AI 中文总结
本研究首次利用GLENS项目数据，探究硫酸盐注入地球工程对PM2.5的影响，发现其可降低全球平均PM2.5浓度，但会改变PM2.5组成，且沉积空间分布差异或影响生态系统。
AI 中文摘要
空气动力学直径小于2.5微米的颗粒物（PM2.5）对人类健康具有重大意义。本研究首次利用地球工程大集合（GLENS）项目的输出结果，探究硫酸盐气溶胶地球工程对PM2.5的影响。GLENS是一组气候模型模拟集合，采用社区地球系统模型第1版（Community Earth System Model, version 1）向平流层注入二氧化硫（SO2），以平衡典型浓度路径8.5（RCP8.5）的辐射强迫。与RCP8.5情景相比，GLENS地球工程降低了全球平均地表PM2.5质量浓度，同时改变了PM2.5的组成，使有机碳和硫酸盐的占比提升。PM2.5的总减少量是沙尘和海盐浓度降低的结果：在GLENS地球工程下，沙漠地区土壤湿度和叶面积指数增加，导致沙尘排放减少；而地球工程应用时风速降低，使得海盐排放减少。若排除沙尘和海盐，GLENS地球工程下的全球平均PM2.5浓度高于RCP8.5情景，这主要是由于气溶胶相二次有机气溶胶（SOA）增多——由于模拟中SOA的气态前体物是固定的，地球工程带来的较冷环境会促使更多气态SOA转化为气溶胶相。应用地球工程引起的PM2.5浓度和组成变化可能对人类健康产生潜在影响。本研究的另一项新发现是，大量注入的SO2并未增加作为PM2.5组分的地表硫酸盐气溶胶，因为到达边界层的大部分硫酸盐气溶胶处于粗模态，仅占PM2.5的极小部分。不过，地球工程与RCP8.5之间的沉积空间分布差异可能对生态系统产生潜在影响。
英文摘要
Particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) is of great concern for human health. Here, for the first time, we examine the impact of sulfate aerosol geoengineering on PM2.5, using the output from the Geoengineering Large Ensemble (GLENS) project. GLENS is an ensemble of climate model simulations injecting SO2 into the stratosphere to balance RCP8.5 forcing using the Community Earth System Model, version 1. GLENS geoengineering reduces global averaged surface PM2.5 mass concentrations compared with RCP8.5 and also changes PM2.5 composition with more percentages of organic carbon and sulfate. The total reduction of PM2.5 is a result of less dust and sea salt concentrations. Dust emission is declined under GLENS geoengineering because of increased soil moisture and leaf area index over desert regions, and less emission of sea salt is due to slower wind speeds when geoengineering is applied. Excluding dust and sea salt, there is more global averaged PM2.5 under GLENS geoengineering relative to RCP8.5, predominantly due to more aerosol phase secondary organic aerosol (SOA). Since gas precursors of SOA are prescribed in the simulations, a cooler environment with geoengineering tends to transfer more gas phase SOA to aerosol phase. Changes in PM2.5 concentration and composition with applied geoengineering may have potential human health impact. Another new finding of this study is that the large amount of injected SO2 does not increase surface sulfate aerosol as a component of PM2.5, as the majority of sulfate aerosol reaching the boundary layer is in the coarse mode, which represents a very small fraction of the PM2.5. But the difference of deposition spatial distribution between geoengineering and RCP8.5 may have potential impacts on ecosystem.
Comments29 pages, 11 figures
