Recent studies of dolomite surface reactivity have shown that the processes controlling the dissolution of this mineral at the microscopic scale are still not well understood and quantified and not always consistent with the results of macroscopic observations. In the present study dolomite dissolution at pH 3 was investigated using both a macroscopic approach (pH-stat system and mixed-flow reactor) and microscopic characterization methods (atomic force and transmission electron microscopies) to quantify the release rates of Ca and Mg from bulk chemical analyses and determine the micro-topographical and chemo-structural changes that accompany the dissolution reaction.

Dolomite dissolution rates from pH-stat and mixed-flow reactor experiments conducted on two distinct dolomite natural samples were found to differ by a factor of 2 between the two samples but falling within the range of values reported in the literature. High-resolution sampling of the aqueous fluid allowed observing frequent fluctuations of the Ca/Mg ratio (1.00 ≤ Ca/Mg ≤ 1.39) and its progressive decrease towards the stoichiometric value of the solid. Such oscillations are related, at the microscopic scale, to the preferential release of Ca from the fresh mineral surface, the concurrent generation of new surface that becomes exposed to the fluid and the temporary surface Mg enrichment occurring as the consequence of the faster departure of Ca ions to the aqueous solution. According to TEM observations, this dissolution mechanism does not bring about any noticeable modification of the dolomite surface structure in contact with the aqueous solution.

Atomic force microscopy (AFM) experiments allowed observing the fast nucleation of high density etch pits during dissolution. The fluid effluent from the AFM cell was enriched in Ca (Ca/Mg =3.2–5.5) compared to the solution of the bulk experiments and the dolomite stoichiometry (Ca/Mg =1.01), but there was no evidence of formation of any Mg-rich secondary precipitate, contrary to what reported by previous studies with much higher Ca/Mg values. The increase of the Ca/Mg ratio in these effluents compared to the pH-stat and mixed-flow runs is likely related to the specific hydrodynamic conditions present within the AFM fluid-cell under transport-controlled dissolution regimes. The concentration of Ca aqueous ions preferentially released from the solid surface is likely further increased following their transport across the diffusive layer formed at the solid-fluid interface because of their higher diffusivity compared to aqueous Mg ions. However, the thermodynamic requirements for the formation of Mg-bearing secondary phases are unlikely to be met within this system under the investigated conditions.

最近对白云石表面反应性的研究表明，在微观尺度上控制这种矿物溶解的过程仍未得到很好的理解和量化，并且与宏观观察的结果并不总是一致。在本研究中，使用宏观方法（pH-stat 系统和混合流反应器）和微观表征方法（原子力和透射电子显微镜）研究了 pH 3 下的白云石溶解，以量化 Ca 和 Mg 的释放速率。化学分析并确定伴随溶解反应的微观形貌和化学结构变化。

发现在两个不同的白云岩天然样品上进行的 pH-stat 和混合流动反应器实验的白云石溶解速率在两个样品之间相差 2 倍，但落在文献报道的值范围内。水性流体的高分辨率采样允许观察 Ca/Mg 比率（1.00 ≤ Ca/Mg ≤ 1.39）的频繁波动及其向固体的化学计量值逐渐降低。在微观尺度上，这种振荡与 Ca 从新鲜矿物表面优先释放、同时产生暴露在流体中的新表面以及由于 Ca 更快离开而发生的临时表面 Mg 富集有关离子到水溶液中。根据 TEM 观察，

原子力显微镜 (AFM) 实验可以观察溶解过程中高密度蚀刻坑的快速成核。与本体实验溶液和白云石化学计量比 (Ca/Mg = 1.01) 相比，来自 AFM 电池的流体流出物富含 Ca (Ca/Mg = 3.2-5.5)，但没有形成任何 Mg 的证据- 丰富的二次沉淀，与先前研究报告的具有更高的 Ca/Mg 值相反。与 pH-stat 和混合流运行相比，这些流出物中 Ca/Mg 比的增加可能与在传输控制的溶解状态下 AFM 流体池中存在的特定流体动力学条件有关。优先从固体表面释放的 Ca 水溶液离子的浓度在它们穿过在固-流体界面形成的扩散层后可能会进一步增加，因为与水溶液 Mg 离子相比，它们具有更高的扩散率。然而，在所研究的条件下，该系统不太可能满足形成含镁第二相的热力学要求。