Chemical Disequilibria in Diffuse Flow Hydrothermal Vents: An Experimental Study on H2-O2 Redox Equilibria in the presence of Fe-Oxides

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ABSTRACT 0752221 (Foustoukos)Intellectual Merit: The research develops a new flow-through reactor that makes possible the controlled study of many redox sensitive reactions in steady-state systems, such as those that involve metals or microbes. The design will allow aqueous solutions enriched in H2(aq) to be hydrothermally pretreated before being mixed with O2(aq)-bearing aqueous solutions at temperatures and pressures (50-200oC/250 bars). The apparatus will allow steady state control and real-time measurements of the redox capacity of the reacting fluids, while maintaining a constant driving force for Knallgas reaction to proceed. The H2(aq)-O2(aq) redox equilibria will be examined in the presence of Fe-oxides, to evaluate the relative capacity of magnetite in promoting H2(aq) oxidation while in equilibria with O2(aq)-enriched fluids. The reactor will be tested by experiments designed to study the relative stability of metastable oxidizing/reducing aqueous species in redox gradients developed within the mixing zone of seawater and hydrothermal vent fluids at seafloor conditions, a system that is important in the transfer of heat and mass in mid-ocean ridge systems. These hydrothermal fluids play a key role in the re-distribution of volatiles and metals in abyssal environments and in providing metabolically active conditions for microbes both on and below the seafloor. Broader Impacts: The project includes training of undergraduate and high-school students through the Carnegie NSF-REU and through local high-school intern programs. It also supports professional development of an early career scientist. A primary impact of the research is the development of a novel, new, flow-through reactor with in-situ sensors that allow real-time measurements of key geochemical solution properties. In addition to building infrastructure for science, the work has crossover potential to the fields of petroleum and chemical engineering and has potential applications to bioremediation of toxic waste.