http://lod.bco-dmo.org/id/dataset/962304
eng; USA
utf8
dataset
Highest level of data collection, from a common set of sensors or instrumentation, usually within the same research project
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
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2025-05-21
ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data
ISO 19115-2:2009(E)
Spectrophotometric determination of bicarbonate dissociation constants (K2) for freshwater, estuarine, and marine waters over a wide range of temperatures
2025-05-21
publication
2025-05-21
revision
Marine Biological Laboratory/Woods Hole Oceanographic Institution Library (MBLWHOI DLA)
2025-05-22
publication
https://doi.org/10.26008/1912/bco-dmo.962304.1
Robert Byrne
University of South Florida
principalInvestigator
Xuewu Liu
University of South Florida
principalInvestigator
Katelyn Schockman
University of Miami Cooperative Institute For Marine And Atmospheric Studies
principalInvestigator
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
publisher
Cite this dataset as: Martin-Mayor, M., Byrne, R., Schockman, K., Liu, X. (2025) Spectrophotometric determination of bicarbonate dissociation constants (K2) for freshwater, estuarine, and marine waters over a wide range of temperatures. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2025-05-21 [if applicable, indicate subset used]. doi:10.26008/1912/bco-dmo.962304.1 [access date]
Spectrophotometric pK2 data Dataset Description: Methods and Sampling: <p>The aqueous carbon dioxide (CO<sub>2</sub>) system stoichiometric dissociation constants <em>K</em><sub>1</sub> and <em>K</em><sub>2 </sub>express the relative concentrations of CO<sub>2</sub>, HCO<sub>3</sub><sup>−</sup> (bicarbonate), and CO<sub>3</sub><sup>2−</sup> (carbonate) in terms of pH. These constants are critical in the study of seawater and the oceans because any mathematical expression that relates the four major CO<sub>2</sub> system parameters requires the use of <em>K</em><sub>1</sub> and <em>K</em><sub>2</sub>.&nbsp;</p>
<p>The seawater CO<sub>2</sub> system can be described using four measurable parameters: total alkalinity (<em>A</em><sub>T</sub>), total dissolved inorganic carbon (<em>C</em><sub>T</sub>), pH (here expressed on the total hydrogen ion concentration scale, pH<sub>T</sub>) and CO<sub>2</sub> fugacity (<em>f</em>CO<sub>2</sub>).&nbsp;</p>
<p>This dataset presents the first spectrophotometric data of <em>K</em><sub>2</sub> at estuarine conditions (0≤S<sub>p</sub>≤20; where S<sub>p</sub> is practical salinity) and over a broad range of temperatures (275.15≤&nbsp;<em>T&nbsp;</em>≤308.15 K; where <em>T</em> is temperature in Kelvin). The low-salinity data were combined with the spectrophotometric data from Schockman and Byrne (2021) and Schockman et al. (2024).&nbsp;</p>
<p>Seawater batches collected from surface waters of the northeastern Gulf of Mexico off the West Florida Shelf were diluted with Milli-Q water to produce salinities within the range of 0 to 20, representing conditions ranging from freshwater to brackish water, respectively. Each seawater batch was prepared immediately prior to use in the lab experiment.&nbsp;</p>
<p>Spectrophotometric pH<sub>T</sub> measurements were done following Clayton &amp; Byrne (1993) and Dickson et al. (2007). Samples were measured in two-window 10cm cylindrical optical glass spectrophotometric cells using an Agilent 8453 diode array spectrophotometer with the UV light lamp turned off. Absorbance was taken at 434, 578, and 730 nanometers (nm) before and after adding 10 microliters (µL) of purified meta-Cresol Purple (mCP) indicator. The pH<sub>T</sub><sub> </sub>was calculated using 578/434 nm absorbance ratio, with 730 nm for baseline correction, using the model of Müller &amp; Rehder (2018).</p>
<p>First, the pH<sub>T </sub>was adjusted with HCl or NaOH to match the expected pH<sub>T</sub><sup>0</sup> based on the sample's salinity (<em>S</em><sub>p</sub>) and temperature (<em>T</em>). Once pH<sub>T</sub> was near pH<sub>T</sub><sup>0</sup>, five replicate pH<sub>T</sub> readings were taken and averaged to get pH<sub>initial</sub>. Then, a known amount of NaHCO₃ (or KHCO₃) was added to the sample and shaken thoroughly. Subsequently, the cell was placed back in the spectrophotometer and five pH<sub>T</sub> replicates were recorded and averaged as pH<sub>final</sub>. Next, the sample's temperature in the spectrophotometric cell was recorded using a digital thermometer (Ertco-Eutechnics Model 4400). Iterative adjustments were made if pH<sub>final</sub> ≠ pH<sub>initial</sub>. The next sample’s pH<sub>initial</sub> was adjusted to better approximate pH<sub>T</sub><sup>0</sup>.&nbsp;</p>
<p>After the daily samples were measured, seawater salinity for each individual sample was measured with a Guildline Portasal 8410A Laboratory Salinometer. &nbsp;S<sub>final</sub> denotes the salinity of each individual sample (i.e., salinity after bicarbonate salt addition), and S<sub>initial</sub> is the salinity of diluted seawater batch. Note: NaHCO₃ additions increase salinity, especially when <em>S</em><sub>p</sub> &lt; 5.</p>
<p>For experiments in which <em>t</em>&lt;15 ºC (where <em>t</em> is temperature in ºC), the setup was moved to an environmental room for additional temperature control (Harris Environmental Systems).&nbsp;</p>
<p>For a more detailed description of the methodology, please refer to Schockman and Byrne (2021) and Martin-Mayor et al. (2025, in review).</p>
<p>The resulting set of p<em>K</em><sub>2</sub> values presented in this dataset was fitted as a function of <em>S</em><sub>P</sub> and <em>T</em> to obtain a new p<em>K</em><sub>2</sub> parameterization for the salinity range 0≤ S<sub>p&nbsp;</sub>≤41 and temperature range 275.15≤<em>T</em>≤308.15 K (Martín-Mayor et al. 2025, in review).&nbsp;</p>
Funding provided by NSF Division of Ocean Sciences (NSF OCE) Award Number: OCE-2042935 Award URL: https://www.nsf.gov/awardsearch/show-award?AWD_ID=2042935
completed
Robert Byrne
University of South Florida
727-553-1508
140 Seventh Ave. South
St. Petersburg
Florida
33701
USA
rhbyrne@usf.edu
pointOfContact
Xuewu Liu
University of South Florida
(727)553-3922
140 7th Avenue S.
St. Petersburg
FL
33701
USA
xwliu@usf.edu
pointOfContact
Katelyn Schockman
University of Miami Cooperative Institute For Marine And Atmospheric Studies
katelyn.schockman@noaa.gov
pointOfContact
asNeeded
Dataset Version: 1
Unknown
Target_Temp
Target_Sp
Sp
Temperature
pH_T0
pH_T0_std_n4
pK2_experimental
pK2_with_parameterization
pK2_residuals
Diode array spectrophotometer (Agilent 8453) with the UV light lamp turned off
Digital hand-held thermometer (Ertco-Eutechnics Model 4400)
Guildline Portasal 8410A Laboratory Salinometer
Harris Environmental System environmental room
theme
None, User defined
water temperature at measurement depth
practical salinity
pH
standard deviation
equilibrium constant
featureType
BCO-DMO Standard Parameters
Agilent 8453 UV-visible spectrophotometer
digital thermometer
Guildline 8410A Portasal
Test chamber
instrument
BCO-DMO Standard Instruments
otherRestrictions
otherRestrictions
Access Constraints: none. Use Constraints: Please follow guidelines at: http://www.bco-dmo.org/terms-use Distribution liability: Under no circumstances shall BCO-DMO be liable for any direct, incidental, special, consequential, indirect, or punitive damages that result from the use of, or the inability to use, the materials in this data submission. If you are dissatisfied with any materials in this data submission your sole and exclusive remedy is to discontinue use.
Spectrophotometric Determinations of Carbonic Acid Dissociation Constants for Estuarine Conditions
https://osprey.bco-dmo.org/project/961585
Spectrophotometric Determinations of Carbonic Acid Dissociation Constants for Estuarine Conditions
<p><em><strong>NSF Award Abstract</strong></em><br />
Human health and well-being are linked in many ways to the health of our estuaries and coastal ocean waters. Yet surprisingly, we know less about some aspects of these important waters than we do the more distant waters of the deep ocean. This project will use state-of-the-art spectrophotometric methods (that is, light- and color-based methods) to advance our understanding of the fundamental and ever-changing chemistry of these waters and, eventually, the effects of these changes on marine life. The focus of this study will be to understand the chemistry of carbon dioxide in seawater. The new tools we will use are recently characterized pH indicators — chemicals that change color in seawater depending on the acidity of that water. These specially selected, purified indicators can be used to measure pH with unsurpassed precision and accuracy. We will use the indicators in laboratory experiments to determine how a critical parameter of the carbon dioxide system (a dissociation constant known as “K2”) changes depending on the temperature and salinity of the water. Characterizing K2 has been a goal of marine chemists for more than 50 years. The better we know K2, the better we can understand and predict how carbon moves through and cycles within natural waters. These measurements will expand our understanding of not only K2 but also the many other seawater characteristics that can be calculated from K2. Ultimately, this work will facilitate the interpretation and prediction of many ocean processes relevant to human health and coastal economies, such as ocean acidification (the lowering of ocean pH due to increasing carbon dioxide in the atmosphere) and calcium carbonate dissolution (the resulting dissolution of seashell material). The results will thus lay the groundwork for new perspectives on how ocean acidification affects the various shelled organisms that serve as food for economically important marine animals/fisheries and for people. The results of this work will also help to improve models of carbon dioxide dynamics in lakes, rivers, underground pore waters, and physiological fluids. As regards broader impacts, this work will help the PI continue to transfer his knowledge on this important topic to the next generation via his training of graduate, undergraduate, and high school students. This project would support one graduate and one undergraduate student, as well as help the current research projects of two minority doctoral students. Lastly, the PI plans to continue his involvement in the Bridge to the Doctoral Program aimed at getting minority students involved in the sciences.</p>
<p>In seawater, two carbonic acid dissociation constants (K1 and K2) describe the relationship between solution pH and the relative concentrations of dissolved carbonate ions, bicarbonate ions, and dissolved carbon dioxide. Accurate characterization of these CO2-system constants over broad ranges of environmental conditions has been a much sought-after goal for more than 50 years because knowledge of these terms is essential for quantitatively interpreting and predicting the biogeochemical cycling of carbon in all natural aqueous systems. The accuracy of CO2-system calculations is especially sensitive to uncertainties in K2, the equilibrium constant that describes the dissociation of bicarbonate ions to produce hydrogen ions and carbonate ions. This research project is designed to use spectrophotometric pH measurements (solely) to characterize this important constant. The purified pH indicators to be used in this work provide seawater pH measurements of unsurpassed precision and accuracy. Using select indicators whose properties have recently been characterized over freshwater-to-seawater ranges of salinity and temperature, we will determine K2 over similar ranges so as to improve the accuracy of CO2-system calculations in estuaries and coastal ocean waters. The resulting insight into equilibrium characteristics will facilitate interpretations and predictions of pH buffering in aqueous systems, provide an improved understanding of calcium carbonate solubility behavior, and lead to improved models of CO2-system behavior in freshwater lakes, rivers, soil and sediment pore waters, and physiological fluids. The longer-term benefits of this project will extend to assessments of the influence of ocean acidification on the life cycles of carbonate-bearing organisms that serve as food for economically important marine organisms.</p>
<p>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.</p>
Spectrophotometric K1K2
largerWorkCitation
project
eng; USA
oceans
2022-04-03
2023-10-31
0
BCO-DMO catalogue of parameters from Spectrophotometric determination of bicarbonate dissociation constants (K2) for freshwater, estuarine, and marine waters over a wide range of temperatures
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
http://lod.bco-dmo.org/id/dataset-parameter/962376.rdf
Name: Target_Temp
Units: degrees Celsius (°C)
Description: <p>Target temperature in degrees Celsius</p>
http://lod.bco-dmo.org/id/dataset-parameter/962377.rdf
Name: Target_Sp
Units: dimensionless
Description: <p>Target practical salinity</p>
http://lod.bco-dmo.org/id/dataset-parameter/962378.rdf
Name: Sp
Units: dimensionless
Description: <p>Practical salinity</p>
http://lod.bco-dmo.org/id/dataset-parameter/962379.rdf
Name: Temperature
Units: degrees Celsius (°C)
Description: <p>Measured temperature in degrees Celsius</p>
http://lod.bco-dmo.org/id/dataset-parameter/962380.rdf
Name: pH_T0
Units: dimensionless
Description: <p>pH value in the total scale at which pH = 1/2 (pK1 + pK2). See Schockman and Byrne (2021) Eq. (14).</p>
http://lod.bco-dmo.org/id/dataset-parameter/962381.rdf
Name: pH_T0_std_n4
Units: dimensionless
Description: <p>standard deviation of the pHT measurement where n=4</p>
http://lod.bco-dmo.org/id/dataset-parameter/962382.rdf
Name: pK2_experimental
Units: dimensionless
Description: <p>experimental pK2 (from experimental pHT0 and pK1 from Waters et al. (2014))</p>
http://lod.bco-dmo.org/id/dataset-parameter/962383.rdf
Name: pK2_with_parameterization
Units: dimensionless
Description: <p>value for pK2 using the new parameterization shown in Martin-Mayor et al. (2025)</p>
http://lod.bco-dmo.org/id/dataset-parameter/962384.rdf
Name: pK2_residuals
Units: dimensionless
Description: <p>value of experimental pK2 minus parameterized pK2 using the Martin-Mayor et al. (2025) equation.</p>
GB/NERC/BODC > British Oceanographic Data Centre, Natural Environment Research Council, United Kingdom
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
4966
https://darchive.mblwhoilibrary.org/server/api/core/bitstreams/50bd7f69-09a1-4afc-9c56-1ec77c49cf09/content
download
https://doi.org/10.26008/1912/bco-dmo.962304.1
download
onLine
dataset
<p>The aqueous carbon dioxide (CO<sub>2</sub>) system stoichiometric dissociation constants <em>K</em><sub>1</sub> and <em>K</em><sub>2 </sub>express the relative concentrations of CO<sub>2</sub>, HCO<sub>3</sub><sup>−</sup> (bicarbonate), and CO<sub>3</sub><sup>2−</sup> (carbonate) in terms of pH. These constants are critical in the study of seawater and the oceans because any mathematical expression that relates the four major CO<sub>2</sub> system parameters requires the use of <em>K</em><sub>1</sub> and <em>K</em><sub>2</sub>.&nbsp;</p>
<p>The seawater CO<sub>2</sub> system can be described using four measurable parameters: total alkalinity (<em>A</em><sub>T</sub>), total dissolved inorganic carbon (<em>C</em><sub>T</sub>), pH (here expressed on the total hydrogen ion concentration scale, pH<sub>T</sub>) and CO<sub>2</sub> fugacity (<em>f</em>CO<sub>2</sub>).&nbsp;</p>
<p>This dataset presents the first spectrophotometric data of <em>K</em><sub>2</sub> at estuarine conditions (0≤S<sub>p</sub>≤20; where S<sub>p</sub> is practical salinity) and over a broad range of temperatures (275.15≤&nbsp;<em>T&nbsp;</em>≤308.15 K; where <em>T</em> is temperature in Kelvin). The low-salinity data were combined with the spectrophotometric data from Schockman and Byrne (2021) and Schockman et al. (2024).&nbsp;</p>
<p>Seawater batches collected from surface waters of the northeastern Gulf of Mexico off the West Florida Shelf were diluted with Milli-Q water to produce salinities within the range of 0 to 20, representing conditions ranging from freshwater to brackish water, respectively. Each seawater batch was prepared immediately prior to use in the lab experiment.&nbsp;</p>
<p>Spectrophotometric pH<sub>T</sub> measurements were done following Clayton &amp; Byrne (1993) and Dickson et al. (2007). Samples were measured in two-window 10cm cylindrical optical glass spectrophotometric cells using an Agilent 8453 diode array spectrophotometer with the UV light lamp turned off. Absorbance was taken at 434, 578, and 730 nanometers (nm) before and after adding 10 microliters (µL) of purified meta-Cresol Purple (mCP) indicator. The pH<sub>T</sub><sub> </sub>was calculated using 578/434 nm absorbance ratio, with 730 nm for baseline correction, using the model of Müller &amp; Rehder (2018).</p>
<p>First, the pH<sub>T </sub>was adjusted with HCl or NaOH to match the expected pH<sub>T</sub><sup>0</sup> based on the sample's salinity (<em>S</em><sub>p</sub>) and temperature (<em>T</em>). Once pH<sub>T</sub> was near pH<sub>T</sub><sup>0</sup>, five replicate pH<sub>T</sub> readings were taken and averaged to get pH<sub>initial</sub>. Then, a known amount of NaHCO₃ (or KHCO₃) was added to the sample and shaken thoroughly. Subsequently, the cell was placed back in the spectrophotometer and five pH<sub>T</sub> replicates were recorded and averaged as pH<sub>final</sub>. Next, the sample's temperature in the spectrophotometric cell was recorded using a digital thermometer (Ertco-Eutechnics Model 4400). Iterative adjustments were made if pH<sub>final</sub> ≠ pH<sub>initial</sub>. The next sample’s pH<sub>initial</sub> was adjusted to better approximate pH<sub>T</sub><sup>0</sup>.&nbsp;</p>
<p>After the daily samples were measured, seawater salinity for each individual sample was measured with a Guildline Portasal 8410A Laboratory Salinometer. &nbsp;S<sub>final</sub> denotes the salinity of each individual sample (i.e., salinity after bicarbonate salt addition), and S<sub>initial</sub> is the salinity of diluted seawater batch. Note: NaHCO₃ additions increase salinity, especially when <em>S</em><sub>p</sub> &lt; 5.</p>
<p>For experiments in which <em>t</em>&lt;15 ºC (where <em>t</em> is temperature in ºC), the setup was moved to an environmental room for additional temperature control (Harris Environmental Systems).&nbsp;</p>
<p>For a more detailed description of the methodology, please refer to Schockman and Byrne (2021) and Martin-Mayor et al. (2025, in review).</p>
<p>The resulting set of p<em>K</em><sub>2</sub> values presented in this dataset was fitted as a function of <em>S</em><sub>P</sub> and <em>T</em> to obtain a new p<em>K</em><sub>2</sub> parameterization for the salinity range 0≤ S<sub>p&nbsp;</sub>≤41 and temperature range 275.15≤<em>T</em>≤308.15 K (Martín-Mayor et al. 2025, in review).&nbsp;</p>
Specified by the Principal Investigator(s)
<p>The resulting set of p<em>K</em><sub>2</sub>&nbsp;values presented in this dataset was fitted as a function of&nbsp; practical salinity (<em>S</em><sub>p</sub>) and temperature (<em>T</em>) to obtain a new p<em>K</em><sub>2</sub>&nbsp;parameterization for the salinity range 0≤S<sub>p</sub>≤41 and temperature range 275.15≤<em>T</em>≤308.15 K (Martín-Mayor et al. 2025, in review).&nbsp;</p>
Specified by the Principal Investigator(s)
- Imported data from source file "Martin-Mayor_Spec_pK2_S0-40_t2-35_FINAL.xlsx" sheet name "All data combined" into the BCO-DMO data system.
- Modified parameter (column) names to conform with BCO-DMO naming conventions.
Specified by BCO-DMO Data Managers
asNeeded
7.x-1.1
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
Diode array spectrophotometer (Agilent 8453) with the UV light lamp turned off
Diode array spectrophotometer (Agilent 8453) with the UV light lamp turned off
PI Supplied Instrument Name: Diode array spectrophotometer (Agilent 8453) with the UV light lamp turned off PI Supplied Instrument Description:Samples were measured in two-window 10cm cylindrical optical glass spectrophotometric cells using an Agilent 8453 diode array spectrophotometer with the UV light lamp turned off. Instrument Name: Agilent 8453 UV-visible spectrophotometer Instrument Short Name:Agilent 8453 Instrument Description: The Agilent 8453 spectrophotometer is a laboratory optical instrument for chemical analysis to extract spectral information in the ultraviolet (UV) and visible light. The instrument radiates a single light beam by optically combining two source lamps: a deuterium-discharge lamp for the UV wavelength range and a tungsten lamp for the visible and short wave near-infrared (SWNIR) wavelength range. The beam passes through the sample, is focused and dispersed within the spectrograph lens, slit and grating, and reaches the diode array in the form of a spectral image. The diode array samples a wavelength range of 190 to 1100 nm at a mean sampling interval of 0.9 nm. The nominal spectral slit width is 1 nm and the stray light is less than 0.03%.
Digital hand-held thermometer (Ertco-Eutechnics Model 4400)
Digital hand-held thermometer (Ertco-Eutechnics Model 4400)
PI Supplied Instrument Name: Digital hand-held thermometer (Ertco-Eutechnics Model 4400) PI Supplied Instrument Description:The sample's temperature in the spectrophotometric cell was recorded using a digital thermometer (Ertco-Eutechnics Model 4400). Instrument Name: digital thermometer Instrument Short Name: Instrument Description: An instrument that measures temperature digitally.
Guildline Portasal 8410A Laboratory Salinometer
Guildline Portasal 8410A Laboratory Salinometer
PI Supplied Instrument Name: Guildline Portasal 8410A Laboratory Salinometer PI Supplied Instrument Description:Seawater salinity for each individual sample was measured with a Guildline Portasal 8410A Laboratory Salinometer. Instrument Name: Guildline 8410A Portasal Instrument Short Name:Guildline 8410A Portasal Instrument Description: Portasal Salinometer 8410A
Guildline 8410A Portasal is a truly portable, high precision instrument from the world leader in salinometers. The Portasal will deliver salinity calculations on-board ship with laboratory level accuracy. It measures accurate conductivity ratios and displays calculated salinity directly as well as measured parameters.
http://www.osil.co.uk/Products/Ignore/tabid/56/agentType/View/PropertyID/68/Default.aspx Community Standard Description: http://www.osil.co.uk/Products/Ignore/tabid/56/agentType/View/PropertyID/68/Default.aspx
Harris Environmental System environmental room
Harris Environmental System environmental room
PI Supplied Instrument Name: Harris Environmental System environmental room PI Supplied Instrument Description:Environmental room for additional temperature control (Harris Environmental Systems) was used for experiments in which t Instrument Name: Test chamber Instrument Short Name:Test chamber Instrument Description: A test chamber is a controlled environment where specific conditions (temperature, humidity, light, etc.) are maintained for testing and research purposes.
Also called climatic chamber, environmental chamber, environmental room, or environmental enclosure