过去20年全球航空业快速增长，相比其他移动源，航空环境影响研究起步较晚，目前对于航空排放特征、空气质量及健康影响和主要碳排放控制政策效益等重大问题缺乏系统、科学和及时的认知。本研究基于实际航空飞行轨迹数据，开发了基于瞬时飞行姿态的轨迹模型。建立了覆盖全球民用航空的CO2和污染物的高时空分辨率排放清单。优化空气质量模拟系统的网格空间设置和分阶段影响解析等关键模块，构建适用于全航段排放对地面空气质量影响及其过程机制的分析方法，定量中国航空排放对典型区域人群健康的影响。对全球民航CO2排放进行追踪和多情景预测研究，分析了新冠疫情对民航CO2排放控制进程的影响。基于瞬时飞行姿态的轨迹模型有效提升了航空排放清单的分辨率和准确性，指出了主流的简化轨迹模型对短途航线排放量的明显低估。2019年全球民航排放CO2 9.2亿吨，NOX，CO，HC，PM分别为4981.8千吨，635.7千吨，77.8千吨和21.9千吨，BC number 1.35×1026个。全球民航CO2排放存在三大活跃区域（亚太、北美、欧洲）和多个活跃枢纽，垂直分布集中于9–12 千米高空。污染物垂直分布受机制影响，热力型机制主导的NOX分布与CO2相近，不完全燃烧主导的CO和HC在地表比例相对CO2较高。中国民用航空对污染物浓度具有显著贡献，PM2.5，NO2，O3年均浓度贡献分别为0.4–1.5 μg·m?3，0.6–1.8 μg·m?3和 10.6–14.5 μg·m?3。高空CCD(上升巡航下降)阶段排放对地面空气质量影响不容忽视，污染物经过垂直传输和地面化学转化，使得其排放对地表污染物浓度贡献与低空LTO(起飞降落循环)阶段基本相当。航空排放贡献的地面PM2.5和O3污染暴露导致中国2017年过早死亡人数约为6.7万，PM2.5和O3暴露相关的健康终点风险占比约为4:6。其中，东部地区人口密集、民航运输活动活跃，受到的影响更为突出，长三角地区可达700例/万平方公里。受新冠疫情影响，2020年国际航班的CO2排放量相比2019年减少约61%–65%，国内减少约37%–39%。2021–2023年(试行阶段)国际航空CO2排放量将比新基线低21%–60%。CORSIA(国际航空碳抵消与减排计划)短期内难以形成有效的减排约束力，建议动态优化CORSIA基线，并考虑将个人平均碳足迹作为补充指标，促进实际减排技术的发展。
Economic growth has led to a surge in civil aviation transportation demand during the past twenty years. Compared with other transportation modes, the research on the environmental impacts from aviation sector has developed relatively late. There lacks systematic, scientific and timely understanding of major issues, such as characterization of aviation emissions of carbon dioxide (CO2) and air pollutants, assessments of air quality and health impact, and benefit analysis of carbon emission control policies.This study developed a high-resolution emission model by using real-world flight trajectory data (Automatic Dependent Surveillance Broadcast, ADS-B), which was utilized to establish a global-scale emission inventory of CO2 and air pollutants with high spatial and temporal resolutions. To quantify the air quality impacts of aviation emissions during both the landing/take-off (LTO) and climb/cruise/descent (CCD) phases, the configurations of air quality simulation system was optimized to better reflect the aviation emissions, such as the dedicated modules of grid setting and altitude-specific analysis. The aviation-attributed pollution exposures of ambient PM2.5 and O3 were simulated to further quantify the health impact from aviation emissions within the domain of China. This study tracked the dynamic CO2 emissions during the COVID-19 pandemic period, and estimated the future trends under multiple scenarios for the post-pandemic period. The future projections of international aviation CO2 emissions would be useful to explore the usefulness of the introduction of the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).This study noted a significant underestimation of aviation emissions for short-distance flights based on the conventional great-circle-based approach compared with the results using real-world trajectory profiles. The total emissions of the global aviation sector were estimated to be 915 Mt, 4981.8 kt, 635.7 kt, 77.8 kt and 21.9 kt for CO2, NOX, CO, HC and PM respectively, and 1.35 × 1026 for BC number in 2019. Three active regions, Asia Pacific, North America and Europe, represented the majority of total aviation emissions, and a few regional hubs also were emission hotspots. Given the long duration of the cruising phase, the vertical distribution of CO2 emissions peaked at an altitude range of 9–12 km. The vertical distribution of air pollutants might differ according to their different production mechanisms. For example, the distribution of NOX, which is predominately produced through the thermal mechanism, was similar to that of CO2; however, due to incomplete combustion under low-thrust conditions, the proportions of CO and HC on the ground level were higher than that of CO2.This study reveals that aviation emissions are estimated to result in significant contributions to ground-level air pollutants. The average aviation-attributed PM2.5, NO2, O3 concentrations were 0.4–1.5 μg·m?3, 0.6–1.8 μg·m?3 and 10.6–14.5 μg·m?3 respectively. It is worth noting that, the contributions of CCD phase (high-altitude) emissions was comparable to those in LTO phase (low-altitude). These ground-level air quality impacts from high-altitude emissions could be imposed through vertical transmission and atmospheric chemical transformation. Aviation emissions are estimated to have caused about 67,000 premature deaths in China in 2017, of which PM2.5 and O3 exposures accounted for 40% and 60% respectively. The eastern regions of China with high population density and busy aviation activities would be more seriously affected; for example, the Yangtze River Delta region was estimated to have an aviation-attributable death density of 700 cases per 10,000 km2.Affected by the COVID-19 pandemic, the CO2 emissions of international aviation in 2020 were reduced by 61%–65% compared with 2019, while those of domestic aviation were reduced by 37%–39%. The annual CO2 emissions of international flights during the pilot stage of CORSIA (2021–2023) will be 21%–60% below the revised baseline (i.e., the emission level of 2019). The major airline companies are expected to have very limited motivations to comply with the CORSIA scheme and proactively implement mitigation actions. Therefore, more progressive actions are suggested to align the industry recovery of global aviation and CO2 mitigation during the post-COVID-19 period. Options would include to dynamically optimize the CORSIA baseline according to the actual recovery trend and consider personal carbon footprint as a supplementary index.
