RSI Research Seminar

Join us every other Monday at noon for lunch and a 30-minute research talk, presented by Resnick Sustainability Institute Graduate Fellows and Caltech researchers funded by the Resnick Sustainability Institute. To see the full schedule of speakers, visit the RSI Research Seminar web page. Seminars currently take place in a hybrid format, both in-person (Jorgensen building first-floor conference room) and via Zoom. For more information and to get the Zoom login info, please reach out to [email protected]

Controls on porewater calcite dissolution kinetics from novel in-situ dissolution experiments

Excess atmospheric CO2is neutralized in the ocean via the dissolution of carbonate minerals, including calcite. The rate at which calcite dissolves influences the timescale of the ocean's response to perturbations in the global carbon cycle. As such, our understanding of global scale chemistry is partly governed by microscopic processes at mineral surfaces. Our group has shown that the kinetics of calcite dissolution as a function of seawater undersaturation can be described by mineral surface energic mechanisms in both laboratory experiments and ocean water column experiments. Quantifying and describing the controls on carbonate mineral dissolution rates in marine sediments is the next step towards a complete description of carbonate cycling in the ocean.

We report results from experiments performed using a novel device for collecting in-situ marine porewater and determining carbonate dissolution rates from deployments on a research cruise in the Eastern Equatorial Pacific in November 2021. Ongoing processing of dissolution experiment data, in conjunction with modeling of our experimental system, is underway to quantify gross and net dissolution rates as a function of undersaturation and depth in the sediment. Preliminary results point to signals of dissolution in porewater even in localities where the overlying water is near saturation. Additionally, we observe a large increase in dissolution signal at undersaturations less than omega = 0.75. In laboratory and water column dissolution experiments our group previously observed a change in the surface energetic mechanism controlling the calcite dissolution rate at omega = 0.75. This suggests the same nanoscale surface processes controlling calcite dissolution rate in the laboratory and water column are likely controlling dissolution rates in porewater. These results have implications for the timescales by which marine carbonate compensation responds to and buffers changes in atmospheric CO2.