In situ Quality Assessment of a Novel Underwater pCO2 Sensor Based on Membrane Equilibration and NDIR Spectrometry
Year: 2013
Type: article
Abstract: This paper presents a detailed quality assessment of a novel underwater sensor for the measurement of CO2 partial pressure (pCO2) based on surface water field deployments carried out between 2008 and 2011. The commercially available sensor, which is based on membrane equilibration and nondispersive IR (NDIR) spectrometry is small and can be integrated into mobile platforms. It is calibrated in water against a proven flow-through pCO2 instrument within a custom-built calibration setup. The aspect of highest concern with respect to achievable data quality of the sensor is the compensation for signal drift inevitably connected to absorption measurements. Three means are used to correct for drift effects: (i) a filter correlation or dual-beam setup, (ii) regular zero gas measurements realized automatically within the sensor, and (iii) a zero-based transformation of two sensor calibrations flanking the time of sensor deployment. Three sensors were tested against an underway pCO2 system during two major research cruises, providing an in situ temperature range from 7.4° to 30.1°C and pCO2 values between 289 and 445 μatm. The average difference between sensor and reference pCO2 was found to be −0.6 ±3.0 μatm with an RMSE of 3.7 μatm.
Institution: GEOMAR Helmholtz Centre for Ocean Research Kiel
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1983617488