Significant reduction of PM 2.5 in eastern China due to regional-scale emission control: evidence from SORPES in 2011–2018

Abstract

Abstract. Haze pollution caused by PM 2.5 is the largest air\nquality concern in China in recent years. Long-term measurements of\nPM 2.5 and the precursors and chemical speciation are crucially important\nfor evaluating the efficiency of emission control, understanding formation\nand transport of PM 2.5 associated with the change of meteorology, and\naccessing the impact of human activities on regional climate change.\nHere we reported long-term continuous measurements of PM 2.5 , chemical\ncomponents, and their precursors at a regional background station, the\nStation for Observing Regional Processes of the Earth System (SORPES), in\nNanjing, eastern China, since 2011. We found that PM 2.5 at the station\nhas experienced a substantial decrease ( −9.1 \u2009%\u2009yr −1 ), accompanied by even\na very significant reduction of SO2 ( −16.7 \u2009%\u2009yr −1 ), since the national\n“Ten Measures of Air” took action in 2013. Control of open biomass\nburning and fossil-fuel combustion are the two dominant factors that\ninfluence the PM 2.5 reduction in early summer and winter, respectively.\nIn the cold season (November–January), the nitrate fraction was significantly\nincreased, especially when air masses were transported from the north. More NH3 \navailable from a substantial reduction of SO2 and increased oxidization\ncapacity are the main factors for the enhanced nitrate formation. The\nchanges of year-to-year meteorology have contributed to 24\u2009% of the PM 2.5 \ndecrease since 2013. This study highlights several important implications on\nair pollution control policy in China.