Phytoremediation potential of willow trees for aquifers contaminated with ethanol-blended gasoline

Ethanol-blended gasoline has been used in Brazil for 20 years and, probably, is going to be more widely used in North America due to the MtBE environmental effects on groundwater. The potential impacts caused by the presence of ethanol in UST spills are related to the co-solvency effect and the preferential degradation of ethanol over the BTEX compounds. These interactions may increase the length of dissolved hydrocarbon plumes and the costs associated with site remediation. This study investigates the advantages of phytoremediation to overcome the problems associated with the presence of ethanol in groundwater contaminanted with gasoline-ethanol mixtures. Experiments were performed under lab conditions with cuttings of Willow tree (Salix babylonica) cultivated hydroponically. Results showed that the cuttings were able to reduce ethanol and benzene concentrations by more than 99% in less than a week. The uptake of both contaminants was confirmed by blank controls and was significantly related to cuttings transpiration capacity. Sorption onto roots biomass also markedly affected the behavior of contaminants in solution. Experiments to evaluate plants' toxicity to ethanol indicated that plants were only affected when aqueous ethanol concentration reached 2000 mg l(-1). Results suggest that phytoremediation can be a good complement to intrinsic remediation in shallow aquifer sites contaminated with ethanol-blended gasoline spills. (C) 2001 Elsevier Science Ltd. All rights reserved.