Feasibility of Labile Zn Phytoextraction Using Enhanced Tobacco and Sunflower: Results of Five- and One-Year Field-Scale Experiments in Switzerland

Abstract

Phytoextraction with somaclonal variants of tobacco and sunflower mutant lines (non-GMs) with enhanced metal uptake and tolerance can be a sustainable alternative to conventional destructive decontamination methods, especially for stripping bioavailable zinc excess in topsoil. The overall results of a 5-year time series experiment at field scale in north-eastern Switzerland confirm that the labile Zn pool in soil can be lowered by 45–70%, whereas subplots without phytoextraction treatment maintained labile Zn concentrations. In 2011, the phytoextraction experiment site was enlarged by a factor of 3, and the labile 0.1 M NaNO₃ extractable Zn concentration in the soil was reduced up to 58% one period after harvest. A Mass Balance Analysis confirmed soil Zn decontamination in line with plant Zn uptake. The plants partially take Zn from the non-labile pool of the total. The sustainability of Zn phytoextraction in subplots that no longer exceed the Swiss trigger value is now assessed over time. In contrary to the phytoextraction of total soil Zn which needs a long cleaning up time, the bioavailable Zn stripping is feasible within a few years period.

KEY WORDS:

• phytoremediation
• bioavailable contaminant stripping
• labile 0.1 M NaNO₃ extractable Zn concentration
• non-GM plant
• feasibility of phytoextraction

ACKNOWLEDGMENTS

This work was part of Swiss Priority Programme 6 “Gentle soil Remediation”, and the three COST Actions 837, 859, FA0905 (BBW C99.0028, SBF C04.0207, and SBF C10.0102). The seeds of M_3-4 sunflower mutants were obtained within EC 5th Framework Programme PHY­TAC (QLRT-2001-00429) and financed by the State Secretariat for Education, Research and Innovation (SERI) of Switzerland and the EC Commission. The research is continued within the 7th Framework Programme, project GREENLAND (KBBE-266124), and is financed by the EC Commission at Brussels. A special thank goes to Immo-Development Ltd. and the farmer family Gall for providing us the test site of Bettwiesen for phytoremediation research.

Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/bijp.