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This study investigates the effectiveness of using nanoscale zero-valent iron (nZVI) to immobilise Pb/Zn in two different soils (acidic and calcareous) and the effects of nZVI treatment on soil physico-chemical and biological properties. Soil samples spiked with Pb(II) or Zn(II) were treated with commercial nZVI suspension at a dose of 20% (28-36 mg Fe(0)/g soil) for 72 h and one month. Sequential extraction procedures showed a significant decrease of Pb/Zn bound to exchangeable and carbonate fractions and an increase of residual fraction after the treatment with nZVI. There were no significant differences in the distribution of Pb/Zn in the soil fractions between the contact times studied; the immobilisation of Pb/Zn with nZVI in the described conditions was stable at least for a month. Better immobilisation results were found for Pb than for Zn. No negative effects on soil physico-chemical and biological properties were observed. In fact, the application of nZVI stimulated the soil respiration and the dehydrogenase activity in both soils, especially in the case of Pb, probably due to the higher immobilisation percentages. These results suggest that the use of nZVI to remediate polluted soils with Pb or Zn is a promising in situ strategy, and more research is required both in the laboratory and field to investigate the effects of such a treatment to the soil ecosystem.

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