Direct and continuous measurement of dissolved carbon dioxide in freshwater aquatic systems — method and applications

Johnson, Mark S.; Billett, Michael F.; Dinsmore, Kerry J.; Wallin, Marcus; Dyson, Kirstie E.; Jassal, Rachhpal S.. 2010 Direct and continuous measurement of dissolved carbon dioxide in freshwater aquatic systems — method and applications. Ecohydrology, 3 (1). 68-78.

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Understanding of the processes that control CO2 concentrations in the aquatic environment has been hampered by the absence of a direct method to make continuous measurements over both short- and long-term time intervals. We describe an in situ method in which a non-dispersive infrared (NDIR) sensor is enclosed in a water impermeable, gas permeable polytetrafluoroethylene (PTFE) membrane and deployed in a freshwater environment. This allows measurements of CO2 concentration to be made directly at a specific depth in the water column without the need for pumps or reagents. We demonstrate the potential of the method using examples from different aquatic environments characterized by a range of CO2 concentrations (0.5–8.0 mg CO2-C L-1, equivalent to ca 40–650 μmol CO2 L-1). These comprise streams and ponds from tropical, temperate and boreal regions. Data derived from the sensor was compared with direct measurements of CO2 concentrations using headspace analysis. Sensor performance following long-term (>6 months) field deployment conformed to manufacturers’ specifications, with no drift detected. We conclude that the sensor-based method is a robust, accurate and responsive method, with a wide range of potential applications, particularly when combined with other in situ sensor-based measurements of related variables.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.1 - Monitor concentrations, fluxes, physico-chemical forms of current and emerging pollutants ...
UKCEH and CEH Sections/Science Areas: Billett (to November 2013)
ISSN: 1936-0584
Additional Keywords: dissolved CO2, terrestrial respiration, in situ monitoring, infrared gas analysis
NORA Subject Terms: Ecology and Environment
Date made live: 12 Apr 2010 14:00 +0 (UTC)

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