Source Apportionment of Atmospheric Iron in Northern China Based on Three-Year Continuous Measurements

Atmospheric iron (Fe) impacts atmospheric chemistry and marine ecosystems. However, the scarcity of long-term observations limits insights into its source variations that may reflect emission controls. From September 2016 to December 2019, Fe in atmospheric fine particles (PM2.5) was measured in Beijing. Positive Matrix Factorization was used to apportion Fe sources. Results showed nearly 50% of Fe originated from anthropogenic sources, primarily industrial processes (30%) and coal combustion (17%). Although PM2.5 concentrations decreased significantly, the Fe component of PM2.5 did not show a significant decline. Instead, annual source contributions changed with dust source rising from 45% to 61%, while combustion sources decreased from 27% to 12%.