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

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