Accurate estimation of contaminant transport in cementitious material using numerical tools plays a key role in the risk assessments of nuclear waste disposal. At the pore scale, the increase of microbial activity, such as microbially induced calcite precipitation on cementitious material, causes changes in solid surface topography, pore network geometry, and pore water chemistry, which affect contaminant transport at the core scale and beyond. Consequently, a meaningful estimation of contaminant migration in the subsurface requires a pore-scale investigation of the influence of microbial activity on transport processes. In this study, a pore-scale reactive transport model is presented to simulate the physicochemical processes resulting from microbially induced calcite precipitation on a cement surface. Numerical investigations focus on modeling the reactive transport in a two-dimensional flow-through cell. The model results are validated by experimental data showing an increase in pH and a decrease in calcium concentration due to microbially induced calcite precipitation. Our results show heterogeneous calcite precipitation under transport-limited conditions and homogeneous calcite precipitation under reaction-limited conditions, resulting in non-uniform and uniform changes in the material surface topography. Moreover, power spectral density analysis of the surface data demonstrates that microbially induced calcite precipitation affects the surface topography via both general changes over the entire frequency and local modifications in the high-frequency region. The sensitivity studies provide a comprehensive understanding of the evolution of surface topography due to the microbially induced calcite precipitation at the pore scale, thus contributing to an improved predictability of contaminant transport at the core scale and beyond.

中文翻译：

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孔隙尺度下水泥表面微生物诱导方解石沉淀的数值模拟和模拟


使用数值工具准确估计水泥材料中污染物的迁移在核废物处置的风险评估中发挥着关键作用。在孔隙尺度上，微生物活动的增加，例如微生物诱导的胶凝材料上的方解石沉淀，会导致固体表面形貌、孔隙网络几何形状和孔隙水化学的变化，从而影响核心尺度及其以外的污染物迁移。因此，对地下污染物迁移的有意义的估计需要对微生物活动对迁移过程的影响进行孔隙尺度的研究。在这项研究中，提出了一种孔隙尺度反应传输模型来模拟微生物诱导的方解石在水泥表面沉淀所产生的物理化学过程。数值研究的重点是对二维流通池中的反应传输进行建模。实验数据验证了模型结果，显示微生物诱导的方解石沉淀导致 pH 值升高和钙浓度降低。我们的结果表明，在传输限制条件下会发生非均质方解石沉淀，而在反应限制条件下会发生均质方解石沉淀，从而导致材料表面形貌的不均匀和均匀变化。此外，表面数据的功率谱密度分析表明，微生物引起的方解石沉淀通过整个频率的一般变化和高频区域的局部修改影响表面形貌。 敏感性研究提供了对由于微生物诱导的孔隙尺度方解石沉淀而导致的表面形貌演变的全面了解，从而有助于提高污染物在核心尺度及以外迁移的可预测性。