Changes of Emission Sources to Nitrate Aerosols in Beijing After the Clean Air Actions: Evidence From Dual Isotope Compositions

Abstract Nitrate (NO 3 − ) is a major contributing species to haze formation in Northern China. So far, formation processes and source apportionments of nitrate aerosols during haze pollution have not yet been well understood. In this study, the PM 2.5 samples were collected in Beijing from 13 November to 24 December 2018. In addition to water‐soluble ions, oxygen (δ 18 O‐NO 3 − ) and nitrogen (δ 15 N‐NO 3 − ) isotopes in particulate NO 3 − were also determined, in order to investigate the formation pathways and potential sources of NO 3 − aerosols. The results showed that NO 3 − was a dominant species (43%) of secondary inorganic aerosols during the sampling period. The δ…