Stable Iron Isotopic Signature Reveals Multiple Sources of Magnetic Particulate Matter in the 2021 Beijing Sandstorms

Airborne magnetic particulate matters (MPs) in PM2.5 have been observed in human tissues, for example, the brain, heart, and pleural effusion, which have attracted widespread concern. Here, we show that the pollution level of MPs in PM2.5 (MPsPM2.5) increased remarkably during the 2021 Beijing sandstorm episodes. Moreover, the stable Fe isotopic compositions of MPsPM2.5 were investigated to identify and constrain the origins of the increased MPsPM2.5 pollution. We presented that the fine MPs pollution in PM2.5 during the Beijing sandstorm episodes in 2021 was emitted from a mixture of natural dust and anthropogenic emissions, rather than only a natural origin. More importantly, anthropogenic emissions played a more important role in MPsPM2.5 during most of the 2021 Beijing sandstorm episodes. Our results were essential for further evaluation of the health risks and climatic impacts of PM2.5, particularly for MPsPM2.5, during the sandstorm episodes. Furthermore, this study indicated that the sources and characteristics of PM2.5 during the 2021 Beijing sandstorms were more complex than previously expected (PM2.5 during the sandstorms was dominated by lithogenic material from arid regions), and hence, high-precision characterizations of their sources, chemical compositions, and toxicologies are needed for future pollution control.