近年来，幸福作为衡量生活质量的重要指标，成为相关政策和舆论关注的重点。然而随着经济的飞速发展，中国居民的幸福感呈现典型的“伊斯特林幸福悖论”：尽管富裕国家的居民普遍比贫困国家的更幸福，但在经济发展达到一定水平后，随着经济增长，幸福感并不会随之增加。与此同时，经济发展带来的环境问题，成为影响幸福感的重要因素。经济发展不仅产生了严重的空气污染问题，城市化的快速进程也在不断挤压着城市绿地的空间。已有研究表明空气污染对主观幸福感产生显著的负面影响，并在城市绿地与居民健康的关系中起到中介作用。但是已有研究存在几个局限性，首先是主要关注长期的主观幸福感，而对短期幸福感关注较少；第二，大部分研究使用基于居住地的空气污染和城市绿地数据，但居民在时空上都是流动的，这会产生地理背景不确定性问题；此外，大多研究利用横截面数据，缺少不同年份的动态视角来讨论活动幸福感的时空变化。

基于此，本文使用2012年、2017年在北京市美和园社区展开的活动日志调查数据、GPS移动轨迹，并结合相应的基于流动性的空气污染和城市绿地数据，从时空行为的视角出发，利用结构方程模型和logistic模型等定量方法深入讨论空气污染和城市绿地对活动满意度的影响机制，以及弱势群体在日常活动中遭受的空气污染与绿地暴露的不平等问题。主要研究结论如下：第一，使用2017年活动日志调查数据的结构方程模型结果显示，与客观测量的空气污染相比，主观评估的空气污染是活动满意度的更为重要和显著的影响因素，而客观污染水平主要通过影响人们的主观污染评估进而对活动幸福感产生间接影响；第二，2012年至2017年对比研究的结果表明，北京市的空气质量有所改善，活动满意度有所提高，客观空气污染对活动满意度的负面影响在工作日变得更加显著，但在休息日却不再显著；此外，与基于监测站的空气污染数据相比，基于便携式传感器的实时空气污染数据具有更高的准确性和更好的模型适用性；第三，加入城市绿地数据后的结构方程模型结果显示，城市绿地对活动满意度具有显著的直接影响，归一化植被指数会显著提高活动满意度，而绿视率则与活动满意度呈现倒U形关系，研究结果也证实了主观空气污染在城市绿地与活动满意度之间起到中介作用；此外，社会经济地位较低的弱势群体，由于其日常活动所选择的环境较差，其承受的空气污染暴露、城市绿地暴露与活动满意度也存在显著分异，这会加剧在健康和福祉方面的环境不公正问题。

In recent years, as an important indicator to measure life quality, wellbeing has attracted much attention from relevant policies and public opinion. However, with the rapid development of the economy, the wellbeing of Chinese residents presents a typical "Easterlin Paradox": although residents in rich countries are generally happier than those in poor countries, after reaching a certain level of economic development, the happiness does not increase with the growth of the national economy. Moreover, environmental issues brought about by economic development have become important factors affecting human wellbeing. Economic development has not only brought serious air pollution problems, but the rapid process of urbanization is also constantly squeezing the space of urban green spaces. Previous studies have shown that air pollution has a significant negative impact on subjective well-being and plays a mediating role in the positive relationship between urban green spaces and residents' health. However, there are still several limitations. First, they mainly focus on long-term subjective well-being, while paying less attention to short-term well-being such as activity satisfaction; second, most studies use the static residence-based environment data but actually people are mobile in time and space which may cause considerably biased estimates; third, the research on the impact mechanisms of air pollution, urban green space, and subjective well-being in China is scarce; fourth, most studies use cross-sectional data, but now there is a lack of a dynamic perspective from multiple years to discuss the temporal changes in activity happiness.

Based on the activity diary survey data and GPS movement trajectory conducted in Meiheyuan, Beijing in 2012 and 2017, combining corresponding mobility based air pollution and urban green space data, from the perspective of space-time behavior, this study measures the relationships across air pollution exposure, urban green spaces and activity satisfaction, and further explore the environmental justice of air pollution and green space exposure faced by vulnerable groups in their daily activities. The main research conclusions are as follows: First, the structural equation model result of survey data in 2017 shows that compared to objective air pollution measurements, subjective assessment of air pollution is a more important and significant predictor of activity satisfaction, and objective pollution levels indirectly affect activity happiness by influencing people's subjective pollution assessment; second, the results of comparative studies from 2012 to 2017 indicate that the air quality in Beijing has improved, and activity satisfaction has increased. The negative impact of objective air pollution on activity satisfaction has become more significant on weekdays, but it is no longer significant on weekends. In addition, real-time air pollution data collected by portable sensors has higher accuracy and better model applicability than the mobility-based air pollution data from monitoring stations. Third, the structural equation model results after adding urban green space data show that urban green space has a significant direct effect on activity satisfaction. Specifically, the normalized vegetation index significantly improves activity satisfaction, while the green visibility rate shows an inverted U-shaped relationship with activity satisfaction. The research results also confirm that subjective air pollution plays a mediating role between urban green space and activity satisfaction. Moreover, the study results also indicate that the vulnerable groups with lower socioeconomic status, due to the poor environment they choose for their daily activities, suffer from significant differences in air pollution exposure, urban green space exposure and activity satisfaction, which will exacerbate environmental injustice in health and wellbeing.