Novel Isotopic Evidence Unveils Greater Contributions of Waste Incineration to PM 2.5 ‐Bound Antimony in Two Mega‐Cities

Abstract PM 2.5 ‐bound antimony (Sb) may threaten human health and sustainable development, necessitating accurate source identification for its effective control. This study pioneered the application of Sb isotope signatures to trace PM 2.5 ‐bound Sb sources, presenting the first isotopic fingerprints of Sb in urban PM 2.5 . We selected two mega‐cities with contrasting profiles: more developed Wuhan in central and less developed Guiyang in southwest China. Urban PM 2.5 in both cities exhibited an ε 123 Sb value of 1.84 ± 0.79‱, with a distinct seasonal pattern, that is, heavier isotopes in spring/winter and lighter in summer/autumn. Isotopic source apportionment revealed waste incineration as the predominant anthropogenic Sb source in PM 2.5 for both cites at 34.0–39.1%, despite their massive economic and industrial differences. Brake wear emerged as the second major anthropogenic source, especially in Wuhan, where vehicle ownership is greater, accounting for 21.2%. Complementary analyses using enrichment factor, elemental ratios, positive matrix factorization modeling, and backward trajectory analysis corroborated the isotopic findings. This study offers a novel isotopic approach to identify PM 2.5 ‐bound Sb sources, unveiling waste incineration and brake wear as major anthropogenic contributors from a new isotopic perspective.