In situ Quality Assessment of a Novel Underwater pCO2 Sensor Based on Membrane Equilibration and NDIR Spectrometry

Fietzek, Peer; Fiedler, Björn; Steinhoff, Tobias; Körtzinger, Arne

doi:10.1175/jtech-d-13-00083.1

Cited by 83 publications

(85 citation statements)

References 29 publications

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“…During that comparison, all sensors showed increasing offsets with time compared to GO (from 15 to 60 μ atm), which emphasized the challenges of intercomparison exercises with longer duration and showed the unknown, and possibly limited endurance of unattended systems. The increasing offsets reflected sensor drift, and laboratory postdeployment calibration of the sensors permitted drift‐corrections (Fietzek et al ) so that comparison of final corrected data showed agreement with GO that was comparable to the results from this study, showing the importance of applying proper procedures, such as drift corrections, to improve data quality. Furthermore, short‐term drifts in the IR cells within each zeroing/spanning cycle must be accounted for, and it is important to note that each system performs different drift corrections (e.g., CO2‐Pro only performs a zero point calibration).…”

Section: Discussionsupporting

confidence: 79%

At‐sea intercomparison of three underway pCO₂ systems

Arruda

Atamanchuk

Cronin

et al. 2019

Limnology & Ocean Methods

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Ocean surface partial pressure of carbon dioxide (pCO2) is a key factor controlling air–sea CO2 fluxes. Most surface pCO2 data are collected with relatively large and complex air–water equilibrators coupled to stand‐alone infrared analyzers installed on Ships of OPportunity (SOOP‐CO2). This approach has proven itself through years of successful deployments, but expansion and sustainability of the future measurement network faces challenges in terms of certification, autonomy, and maintenance, which motivates development of new systems. Here, we compare performance of three underway pCO2 measurement systems (General Oceanics, SubCtech, and Pro‐Oceanus), including a recently developed compact flow‐through, sensor‐based system. The systems were intercompared over a period of 34 days during two crossings of the subpolar North Atlantic Ocean. With a mean difference from the General Oceanics system of −5.7 ± 4.0 μatm (Pro‐Oceanus) and −4.7 ± 2.9 μatm (SubCtech) during the 1st crossing, our results indicate potential for good agreement between the systems. The study highlighted the challenge of assuring accuracy over long periods of time, particularly seen in a worse agreement during the 2nd crossing, and revealed a number of sources of systematic errors. These can influence accuracy of the measurements, agreement between systems and include slow response of membrane‐based systems to pCO2 changes, “within‐ship” respiration due to biofouling, and bias in measurement of the temperature of equilibration. These error sources can be controlled or corrected for, however, if unidentified, their magnitude can be significant relative to accuracy criteria assigned to the highest‐quality data in global databases. The advantages of the compact flow‐through system are presented along with a discussion of future solutions for improving data quality.

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Section: Discussionsupporting

confidence: 79%

At‐sea intercomparison of three underway pCO₂ systems

Arruda

Atamanchuk

Cronin

et al. 2019

Limnology & Ocean Methods

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“…For example, Degrandpre et al () demonstrate a SAMI‐CO 2 accuracy/precision of ± 2 μatm and ± 1 μatm, respectively, although an intercomparison with a NDIR‐based equilibrator system resulted in an overall offset between the two systems of 3.7 μatm. In comparison to a NDIR‐based equilibrator system, Fietzek et al () found a Contros Hydro‐C offset and precision of −0.6 μatm and ± 3 μatm, respectively. However, after careful characterization against a validation system the SIPCO2 sensor performance is comparable to that of some of the systems presented in Table .…”

Section: Discussionmentioning

confidence: 99%

SIPCO2: A simple, inexpensive surface water pCO₂ sensor

Hunt

Snyder

Salisbury

et al. 2017

Limnology & Ocean Methods

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Efforts to estimate air‐water carbon dioxide (CO2) exchange on regional or global scales are constrained by a lack of direct, continuous surface water CO2 observations. Sensor technology for the in situ measurement of the partial pressure of carbon dioxide (pCO2) has progressed, but still poses limitations including expense and biofouling concerns. We describe a simple, inexpensive, in situ pCO2 method (SIPCO2) in which a non‐dispersive infrared (NDIR) detector is paired with an air pump in an enclosed housing to produce air‐sea equilibration. We first evaluated this approach in a laboratory setting, then in an estuarine‐coastal ocean laboratory for several months to continuously monitor aquatic pCO2. An accepted, accurate NDIR‐based CO2 measurement technique was employed alongside SIPCO2 to provide an assessment of sensor performance. SIPCO2 allows for low‐cost, relatively accurate measurements of pCO2 (mean difference of −5 ± 5 μatm from validation system after laboratory calibration) without reagents or membranes, and can be assembled and operated with a minimal amount of technical skill. While not suitable for some exacting applications, this SIPCO2 approach could rapidly and effectively increase the number of quality CO2 observations in a range of aquatic environments. We also provide detailed instructions for the assembly of SIPCO2 from commercially available components.

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“…The HydroC sensor was serviced and calibrated yearly by Contros. The relative standard deviation (RSD) of the pCO 2 measurement has been estimated to be 1 % (Fietzek et al, 2014).…”

Section: Datamentioning

confidence: 99%

Glacial meltwater and primary production are drivers of strong CO<sub>2</sub> uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

et al. 2015

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Abstract. The Greenland Ice Sheet releases large amounts of freshwater, which strongly influences the physical and chemical properties of the adjacent fjord systems and continental shelves. Glacial meltwater input is predicted to strongly increase in the future, but the impact of meltwater on the carbonate dynamics of these productive coastal systems remains largely unquantified. Here we present seasonal observations of the carbonate system over the year 2013 in the surface waters of a west Greenland fjord (Godthåbsfjord) influenced by tidewater outlet glaciers. Our data reveal that the surface layer of the entire fjord and adjacent continental shelf are undersaturated in CO 2 throughout the year. The average annual CO 2 uptake within the fjord is estimated to be 65 g C m −2 yr −1 , indicating that the fjord system is a strong sink for CO 2 . The largest CO 2 uptake occurs in the inner fjord near to the Greenland Ice Sheet and high glacial meltwater input during the summer months correlates strongly with low pCO 2 values. This strong CO 2 uptake can be explained by the thermodynamic effect on the surface water pCO 2 resulting from the mixing of fresh glacial meltwater and ambient saline fjord water, which results in a CO 2 uptake of 1.8 mg C kg −1 of glacial ice melted. We estimated that 28 % of the CO 2 uptake can be attributed to the input of glacial meltwater, while the remaining part is due to high primary production. Our findings imply that glacial meltwater is an important driver for undersaturation in CO 2 in fjord and coastal waters adjacent to large ice sheets.

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In situ Quality Assessment of a Novel Underwater pCO2 Sensor Based on Membrane Equilibration and NDIR Spectrometry

Cited by 83 publications

References 29 publications

At‐sea intercomparison of three underway pCO₂ systems

At‐sea intercomparison of three underway pCO₂ systems

SIPCO2: A simple, inexpensive surface water pCO₂ sensor

Glacial meltwater and primary production are drivers of strong CO<sub>2</sub> uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

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In situ Quality Assessment of a Novel Underwater pCO2 Sensor Based on Membrane Equilibration and NDIR Spectrometry

Cited by 83 publications

References 29 publications

At‐sea intercomparison of three underway pCO2 systems

At‐sea intercomparison of three underway pCO2 systems

SIPCO2: A simple, inexpensive surface water pCO2 sensor

Glacial meltwater and primary production are drivers of strong CO&lt;sub&gt;2&lt;/sub&gt; uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet

Contact Info

Product

Resources

About

At‐sea intercomparison of three underway pCO₂ systems

At‐sea intercomparison of three underway pCO₂ systems

SIPCO2: A simple, inexpensive surface water pCO₂ sensor

Glacial meltwater and primary production are drivers of strong CO<sub>2</sub> uptake in fjord and coastal waters adjacent to the Greenland Ice Sheet