Development and Evaluation of pH and CO2 Microelectrodes for In Situ Determination of Deep Sea Pore Water Carbonate Chemistry and Carbon Recycling Rate

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9401908 CAI This project is aimed at developing a fast and stable pCO2 microelectrode based on a flat tip Iroxide pH microelectrode and evaluating the accuracy and applicability of pH and pCO2 sensors for measuring benthic carbon recycling rates and pore water CO2 chemistry. The pCO2 microelectrode will be a marked improvement of an earlier pCO2 sensor. It is planned to enhance and optimize the response rate, stability, and precision of the pCO2 electrode. The accuracy of the pH and pCO2 microelectrode measurements will be evaluated by profiling various laboratory incubated sediments and comparing the results with TCO2 concentrations from whole core squeezing samples. In situ measurements and evaluation also will be conducted in two coastal environments. A goal in the future is not only to collect high resolution and artifact-free in situ profiles with microelectrodes, but also to over-determine the pore water carbonate system by combining the in situ microelectrode measurements (O2,pH, and pCO2) and the in situ sampling techniques (TA, TCO2, and nutrients) in a single device. The measurements will define the O2/C/N ratios during organic carbon early digenesis. This strategy will also give the three state-of-the-art approaches, microelectrode, whole core squeezing, and benthic chamber incubation, a reliability and internal consistency check. This combined approach is essential for determining benthic response to the seasonal changes of C input and in delineating controls over the pore water carbonate system and CaCO3 preser- vation and dissolution.