Abstract We present the first examination of calcite dissolution in seawater using Atomic Force Microscopy (AFM). We quantify step retreat velocity and etch pit density to compare dissolution in seawater to low ionic strength water, and also to compare calcite dissolution under AFM conditions to those conducted in bulk solution experiments (e.g. Subhas et al., 2015 , Dong et al., 2018 ). Bulk dissolution rates and step retreat velocities are slower at high and mid-saturation state (Ω) values and become comparable to low ionic strength water rates at low Ω. The onset of defect-assisted etch pit formation in seawater is at Ω ∼ 0.85 (defined as Ωcritical), higher than in low ionic strength water (Ω ∼ 0.54). There is an abrupt increase in etch pit density (from ∼106 cm−2 to ∼108 cm−2) occurring when Ω falls below 0.7 in seawater, compared to Ω ∼ 0.1 in low ionic strength water, suggesting a transition from defect-assisted dissolution to homogeneous dissolution much closer to equilibrium in seawater. The step retreat velocity (v) does not scale linearly with undersaturation (1-Ω) across an Ω range of 0.4 to 0.9 in seawater, potentially indicating a high order correlation between kink rate and Ω for non-Kossel crystals such as calcite, or surface complexation processes during calcite dissolution in seawater.

中文翻译：

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海水中方解石溶解的原子力显微镜研究

摘要 我们首次使用原子力显微镜 (AFM) 对海水中的方解石溶解进行了检测。我们量化步退速度和蚀刻坑密度，以比较海水中的溶解与低离子强度水中的溶解，并将 AFM 条件下的方解石溶解与本体溶液实验中的进行比较（例如 Subhas 等，2015，Dong 等， 2018 年）。在高饱和状态 (Ω) 值和中等饱和状态 (Ω) 值下，整体溶解速率和步进后退速度较慢，并且可与低 Ω 下的低离子强度水速率相媲美。海水中缺陷辅助蚀刻坑形成的起始点为 Ω ∼ 0.85（定义为 Ωcritical），高于低离子强度水（Ω ∼ 0.54）。与Ω ∼ 0 相比，当 Ω 在海水中低于 0.7 时，蚀刻坑密度突然增加（从∼106 cm−2 到∼108 cm−2）。1 在低离子强度水中，表明从缺陷辅助溶解过渡到更接近于海水中的平衡的均匀溶解。在海水中，在 0.4 到 0.9 Ω 范围内，阶跃后退速度 (v) 与不饱和度 (1-Ω) 不成线性比例，这可能表明非科塞尔晶体（如方解石）的扭结率和 Ω 之间存在高阶相关性，或方解石在海水中溶解过程中的表面络合过程。