HR: 0830h
AN: B21C-0726    [PDF]
TI: Interaction of Strontium With the Calcite Cleavage Surface
AU: * Vinson, M D
EM: mvinson@rice.edu
AF: Rice University, Dept. of Earth Science MS-126 P.O. Box 1892, Houston, TX 77251-1892 United States
AU: Arvidson, R S
EM: rsa4046@rice.edu
AF: Rice University, Dept. of Earth Science MS-126 P.O. Box 1892, Houston, TX 77251-1892 United States
AU: Amonette, J E
AF: Pacific Northwest National Laboratory, Environmental Molecular Sciences Laboratory P.O. Box 999, Richland, WA 99352 United States
AU: Luttge, A
EM: aluttge@rice.edu
AF: Rice University, Dept. of Earth Science MS-126 P.O. Box 1892, Houston, TX 77251-1892 United States
AB: The interaction of Sr$^{2+}$ and carbonate minerals is an important component in our overall understanding of the cycling and sequestration of trace metals in terrestrial environments. For example, uptake of ${}^{90}$Sr by carbonates has significance for the subsurface migration of radioactive contaminants. Past work has confirmed the general inhibition of calcite dissolution in the presence of Sr$^{2+}$, and has suggested that Sr$^{2+}$ may inhibit dissolution by (1) incorporation at kink sites associated with etch pits or (2) precipitation of a secondary phase at the crystal surface. However, these studies have fallen short of resolving the processes of Sr$^{2+}$ inhibition at a mechanistic level. We have used atomic force microscopy (AFM) and vertical scanning interferometry (VSI) to examine calcite crystal dissolution in the presence of Sr$^{2+}$ over a wide range of dissolved carbon concentrations. Although we do see a decrease in dissolution rates with increasing strontium concentrations, we do not see a change in etch pit morphology at solution pH 8-9, or significant precipitation of a secondary phase at concentrations of 25 $\mu$M Sr$^{2+}$. At higher concentrations (250 $\mu$M Sr$^{2+}$), our experimental results do suggest that Sr$^{2+}$ may produce variable inhibition through new nucleation not necessarily related crystallographically with the cleavage surface. These relationships in conjunction with complementary work on the interactions of Mg and Mn with calcite will enable us to develop a general model for the incorporation of trace metals during dissolution of the pure solid.
DE: 1030 Geochemical cycles (0330)
DE: 1045 Low-temperature geochemistry
DE: 1094 Instruments and techniques
DE: 1615 Biogeochemical processes (4805)
DE: 1886 Weathering (1625)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting