Abstract：
Ocean Alkalinity Enhancement (OAE) is a proposed Negative Emissions Technology (NET) to remove atmospheric CO2 through the dispersion of alkaline materials (e.g.: calcium hydroxide, slaked lime, SL) into seawater, simultaneously counteracting ocean acidification. This study considers aircraft discharge of SL and its consequent dry deposition, extending to the marine environment a technique used in freshwater. A feasibility analysis assesses potential, costs, benefits, and disadvantages, considering scenarios with different assumptions on aircraft size, discharge height and duration, and wind conditions. Due to the small size of SL particles (median diameter 9 μm), the dispersion from aircraft is highly enhanced by wind drift; the smallest SL particles may drift thousands of kilometres, especially if discharged from elevated altitudes. This could pose problems related to powders particles settling on remote lands. Although calcium hydroxide maximum concentration into water (from 0.01 to 82 mg L-1) is for almost all the scenarios lower than the most stringent threshold for the ecosystem impacts on a 96-h exposure, the ecologically sensitive sea surface microlayer (SML) should be considered in detail. The high CO2 emissions of the Landing to Take-Off Cycle (LTO) of the aircraft and their limited payload lead to a significant CO2 penalty, ranging in analysed scenarios between 28% and 77% of the CO2 removal potential; very fast discharge could reduce the penalty to 11% - 32%. Preliminary cost analysis shows that the cost of the SL discharge through aircraft is high, between € 30 and € 1846 per ton of CO2 removed (neglecting the lime cost), substantially higher than the cost for discharge by surface vessels resulting from previous studies, which restricts the practical use of this strategy.
摘要：
海洋碱度增强（OAE）是一项拟议的负排放技术（NET），用于通过分散碱性材料（例如：氢氧化钙，熟石灰,SL)进入海水，同时抵消海洋酸化。这项研究考虑了飞机排放的SL及其随之而来的干沉积，将淡水中使用的技术扩展到海洋环境。可行性分析评估潜力，成本,好处,和缺点，考虑对飞机尺寸有不同假设的情况，排放高度和持续时间，和风况。由于SL颗粒的尺寸较小（中值直径9μm），风漂移大大增强了飞机的扩散；最小的SL粒子可能会漂移数千公里，特别是如果从高海拔地区排放。这可能会带来与粉末颗粒在偏远土地上沉降有关的问题。尽管氢氧化钙进入水中的最大浓度（从0.01到82mgL-1）几乎在所有情况下都低于96小时暴露对生态系统影响的最严格阈值，应详细考虑生态敏感的海面微层（SML）。飞机着陆起飞周期（LTO）的高二氧化碳排放量及其有限的有效载荷导致了显着的二氧化碳损失，在分析的情况下，二氧化碳去除潜力的28%到77%之间；非常快速的排放可以将惩罚减少到11%-32%。初步成本分析表明，SL通过飞机排放的成本很高，每吨二氧化碳去除30欧元至1846欧元(忽略石灰成本)，大大高于先前研究得出的水面船只排放成本，这限制了该策略的实际使用。
