An Assessment of the Feasibility of Phytoextraction for the Stripping of Bioavailable Metals from Contaminated Soils

Phytoextraction has been proposed in many papers as a low-cost method for remediating contaminated soil. However, if national regulation is based on total metal(loid) concentrations in soil, phytoextraction is generally infeasible because of the long time required for remediation. Assessing phytoextraction requires determination of the dynamic rate of metal removal from soil. Phytoextraction may be feasible if the main goal is to reduce the soluble fraction of the metal(loid) with the goal of reducing bioavailability. However, it has been reported that there is a large mass balance mismatch between the reduction of the soluble metal fraction in contaminated soil and metal uptake by plants. Several studies report that the decrease of soluble fraction of metals in soil is higher than can be accounted for by plant uptake. In other words, studies generally overestimate the feasibility of bioavailable contaminant stripping. Therefore, a more rigorous approach is advisable to ensure that papers on bioavailable contaminant stripping include relevant information on mass balances. Furthermore, to implement the concept of bioavailable contaminant stripping, regulations must distinguish between the bioavailable fraction and the total metal concentration in soil. Environ Toxicol Chem 2022;00:1-8. (c) 2022 SETAC

Automated summary

Phytoextraction has been proposed as a low-cost method for remediating contaminated soil, but it may not be feasible if national regulations are based on total metal concentrations. Assessing phytoextraction requires determining the dynamic rate of metal removal from soil, and it has been found that the decrease in soluble metal fraction in soil is often higher than what can be accounted for by plant uptake. Therefore, a stricter approach is needed to ensure accurate evaluation of bioavailable contaminant stripping, and regulations must differentiate between the bioavailable fraction and total metal concentration in soil.