Sequential application of soil washing and phytoremediation in the land of fires

This paper presents an experimental study aimed at verifying the efficiency of a double-stage remediation process to be applied in former agricultural sites contaminated by illegal dumping of industrial wastes. The process, which includes an EDDS (Ethylenediamine-N,N'-disuccinic acid) enhanced washing, followed by a phytoremediation treatment, is applied at the lab scale for the remediation of a soil sampled in a territory known as Land of Fires (Italy) contaminated with Cu (∼400 mg kg-1) and Zn (∼250 mg kg-1). Phytoremediation is conducted using Lactuca sativa to verify, together with process efficiency, the potential risks due to metal accumulation in edible species. The results of the washing process show the possibility of removing the potential toxic metals from 44% to 77% for Cu and from 18% to 47% for Zn. The removal is well distributed among all soil fractions. There is almost no removal of other components which are fundamental for an agricultural soil. Results of the subsequent phytoremediation treatment indicate that both the contaminants and the residual EDDS/EDDS-chelates adsorbed into the soil generally negatively affect plant growth, reducing the number of germinated seeds up to 43%, and the shoot length up to 63%. Nonetheless, whenever the efficiency of the washing stage is high enough, no adverse effect is obtained on the plants. The efficiency of the phytoremediation stage mainly relies on leaf uptake, which accounts for up to 88% of the total removed Cu and up to 95% of the total removed Zn. Stabilization in the underground part of the plant is more contained because of the limited mass of the roots.