Field assessment of the effectiveness of organic amendments for aided phytostabilization of a Pb-Zn contaminated mine soil

A field trial was carried out to assess the effectiveness of organic amendments (COW: cow slurry; POULTRY: poultry manure; PAPER: paper mill sludge mixed with poultry manure) for the aided phytostabilization of vegetated and non-vegetated sites of an abandoned Pb/Zn contaminated mine. A native ecotype of Festuca rubra L. was used for colonizing the initially non-vegetated sites. Two and six months after amendment application, soil Pb and Zn availability (CaCl2-extractability) decreased. COW and POULTRY treatments resulted in highest reduction in Pb extractability in non-vegetated sites. In vegetated sites, COW-treated plots showed the highest decrease in metal extractability at 6 months. All amendments, especially POULTRY, led to higher F. rubra biomass and vegetation cover in vegetated and initially non-vegetated sites, respectively. Two months after soil treatment, soil basal and substrate-induced respiration peaked in vegetated sites. Based on a root elongation bioassay with Lactuca sativa L., beneficial effects of soil amendments were also observed in terms of soil phytotoxicity. The problem of high variability (spatial, temporal and environmental) of vegetated and non-vegetated mine soils for an effective aided phytostabilization is discussed.