Novel Isotopic Evidence Unveils Greater Contributions of Waste Incineration to PM2.5-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 ε¹²³Sb 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.