成都市道路移动源减排对空气质量的短期影响

近年来随着经济社会的高速发展，我国的空气污染问题日渐突出.管控污染源以减少污染物排放是改善空气质量的主要手段，且其效率如何会极大地影响空气质量的改善效果.但通常情况下，单一减排手段的实施对空气质量的改善的实际贡献往往在短时间内较难做出客观评价.本研究借助新冠疫情期间以道路移动源为主的各类污染源排放短期内大量下降的机会，通过疫情管控措施实施前后交通条件和空气质量的对比，分析道路移动源减排对空气质量改善的短期影响.结果表明，实施管控措施后，城市范围内道路交通条件明显改善，拥堵路段基本消失.受此影响，各类主要污染物浓度出现不同程度的下降，其中，受道路移动源贡献较大的NO₂浓度下降比例达40%~60%，PM_2.5因受气象条件影响较大而下降幅度较小.结合实时的交通数据估算其相应的尾气排放结果表明，疫情期间道路移动源排放的NO_x、HC、CO分别下降59.7%、59.9%和58.8%.本研究对于分析短时间内急速减排等应急措施对环境改善的效果，以及削减污染物排放对空气质量改善的潜力有重要的实际参考价值.

The short-term effect of on-road vehicle emissions reduction on air quality in Chengdu

With the rapid development of economy in recent years, air pollution in China has become increasingly prominent. Emission control is the key measure for air quality improvement with its efficacy in reduction being the dominating factor. However, due to the complex of air pollution in nature, it is generally difficult to evaluate the efficacy of an emission control measure in air quality improvement under real-world conditions. The objective of this study is to evaluate the short-term effect of on-road vehicle emission reductions on air quality improvement by comparing several criteria pollutants concentrations and its corresponding traffic conditions in the study area before and after the lock-down of the city for COVID-19 prevention. Results showed that after the city was locked down, roadway traffic had been significantly improved without observable congestions. Correspondingly, the atmospheric NO₂ concentration decreased by 40%~60%. The PM_2.5 concentrations only slightly decreased due to relatively stagnant meteorological conditions. Combined with real-time traffic data of the same study period, NO_x, HC and CO emissions from on-road vehicles were estimated to decrease by 59.7%, 59.9% and 58.8% respectively. Findings of this study can provide useful insights of the impact of emission reductions on air quality improvement regarding the extent and its efficacy.