Contamination Characteristics and Human Health Risks of Heavy Metals in Brownfield Soil from a Decommissioned Electroplating Factory, Shandong Province, China

The relocation and closure of electroplating industries have generated numerous contaminated brownfields, many of which are located in areas with potential for residential and commercial redevelopment. However, information regarding the distribution characteristics, migration, and health risks of heavy metals at decommissioned electroplating sites remain limited. In this study, 160 soil samples were collected from a decommissioned electroplating factory in Dezhou, Shandong Province, China, to characterize the spatial distribution and migration behavior of Ni, Zn, and Cr(VI), identify contamination hotspots and potential pollution sources, and evaluate associated carcinogenic and non-carcinogenic risks under the planned future land-use scenario. Human health risks were quantitatively evaluated using the United States Environmental Protection Agency (USEPA) risk assessment model with exposure parameters adapted to the local Chinese population. Results showed that the site was severely contaminated by heavy metals, with 27.5% [Cr(VI)], 6.9% (Ni), and 1.9% (Zn) of the samples exceeding the applicable screening values. The maximum concentrations reached 10,600 mg·kg−1 for Ni, 17,300 mg·kg−1 for Zn, and 390 mg·kg−1 for Cr(VI). Contamination hotspots were concentrated in former production workshops and the wastewater treatment area. The depth profiles suggested contaminant-specific migration patterns, with Cr(VI) detected at a depth of 6.5 m, indicating its strong mobility in subsurface soils. Health risk assessment revealed that oral exposure was the dominant exposure pathway for both adults and children, while inhalation contributed negligibly to overall exposure. Estimated non-carcinogenic risks were higher for children than for adults, with the HI for Ni reaching 2.70. Furthermore, the maximum total carcinogenic risk estimated for Ni exposure in children was 7.50 × 10−3, exceeding the acceptable risk threshold. These findings demonstrate the importance of integrating contaminant distribution, source identification, and human health risk assessment when managing decommissioned electroplating brownfields and provide a scientific basis for risk-based remediation and sustainable redevelopment.