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A fast-responding CO2 microelectrode for profiling sediments, microbial mats, and biofilms

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A new CO2 microelectrode with a tip diameter of 10 μm and a response time (t90) of ~10 s is presented. The sensor allows CO2 measurements with a detection limit of <3 μM. The microsensor was tested in experimental systems of increasing complexity. A diffusion-reaction simulation model was used to calculate CO2 profiles in order to check the reliability of the measured profiles. Measured CO2 and O2 profiles showed that, in highly active layers with photosynthetic and respiratory organisms, local equilibrium of the carbonate system cannot be assumed. In such highly active systems, the CO2 profiles were determined by the slow CO2 hydration rate, the biological conversion rates, and the diffusion of all species of the carbonate system. We concluded that measured CO2 profiles cannot easily be extrapolated to describe the total carbonate concentration profile, because CO2 may not be in equilibrium with the rest of the carbonate system, and because a very accurate alignment of pH and CO2 profiles is needed to calculate C(r). However, the new CO2 microelectrode is useful in research involving biological processes directly producing or consuming CO2 such as photosynthesis or respiration.

OriginalsprogEngelsk
TidsskriftLimnology and Oceanography
Vol/bind42
Udgave nummer7
Sider (fra-til)1590-1600
Antal sider11
ISSN0024-3590
DOI
StatusUdgivet - 1 jan. 1997

ID: 201683868