A novel ion chromatography system for Earth, Ocean, and Environmental Science

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This proposal is requesting funding for a novel and highly flexible ion chromatography (IC) system necessary for the separation of individual elements prior to measurements of isotope ratios using mass spectrometry. This type of high-throughput and high-quality ion chromatography system is essential for several established and early career research (ECR) programs within SEOS. For example, an overarching theme of the applicants' research programs is understanding the controls on the composition of the ocean over many time scales. Currently, anthropogenic CO2 emission have dramatic impacts on ocean chemistry, causing perturbations to biological productivity, acidification, de-oxygenation, and the release of harmful contaminants. To accurately predict the extent of these changes and mitigate the impacts, we need to better understand changes to ocean chemistry on both long and short time scales. A powerful method to track changes in ocean chemistry is by measuring the isotopic composition of different elements in seawater and ancient sediments - measurements that require sample purification by ion chromatography. For example, an important component of Ahm's research program is the measurement of Ca isotopes to investigate how the Earth systems responds to long-term changes in CO2. Since we cannot directly sample seawater from deep time, the Ca isotopic ratio of ancient sediments provide essential insights into the foundational processes that have shaped Earth's climate across geological time. The removal of CO2 from the ocean is ultimately controlled by the reaction between Ca and CO2 though the burial of carbonate sediments (CaCO3), linking the global calcium and carbon cycles. As a consequence, the ratio of Ca isotopes (44Ca/40Ca) in ancient carbonate sediments can be used to track both long-term changes in seawater and to elucidate short-term climate perturbations. In addition to Ca isotopes, the measurements of other non-traditional isotope system are also important to the applicants research programs. Coogan's research rely on measurements of metal isotope systems, such as Li, Mg, and K isotopes, in the ocean crust to constrain models of Earth's carbon cycle and to monitor the efficacy of developing carbon sequestration techniques. Cullen's research group utilize novel Cd isotope measurements as tracers to investigate the human-driven impacts on biological productivity and the decrease of oxygen in the modern ocean. In addition to the applicants, the requested IC system will represent a facility for multiple research programs within SEOS, build regional analytical capacity, train numerous HQP, and facilitate new research directions which exploit non-traditional metal isotopes to study the links between the evolution of Earth's ocean chemistry and climate system.