Xie et al. 2023 — Heavy metal pollution from antimony smelter soils, Hunan, China
This study systematically characterised heavy metal pollution in soils surrounding a hydrometallurgical antimony (Sb) smelter in Lengshuijiang city, Hunan Province (the “antimony capital” of the world), combining GIS spatial mapping, positive matrix factorization (PMF) source apportionment, pollution indices, and health risk assessment. Soil samples from 32 sites (including paddy, dry land, and forest) were analysed for Hg, Pb, Cd, Cr, As, and Sb. Cadmium (76.9%) and arsenic (57.7%) were predominantly attributable to agricultural activity, while antimony smelting contributed 12.7% of Cd and 25% of As. The potential ecological risk index (PERI) of 407.54 indicated high ecological risk overall, with Cd as the dominant contributing element (PERI 323.4).
Key numbers
Mean soil concentrations (mg/kg): Hg 0.06, Pb 47.77, Cd 2.88, Cr 53.12, As 21.22, Sb 20.53. Background values for Hunan Mountain soils: Hg 0.09 mg/kg, Pb 38 mg/kg, Cd 0.11 mg/kg, Cr 54 mg/kg, As 14 mg/kg, Sb 2.98 mg/kg. Concentration factors (mean CF, ratio to background): Hg 0.94, Pb 1.26, Cd 26.18 (most elevated), Cr 1.52, As 6.89. Cadmium average was 4.8× the agricultural soil risk screening value (0.6 mg/kg at pH 6.5–7.5); 46.15% of sites exceeded the RSV. PERI for Cd alone: 323.4 (high risk). Source apportionment (PMF): agricultural activities contributed 76.9% of Cd; Sb smelting 12.7% of Cd; atmosphere/transportation 40.6% of Hg; natural geological background 69.7% of Cr. Non-carcinogenic HI for children exceeded 1 via all three exposure pathways; total carcinogenic risk exceeded 1×10⁻⁴ for both adults and children, driven primarily by oral ingestion of arsenic.
Methods (brief)
32 soil sampling sites (surface 0–0.20 m, mid-depth 0.20–0.50 m, deep 0.50–1.00 m profiles for 10 sites). Mixed sample (~1 kg) from 5 surface subsamples per site. HCl/HNO3/HF/HClO4 digestion. Hg, Pb, Cd, Cr, As, Sb quantified by AAS (AA-7002A, Perkin East & West). PMF model (US EPA PMF 5.0). Health risk: US EPA IRIS reference doses and slope factors. ArcGIS 10.2 for spatial distribution mapping.
Limitations
Small site count (n=32) around a single point-source smelter; results are not generalisable to regional agricultural soils. Sb-specific co-contamination profile differs from typical agricultural fertiliser pathways. No food-crop Cd or As measurements; soil values require transfer-factor assumptions to estimate dietary exposure.
Implications
- Certification: Establishes that soils near Sb smelters in Hunan generate severe Cd enrichment (26× background), which is a relevant supply-chain risk indicator for any ingredient sourced from that region. Supports geographic sourcing diligence for rice, vegetables, and tea grown in Hunan Province near smelter zones.
- Courses: Useful case study for industrial contamination pathways (smelter vs agricultural vs geological) and the relative contribution of each source using PMF methodology.
- App: Supply-chain context for ingredients grown in Hunan mining districts; Cd and As in soils at these levels would substantially elevate food-crop contamination risk above Chinese commercial averages.
- Microbiome: Not applicable.