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

Abstract

Phytostabilization has been proposed as a promising tool 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 are 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 is conducted on technosols amended with compost, garden soil, slag, and biochar. The physicochemical properties of soil pore water (SPW) are determined as well as the phyto‐available concentrations of metal(loid)s by simple extraction tests. All amendments used are 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 improve bean growth and tend 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 show a significant positive correlation with the extraction procedures. In contrast, the phytoavailable As shows a weak correlation with As concentrations in the aerial parts. The 1‐M NH4NO3 extraction procedure is the most appropriate and provides the most useful indications of the phyto‐availability for the studied elements.