Characterization and Tracing of Soilborne Lead-Containing Nanoparticles by Single-Particle Inductively Coupled Plasma...

Soil lead (Pb) contamination represents a global environmental challenge, with well-documented adverse effects on both ecosystems and human health. Although Pb-containing nanoparticles (Pb NPs) constitute a significant, yet poorly characterized, fraction of Pb in soils, their origins remain difficult to ascertain due to the chemical complexity of soil matrices and the heterogeneity of Pb contamination sources. In this study, we developed a comprehensive strategy for the characterization and source tracing of Pb NPs in soils using single-particle inductively coupled plasma-mass spectrometry (spICP-MS). First, we established a robust protocol for the qualitative and quantitative characterization of tetrasodium pyrophosphate (TSPP)-extracted Pb NPs from soil samples using spICP-quadrupole-MS (spICP-Q-MS). Then, by leveraging quasi-instantaneous, multi-isotope Pb measurements (²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb) at the single-particle level via spICP-time-of-flight-MS (spICP-TOF-MS), we identified the region-specific sources of soilborne Pb NPs across four representative Chinese cities (Beijing, Shaoguan, Xiong'an, and Zhuzhou) by integrating isotopic fingerprinting (²⁰⁸Pb/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁷Pb) with the MixSIAR Bayesian mixing model. Our results demonstrate that Pb NPs can serve as highly sensitive tracers for assessing the extent of soil Pb pollution and for distinguishing geographically distinct Pb contamination sources. We anticipate that this approach will advance the mechanistic understanding of Pb biogeochemistry and improve source apportionment in soil ecosystems.