Mechanisms and applications of gas-driven mineral weathering: Implications for the geologic carbon cycle and engineered carbon storage

二氧化碳驱动的硅酸盐矿物风化作用从大气中去除二氧化碳，并释放植物和微生物生长所必需的营养物质，而氧气驱动的硫化物风化作用可以释放二氧化碳。这些由气体驱动的矿物风化过程，随后是碳酸盐矿物在海洋中的沉淀，在地质时期内调节着大气中的二氧化碳浓度和全球气候。此外，设计这些自然过程以加速二氧化碳储存，是帮助缓解温室气体引发的气候变化的一个有前途的战略。尽管气体驱动的矿物风化反应在全球范围内的影响已经被认识到，但在水不饱和的地球材料中控制它们反应的机制仍然知之甚少。这项拟议的研究旨在阐明气体驱动矿物风化的物理和化学控制，并将包括三个主要主题：1)二氧化碳浓度对矿物风化的影响，2)水在矿物风化反应中的作用，3)设计工程二氧化碳储存策略。将采用实验方法来确定气体驱动的矿物风化反应的机制，并将使用反应迁移和地球化学模拟来将实验结果外推到更大的空间和时间尺度。通过主题1和2揭示的气体驱动矿物风化反应的基本机制将为设计工程二氧化碳储存策略提供信息，该策略利用自然风化过程来捕获和储存人为二氧化碳。实验将测试在天然岩石和采矿业废物加速风化过程中优化二氧化碳储存的策略。来自某些矿场的细粒废物产品，即所谓的尾矿，具有捕获和储存大气二氧化碳的巨大但尚未开发的潜力。反应迁移模型将用于根据气候和尾矿或岩石的化学性质等特征，针对特定地点定制二氧化碳封存策略。总之，这些研究将提供对在地质时期帮助缓和地球气候的机制的洞察，使人们能够更好地评估矿物风化反应对气候变化引起的水可获得性变化的反应，并有助于气候变化缓解战略的设计。通过生产可供学术和工业用户使用的反应性传输模型来模拟环境变化对风化反应的影响，并设计二氧化碳储存策略，将获得切实的好处。这样的二氧化碳储存战略将有助于加拿大实现雄心勃勃的温室气体减排目标。在这项研究中，高素质的人员将接受分析、实验和建模技术方面的培训，并获得可转让的技能。这项技能可应用于环境政策、环境咨询或继续学术研究。

The CO2-driven weathering of silicate minerals removes CO2 from the atmosphere as well as releasing nutrients essential for plant and microbial growth, whereas O2-driven sulphide weathering can release CO2. These gas-driven mineral weathering processes, followed by the precipitation of carbonate minerals in the oceans, regulate atmospheric CO2 concentrations and global climate over geologic time. Moreover, the engineering of these natural processes to accelerate CO2 storage is a promising strategy to help mitigate greenhouse gas-fuelled climate change. Although the global-scale implications of gas-driven mineral weathering reactions have been recognized, the mechanisms that control their reaction in water-unsaturated Earth materials remains poorly understood. The proposed research aims to elucidate the physical and chemical controls on gas-driven mineral weathering, and will comprise three main themes: 1) the impact of CO2 concentration on mineral weathering, 2) the role of water in mineral weathering reactions, and 3) designing engineered CO2 storage strategies. An experimental approach will be taken to determine mechanisms of gas-driven mineral weathering reactions, and reactive transport and geochemical modelling will be used to extrapolate experimental results to larger spatial and temporal scales. Fundamental mechanisms of gas-driven mineral weathering reactions revealed through Themes 1 and 2 will inform the design of engineered CO2 storage strategies that exploit natural weathering processes to capture and store anthropogenic CO2. Experiments will test strategies to optimize CO2 storage during accelerated weathering of natural rock as well as waste products from the mining industry. Fine grained waste products, known as tailings, from certain mine sites have a significant but untapped potential to capture and store atmospheric CO2. Reactive transport modelling will be used to tailor CO2 sequestration strategies to particular sites based on characteristics such as climate and chemical properties of the tailings or rock. Together, these studies will provide insight into the mechanisms that have helped moderate Earth's climate through geologic time, permit better assessment of the response of mineral weathering reactions to changes in water availability due to climate change, and contribute to the design of climate change mitigation strategies. Tangible benefits will be achieved through the production of reactive transport models that can be used by academic and industrial users to simulate the consequence of environmental change on weathering reactions, and design CO2 storage strategies. Such CO2 storage strategies will help Canada to meet ambitious greenhouse gas reduction targets. During this research, highly qualified personnel will be trained in analytical, experimental, and modelling techniques, and gain transferable skills. This skill set can be applied to environmental policy, environmental consulting, or continued academic research.