Categorization of mining waste based on geochemical and toxicological characterization data in restoration/remediation projects. Case study of the San Quintín Pb-Zn mine (Ciudad Real, Spain)

San Quintín is one of the derelict mines in Alcudia Valley Mining District, where large amounts of mining wastes have been disseminated during the last two centuries. These dumps and tailings materials are an important source of contamination of heavy metals and metalloids in the area. Nowadays, the restoration project for the abandoned mining area is beginning to be drafted, including a risk assessment of the wastes before restoration works. In this work, we carried out toxicity studies of these polluted materials, including data about total and soluble contain of As, Cd, Pb, Zn and Fe, mineralogical composition, and some bioassays to determine the toxicity effect of the samples to crustaceans (D. magna and T. platyurus) and algae (R. subcapitata). The pollution load index (PLI) has been calculated for each sample based on the pollution index (PI). Multielemental data and the indices calculated show that most of the samples present extremely high values of potentially toxic elements, and high values of contamination respect the background levels: 444 mg kg^-1 Cd, 144,900 mg kg^-1 Pb, 47,700 mg kg^-1 Zn, 202,600 mg kg^-1 Fe and 549 mg kg^-1 As. The bioassays suggest a relationship with pH, conductivity and grainsize. The EC₅₀ values were 458.7 to <2 of toxic units (TU) for D. Magna whereas for T. Platyurus the results oscillated between 2500 to <2. On the other hand, for algae organisms were 2083.3 to <2 TU. The studies carried out reveal the large accumulation of potentially toxic elements in mining waste and the risk they may pose to the associated ecosystems that develop in the area, as well as to human health.