pH Limitations in environmental geochemical monitoring

Senior thesis written for Oceanography 445

[author abstract] Development of methods for measuring in situ remineralization rates of carbon in the ocean is necessary to accurately model the ocean’s capacity to sequester atmospheric carbon dioxide and the future ramifications of climate change, including ocean acidification and increases in sea surface temperature (Devol and Hartnett 2001; Boyd and Trull 2007; Buesseler et al. 2007; Workshop 2008; Honjo et al. 2008). Currently, the Keil Lab has developed PHORCYS –PHotosynthesis, Respiration, Carbon balance Yielding System–a sediment trap incubator that measures in situ respiration rates. PHORCYS is restricted to a maximum depth of 200 meters due to the rating of the pH sensor and data logging package. Thus, this study seeks to improve Phorcys’ system so that in situ respiration rates can be measured up to 1000 meters below the ocean’s surface. This will be accomplished by retrofitting PHORCYS with a DuraFET iii pH electrode, and switching from a YSI EXO2 Multiparameter Data Sonde ® to an Arduino-based data logger that will serve as the communication center between the instrument and probes. These changes will enable greater sensitivity in pH measurements (from .01 to .001 pH units precision), and allow measurement of in situ remineralization rate at depths up to 1000 meters.

University of Washington School of Oceanography