Source apportionment and risk assessment of heavy metal contamination in soils surrounding the tailings based on copper isotopes

The long-term mining activities serve as a typical source of heavy metal contamination in local soil. This study investigated the heavy metal pollution dominated by Cu in soils surrounding the Tongling Shuimuchong tailing reservoir, and conducted quantitative source tracing of Cu contamination using non-traditional stable metal isotopes. Results revealed that the mean Cu content in local soils reached 1226.1 mg/kg, significantly exceeding regional background values and indicating severe contamination. The contents of Zn, As, Cd, Pb, and Hg in soils also surpassed background values to varying degrees, demonstrating moderate pollution. Based on δ 65 Cu abundance measurements, the study identified the tailing reservoir as the primary source of soil Cu. A mixing end-member model calculation showed that the tailing reservoir contributed 70 % of the total Cu in soils. Ecological risk assessment indicated widespread severe heavy metal contamination in the study area, primarily concentrated in Cu, Cd, and Zn. Human health risk assessments revealed acceptable non-carcinogenic hazard index (HI) levels and carcinogenic risks (CR), with As and Cr being the predominant hazardous elements. • Severe Cu contamination in soils near tailing reservoir. • Tailing reservoir contributes 70 % of soil Cu via δ⁶⁵Cu isotope tracing. • Ecological risks dominated by Cu, Cd, Zn; severe overall pollution. • Acceptable health risk assessment, As and Cr contribute the most.