Changes in Trans-Boundary Air Pollution over Japan during COVID-19 Lockdown in China

Abstract:

In order to prevent the spread of COVID-19, Chinese government imposed a lockdown. During this period, anthropogenic emissions will be reduced; therefore, the trans-boundary air pollution will be changed. The analysis of surface observation by automated aerosol chemical speciation analyzer (ACSA) in Japan showed that the dramatical reduction with 30-50% of PM_2.5, sulfate (SO₄^2-), and nitrate (NO₃^-) on February-March 2020 compared to 2018-2019. Based on the satellite-based OMI observation, NO₂ column decreased 35%, 47%, and 6% over central eastern China region on January, February, and March 2020 compared to 2018-2019. In order to investigate the reason of dramatical reduction of PM_2.5, SO₄^2-, and NO₃^- found over Japan, these satellite-based reductions and surface concentration changes taken from literatures are applied for regional chemical transport model analysis. The results of modeling analysis suggested that the reduction of SO₄^2- was mostly caused by SO₂ emission reduction whereas that of NO₃^- could be also dominated by the meteorological variability. We would like to present such a dramatical variation of air quality over Japan during Chinese lockdown.