Combining grass and legume species with compost for assisted phytostabilization of contaminated soils

Assisted phytoremediation, i.e. the combination of amendment and plant cultivation to remove potentially toxic elements (PTE) from soil, or to reduce their mobility and toxicity, can represent an effective gentle remediation option for the recovery of PTE contaminated soils. The aim of this study was to evaluate the suitability of different grass and legume species, such as Arundo donax L., Hordeum vulgare L. and Lupinus albus L., in assisted phytoremediation programs of PTE-contaminated soils in combination with a municipal solid waste compost (MSWC) used at 2 and 4% rates. The soil was heavily contaminated by different PTE, i.e. Pb (15,383 mg kg−1), Zn (4,076 mg kg−1), Sb (109 mg kg−1), Cd (67 mg kg−1) and As (49 mg kg−1). The selected plant species were able to grow in the contaminated soil, and their biomass production was significantly influenced by the compost either positively (e.g. A. donax) or negatively (e.g. H. vulgare roots). Compost addition significantly decreased or did not influence the PTE uptake and bioaccumulation factors of A. donax and H. vulgare roots and shoots, while it increased those of L. albus (particularly in roots) with respect to As, Sb, Pb and Cu. Finally, MSWC increased the PTE removal efficiency of A. donax (and partially of L. albus but not by H. vulgare), i.e. its ability to bioaccumulate PTE in the below ground organs, especially when grown in soils amended with 4% MSWC. The results indicated that A. donax, and in selected cases L. albus, can be used in combination with MSWC for the phytostabilization of PTE-contaminated soils.