Mimicking Ocean Conditions to Study the Growth of Calcium Carbonate
College
College of Arts and Sciences
Department
Chemistry, Physics, Geology, & the Environment
Faculty Mentor
Dr. Maria Gelabert
Abstract
Calcium carbonate is a very prominent biomineral in the ocean that accounts for the skeletons of coral and the shells of other aquatic organisms. In descending stability order, the three polymorphs of calcium carbonate are calcite, aragonite, and vaterite. As a result of recent increases in the atmospheric carbon dioxide pressure, the ocean has been gradually acidifying. As the ocean becomes more acidic, we expect the concentration of carbonate as well as the formation of calcite to decline. This was studied this summer by mimicking ocean conditions and artificial seawater. The role that magnesium partakes in the formation of calcium carbonate was studied at room temperature and a polar temperature of approximately 4 °C. Magnesium is believed to stabilize the metastable polymorphs at high concentrations or incorporate into the crystal lattice at low concentrations, forming dolomite. Through synthesis, analysis with optical imaging and scanning electron microscopy (SEM), X-ray diffraction, thermogravimetic analysis, and differential scanning calorimetry, magnesium was found to impact the morphology of calcium carbonate crystals. The 1:1 magnesium to calcium samples provided a mixture of crystal shapes, while the 8:1 ratio provided solely zinnia-like crystal morphology. Thermal analysis verified the decomposition of calcite at elevated temperatures. As expected, magnesium incorporated into the lattice of the low ratio samples and a less stable polymorph, not calcite, was formed at the higher ratios.
Grant Support?
Supported by a grant from the South Carolina EPSCoR/IDeA Program
Start Date
22-4-2016 2:00 PM
End Date
22-4-2016 2:15 PM
Mimicking Ocean Conditions to Study the Growth of Calcium Carbonate
West Center,Room 217
Calcium carbonate is a very prominent biomineral in the ocean that accounts for the skeletons of coral and the shells of other aquatic organisms. In descending stability order, the three polymorphs of calcium carbonate are calcite, aragonite, and vaterite. As a result of recent increases in the atmospheric carbon dioxide pressure, the ocean has been gradually acidifying. As the ocean becomes more acidic, we expect the concentration of carbonate as well as the formation of calcite to decline. This was studied this summer by mimicking ocean conditions and artificial seawater. The role that magnesium partakes in the formation of calcium carbonate was studied at room temperature and a polar temperature of approximately 4 °C. Magnesium is believed to stabilize the metastable polymorphs at high concentrations or incorporate into the crystal lattice at low concentrations, forming dolomite. Through synthesis, analysis with optical imaging and scanning electron microscopy (SEM), X-ray diffraction, thermogravimetic analysis, and differential scanning calorimetry, magnesium was found to impact the morphology of calcium carbonate crystals. The 1:1 magnesium to calcium samples provided a mixture of crystal shapes, while the 8:1 ratio provided solely zinnia-like crystal morphology. Thermal analysis verified the decomposition of calcite at elevated temperatures. As expected, magnesium incorporated into the lattice of the low ratio samples and a less stable polymorph, not calcite, was formed at the higher ratios.
