The relationship between the strontium partition coefficient in calcite (K_sr) and calcite precipitation rate (R_p) has been found to change systematically with pH of the solution in precipitation experiments of synthetic calcite. We hypothesize that the observed pH dependence of strontium partitioning is due to the involvement of HCO₃⁻ during calcite precipitation. We use an ion-by-ion calcite growth model which considers the contribution of both HCO₃⁻ and CO₃²⁻ to calcite precipitation to test this hypothesis. Three groups of experimental data of inorganic calcite precipitation at various pH at room temperature were fit successfully with one set of parameters. The results indicate that the speciation of carbonate can explain the pH dependence of the strontium partition coefficient. Our model also reproduces observed K_Sr-R_p relationships at various temperatures of 5, 25 and 40 °C. This general model predicts calcite precipitation rates and strontium partition coefficients with known aqueous carbonate chemistry and provides a useful framework for understanding strontium partitioning in inorganic and biogenic calcite.

在合成方解石的沉淀实验中发现，方解石中的锶分配系数（K _sr）和方解石沉淀速率（R _{p ）之间的关系会随着溶液的 pH 值而系统地变化。}我们假设观察到的锶分配的pH依赖性是由于方解石沉淀过程中HCO ₃ ^{-的参与。}我们使用逐离子方解石生长模型，该模型考虑了 HCO ₃ ^-和 CO ₃ ^2-的贡献方解石沉淀来检验这个假设。用一组参数成功拟合了室温下不同pH下无机方解石沉淀的三组实验数据。结果表明，碳酸盐的形态可以解释锶分配系数对 pH 的依赖性。我们的模型还重现了在 5、25 和 40 °C 的各种温度下观察到的K _Sr -R _p关系。这个通用模型预测了已知水性碳酸盐化学的方解石沉淀速率和锶分配系数，并为理解无机和生物方解石中的锶分配提供了有用的框架。