Establishing a Baseline for Kinetic and Thermodynamic Origins of Vital Effects: Toward an Understanding of Factors Controlling Mg Signatures in Calcite
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Using in situ Atomic Force Microscopy, controlled solution chemistries, and different ion microprobe techniques, this dissertation investigates the kinetics and thermodynamics of calcite growth to establish an inorganic baseline for uptake of Mg. I use this information to quantify the enhancement in Mg/Ca due to the presence of hydrophilic 27-mer peptides, demonstrating a possible origin of vital effects. Likewise I measure the effect of ionic strength on signatures and find that growth rate and background electrolyte proved more important than salinity in determining Mg contents.
The findings contribute to the ongoing discussion regarding the relative importance of unique seawater parameters in determining Mg/Ca in calcite. Mg contents are significantly enhanced by biomolecules relative to the amounts attributed to temperature differences, while Mg content is less influenced by salinity variation than by changing supersaturation or driving force. In addition to sorting out the relative importance of environmental factors, our results begin to address the interplay of these different parameters in concert, and at different scales. At sites of calcification, the local biochemistry within an organism may shift in response to more saline waters. At a geological scale, interpreting past temperatures and particularly those of the Last Glacial Maximum depends on our ability to sort out and account for this interplay of salinity and temperature on Mg/Ca. Processes underlying inorganic and biogenic carbonate mineralization and interpretations of their formation environments are better understood by examining the influence of environmental parameters and biomolecular chemistry on kinetics and thermodynamics of calcite growth and stability.
- Doctoral Dissertations