Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 13, issue 13
Biogeosciences, 13, 3915-3930, 2016
https://doi.org/10.5194/bg-13-3915-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 3915-3930, 2016
https://doi.org/10.5194/bg-13-3915-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Technical note 07 Jul 2016

Technical note | 07 Jul 2016

Technical note: Assessing gas equilibration systems for continuous pCO2 measurements in inland waters

Tae Kyung Yoon1,a, Hyojin Jin1, Neung-Hwan Oh2, and Ji-Hyung Park1 Tae Kyung Yoon et al.
  • 1Department of Environmental Science and Engineering, Ewha Womans University, Seoul 03760, Republic of Korea
  • 2Graduate School of Environmental Studies, Seoul National University, Seoul 08826, Republic of Korea
  • aCurrently at: Environmental Planning Institute, Seoul National University, Seoul 08826, Republic of Korea

Abstract. High-frequency continuous measurements of the partial pressure of CO2 (pCO2) are crucial for constraining the spatiotemporal dynamics of CO2 emissions from inland water systems. However, direct measurements of pCO2 are scarce, and no systematic comparisons have been conducted on the suitability of the widely used measurement systems for continuous underway or long-term deployment in various field conditions. We compared spray- and marble-type equilibrators and a membrane-enclosed CO2 sensor to assess their suitability for continuous long-term or underway pCO2 measurements in an urbanized river system in Korea. Both equilibrators had a shorter response time compared with the membrane-enclosed sensor, and could capture large spatial variations of pCO2 during a transect study along a highly urbanized river reach. The membrane-enclosed sensor based on passive equilibration provided comparable underway measurements along the river sections where pCO2 varied within the sensor detection range. When deployed in a eutrophic river site, the membrane-enclosed sensor was able to detect large diel variations in pCO2. However, biofouling on the membrane could reduce the accuracy of the measurement during long deployments exceeding several days. The overall results suggest that the fast response of the equilibrator systems facilitates capturing large spatial variations in pCO2 during short underway measurements. However, the attendant technical challenges of these systems, such as clogging and desiccant maintenance, have to be addressed carefully to enable their long-term deployment. The membrane-enclosed sensor would be suitable as an alternative tool for long-term continuous measurements if membrane biofouling could be overcome by appropriate antifouling measures such as copper mesh coverings.

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Spray- and marble-type equilibrators and a membrane-enclosed CO2 sensor were compared to assess their suitability for continuous pCO2 measurements in inland waters. The results suggest that the fast response of the equilibration systems facilitates capturing large spatial variations in pCO2 during short underway measurements. The membrane-enclosed sensor would be suitable for long-term continuous measurements if biofouling could be overcome by antifouling measures such as copper mesh coverings.
Spray- and marble-type equilibrators and a membrane-enclosed CO2 sensor were compared to assess...
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