Significant Reduction of PM2.5 in Eastern China Due to Regional-Scale Emission Control: Evidences from the Sorpes Station, 2011-2018

Haze pollution caused by PM_2.5 is the largest air quality concern in China in recent years. Long-term measurements of PM_2.5 and the precursors and chemical speciation is crucially important for evaluating the efficiency of emission control, understanding formation and transport of PM_2.5 associated with the change of meteorology and for accessing the impact of human activities to regional climate change. In this study, we report long-term continuous measurements of PM_2.5, chemical components, and their precursors at a regional background station, the Station for Observing Regional Processes of the Earth System (SORPES), in Nanjing eastern China since 2011. PM_2.5 at the station has experienced a substantial decrease (-9.1%/yr), accompanied with even much significant reduction of SO₂ (-16.7%/yr), since the national “Ten measures” for air took action in 2013. Control of open biomass burning and fossil-fuel combustion are the two dominant factors that influence the PM_2.5 reduction in early summer and winter, respectively. In cold season (November-January), increased nitrate fraction was observed with more NH₃ available from a substantial reduction of sulfate, and the change of year-to-year meteorology contributed to 24% of the PM_2.5 decrease since 2013. This study highlights several important implications on air pollution control policy in China.