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.