Today, carbon dioxide removal from the atmosphere is the most ambitious challenge to mitigate climate changes. Basalt rocks are abundant on the Earth’s surface (≈ 10%) and very abundant in the ocean floors and subaerial environments. Glassy matrix and minerals constituting these rocks contain metals (Ca2+, Mg2+, Fe2+) that can react with carbonic acid to form metal carbonates (CaCO3, MgO3 and FeCO3). Here, we present a data compilation of the chemical composition of waters circulating in basalt aquifers worldwide and the results of simple basalt-water-CO2 experiments. Induced or naturally occurring weathering of basalts rocks release elements in waters and elemental concentration is closely dependent on water CO2 concentration (and hence on water pH). We also performed two series of experiments where basaltic rock powder interacts with CO2-charged waters for one month at room temperature. Laboratory experiments evidenced that in the first stages of water-rock interaction, the high content of CO2 dissolved in water accelerates the basalt weathering process, releasing in the water not only elements that can form carbonate minerals but also other elements, which depending on their concentration can be essential or toxic for life. Relative mobility of elements such as Fe and Al, together with rare earth elements, increases at low pH conditions, while it decreases notably at neutral pH conditions. The comparison between experimental findings and natural evidence allowed to better understand the geochemical processes in basaltic aquifers hosted in active and inactive volcanic systems and to discuss these findings in light of the potential environmental impact of CO2 storage in mafic and ultramafic rocks.

中文翻译：

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玄武岩-水-二氧化碳相互作用过程中的元素迁移率：自然系统中的观察与实验室实验以及对碳储存的影响


如今，从大气中去除二氧化碳是缓解气候变化面临的最艰巨的挑战。玄武岩在地球表面丰富（约 10%），在海底和地下环境中也非常丰富。构成这些岩石的玻璃质基质和矿物质含有金属（Ca2+、Mg2+、Fe2+），它们可以与碳酸反应形成金属碳酸盐（CaCO3、MgO3 和 FeCO3）。在这里，我们介绍了全世界玄武岩含水层中循环水的化学成分的数据汇编以及简单的玄武岩-水-二氧化碳实验的结果。玄武岩的诱发或自然风化会在水中释放元素，元素浓度密切依赖于水中的二氧化碳浓度（因此也依赖于水的 pH 值）。我们还进行了两项系列实验，其中玄武岩粉末与充有二氧化碳的水在室温下相互作用一个月。实验室实验证明，在水-岩相互作用的第一阶段，溶解在水中的高含量二氧化碳加速了玄武岩的风化过程，不仅在水中释放出可形成碳酸盐矿物的元素，而且还释放出其他元素，具体取决于其浓度可能对生命至关重要或有毒。 Fe 和 Al 等元素以及稀土元素的相对迁移率在低 pH 条件下增加，而在中性 pH 条件下显着降低。实验结果与自然证据之间的比较可以更好地了解活动和非活动火山系统中玄武岩含水层的地球化学过程，并根据镁铁质和超镁铁质岩石中二氧化碳储存的潜在环境影响来讨论这些发现。