TY - JOUR
T1 - Calcite growth kinetics: Modeling the effect of solution stoichiometry
AU - Wolthers, M.
AU - Nehrke, G.
AU - Gustafsson, J.P.
AU - Van Cappellen, P.
PY - 2012
Y1 - 2012
N2 - Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite
the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the
dependence of the calcite crystal growth rate on the cation to anion ratio in solution, we extend the growth model for binary
symmetrical electrolyte crystals of Zhang and Nancollas (1998) by combining it with the surface complexation model for the
chemical structure of the calcite–aqueous solution interface of Wolthers et al. (2008). To maintain crystal stoichiometry, the rate
of attachment of calcium ions to step edges is assumed to equal the rate of attachment of carbonate plus bicarbonate ions. The
model parameters are optimized by fitting the model to the step velocities obtained previously by atomic force microscopy
(AFM, Teng et al., 2000; Stack and Grantham, 2010). A variable surface roughness factor is introduced in order to reconcile
the new process-based growth model with bulk precipitation rates measured in seeded calcite growth experiments. For practical
applications, we further present empirical parabolic rate equations fitted to bulk growth rates of calcite in common background
electrolytes and in artificial seawater-type solutions. Both the process-based and empirical growth rate equations agree with
measured calcite growth rates over broad ranges of ionic strength, pH, solution stoichiometry and degree of supersaturation.
AB - Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite
the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the
dependence of the calcite crystal growth rate on the cation to anion ratio in solution, we extend the growth model for binary
symmetrical electrolyte crystals of Zhang and Nancollas (1998) by combining it with the surface complexation model for the
chemical structure of the calcite–aqueous solution interface of Wolthers et al. (2008). To maintain crystal stoichiometry, the rate
of attachment of calcium ions to step edges is assumed to equal the rate of attachment of carbonate plus bicarbonate ions. The
model parameters are optimized by fitting the model to the step velocities obtained previously by atomic force microscopy
(AFM, Teng et al., 2000; Stack and Grantham, 2010). A variable surface roughness factor is introduced in order to reconcile
the new process-based growth model with bulk precipitation rates measured in seeded calcite growth experiments. For practical
applications, we further present empirical parabolic rate equations fitted to bulk growth rates of calcite in common background
electrolytes and in artificial seawater-type solutions. Both the process-based and empirical growth rate equations agree with
measured calcite growth rates over broad ranges of ionic strength, pH, solution stoichiometry and degree of supersaturation.
U2 - 10.1016/j.gca.2011.11.003
DO - 10.1016/j.gca.2011.11.003
M3 - Article
SN - 0016-7037
VL - 77
SP - 121
EP - 134
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 4
ER -