Heavy metal(loid)s in the topsoil of county region Zhucheng city, East China: concentrations, risk assessment, and potential sources

Abstract Heavy metal(loid)s (HMs) represent a significant threat to soil ecosystems and human health. This study offers a high-density assessment of eight HMs (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in the topsoil of Zhucheng City, southeastern Shandong Peninsula, China, based on an analysis of 11,576 samples. The findings indicate the following: (1) The average concentrations of HMs followed the order: Cr > Zn > Pb > Ni > Cu > As > Cd > Hg. The mean concentrations of Pb (24.22 μg g −1 ), Cd (0.12 μg g −1 ) and Hg (0.035 μg g −1 ) exceeded their local background values by approximately 6%, 5% and 9%, respectively, with extreme hotspots reaching concentrations of 5259.9 μg g −1 for Pb and 5.13 μg g −1 for Hg. (2) About 7.24% sampling sites posed moderate to high ecological risks. Cd and Hg were identified as the primary risk drivers, with mean potential ecological risk indices (E r i ) of 31.37 for Cd and 44.58 for Hg. Notably, 12.4% and 9.5% of samples exhib i ted significant enrichment of Hg and Cd (I geo > 0), respectively. (3) The Positive Matrix Factorization (PMF) model identified six distinct sources with quantified contributions: coal combustion in brick and cement plants (accounting for 90.1% of As), agricultural irrigation (Cr: 85.1%, Ni: 75.3%), composite agricultural and mining sources (Zn: 93.1%, Cd: 80.4%), the foundry industry (Hg: 89.1%), transportation and machinery (Cu: 74.7%), and the use of plastic film in greenhouses and leaded petrol (Pb: 76.2%). This study provides a data-driven foundation for targeted source-oriented soil management in Zhucheng and similar urban-agricultural regions.