Aided phytostabilisation of As- and Cu-contaminated soils using white lupin and combined iron and organic amendments

An aided phytostabilisation strategy consisting of several composite amendments of iron sulphate and organic materials combined with Lupinus albus L. (white lupin) was evaluated for remediation of an As- and Cu-contaminated soil. Iron sulphate was combined with lime, paper mill sludge (PS), olive mill waste compost (OMWC) or holm oak biochar (BC) and applied to a slightly acidic soil with high concentration of As (∼2200 mg kg−1) and Cu (∼150 mg kg−1). White lupin was grown for 48 days in pots containing amended and non-amended soils and the effect of soil treatments on soluble and extractable trace elements, soil fertility and plant growth and composition was evaluated. The addition of the amendments raised soil pH and reduced soluble As (50–93%) and extractable As and Cu (50–89%). Despite the reduction of As- and Cu-extractable fractions, plant As and Cu uptake was not greatly affected by the amendments. Variations in soil pH and P-Olsen seemed to have influenced As dynamics in the treated soils, although they did not provoke its mobilisation with respect to the non-amended soil. Our results suggest that the freshly formed iron oxides resulting from addition of iron sulphate controlled As dynamics in the treated soils, avoiding its mobilisation due to application of organic materials. The combination of iron sulphate with OMWC and BC is shown as appropriate for aided phytostabilisation of metal(loid)s contaminated soils, as it improved soil fertility and plant nutrition while reduced As and Cu mobility. •Four composite amendments were assessed for remediation of As and Cu contaminated soils.•The amendments reduced soluble and extractable As and Cu.•Porewater pH and available P affected As mobility within the treated soils.•Plant As and Cu uptake was not affected by the amendments.•Iron sulphate combined with compost or biochar improved soil fertility and plant growth.