Potentially Toxic Elements in Historical Metallurgical Areas: Environmental Impact and Revaluation Possibility at the San Pablo Pb Smelting, Spain

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In Spain, metallic mining has been highly significant throughout its history. Today, numerous mines in a state of abandonment have been registered, posing not only an environmental risk but also a health risk to humans. Some of these mines were equipped with their own metallurgical system to obtain the desired metal from the ore. Other small-scale mines were located nearby, supplying a single metallurgical core, such as the San Pablo Smelting. This smelter is located in the southwest of the Castilla La Mancha region (South-Central Spain), in the municipality of Chillón (Ciudad Real). Although historical information about its operation is limited, it is known that this metallurgical center was of great importance between the 2nd and 1st centuries BC. Subsequently, its slag heaps were reprocessed several times, the last in the 1960s. In the immediate vicinity of this smelter, numerous slag heaps have been found, with considerable volumes of slag materials with distinguishable aspects. This variability suggests differences in the efficiency of metallurgical recovery processes, in this case, of lead (Pb) which could reflect various periods of activity. In this area, 6 samples corresponding to slag materials and 11 soil samples were collected. To determine the total content of trace elements in these samples, the technique of energy-dispersive X-ray fluorescence (ED-XRF) was used. The analyses revealed an average content of Pb and Cu of 3.14% and 0.16% in soil samples, respectively. Both elements exceed the legal limits by 320% for Cu and 3140% for Pb in forest-type soils. Regarding the slag material, three samples were identified with a Pb content of less than 8% and another three exceeding 15%. These metal contents in soils confirm the need for environmental intervention, or a possible enhancement of the existing materials in the area. In light of the results obtained, a revaluation for the extraction of Pb using updated metallurgical techniques is proposed. Leaching with sodium citrate presents an environmentally viable alternative to traditional pyrometallurgical methods, reducing emissions of harmful compounds such as sulfur oxide and carbon dioxide.

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