| Contributors | Affiliation | Role |
|---|---|---|
| Byrne, Robert | University of South Florida (USF) | Principal Investigator |
| Martin Mayor, Macarena | University of South Florida (USF) | Student |
| Rauch, Shannon | Woods Hole Oceanographic Institution (WHOI BCO-DMO) | BCO-DMO Data Manager |
Potentiometric measurements were made using a glass electrode that was spectrophotometrically calibrated following the methods described in Easley and Byrne (2012) and Martell-Bonet and Byrne (2020). The spectrophotometric measurements were made following the guidelines of Clayton and Byrne (1993) and Dickson et al. (2007).
Following the methodology introduced by Byrne and Kester (1974), sodium borate decahydrate (borax) was added to natural seawater at different SP-T pairs to determine the pHT at which the salt addition caused no change in pHT. The pHT at which the addition of borax causes no change is the pKB for that specific SP-T pair. For each SP-T pair, approximately 15 samples were analyzed. From these, two samples were selected: (1) the sample with the lowest pHinitial that lowered upon the addition of borax, and (2) the sample with the highest pHinitial that increased upon the addition of borax. The experimental pKB (exp-pKB) for each SP–T pair was calculated as the mean of the initial and final pH values of the two selected samples; specifically, as the average of pHinitial for samples (1) and (2) and the average of pHfinal for samples (1) and (2).
- Imported data from original file "pKB_data_MMB26.xlsx" (sheet 1) into the BCO-DMO system.
- Saved the final file as "1000973_v1_pkb_data_mmb26.csv".
| File |
|---|
1000973_v1_pkb_data_mmb26.csv (Comma Separated Values (.csv), 7.18 KB) MD5:cc2ee326d23b95a91c1c01b2e886704b Primary data file for dataset ID 1000973, version 1 |
| Parameter | Description | Units |
| source | The source paper. 'D90' = Dickson (1990) ; 'MMB26' = Martin-Mayor and Byrne (in prep), 'M79' = Millero (1979). See Related Publications for further information about these sources. | unitless |
| Target_t_C | target temperature in degrees celsius | degrees Celsius (°C) |
| Target_T_K | target temperature in Kelvin | Kelvin (K) |
| Target_Sal | target practical salinity | PSS-78 |
| Temp_C | actual temperature in degrees celsius | degrees Celsius (°C) |
| Temp_K | actual temperature in Kelvin | Kelvin (K) |
| Sal | actual practical salinity | PSS-78 |
| exp_pKB_combined | experimental pKB values | unitless |
| borax_added_mg | average amount of sodium tetraborate decahydrate (n=2) added | milligrams (mg) |
| sw_origin | description of seawater origin | unitless |
| sw_collection_year | Year when the sample was originally collected | unitless |
| Dataset-specific Instrument Name | Agilent 8453 |
| Generic Instrument Name | Agilent 8453 UV-visible spectrophotometer |
| Dataset-specific Description | All pHT measurements were conducted using a Thermo Scientific Orion ROSS Ultra glass combination pH electrode with BNC connector in the absolute millivolt mode (3 M NaCl filling solution) and a Keithley 6517A Electrometer/High Resistance Meter (0.01 mV resolution). Electrode calibrations were performed using a diode array spectrophotometer (Agilent 8453) with the UV light lamp turned off. Samples were measured in a Teflon open-top custom-made cell holder with a volume of 120mL cleaned regularly with HCl. |
| Generic 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%. |
| Dataset-specific Instrument Name | Ertco-Eutechnics Model 4400 |
| Generic Instrument Name | digital thermometer |
| Dataset-specific Description | A digital hand-held thermometer (Ertco-Eutechnics Model 4400) with a stainless-steel probe was used to measure the temperature of each sample (±0.025ºC). |
| Generic Instrument Description | An instrument that measures temperature digitally. |
| Dataset-specific Instrument Name | Guildline Portasal 8410A Laboratory Salinometer |
| Generic Instrument Name | Guildline Portasal 8410 series salinometer |
| Dataset-specific Description | Seawater salinity was measured with a Guildline Portasal 8410A Laboratory Salinometer. |
| Generic Instrument Description | The Guildline Portasal 8410 series salinometer is a portable instrument for laboratory or field use that determines salinity of a water sample by comparison of its electrical conductivity with a standard solution. The system employs a continuous flow system, where the sample is drawn into the unit under low air pressure. A high stability temperature control bath and heat exchanger maintain the sample at a precisely defined, user selected temperature during analysis. The instrument can operate over a conductivity range of 0.004 to 76 mS/cm with a resolution of 0.0003 mS/cm (15 deg C and 35 PSU) or 0.0003 Equivalent PSU, and an accuracy of ± 0.003 Equivalent PSU (same set point temperature as standardization and within -2 deg C and +4 deg C of ambient).
The series consists of 2 known models: 8410 and 8410A. The models have the same specifications although the 8410A has an RS232 interface. The reference number 8410N refers to an operational manual update only. |
| Dataset-specific Instrument Name | Thermo Scientific Orion ROSS Ultra glass combination pH electrode |
| Generic Instrument Name | Thermo Fisher Scientific ORION Ross pH electrode series |
| Dataset-specific Description | All pHT measurements were conducted using a Thermo Scientific Orion ROSS Ultra glass combination pH electrode with BNC connector in the absolute millivolt mode (3 M NaCl filling solution) and a Keithley 6517A Electrometer/High Resistance Meter (0.01 mV resolution). Electrode calibrations were performed using a diode array spectrophotometer (Agilent 8453) with the UV light lamp turned off. Samples were measured in a Teflon open-top custom-made cell holder with a volume of 120mL cleaned regularly with HCl. |
| Generic Instrument Description | A series of pH electrodes that have been in production for over 35 years that are capable of measuring pH in TRIS, protein and sulfide samples. Measurement is based on the degree of potential that develops across a sensing membrane surface when the sensing element comes into contact with a sample. An internal reference electrode provides a second, unvarying potential to quantitatively compare the changes of the sensing membrane potential. This series of electrodes use a Ross Reference System that is based on [I3-/I-] iodide/triiodide ion pair chemistry with platinum wire. The probes typically have 0.01 pH precision. |
NSF Award Abstract
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.
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.
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.
| Funding Source | Award |
|---|---|
| NSF Division of Ocean Sciences (NSF OCE) |