HR: 1330h
AN: B32A-0369    [PDF]
TI: Carbonate Dissolution and Precipitation in Coastal Environments
AU: * Berkowitz, B
EM: brian.berkowitz@weizmann.ac.il
AF: Weizmann Institute of Science, Department of Environmental Sciences and Energy Research, Rehovot, 76100 Israel
AU: Singurindy, O
EM: olga.singurindy@weizmann.ac.il
AF: Weizmann Institute of Science, Department of Environmental Sciences and Energy Research, Rehovot, 76100 Israel
AU: Lowell, R P
EM: bob.lowell@eas.gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA 30332-0340 United States
AB: In order to better understand and quantify mixing-driven mineral precipitation and dissolution in coastal environments, we conducted laboratory experiments designed to investigate dissolution and precipitation of CaCO$_{3}$ upon mixing between carbonate-saturated fresh- and salt-water solutions under different CO$_{2}$ partial pressures, and for different mixing ratios. Mixing of seawater or saline subsurface water with fresh water can be of major importance in the chemical diagenesis of carbonate rocks and sediments. We used both artificial seawater and NaCl solutions of different strengths. Two-dimensional flow cells filled with glass beads and crushed calcium carbonate rock were used, respectively, to measure calcium carbonate precipitation and dissolution. An important feature of these experiments is that the results are shown to agree well with a relatively simple transport theory describing mineral precipitation and dissolution that results from the non-linear dependence of CaCO$_{3}$ saturation upon electrolyte concentration. The theory demonstrates that the rate of dissolution or precipitation depends linearly on the dispersivity, specific discharge, and curvature (and sign) of the solubility as a function of salinity, but varies as the inverse square of the mixing zone width. The theory is largely scale independent and depends upon field parameters that can be determined. Analysis of data from three field sites (Yucatan peninsula, Bermuda, Mallorca) demonstrates excellent agreement between field observations and theory.
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1832 Groundwater transport
DE: 4546 Nearshore processes
DE: 4825 Geochemistry
SC: Biogeosciences [B]
MN: 2003 Fall Meeting