Effects of carbon-based materials and redmuds on metal(loid) immobilization and growth of Salix dasyclados Wimm. on a former mine Technosol contaminated by arsenic and lead

Metal(loid) soil contamination is a widespread issue and its remediation a priority. Phytoremediation involves the use of plants to stabilize/extract metal(loid)s and prevent spreading of contaminants. Salicaceae are fast growing trees that can tolerate and accumulate metal(loid)s. Amendments may be needed to facilitate plant growth on the contaminated substrate. Biochar, the solid product of pyrolysis, can ameliorate soil properties and reduce metal(loid) bioavailability but showed low affinity toward arsenic. Redmud, a waste product, can immobilize arsenic and other metal(loid)s and improve soil conditions. To evaluate the potential of those amendments to immobilize metal(loid)s and facilitate the establishment of a cover vegetation with willow (Salix dasyclados Wimm.), a pot experiment was conducted using several carbon-based materials (biochar and activated carbon) and redmuds. Two carbon-based materials and two redmuds were selected for the pot experiment based on characteristics and sorption tests. A former mining soil was amended with these products and Salix dasyclados cuttings were planted. Biochar and one redmud improved growth of Salix dasyclados Wimm. Redmud, which is cheaper than biochar, performed equally well as the biochar at a lower application rate. It can therefore be concluded that the application of redmud, associated to Salix dasyclados, could be an option for the phytoremediation of an As and Pb contaminated soil. However, these results need to be evaluated on a bigger scale to assess the gain brought by the combination of redmud and Salix dasyclados on the contaminated area.