A new high pressure liquid chromatography system for in situ measurements in marine pore waters

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The PIs request funding to develop a new underwater instrument based on high pressure liquid chromatographic and voltammetric techniques to measure the concentrations of pore wateranions, cations, and redox species in situ in marine sediments at any water depth.The instrument developed during this project will be the first to adapt HPLC methods for the in situ geochemical analysis of pore waters in marine sediments and couple this HPLC system to existing in situ electrochemical analyzers. This instrument will benefit from the recent developments in microbore technology to limit consumption of effluents such that it will be deployable for long periods of time. This instrument will complement a number of commercial instruments already available for in situ measurements in marine sediments. More importantly, this instrument will for the first time provide a mean to determine the vertical distribution of anions, cations, and redox species involved in early diagenetic processes. Chloride is a chemical tracer that has been used to trace mixing processes in estuarine sediments and phase separation in hydrothermal systems. Nitrogen species can provide information on denitrification, dissimilatory reduction to ammonium (DNRA), and nitrification processes in sediments. Sulfate reduction is a significant terminal electron accepting process in coastal sediments and near cold seeps that can deplete sulfate from pore waters. Finally, calcium and magnesium are tracers of natural organic matter remineralization processes, carbonate dissolution and precipitation processes, and mixing of freshwater with marine waters. Broader Impacts: The PI will actively involve both undergraduate and graduate students in his work here, as he has done in past studies. He will also incorporate the technology he uses in his research into an undergraduate field studies class as he has done in the past. This is good for the education of the students and good for the marine science community. Both PI's are involved in K12 outreach efforts.