Efficiency of soil organic and inorganic amendments on the remediation of a contaminated mine soil: II. Biological and ecotoxicological evaluation

•Soil health enhanced after combined addition of organic and inorganic amendments.•Amendments reduced the soil toxicity to plants, invertebrates and microorganisms.•Organic materials reactivated nutrients cycles and improved the soil habitat function.•Compost and pig slurry plus lime showed high potential to remediate acidic mine soils.•Ecotoxicological tests are useful to evaluate the soil remediation effectiveness.

The feasibility of two organic materials (pig slurry and compost) in combination with hydrated lime for the remediation of a highly acidic trace elements (TEs) contaminated mine soil was assessed in a mesocosm experiment. The effects of the amendments on soil biochemical and ecotoxicological properties were evaluated and related with the main physicochemical characteristics of soil and soil solution. The original soil showed impaired basic ecological functions due to the high availability of TEs, its acidic pH and high salinity. The three amendments slightly reduced the direct and indirect soil toxicity to plants, invertebrates and microorganisms as a consequence of the TEs' mobility decrease in topsoil, reducing therefore the soil associated risks. The organic amendments, especially compost, thanks to the supply of essential nutrients, were able to improve soil health, as they stimulated plant growth and significantly increased enzyme activities related with the key nutrients in soil. Therefore, the use of compost or pig slurry, in combination with hydrated lime, decreased soil ecotoxicity and seems to be a suitable management strategy for the remediation of highly acidic TEs contaminated soils.