Abstract：
Enhancing silicate weathering to increase oceanic alkalinity, thereby facilitating the absorption of atmospheric carbon dioxide (CO2), is considered a highly promising technique for carbon sequestration. This study aims to evaluate the feasibility and potential of olivine-based ocean alkalinity enhancement (OAE) for the removal of atmospheric CO2 and its storage in seawater as bicarbonates in the East and South China Seas (ESCS). A particular focus is placed on the potential ecological impacts arising from the release of nickel (Ni) and chromium (Cr) during the olivine weathering process. We considered two extreme scenarios: one where Ni and Cr are entirely retained in seawater, and another where they are completely deposited in sediments. These scenarios respectively represent the maximum permissible concentrations of Ni and Cr in seawater and sediments during the OAE process. Current marine environmental quality standards (EQS) were utilized as the threshold limits for Ni and Cr in both seawater and sediment, with concentrations exceeding these EQS potentially leading to significant adverse effects on marine life. When all released Ni is retained in seawater, the allowable dosage of olivine varies from 0.05 to 13.7 kg/m2 (depending on olivine particle size, temperature, and water depth); when all released Ni is captured by sediment, the permissible addition of olivine ranges from 0.21 to 2.1 kg/m2 (depending on mixing depth). Given the low solubility of Cr, it is not necessary to consider the scenario where Cr exceeds the limit in seawater. The allowable amount of Cr entirely retained in sediments ranges from 0.69 to 47.2 kg/m2.In most scenarios, the accumulation of metals in sediments preferentially exceeds the corresponding threshold value rather than remaining in seawater. Therefore, we recommend using alkalization equipment to fully dissolve olivine before discharging into the sea, enabling a larger-scale application of olivine without significant negative ecological impacts.
摘要：
增强硅酸盐风化以增加海洋碱度，从而促进大气二氧化碳（CO2）的吸收，被认为是一种非常有前途的碳封存技术。这项研究旨在评估基于橄榄石的海洋碱度增强（OAE）的可行性和潜力，以去除大气中的CO2及其在东海和南海（ESCS）的碳酸氢盐形式储存在海水中。特别关注橄榄石风化过程中镍（Ni）和铬（Cr）释放产生的潜在生态影响。我们考虑了两种极端情况：一种是Ni和Cr完全保留在海水中，和另一个完全沉积在沉积物中的地方。这些情况分别代表OAE过程中海水和沉积物中Ni和Cr的最大允许浓度。当前的海洋环境质量标准（EQS）被用作海水和沉积物中Ni和Cr的阈值限值，浓度超过这些EQS可能会对海洋生物产生重大不利影响。当所有释放的镍都保留在海水中时，橄榄石的允许剂量从0.05到13.7kg/m2不等(取决于橄榄石颗粒大小，温度,和水深)；当所有释放的镍被沉积物捕获时，橄榄石的允许添加范围为0.21至2.1kg/m2（取决于混合深度）。考虑到Cr的低溶解度,没有必要考虑海水中Cr超过极限的情况。沉积物中完全保留的Cr的允许量为0.69至47.2kg/m2。在大多数情况下，金属在沉积物中的积累优先超过相应的阈值，而不是留在海水中。因此,我们建议使用碱化设备在将橄榄石排入大海之前完全溶解，能够大规模应用橄榄石，而不会对生态产生重大负面影响。
