Remediation of a copper mine soil with organic amendments: Compost and biochar versus Technosol and biochar

The contamination produced by metal mining activities is a major environmental problem; for this reason, sustainable management strategies are required for remediating mine soils. The present study focused on the effect of applying organic amendments combined with vegetation in a settling pond soil of a depleted copper mine of Touro (Spain). Two different amendments were applied in different soil/substrate ratios: (1) a mixture made of Technosol and biochar and (2) a mixture of compost and biochar. A 3-month greenhouse experiment was carried out to evaluate the effect of both amendments and mustard plants on the chemical characteristics of the mine soil and the metal uptake by plants. The results showed that the addition of both amendments and planting mustards significantly increased soil pH as well as C and N soil concentrations. The treatments also reduced the CaCl2-extractable metal concentrations in the soil. However, the amendments increased the pseudototal concentration of Zn in the mixtures, since Zn was present in the Technosol and the compost used. Mustard plants extracted Ni from the soil amended with compost and biochar, and Zn from the soil amended with Technosol and biochar. These results suggest Brassica juncea L. is a potential candidate to revegetate mine soil for their tolerance to Ni and Zn.