Leaves as bioarchives highlight traffic-derived pollution in an urban environment

Summary Accurate identification of potentially toxic element (PTE) sources is crucial for effective risk mitigation; however, the complex solubility of trace elements hinders such identification. Here, levels of PTEs in the dust of 105 leaf samples from 21 sites in urban Guiyang (China) were measured and positive matrix factorization was applied to help identify PTE sources. These results were validated through correlating PTE concentrations with the land-use areas surrounding the sample sites. Ni and As in the leaf dust were linked to the cleanest conditions, followed by Cr. Conversely, Zn, Cu, Cd and Pb were associated with higher pollution levels. Three primary sources of PTEs were identified, with traffic-agriculture emissions being the largest contributor at 40.42%. Natural sources followed closely at 39.41%, while industrial processes accounted for the remaining 20.17%. High-pollution areas were clustered around traffic hubs, where frequent vehicle idling and acceleration increased emissions. As traffic emission was a major source of atmospheric pollution, targeted flow optimization is needed to reduce risks of human exposure.