Measurement report: The importance of biomass burning in light extinction and direct radiative effect of urban aerosol during the COVID-19 lockdown in China

To explore the impacts of anthropogenic emissions on aerosol optical properties and direct radiative effect (DRE), a series of real-time measurements was conducted in an urban area of China before and during the lockdown of Coronavirus Disease 2019. The generalized addictive model analysis shows that the light extinction coefficient (<em>b</em>_ext) decreased largely during the lockdown due to the sharp reductions in anthropogenic emissions. Organic aerosol was the largest contributor to <em>b</em>_ext based on the ridge regression analysis. A hybrid environmental receptor model combining with chemical and optical variables shows that <em>b</em>_ext from biomass burning increased in the lockdown due to the undiminished needs of residential cooking and heating in winter. Biomass burning contributed the largest positive effect to aerosol DRE in the atmosphere during the lockdown, highlighting the importance of controlling biomass burning for mitigating climate change in China in the future.为探究人为排放对气溶胶光学特性与直接辐射效应（Direct Radiative Effect, DRE）的影响，本研究于中国某城区开展了2019冠状病毒病（COVID-19）封控前后的一系列实时观测。广义加性模型分析结果显示，封控期间因人为排放大幅削减，大气消光系数（b_ext）显著下降。基于岭回归分析，有机气溶胶是大气消光系数的最大贡献组分。结合化学与光学变量的复合环境受体模型表明，由于冬季民用炊事与供暖需求未减，封控期间生物质燃烧贡献的消光系数有所升高。封控期间，生物质燃烧对大气气溶胶直接辐射效应的正向贡献最为显著，这凸显了未来中国通过管控生物质燃烧以减缓气候变化的重要性。