The impact of buried historical copper slags on contemporary soil contamination

Abstract

This study focuses on the impact of historical metallurgical slags on contemporary soil and soil pore water contamination, and potential phytoavailibility of metal(loid)s based on the example of the former smelter (16th–18th century) in Miedziana Góra (Holy Cross Mountains, Poland). The slags buried in soil exhibit elevated concentrations of Pb (57,400 mg·kg⁻¹), Zn (9000 mg·kg⁻¹), Cu (8890 mg·kg⁻¹), and As (325 mg·kg⁻¹). Mineralogical analysis reveals that the main carriers of these metal(loid)s are sulfides (Cu, As), metallic phases (Cu), and glass (Pb, Zn). Based on leaching tests using deionized water, it was found that the metal(loid)s contained in the slags are hardly mobilized. Similarly, the pH-static leaching tests indicate that, under natural soil pH conditions (~ 6.5), contaminants leaching from slag is limited, with metals stabilizing primarily in secondary phases, mainly in the form of oxides, carbonates, and phosphates. Despite the limited mobility, surrounding soils show high concentrations of Pb (up to 31,200 mg·kg⁻¹), Cu (up to 13,900 mg·kg⁻¹), Zn (up to 11,800 mg·kg⁻¹), and As (up to 985 mg·kg⁻¹). Leaching tests on soil samples using CaCl₂ as a leaching agent reveal mobilized concentrations up to 19.1 mg·kg⁻¹ Zn, 7.20 mg·kg⁻¹ Cu, and 6.40 mg·kg⁻¹ Pb, with Sb (1.81 % of the total) and Cd (1.56 % of the total) showing the highest mobility. A Pb concentration exceeding 100 μg·l⁻¹ in the tested pore water sample indicates poor water quality, underscoring the significant environmental impact of historical metallurgy on present ecosystem.