The Calibration of Indicator Dyes for the Measurement of Oceanic pH

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The final goal of the research is to establish spectrophotometric pH measurements as a key analysis in the study of the oceanic carbon dioxide system. The bulk of the work will be focussed on calibrating the dyes for use as pH indicators by direct reference to measurements using the highly reproducible hydrogen / silver-silver chloride cell. Additional work will be performed to assess the stability of the indicator dyes and the importance of impurities in commercially available chemicals. Experiments will also be conducted to demonstrate that these pH measurements are thermodynamically consistent with measurements of dissolved inorganic carbon, total alkalinity, and f(CO2). Furthermore, an additional pH buffer for use in the electrometric measurement of oceanic pH, will be established. Detailed and precise pH profiles will be obtained in the North Pacific Ocean in conjunction with the CO2 system measurements of NOAA personnel. The proposed work entails measurements of spectrophotometric pH on each seawater sample analyzed by NOAA personnel for total inorganic carbon, CO2 partial pressure, and total alkalinity. These measurements will be used to assist in long term NOAA investigations of oceanic-atmospheric CO2 exchange and will also be used to verify the accuracy of pH determinations involving indicator dyes by demonstrating internal consistency in alkalinity, total CO2, pCO2 and pH data sets.