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Data for Novel field trial for ocean alkalinity enhancement using electrochemically derived aqueous alkalinity from 2024-11-07 to 2025-02-08 (NCEI Accession 0307424)

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Ocean alkalinity enhancement is a proposed method of marine carbon dioxide removal that enhances the ocean’s uptake of atmospheric carbon dioxide (CO2) and converts it to dissolved bicarbonate for long-term ocean storage. This method of marine carbon dioxide removal has been gaining attention for its potential to durably (10,000+ years) store large amounts of CO2 (Gt+ where 1 Gt = 1 x 10^9 tons), while potentially ameliorating acidification in the vicinity of the alkalinity release. This study focuses on a novel release of electrochemically derived aqueous alkalinity into Sequim Bay, WA, through a previously established wastewater treatment plant (WWTP). This research was made possible through the collaboration of industry, academic, and federal partners, which enabled the establishment of an Ebb Carbon electrochemical mCDR system at the Pacific Northwest National Laboratory in Sequim, WA, for ocean alkalinity enhancement field trials. During these field trials, pH was measured across the WWTP system from the initial alkalinity dosing, throughout the WWTP, and at the outfall. We use the NBS scale for pH throughout this study as it is the scale used in discharge permit limits specified for WWTP and NPDES regulation and compliance monitoring. The background pHNBS of Sequim Bay seawater was between 7.5 to 7.7 for the November and February field tests. The mixing tank's pHNBS was raised to the maximum value permitted for the WWTP (9.0) and maintained across the system (±0.2) during the outfall releases. At the outfall, the elevated pH and alkalinity was quickly diluted, such that the region with a measurable signal was limited to within ~2.5 m of the discharge pipe. We were able to successfully monitor an increase in pHNBS across all four pulses of alkalinity-enhanced seawater discharge during the February 2025 field trial, with peak pHNBS values of 8.3 or 8.1, as recorded by outfall-adjacent YSI Exo 2 sonde and SAMI-pH sensors, respectively. The alkalinity-enhanced seawater did not measurably alter the surrounding waters' temperature, salinity, turbidity, or oxygen. This study provides proof-of-concept for a conservative small-scale release of electrochemically generated alkalinity-enhanced seawater from a coastal outfall.

Dataset Citation

Cite as: Savoie, Allison M.; Ringham, Mallory; Torres Sanchez, Carolina; Carter, Brendan R.; Dougherty, Sean; Feely, Richard A.; Hegeman, Dave; Herndon, Julian; Khangaonkar, Tarang; Loretz, Jeremy; Minck, Tyson; Pelman, Todd; Premathilake, Lakshitha; Subban, Chinmayee; Vance, Jesse; Ward, Nicholas D. (2025). Data for Novel field trial for ocean alkalinity enhancement using electrochemically derived aqueous alkalinity from 2024-11-07 to 2025-02-08 (NCEI Accession 0307424). [indicate subset used]. NOAA National Centers for Environmental Information. Dataset. https://doi.org/10.25921/7zf4-3135. Accessed [date].

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gov.noaa.nodc:0307424

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Distributor	NOAA National Centers for Environmental Information +1-301-713-3277 ncei.info@noaa.gov
Dataset Point of Contact	NOAA National Centers for Environmental Information ncei.info@noaa.gov

Time Period	2024-11-07 to 2025-02-08
Spatial Bounding Box Coordinates	West: -123.045 East: -123.045 South: 48.078611 North: 48.078611
Spatial Coverage Map

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Associated Resources

Savoie, A. M., Ringham, M., Torres Sanchez, C., Carter, B. R., Dougherty, S., Feely, R. A., Hegeman, D., Herndon, J., Khangaonkar, T., Loretz, J., Minck, T., Pelman, T., Premathilake, L., Subban, C., Vance, J., & Ward, N. D. (2025). Novel field trial for ocean alkalinity enhancement using electrochemically derived aqueous alkalinity. Frontiers in Environmental Engineering, 4. https://doi.org/10.3389/fenve.2025.1641277
- https://doi.org/10.3389/fenve.2025.1641277
  related journal article
NOAA National Centers for Environmental Information (2022). Ocean Carbon and Acidification Data System (OCADS). NOAA National Centers for Environmental Information. https://www.ncei.noaa.gov/products/ocean-carbon-acidification-data-system
- https://www.ncei.noaa.gov/products/ocean-carbon-acidification-data-system
  OCADS website

Publication Dates	publication: 2025-09-02
Data Presentation Form	Digital table - digital representation of facts or figures systematically displayed, especially in columns
Dataset Progress Status	Complete - production of the data has been completed Historical archive - data has been stored in an offline storage facility
Data Update Frequency	As needed
Supplemental Information	This data package (Submission ID: BJGACDDN4) was acquired by NCEI from the Scientific Data Integration System (SDIS) at the NOAA Pacific Marine Environmental Laboratory (PMEL) in accordance with the archival submission agreement between NCEI and PMEL.
Purpose	This dataset is available to the public for a wide variety of uses including scientific research and analysis.
Use Limitations	accessLevel: Public Distribution liability: NOAA and NCEI make no warranty, expressed or implied, regarding these data, nor does the fact of distribution constitute such a warranty. NOAA and NCEI cannot assume liability for any damages caused by any errors or omissions in these data. If appropriate, NCEI can only certify that the data it distributes are an authentic copy of the records that were accepted for inclusion in the NCEI archives.

Dataset Citation	Cite as: Savoie, Allison M.; Ringham, Mallory; Torres Sanchez, Carolina; Carter, Brendan R.; Dougherty, Sean; Feely, Richard A.; Hegeman, Dave; Herndon, Julian; Khangaonkar, Tarang; Loretz, Jeremy; Minck, Tyson; Pelman, Todd; Premathilake, Lakshitha; Subban, Chinmayee; Vance, Jesse; Ward, Nicholas D. (2025). Data for Novel field trial for ocean alkalinity enhancement using electrochemically derived aqueous alkalinity from 2024-11-07 to 2025-02-08 (NCEI Accession 0307424). [indicate subset used]. NOAA National Centers for Environmental Information. Dataset. https://doi.org/10.25921/7zf4-3135. Accessed [date].
Cited Authors	Savoie, Allison M. Pacific Northwest National Laboratory Ringham, Mallory Ebb Carbon, Inc Torres Sanchez, Carolina Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL) Carter, Brendan R. Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington, under grant from NOAA Pacific Marine Environmental Laboratory Dougherty, Sean NOAA Pacific Marine Environmental Laboratory (PMEL) Feely, Richard A. NOAA Pacific Marine Environmental Laboratory (PMEL) Hegeman, Dave Ebb Carbon, Inc Herndon, Julian Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington under grant from NOAA Pacific Marine Environmental Laboratory Khangaonkar, Tarang Pacific Northwest National Laboratory and University of Washington Salish Sea Modeling Center Loretz, Jeremy Ebb Carbon, Inc Minck, Tyson Ebb Carbon, Inc Pelman, Todd Ebb Carbon, Inc Premathilake, Lakshitha Pacific Northwest National Laboratory and University of Washington Salish Sea Modeling Center Subban, Chinmayee Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL) Vance, Jesse Ebb Carbon, Inc Ward, Nicholas D. Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL)
Principal Investigators	Mallory Ringham Ebb Carbon, Inc Carolina Torres Sanchez Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL) Brendan Carter Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington, under grant from NOAA Pacific Marine Environmental Laboratory Sean Dougherty NOAA Pacific Marine Environmental Laboratory (PMEL) Richard Feely NOAA Pacific Marine Environmental Laboratory (PMEL) Dave Hegeman Ebb Carbon, Inc Julian Herndon Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington under grant from NOAA Pacific Marine Environmental Laboratory Tarang Khangaonkar Pacific Northwest National Laboratory and University of Washington Salish Sea Modeling Center Jeremy Loretz Ebb Carbon, Inc Tyson Minck Ebb Carbon, Inc Todd Pelman Ebb Carbon, Inc Lakshitha Premathilake Pacific Northwest National Laboratory and University of Washington Salish Sea Modeling Center Chinmayee Subban Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL) Jesse Vance Ebb Carbon, Inc Nicholas D. Ward Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL)
Contributors	Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL) University of Washington Cooperative Institute for Climate, Ocean and Ecosystem Studies (CICOES) NOAA Pacific Marine Environmental Laboratory (PMEL)
Resource Providers	Allison M. Savoie Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL) Battelle Memorial Institute, Pacific Northwest National Laboratory (PNNL)
Publishers	NOAA National Centers for Environmental Information
Acknowledgments	Funding Information: NOAA-OAP (Electrochemical Acid Sequestration to Ease Ocean Acidification (EASE-OA)) Funding Information: Climateworks Foundation (22-2361) Funding Information: US DOE Water Power Technologies Office Funding Information: Ebb Carbon, Inc.

Theme keywords	NODC DATA TYPES THESAURUS BAROMETRIC PRESSURE CONDUCTIVITY DISSOLVED INORGANIC CARBON (DIC) partial pressure of carbon dioxide - water pH SALINITY total alkalinity turbidity WATER TEMPERATURE NODC OBSERVATION TYPES THESAURUS chemical laboratory experiments water chemistry WMO_CategoryCode oceanography Global Change Master Directory (GCMD) Science Keywords EARTH SCIENCE > ATMOSPHERE > ATMOSPHERIC PRESSURE EARTH SCIENCE > OCEANS > OCEAN CHEMISTRY > ALKALINITY EARTH SCIENCE > OCEANS > OCEAN CHEMISTRY > CARBON DIOXIDE EARTH SCIENCE > OCEANS > OCEAN CHEMISTRY > INORGANIC CARBON EARTH SCIENCE > OCEANS > OCEAN CHEMISTRY > PH EARTH SCIENCE > OCEANS > OCEAN OPTICS > TURBIDITY EARTH SCIENCE > OCEANS > OCEAN TEMPERATURE > WATER TEMPERATURE EARTH SCIENCE > OCEANS > SALINITY/DENSITY > CONDUCTIVITY EARTH SCIENCE > OCEANS > SALINITY/DENSITY > SALINITY OCADS Study Type Field experiment mCDR Provider Variable Abbreviations DIC TA pCO2 pH
Data Center keywords	NODC COLLECTING INSTITUTION NAMES THESAURUS Battelle Memorial Institute, Pacific Northwest National Laboratory NOAA Pacific Marine Environmental Laboratory University of Washington Cooperative Institute for Climate, Ocean and Ecosystem Studies NODC SUBMITTING INSTITUTION NAMES THESAURUS Battelle Memorial Institute, Pacific Northwest National Laboratory Global Change Master Directory (GCMD) Data Center Keywords DOC/NOAA/OAR/PMEL > Pacific Marine Environmental Laboratory, OAR, NOAA, U.S. Department of Commerce
Platform keywords	NODC PLATFORM NAMES THESAURUS CHARTERED VESSEL
Instrument keywords	NODC INSTRUMENT TYPES THESAURUS carbon dioxide (CO2) gas analyzer multi-parameter water quality sensor pH sensor salinometer temperature sensor titrator Global Change Master Directory (GCMD) Instrument Keywords CO2 ANALYZERS > CO2 ANALYZERS PH METERS > PH METERS SALINOMETERS TEMPERATURE SENSORS > TEMPERATURE SENSORS
Place keywords	NODC SEA AREA NAMES THESAURUS North Pacific Ocean West Coast - US/Canada Global Change Master Directory (GCMD) Location Keywords OCEAN > PACIFIC OCEAN > NORTH PACIFIC OCEAN Provider Geographic Names North Pacific Ocean Sequim Bay U.S. West Coast
Project keywords	NODC PROJECT NAMES THESAURUS Ocean Carbon and Acidification Data System (OCADS) Ocean Acidification Search Keywords Ocean Carbon and Acidification Data System (OCADS) Project Research Projects Electrochemical Acid Sequestration to Ease Ocean Acidification (EASE-OA)
Keywords	NCEI ACCESSION NUMBER 0307424

Use Constraints	Cite as: Savoie, Allison M.; Ringham, Mallory; Torres Sanchez, Carolina; Carter, Brendan R.; Dougherty, Sean; Feely, Richard A.; Hegeman, Dave; Herndon, Julian; Khangaonkar, Tarang; Loretz, Jeremy; Minck, Tyson; Pelman, Todd; Premathilake, Lakshitha; Subban, Chinmayee; Vance, Jesse; Ward, Nicholas D. (2025). Data for Novel field trial for ocean alkalinity enhancement using electrochemically derived aqueous alkalinity from 2024-11-07 to 2025-02-08 (NCEI Accession 0307424). [indicate subset used]. NOAA National Centers for Environmental Information. Dataset. https://doi.org/10.25921/7zf4-3135. Accessed [date].
Data License	This dataset is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) License. SPDX License: Creative Commons Attribution 4.0 International (CC-BY-4.0)
Access Constraints	Use liability: NOAA and NCEI cannot provide any warranty as to the accuracy, reliability, or completeness of furnished data. Users assume responsibility to determine the usability of these data. The user is responsible for the results of any application of this data for other than its intended purpose.
Fees	In most cases, electronic downloads of the data are free. However, fees may apply for custom orders, data certifications, copies of analog materials, and data distribution on physical media.

Lineage information for: dataset
Processing Steps	2025-09-02T15:51:35Z - NCEI Accession 0307424 v1.1 was published.
Output Datasets	NCEI Accession 0307424 v1.1 NCEI Accession 0307424 v1.1 (download) published 2025-09-02T15:51:35Z

Lineage information for: nonGeographicDataset
Processing Steps	Parameter or Variable: Dissolved Inorganic Carbon; Abbreviation: DIC; Unit: μmol/kg; Observation type: Surface (discrete samples); In-situ / Manipulation / Response variable: IN-SITUOBSERVATION; Measured or calculated: MEASURED; Analyzing instrument: Apollo Scitech AS-C6 DIC Analyzer; Detailed sampling and analyzing information: Discrete water samples for dissolved inorganic carbon (DIC) analysis were periodically collected from beginning to end of the experiment following standard methods outlined in Dickson et al. (2007). DIC was analyzed on an Apollo SciTech Dissolved Inorganic Carbon Analyzer (Model: AS-C6L) and referenced against certified reference materials (CRMs) supplied by the Dickson laboratory at Scripps Institution of Oceanography. The precision based on the repeated measurement of CRMs during sample analysis for DIC was determined to be ±1 µmol kg-1.; Preservation method: HgCl2; Preservative volume: 100 μL of fully saturated HgCl2; Uncertainty: 1 μmol/kg; Researcher name: Nicholas Ward, Carolina Torres Sanchez, Allison Savoie; Researcher institution: Pacific Northwest National Laboratory Parameter or Variable: Total alkalinity; Abbreviation: TA; Unit: μmol/kg; Observation type: Surface (discrete samples); In-situ / Manipulation / Response variable: IN-SITUOBSERVATION; Measured or calculated: MEASURED; Analyzing instrument: Apollo Sci-Tech AS-ALK3 Total Alkalinity Titrator; Detailed sampling and analyzing information: Discrete water samples for total alkalinity (TA) analysis were periodically collected from beginning to end of the experiment following standard methods outlined in Dickson et al. (2007). TA was analyzed on an Apollo SciTech Total Alkalinity Titrator (AS-ALK3) and referenced against certified reference materials (CRMs) supplied by the Dickson laboratory at Scripps Institution of Oceanography. The precision based on the repeated measurement of CRMs during sample analysis for TA was determined to be ±1 µmol kg-1.; Preservation method: HgCl2; Preservative volume: 100 μL of fully saturated HgCl2; Uncertainty: 1 μmol/kg; Researcher name: Nicholas Ward, Carolina Torres Sanchez, Allison Savoie; Researcher institution: Pacific Northwest National Laboratory Parameter or Variable: pH; Abbreviation: pH; pH scale: NBSSCALE(NBSORNIST); Observation type: Time-series; In-situ / Manipulation / Response variable: IN-SITUOBSERVATION; Measured or calculated: MEASURED; Sampling instrument: YSI ProDSS; YSI Exo2; Seabird HydroCAT EP-V2; SAMI pH; Detailed sampling and analyzing information: YSI Pro DSS sondes were deployed to monitor seawater temperature, salinity, turbidity, dissolved oxygen (DO), and pHNBS every minute within- 1) the flow-through mixing tank; 2) GW Cell 3 ; and 3) GW Cell 2. YSI Exo 2 sondes were deployed to monitor seawater temperature, salinity, turbidity, dissolved oxygen (DO), and pHNBS every minute at two locations- 1) on a cage deployed by divers immediately in front of the WWTP outfall and 2) hanging at 2 m depth from the pier, ~70 m away from the outfall (November only) (Fig. 1 & 3). A Seabird Hydrocat EP-V2 was deployed from the pier in February instead of a YSI Exo2 sonde and collected measurements every 3 minutes on the first day and then every 10 minutes on the following days to ensure battery life for the experiment. A Sunburst SAMI-CO2 sensor was deployed at the outfall during both the November and February experiments, which collected data every hour in November and every 30 minutes in February for higher resolution (DeGrandpre et al., 1995, Lai et al., 2018). A SAMI-pH sensor was added to the outfall cage and the pier station for the February 2025 experiment and collected data every 15 minutes (Seidel et al., 2008, Lai et al., 2018). The YSI sondes were calibrated using Orion pHNBS 4.01, 7, and 10.01 buffers. The YSI Exo2 sondes deployed at the outfall were calibrated 6 days in advance of the November alkaline release and within 24 hours of deployment before the February release, while the Pro DSS sondes were calibrated the day of the alkalinity release. The YSI Exo2 sonde was calibrated in further advance in November’s field trial due to diver availability for deployment of the sensors near the outfall. It remained off underwater until it was programmed to collect data, similar to the SAMIs. All YSI sondes measured pH at ± 0.1 accuracy and ± 0.01 resolution. The Seabird Hydrocat EP-V2 was calibrated for pH immediately before deployment at the pier using 3 colorless NBS buffers (4.01, 7.0, 10.01). This sensor had an estimated accuracy of ± 0.1 and a resolution of 0.01 units. The SAMI-pH sensors were calibrated annually following manufacturer recommendations by Sunburst Sensors. The SAMI-pH sensors collected measurements at an accuracy of ± 0.003 units and precision of 0.001 (in total scale). SAMI-pH data were processed using salinity data from the sondes deployed alongside them using the QC_pH program from Sunburst Sensors. YSI sondes and Seabird Hydrocat EP-V2 sensors output pH on the NBS scale by default. SAMI-pH data is on the total scale, therefore these values were input to CO2SYS to convert them to the NBS scale for comparison with the other sensors (Sharp et al., 2020).; Standardization frequency: Prior to deployment; pH standard values: 4.01, 7.00, 10.01; Researcher name: Nicholas Ward, Carolina Torres Sanchez, Allison Savoie; Researcher institution: Pacific Northwest National Laboratory Parameter or Variable: pCO2 (fCO2) autonomous; Abbreviation: pCO2; Unit: μatm; Observation type: Time-series; In-situ / Manipulation / Response variable: IN-SITUOBSERVATION; Measured or calculated: MEASURED; Sampling instrument: SAMI-CO2; Detailed sampling and analyzing information: A Sunburst SAMI-CO2 sensor was deployed at the outfall during both the November and February experiments, which collected data every hour in November and every 30 minutes in February for higher resolution. The SAMI-CO2 sensors were calibrated annually following manufacturer recommendations by Sunburst Sensors. The SAMI-CO2 collected measurements at an estimated accuracy of ± 3 µatm and precision of 1 µatm.; Uncertainty: ±3 μatm; Researcher name: Nicholas Ward, Carolina Torres Sanchez, Allison Savoie, Mallory Ringham; Researcher institution: Pacific Northwest National Laboratory; Ebb Carbon, Inc.

Lineage information for: nonGeographicDataset

Processing Steps

Parameter or Variable: Dissolved Inorganic Carbon; Abbreviation: DIC; Unit: μmol/kg; Observation type: Surface (discrete samples); In-situ / Manipulation / Response variable: IN-SITUOBSERVATION; Measured or calculated: MEASURED; Analyzing instrument: Apollo Scitech AS-C6 DIC Analyzer; Detailed sampling and analyzing information: Discrete water samples for dissolved inorganic carbon (DIC) analysis were periodically collected from beginning to end of the experiment following standard methods outlined in Dickson et al. (2007). DIC was analyzed on an Apollo SciTech Dissolved Inorganic Carbon Analyzer (Model: AS-C6L) and referenced against certified reference materials (CRMs) supplied by the Dickson laboratory at Scripps Institution of Oceanography. The precision based on the repeated measurement of CRMs during sample analysis for DIC was determined to be ±1 µmol kg-1.; Preservation method: HgCl2; Preservative volume: 100 μL of fully saturated HgCl2; Uncertainty: 1 μmol/kg; Researcher name: Nicholas Ward, Carolina Torres Sanchez, Allison Savoie; Researcher institution: Pacific Northwest National Laboratory
Parameter or Variable: Total alkalinity; Abbreviation: TA; Unit: μmol/kg; Observation type: Surface (discrete samples); In-situ / Manipulation / Response variable: IN-SITUOBSERVATION; Measured or calculated: MEASURED; Analyzing instrument: Apollo Sci-Tech AS-ALK3 Total Alkalinity Titrator; Detailed sampling and analyzing information: Discrete water samples for total alkalinity (TA) analysis were periodically collected from beginning to end of the experiment following standard methods outlined in Dickson et al. (2007). TA was analyzed on an Apollo SciTech Total Alkalinity Titrator (AS-ALK3) and referenced against certified reference materials (CRMs) supplied by the Dickson laboratory at Scripps Institution of Oceanography. The precision based on the repeated measurement of CRMs during sample analysis for TA was determined to be ±1 µmol kg-1.; Preservation method: HgCl2; Preservative volume: 100 μL of fully saturated HgCl2; Uncertainty: 1 μmol/kg; Researcher name: Nicholas Ward, Carolina Torres Sanchez, Allison Savoie; Researcher institution: Pacific Northwest National Laboratory
Parameter or Variable: pH; Abbreviation: pH; pH scale: NBSSCALE(NBSORNIST); Observation type: Time-series; In-situ / Manipulation / Response variable: IN-SITUOBSERVATION; Measured or calculated: MEASURED; Sampling instrument: YSI ProDSS; YSI Exo2; Seabird HydroCAT EP-V2; SAMI pH; Detailed sampling and analyzing information: YSI Pro DSS sondes were deployed to monitor seawater temperature, salinity, turbidity, dissolved oxygen (DO), and pHNBS every minute within- 1) the flow-through mixing tank; 2) GW Cell 3 ; and 3) GW Cell 2. YSI Exo 2 sondes were deployed to monitor seawater temperature, salinity, turbidity, dissolved oxygen (DO), and pHNBS every minute at two locations- 1) on a cage deployed by divers immediately in front of the WWTP outfall and 2) hanging at 2 m depth from the pier, ~70 m away from the outfall (November only) (Fig. 1 & 3). A Seabird Hydrocat EP-V2 was deployed from the pier in February instead of a YSI Exo2 sonde and collected measurements every 3 minutes on the first day and then every 10 minutes on the following days to ensure battery life for the experiment. A Sunburst SAMI-CO2 sensor was deployed at the outfall during both the November and February experiments, which collected data every hour in November and every 30 minutes in February for higher resolution (DeGrandpre et al., 1995, Lai et al., 2018). A SAMI-pH sensor was added to the outfall cage and the pier station for the February 2025 experiment and collected data every 15 minutes (Seidel et al., 2008, Lai et al., 2018). The YSI sondes were calibrated using Orion pHNBS 4.01, 7, and 10.01 buffers. The YSI Exo2 sondes deployed at the outfall were calibrated 6 days in advance of the November alkaline release and within 24 hours of deployment before the February release, while the Pro DSS sondes were calibrated the day of the alkalinity release. The YSI Exo2 sonde was calibrated in further advance in November’s field trial due to diver availability for deployment of the sensors near the outfall. It remained off underwater until it was programmed to collect data, similar to the SAMIs. All YSI sondes measured pH at ± 0.1 accuracy and ± 0.01 resolution. The Seabird Hydrocat EP-V2 was calibrated for pH immediately before deployment at the pier using 3 colorless NBS buffers (4.01, 7.0, 10.01). This sensor had an estimated accuracy of ± 0.1 and a resolution of 0.01 units. The SAMI-pH sensors were calibrated annually following manufacturer recommendations by Sunburst Sensors. The SAMI-pH sensors collected measurements at an accuracy of ± 0.003 units and precision of 0.001 (in total scale). SAMI-pH data were processed using salinity data from the sondes deployed alongside them using the QC_pH program from Sunburst Sensors. YSI sondes and Seabird Hydrocat EP-V2 sensors output pH on the NBS scale by default. SAMI-pH data is on the total scale, therefore these values were input to CO2SYS to convert them to the NBS scale for comparison with the other sensors (Sharp et al., 2020).; Standardization frequency: Prior to deployment; pH standard values: 4.01, 7.00, 10.01; Researcher name: Nicholas Ward, Carolina Torres Sanchez, Allison Savoie; Researcher institution: Pacific Northwest National Laboratory
Parameter or Variable: pCO2 (fCO2) autonomous; Abbreviation: pCO2; Unit: μatm; Observation type: Time-series; In-situ / Manipulation / Response variable: IN-SITUOBSERVATION; Measured or calculated: MEASURED; Sampling instrument: SAMI-CO2; Detailed sampling and analyzing information: A Sunburst SAMI-CO2 sensor was deployed at the outfall during both the November and February experiments, which collected data every hour in November and every 30 minutes in February for higher resolution. The SAMI-CO2 sensors were calibrated annually following manufacturer recommendations by Sunburst Sensors. The SAMI-CO2 collected measurements at an estimated accuracy of ± 3 µatm and precision of 1 µatm.; Uncertainty: ±3 μatm; Researcher name: Nicholas Ward, Carolina Torres Sanchez, Allison Savoie, Mallory Ringham; Researcher institution: Pacific Northwest National Laboratory; Ebb Carbon, Inc.

Acquisition Information (collection)
Instrument	carbon dioxide (CO2) gas analyzer multi-parameter water quality sensor pH sensor salinometer temperature sensor titrator
Platform	CHARTERED VESSEL

Last Modified: 2025-11-13T13:11:40Z
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Data for Novel field trial for ocean alkalinity enhancement using electrochemically derived aqueous alkalinity from 2024-11-07 to 2025-02-08 (NCEI Accession 0307424)

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