Phytoremediation towards the future: focus on bioavailable contaminants

The hypothesis that one of the possible future trends of phytoextraction should be the removal of the bioavailable contaminants has recently received renewed and increasing interest. This fraction is the most hazardous to the environment and human health. The evaluation of contaminant bioavailability is essential for the appropriate application of the technology. Before selecting a phytoextraction process, it is necessary to consider the specific characteristics of the soil at the contaminated site in order to evaluate how the soil properties will influence the final result of remediation in the field. With this approach based on the concept of bioavailable contaminant stripping (BCS), an evaluation of the hazards of the residual fraction not removed by plants is left to a risk assessment procedure. This approach can be safely applied, if the soil ability to replenish the bioavailable pools in the long term is considered. This problem can be overcome by enhanced bioavailable contaminant stripping (EBCS) which evaluates this amount through the combined use of chemical extraction with a mobilizing agent, specific for each metal, and pot experiments in which successive growing cycles must confirm the absence of the bioavailable fractions. Phytoextraction can be selected as "green remediation" to minimize the mobile and bioavailable fractions of contaminants, while improving soil quality.