Integrated approach for the characterization and risk assessment of soils in environmental liabilities derived from metallurgy

The assessment of environmental liabilities associated with metallurgy requires integrating chemical, physical, and biological indicators to estimate risks and inform remediation strategies. In this case study, a smelting complex was investigated through georeferenced sampling at a site in southwestern Spain, within the Almadén region, affected by historical metallurgical slags. Part of these slags was reused during a partial reactivation of the area, resulting in heterogeneous materials that may serve as sources of contamination. At present, the site is embedded in a forested environment that supports wildlife, thereby increasing the ecological relevance of the study.

Soil pH (6.26–8.23) and electrical conductivity (30–1,539 µS·cm⁻¹) were determined, together with multielemental composition by XRF-ED and enzymatic bioindicators (acid phosphatase, β-glucosidase, and dehydrogenase). Extremely high concentrations of Pb (up to 121,235 mg·kg⁻¹), Zn (1,525 mg·kg⁻¹), Cu (3,110 mg·kg⁻¹), As (663 mg·kg⁻¹), and Sb (1,510 mg·kg⁻¹) were detected, largely exceeding guideline values for contaminated soils. Multivariate analysis revealed a coherent polymetallic association (Pb-Zn-Cu-As-Sb) associated with the dispersion and reuse of slags, which is distinguishable from the natural geochemical background.

Acid phosphatase and β-glucosidase activities remained at moderate levels even in areas with high metal loads. In contrast, dehydrogenase activity was inhibited by more than 60%, indicating a marked impact on soil biological quality. These findings highlight the need for integrated assessments to effectively manage environmental impacts and ecological risks associated with metallurgy-derived liabilities.