Dr Rolf Herzig, Phytotech Foundation, Bern, Switzerland (Main Applicant); Dr Jean-Paul Schwitzguébel, Erika Nehnevajova
Federal Office for Education and Science (EU project QLRT-2001-00429)
July 2002 – January 2006
Prof. Jaco Vangronsveld, Hasselt University, Belgium.
Different green plants are able to accumulate heavy metals from contaminated environment, acting as solar driven pumps, thus offering the possibility to clean up polluted soils and sites. However most of the metal hyperaccumulating plants only produce a low biomass and most plants producing high biomass accumulate only moderate amounts of metals. Overcoming this deficiency is requested to optimize metal phytoextraction. The main goal of this study was thus to improve the accumulation of heavy metals by high yielding oil crops, such as sunflower (Helianthus annuus) and Indian mustard (Brassica juncea), producing a high biomass. As an alternative to genetic engineering, a stimulation of soil metal bioavailability and a non-GMO approach were used as tools to enhance the extraction of metals by both plant species.
The first experimentation was focused on the screening of 15 commercial sunflower varieties growing on a field contaminated with different metals and on the effect of classical fertilizers on metal accumulation and extraction. Highly significant differences were found between cultivars for the extraction of cadmium, zinc and lead. Sulfate fertilization enhanced Zn and Pb extraction, whereas ammonium nitrate usually enhanced Cd phytoextraction. Then classical mutation breeding techniques were used successfully to significantly improve the accumulation and extraction properties of Indian mustard and sunflower, tested in pot experiments and in the field, respectively. From a practical point of view, the improvement obtained looks very promising for the application of phytoextraction of metals from contaminated soils. After harvesting, contaminated biomass could be pyrolysed, producing a liquid fuel that can be transported, stored and used to generate heat and electricity by combustion in gas burners, engines and turbines. Additionally sunflower oil containing only negligible metal amounts could be used as lubricant or as a renewable source of energy.