I study the geochemical kinetics of environmentally-relevant mineral-water interfaces using synchrotron x-ray techniques and atomic force microscopy. The minerals I study (barite, calcite) can be used as hosts for contaminant remediation by co-precipitating radioactive contaminants (90Sr, Ra) into their crystal structures. Major questions I addressed include the mechanism of binding, effect on crystal growth rate and extent of incorporation of the contaminants. I utilize surface x-ray diffraction to study the structure and reactivity of terraces between the steps and atomic force microscopy to study the dynamics of steps and adsorbed sites along a step (kink sites). Traditionally these studies are conducted near room temperature, however my research focuses on extending these techniques to elevated temperatures and pressures that more closely mimic conditions under which environmental processes such as carbon sequestration and contaminant remediation occur.
- GEOL 099 – Planet Earth: Resources and Hazards for the 21st Century
- GEOL 799 – Analytical Techniques in Environmental Geosciences
- GEOL 799.3 – Geochemistry
My goal in teaching is to ensure students are confident in their foundational knowledge of earth science, which includes the ability to understand science written by leading researchers in the field of focus for each class. As an undergraduate and graduate student, the courses I best retained information from were those which used an active learning approach, rather than classes which relied on more traditional lecture style techniques. As such, I incorporate active learning activities and discussion of publications into my courses.
J. Weber, J.N. Bracco, J.D. Poplawsky, A. Ievlev, K.L. More, M. Lorenz, A. Bertagni, S. Jindra, V. Starchenko, S. Higgins, A.G. Stack. Unraveling the Effects of Strontium Incorporation on Barite Growth—In Situ and Ex Situ Observations Using Multiscale Chemical Imaging. Cryst. Growth Des., 2018, 18 (9), 5521–5533.
Jindra, SA; Bertagni, A; Bracco, JN; Higgins, SR. Hydrothermal Atomic Force Microscopy Investigation of Barite Growth: The Role of Spectator Ions in Elementary Step Edge Growth Kinetics and Hillock Morphology. Cryst. Growth Des., 2017, 17(11), 6085–6095.
Bracco, JN; Lee, SS; Stubbs, JE; Eng, PJ; Heberling, F; Fenter, P; Stack, AG. Hydration Structure of the Barite (001)-Water Interface: Comparison of X-ray Reflectivity with Molecular Dynamics Simulations. Journal of Physical Chemistry C 2017, 121, 12236-12248.
Bracco, JN; Gooijer, Y; Higgins, SR. Hydrothermal atomic force microscopy observations of barite step growth rates as a function of the aqueous barium-to-sulfate ratio. Geochim. Cosmochim. Acta 2016, 183, 1-13.
Bracco, JN; Gooijer, Y; Higgins, SR. Growth kinetics of step edges on celestite (001) surfaces as a function of temperature, saturation state, ionic strength, and aqueous strontium:sulfate ratio: An in situ atomic force microscopy study. Geochim. Cosmochim. Acta 2016, 175, 222-238.
Bracco, JN; Stack, AG; Higgins, SR. Magnesite step growth rates as a function of the aqueous magnesium:carbonate ratio. Cryst. Growth Des. 2014, 14, 6033-6040.
Bracco, JN; Stack, AG; Steefel, CI. Upscaling calcite growth rates from the meso- to the macro- scale. Environ. Sci. Technol. 2013, 47, 7555-7562.
Bracco, JN; Grantham, MC; Stack, AG. Calcite growth rates as a function of aqueous calcium-to-carbonate ratio, saturation index, and inhibitor concentration: insight into the mechanism of reaction and poisoning by strontium. Cryst. Growth Des. 2012, 12, 3540-3548.