Sub-seabed geological CO₂ storage is discussed as a climate mitigation strategy, but the impact of any leakage of stored CO₂ into the marine environment is not well known. In this study, leakage from a CO₂ storage reservoir through near-surface sediments was mimicked for low leakage rates in the North Sea. Field data were combined with laboratory experiments and transport-reaction modelling to estimate CO₂ and mineral dissolution rates, and to assess the mobilization of metals in contact with CO₂-rich fluids and their potential impact on the environment. We found that carbonate and silicate minerals reacted quickly with the dissolved CO₂, increasing porewater alkalinity and neutralizing about 5% of the injected CO₂. The release of Ca, Sr, Ba and Mn was mainly controlled by carbonate dissolution, while Fe, Li, B, Mg, and Si were released from silicate minerals, mainly from deeper sediment layers. No toxic metals were released from the sediments and overall the injected CO₂ was only detected up to 1 m away from seabed CO₂ bubble streams. Our results suggest that low leakage rates of CO₂ over short timescales have minimal impact on the benthic environment. However, porewater composition and temperature are effective indicators for leakage detection, even at low CO₂ leakage rates.

海底地质 CO ₂储存被讨论为气候缓解策略，但储存的 CO ₂泄漏到海洋环境中的影响尚不清楚。在这项研究中，由于北海的低泄漏率，模拟了从 CO ₂储存库通过近地表沉积物的泄漏。现场数据与实验室实验和输运反应模型相结合，以估算 CO ₂和矿物溶解速率，并评估与富含CO _{2 的}流体接触的金属的流动性及其对环境的潜在影响。我们发现碳酸盐和硅酸盐矿物与溶解的 CO ₂反应迅速，增加孔隙水碱度并中和约 5% 的注入 CO ₂。Ca、Sr、Ba和Mn的释放主要受碳酸盐溶解控制，而Fe、Li、B、Mg和Si则主要从硅酸盐矿物中释放，主要来自较深的沉积层。沉积物中没有释放有毒金属，总体而言，注入的 CO ₂仅在距离海底 CO ₂气泡流1 m 处检测到。我们的结果表明，在短时间内CO _{2 的}低泄漏率对底栖环境的影响最小。然而，孔隙水成分和温度是泄漏检测的有效指标，即使在低 CO ₂泄漏率下也是如此。