Influence of biochars, compost and iron grit, alone and in combination, on copper solubility and phytotoxicity in a Cu-contaminated soil from a wood preservation site

International audienceTwo biochars, a green waste compost and iron grit were used, alone and in combination, as amendment to improvesoil properties and in situ stabilize Cu in a contaminated soil (964 mg Cu kg−1) from a wood preservationsite. The pot experiment consisted in 9 soil treatments (% w/w): untreated Cu-contaminated soil (Unt); Unt soilamended respectively with compost (5%, C), iron grit (1%, Z), pine bark-derived biochar (1%, PB), poultry-manure-derived biochar (1%, AB), PB or AB + C (5%, PBC and ABC), and PB or AB + Z (1%, PBZ and ABZ). After a3-month reaction period, the soil pore water (SPW) was sampled in potted soils and dwarf beans were grownfor a 2-week period. In the SPW, all amendments decreased the Cu2+ concentration, but total Cu concentrationincreased in all AB-amended soils due to high dissolved organic matter (DOM) concentration. No treatment improvedroot and shoot DWyields, which even decreased in the ABC and ABZ treatments. The PBZ treatment decreasedtotal Cu concentration in the SPWwhile reducing the gap with common values for root and shoot yieldsof dwarf bean plants. A field trial is underway before any recommendation for the PB-based treatments