Field Evaluation of New pH and pCO2 Microelectrodes and an In Situ Profiler

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ABSTRACTOCE-9911786A clear understanding of microbial remineralization of organic matter in marine sediments is critical to our understanding of global O2, carbon and nutrient mass balances. However, establishing remineralization rates of organic matter are difficult because steep porewater profiles of O2, pH, pCO2, NO3-, Mn2+, Fe2+, NH4+ and HS- are generally established near the sediment-seawater interface as a result of both microbial and chemical reactions. These steep porewater gradients are hard to quantify using conventional sampling techniques that sample over cm versus mm sediment intervals (ie. collecting porewater via centrifugation or squeezing) and limitations imposed by pressure, temperature and other environmental conditions. Microelectrodes have the potential to provide reliable, very fine scale and in-situ measurements with minimum disturbance of the system. For this reason, the PI proposes to field test newly developed neutral carrier-based polymeric membrane pH and pCO2 microelectrodes and a profiler system. The primary objective of the proposed work will be to determine the analytical precision and accuracy of the combined microelectrodes and profiler such that they can be used to study the rates and mechanisms of organic carbon diagenesis and CaCO3 in a variety of marine environments.