Phytoremediation of soils contaminated by organic compounds: hype, hope and facts

The present opinion paper is focused on the phytoremediation of organic pollutants and is based on the lectures given by the author during the International Congress of Phytoremediation of Polluted Soils, held at Vigo, Spain, 29-30 July 2014. The aim of this position paper is (1) to highlight some progress made within the last few years (after the end of COST Action 859 in October 2009) in the phytoremediation of selected organic pollutants and (2) to suggest new research and approaches, which seem important and promising in the opinion of the author to make this environmentally friendly remediation technique more attractive and more successful. Depending on the type of soil to be treated, as well as on the xenobiotic contaminants, their concentration and ageing, different approaches can be considered and are briefly presented with some recent and successful applications, but also highlighting their limitations and needs for future developments: phytoextraction of hydrophobic xenobiotic compounds like polychlorobiphenyls (PCBs), phytodegradation of xenobiotics and its possible impacts on primary and secondary metabolism of the plant and phytostimulation of rhizospheric microorganisms by root exudates for the rhizodegradation of petroleum hydrocarbons. Finally, some promising approaches are suggested for overcoming the bottlenecks and making phytoremediation a reliable, mature and sustainable technology: how to deal with mixed pollution; the potential of endophytic bacteria; possible improvements by soil amendments and co-cropping; validation of laboratory results by field experimentation; evolution of regulations from the total concentration of a pollutant to its bioavailable fraction; and the use of biomass for added-value products, fine chemicals and biofuels in biorefineries or the production of ornamental plants.