Quantifying and tracing urban soil pollution sources by coupling magnetic and geochemical methods: A case study from...

Urban soil pollution is inherently complex, and integrating environmental magnetism with geochemistry provides an effective strategy for precise source apportionment and targeted remediation. This study systematically characterized the magnetic and geochemical pollution of surface soils in Hangzhou, employing correlation analysis, principal component analysis (PCA), and the absolute principal component scores-multiple linear regression (APCS-MLR) model to trace and quantify the sources of magnetic particles and heavy metal contaminants. Results indicate that topsoil magnetism is dominated by low-coercivity pseudo-single-domain (PSD) and multi-domain (MD) ferromagnetic minerals, with pronounced enrichment in industrial zones and traffic-congested areas. Spatial distribution patterns of geochemical elements exhibit a clear anthropogenic-natural composite signature, with elevated concentrations of Ca, Cu, Pb, and Zn primarily in Gongshu, Xihu, and Shangcheng districts, while Al, Fe, Ti, Ce, and V are largely controlled by natural backgrounds. Significant correlations between χ_lf, χ_ARM, SIRM, SOFT and Ca, Zn, Cr confirm the utility of magnetic parameters as proxies for heavy metal monitoring. APCS-MLR analysis identified five major soil pollution sources: industrial emissions (28.29%), natural background (25.29%), traffic emissions (18.03%), construction dust (17.48%), and agricultural inputs (10.91%). Magnetic particles predominantly originate from industrial activities, whereas heavy metals result from multiple combined sources. Notably, heavy metal pollution in Hangzhou's topsoil has transitioned from a conventional "industrial + traffic" pattern to a more complex "industrial + traffic + construction dust" regime. Collectively, these findings provide a scientific basis for precision soil management in Hangzhou and introduce an innovative magnetic-geochemical coupled framework for urban soil source apportionment, offering methodological novelty and technical guidance for pollution control in complex urban environments.