Ecotoxicological risks of the abandoned F-Ba-Pb-Zn mining area of Osor (Spain)

Abstract

Due to its potential toxic properties, metal mobilization is of major concern in areas surrounding Pb-Zn mines. In the present study, metal contents and toxicity of soils, water extracts from soils, and mine drainage waters from an abandoned F-Ba-Pb-Zn mining area in Osor (Girona, NE Spain) were evaluated through chemical extractions and ecotoxicity bioassays. Toxicity assessment in the terrestrial compartment included lethal and sublethal endpoints on earthworms Eisenia foetida, arthropods Folsomia candida and several plant species whereas aquatic tests involved bacteria Vibrio fischeri, microalgae Raphidocelis subcapitata and crustaceans Daphnia magna. Metal quantifications revealed high concentrations of Ba (250-5110 mg kg-1), Pb (940->5000 mg kg-1) and Zn (2370-11300 mg kg-1) that exceeded intervention values to protect human health. Risks for the aquatic compartment were identified through the release of drainage waters and by leaching and run-offs from metal-contaminated soils. Cd (1.98-9.15 µg L-1), Pb (2.11-326 µg L-1) and Zn (280-2900 µg L-1) in water samples surpassed international values of aquatic life criteria. Terrestrial ecotoxicity tests were in accordance with metal quantifications and identified the most polluted soil as the most toxic. Avoidance and reproduction tests with earthworms showed the highest sensitivity to metal contamination. Aquatic bioassays with extracts from soils confirmed the results from terrestrial tests and detected severe toxic effects caused by the mine drainage waters. Algal growth inhibition was the most sensitive aquatic endpoint. In view of the results, the application of a containment or remediative procedure in the area is encouraged.