Simultaneous Spectrophotometric Flow-through Measurements of PH, Carbon Dioxide Fugacity, and Total Inorganic Carbon in Seawater
An autonomous multi-parameter flow-through CO2 system has been developed to simultaneously measure surface seawater pH, carbon dioxide fugacity (fCO2), and total dissolved inorganic carbon (DIC). All three measurements are based on spectrophotometric determinations of solution pH at multiple wavelen...
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ftunisfloridatam:oai:digitalcommons.usf.edu:msc_facpub-2648 2023-05-15T18:21:18+02:00 Simultaneous Spectrophotometric Flow-through Measurements of PH, Carbon Dioxide Fugacity, and Total Inorganic Carbon in Seawater Wang, Zhaohui Aleck Liu, Xuewu Byrne, Robert H. Wanninkhof, Rik Bernstein, Renate E. Kaltenbacher, Eric A. Patten, James 2007-01-01T08:00:00Z https://digitalcommons.usf.edu/msc_facpub/1752 https://doi.org/10.1016/j.aca.2007.05.048 unknown Digital Commons @ University of South Florida https://digitalcommons.usf.edu/msc_facpub/1752 https://doi.org/10.1016/j.aca.2007.05.048 Marine Science Faculty Publications Autonomous carbon measurements Spectrophotometric Carbon dioxide pH fugacity Dissolved inorganic carbon Life Sciences article 2007 ftunisfloridatam https://doi.org/10.1016/j.aca.2007.05.048 2022-01-20T18:40:25Z An autonomous multi-parameter flow-through CO2 system has been developed to simultaneously measure surface seawater pH, carbon dioxide fugacity (fCO2), and total dissolved inorganic carbon (DIC). All three measurements are based on spectrophotometric determinations of solution pH at multiple wavelengths using sulfonephthalein indicators. The pH optical cell is machined from a PEEK polymer rod bearing a bore-hole with an optical pathlength of ∼15 cm. The fCO2 optical cell consists of Teflon AF 2400 (DuPont) capillary tubing sealed within the bore-hole of a PEEK rod. This Teflon AF tubing is filled with a standard indicator solution with a fixed total alkalinity, and forms a liquid core waveguide (LCW). The LCW functions as both a long pathlength (∼15 cm) optical cell and a membrane that equilibrates the internal standard solution with external seawater. fCO2 is then determined by measuring the pH of the internal solution. DIC is measured by determining the pH of standard internal solutions in equilibrium with seawater that has been acidified to convert all forms of DIC to CO2. The system runs repetitive measurement cycles with a sampling frequency of ∼7 samples (21 measurements) per hour. The system was used for underway measurements of sea surface pH, fCO2, and DIC during the CLIVAR/CO2 A16S cruise in the South Atlantic Ocean in 2005. The field precisions were evaluated to be 0.0008 units for pH, 0.9 μatm for fCO2, and 2.4 μmol kg−1 for DIC. These field precisions are close to those obtained in the laboratory. Direct comparison of our measurements and measurements obtained using established standard methods revealed that the system achieved field agreements of 0.0012 ± 0.0042 units for pH, 1.0 ± 2.5 μatm for fCO2, and 2.2 ± 6.0 μmol kg−1 for DIC. This system integrates spectrophotometric measurements of multiple CO2 parameters into a single package suitable for observations of both seawater and freshwater. Article in Journal/Newspaper South Atlantic Ocean Digital Commons University of South Florida (USF) Analytica Chimica Acta 596 1 23 36 |
institution |
Open Polar |
collection |
Digital Commons University of South Florida (USF) |
op_collection_id |
ftunisfloridatam |
language |
unknown |
topic |
Autonomous carbon measurements Spectrophotometric Carbon dioxide pH fugacity Dissolved inorganic carbon Life Sciences |
spellingShingle |
Autonomous carbon measurements Spectrophotometric Carbon dioxide pH fugacity Dissolved inorganic carbon Life Sciences Wang, Zhaohui Aleck Liu, Xuewu Byrne, Robert H. Wanninkhof, Rik Bernstein, Renate E. Kaltenbacher, Eric A. Patten, James Simultaneous Spectrophotometric Flow-through Measurements of PH, Carbon Dioxide Fugacity, and Total Inorganic Carbon in Seawater |
topic_facet |
Autonomous carbon measurements Spectrophotometric Carbon dioxide pH fugacity Dissolved inorganic carbon Life Sciences |
description |
An autonomous multi-parameter flow-through CO2 system has been developed to simultaneously measure surface seawater pH, carbon dioxide fugacity (fCO2), and total dissolved inorganic carbon (DIC). All three measurements are based on spectrophotometric determinations of solution pH at multiple wavelengths using sulfonephthalein indicators. The pH optical cell is machined from a PEEK polymer rod bearing a bore-hole with an optical pathlength of ∼15 cm. The fCO2 optical cell consists of Teflon AF 2400 (DuPont) capillary tubing sealed within the bore-hole of a PEEK rod. This Teflon AF tubing is filled with a standard indicator solution with a fixed total alkalinity, and forms a liquid core waveguide (LCW). The LCW functions as both a long pathlength (∼15 cm) optical cell and a membrane that equilibrates the internal standard solution with external seawater. fCO2 is then determined by measuring the pH of the internal solution. DIC is measured by determining the pH of standard internal solutions in equilibrium with seawater that has been acidified to convert all forms of DIC to CO2. The system runs repetitive measurement cycles with a sampling frequency of ∼7 samples (21 measurements) per hour. The system was used for underway measurements of sea surface pH, fCO2, and DIC during the CLIVAR/CO2 A16S cruise in the South Atlantic Ocean in 2005. The field precisions were evaluated to be 0.0008 units for pH, 0.9 μatm for fCO2, and 2.4 μmol kg−1 for DIC. These field precisions are close to those obtained in the laboratory. Direct comparison of our measurements and measurements obtained using established standard methods revealed that the system achieved field agreements of 0.0012 ± 0.0042 units for pH, 1.0 ± 2.5 μatm for fCO2, and 2.2 ± 6.0 μmol kg−1 for DIC. This system integrates spectrophotometric measurements of multiple CO2 parameters into a single package suitable for observations of both seawater and freshwater. |
format |
Article in Journal/Newspaper |
author |
Wang, Zhaohui Aleck Liu, Xuewu Byrne, Robert H. Wanninkhof, Rik Bernstein, Renate E. Kaltenbacher, Eric A. Patten, James |
author_facet |
Wang, Zhaohui Aleck Liu, Xuewu Byrne, Robert H. Wanninkhof, Rik Bernstein, Renate E. Kaltenbacher, Eric A. Patten, James |
author_sort |
Wang, Zhaohui Aleck |
title |
Simultaneous Spectrophotometric Flow-through Measurements of PH, Carbon Dioxide Fugacity, and Total Inorganic Carbon in Seawater |
title_short |
Simultaneous Spectrophotometric Flow-through Measurements of PH, Carbon Dioxide Fugacity, and Total Inorganic Carbon in Seawater |
title_full |
Simultaneous Spectrophotometric Flow-through Measurements of PH, Carbon Dioxide Fugacity, and Total Inorganic Carbon in Seawater |
title_fullStr |
Simultaneous Spectrophotometric Flow-through Measurements of PH, Carbon Dioxide Fugacity, and Total Inorganic Carbon in Seawater |
title_full_unstemmed |
Simultaneous Spectrophotometric Flow-through Measurements of PH, Carbon Dioxide Fugacity, and Total Inorganic Carbon in Seawater |
title_sort |
simultaneous spectrophotometric flow-through measurements of ph, carbon dioxide fugacity, and total inorganic carbon in seawater |
publisher |
Digital Commons @ University of South Florida |
publishDate |
2007 |
url |
https://digitalcommons.usf.edu/msc_facpub/1752 https://doi.org/10.1016/j.aca.2007.05.048 |
genre |
South Atlantic Ocean |
genre_facet |
South Atlantic Ocean |
op_source |
Marine Science Faculty Publications |
op_relation |
https://digitalcommons.usf.edu/msc_facpub/1752 https://doi.org/10.1016/j.aca.2007.05.048 |
op_doi |
https://doi.org/10.1016/j.aca.2007.05.048 |
container_title |
Analytica Chimica Acta |
container_volume |
596 |
container_issue |
1 |
container_start_page |
23 |
op_container_end_page |
36 |
_version_ |
1766200485044289536 |