Measurement of seawater pH: a theoretical and analytical investigation

Posted on EPOCA: 18 Dec 2012

 The emission of anthropogenic carbon is leading to the influx of additional CO2 to the atmosphere and global ocean. While the flux of anthropogenic CO2 from the atmosphere to the ocean may be leading to the mitigation of global climate change, it is also leading to the decline of global ocean pH – a process referred to as Ocean Acidification. The net effects Ocean Acidification will have on physical, biogeochemical, and ecological processes are currently not well constrained, but there is significant research interest in evaluating the effects of decreased pH on ocean processes. Seawater pH is the essential measurement required to analyze these changes, but there is no universally accepted definition of pH for ionic media. This absence leads to increased confusion in the measurement of seawater pH, which can lead to decreased inter-comparability of the pH and related carbon system measurements. This dissertation focuses on advancement of the theoretical and analytical aspects of seawater pH, which is achieved through: 1) development of a semi-autonomous system for the spectrophotometric measurement of pH and total alkalinity in seawater, 2) re- evaluation of the standard potential for the free pH concentration scale and bisulfate dissociation constant in seawater, 3) analytical comparisons of pH determined with un- purified colorimetric pH indicators over a of range salinities and initial solution pH values, and 4) determination of the rates of increase in anthropogenic CO2 and decrease in ocean pH. Such progressions will lead to greater understanding and comparability of ocean pH and carbon measurements, thus advancing future research in chemical, physical, and biological processes related to Ocean Acidification.


Waters J. F., 2012. Measurement of seawater pH: a theoretical and analytical investigation. PhD thesis, University of Miami, 180 p. Open Access Dissertations. Paper 908. Thesis.