Effect of Biochar and Amendments on Pb and As Phytotoxicity and Phytoavailability in a Technosol

Abstract : Phytostabilization have been proposed as promising tools for long-term management of polluted sites. Optimization of the process efficiency involves choosing suitable amendments to allow both efficient plant growth and the immobilization of contaminants. The objectives of this study were to evaluate the effect of amendments on (i) the physicochemical properties of technosol and (ii) the mobility and phyto-availability of metal(loid)s. A dwarf bean growth test was conducted on technosols amended with compost, garden soil, slag and biochar. The physicochemical properties of soil pore water (SPW) were determined as well as the phyto-available concentrations of metal(loid)s by simple extraction tests. All amendments used were able to increase SPW pH and electrical conductivity, allowing a decrease in the lead concentration in SPW by 90 % and the lead phytoavailable part by 93 %. However, for all amendments, SPW As concentration increased. Lastly, the amendments improved bean growth and tended to decrease the metal(oid) concentrations in aerial organs. As concentration in roots did not decrease whereas Pb concentration decreased. Metal(loid) concentrations of Pb accumulated in the aerial parts of beans and their extractable concentrations showed a significant positive correlation with the extraction procedures. In contrast, the phytoavailable As showed a weak correlation with As concentrations in the aerial parts. The 1-M NH4NO3 extraction procedure was the most appropriate and provided the most useful indications of the phyto-availability for the studied elements.