottery clay was a convenient sealing material, while the use of on-site material produced artefacts. We confirmed that CO2 fluxes from dry aquatic sediments were similar to fluxes from normal soils.