This study investigates the potential of stable isotope (δC) methods for exploring the carbonation process of cementitious materials, including well cement paste, portlandite (CH), and calcium silicate hydrate (C–S–H). Through comprehensive chemical and isotopic characterization, along with extensive data analysis, several key conclusions emerge. Firstly, the pH of the solution, as well as the solubility and pH characteristics of mineral phases (CH and C–S–H), are identified as influential factors impacting the kinetics, thermodynamics, and distribution of carbon isotopes (C and C) during the reaction process. Secondly, the study uncovered that higher final pH values correlated with a DIC pool enriched with C and a higher ε isotopic enrichment factor (10.7–12.6 ‰). Furthermore, higher levels of DIC content, solution electrical conductivity, and lower pH lead to higher δC–CaCO and greater ε isotope fractionation (−12.9 to −7.5 ‰). These conditions favor the formation of carbonate minerals with higher isotopic signature (δC–CaCO), thus better preserving the δC-DIC isotope ratio. It was identified that the carbonate mineral (δC–CaCO) formed through the carbonation of cementitious materials (class G cement, CH, and C–S–H) appears to preserve the isotopic signature of the δC–CO source. In conclusion, stable isotope methods could be a valuable tool for assessing and monitoring the cement carbonation process in Carbon Capture and Storage (CCS) wells, particularly when it is crucial to distinguish between injected and endogenous CO.

中文翻译：

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探索稳定同位素方法识别碳捕获和储存环境中胶凝材料碳化过程中二氧化碳来源的潜力

本研究探讨了稳定同位素 (δ13C) 方法在探索胶凝材料碳化过程中的潜力，包括井水泥浆、硅酸钙石 (CH) 和水合硅酸钙 (C-S-H)。通过全面的化学和同位素表征以及广泛的数据分析，得出了几个关键结论。首先，溶液的 pH 值以及矿物相（CH 和 C-S-H）的溶解度和 pH 特性被确定为影响动力学、热力学和碳同位素（C 和 C）分布的影响因素在反应过程中。其次，研究发现较高的最终 pH 值与富含 C 的 DIC 池和较高的 ε 同位素富集因子 (10.7–12.6 ‰) 相关。此外，较高水平的 DIC 含量、溶液电导率和较低 pH 值会导致较高的 δ13C-CaCO3 和较高的 ε 同位素分馏（-12.9 至 -7.5 ‰）。这些条件有利于形成具有较高同位素特征 (δ13C-CaCO) 的碳酸盐矿物，从而更好地保持 δ13C-DIC 同位素比。研究发现，通过胶凝材料（G 类水泥、CH 和 C-S-H）碳化形成的碳酸盐矿物 (δ13C-CaCO3) 似乎保留了 δ13C-CO 源的同位素特征。总之，稳定同位素方法可能是评估和监测碳捕获与封存 (CCS) 井中水泥碳化过程的宝贵工具，特别是在区分注入二氧化碳和内源二氧化碳至关重要时。