Tobacco, Sunflower and High Biomass SRC Clones Show Potential for Trace Metal Phytoextraction on a Moderately Contaminated Field Site in Belgium.

Sofie Thijs,Nele Weyens,Stijn Van Slycken,Linda Meiresonne,Michel Mench,Erik Meers,Ann Ruttens,Nele Witters,Rolf Herzig,Jolien Janssen,Jaco Vangronsveld

doi:10.3389/fpls.2018.01879

Abstract

Phytoextraction could be a potential management option for diffusely Cd-Zn-Pb-polluted agricultural land in Northeast Belgium. The use of high yielding crops with a sufficiently high metal accumulation is preferred as these are expected to both gradually decontaminate the soil while generating an income through biomass valorization. To find out which high biomass crop possessed the highest and most constant (in time) phytoextraction potential on these soils, different plant species and different mutants or clones of each species, were evaluated during consecutive years. Biomass production and metal accumulation of pre-selected tobacco somaclonal variants (Nicotiana tabacum L.) and pre-selected sunflower mutants (Helianthus annuus L.) were investigated for two productivity years, while the phytoextraction potential of experimental poplar (Populus) and willow (Salix) in short rotation coppice (SRC) was assessed at the end of the second cutting cycle (after two times four growing seasons). The tobacco clones and the sunflower mutants showed efficient extraction of, respectively, Cd and Zn, while the highest simultaneous extractions of Cd and Zn were gained with some SRC clones. Variation in biomass production and metal accumulation were high for all crops over the years. The highest biomass production was observed for the experimental poplar clone of the crossing type Populus deltoides (P. maximowiczii x P. trichocarpa) with 9.9 ton DW per ha per year. The remediation period to reach legal threshold values for the pseudo-total content of Cd in this specific soil was estimated to be at least 60 years. Combining estimated phytoextraction potential and economic and environmental aspects, the SRC option is proposed as the most suitable crop for implementing metal phytoextraction in the investigated area.

Highlights

In the northeast of Belgium, an area of about 280 km2 is historically polluted by mainly cadmium (Cd), zinc (Zn) and lead (Pb) (Vangronsveld et al, 1995; Hogervorst et al, 2007)
This paper addresses differences in biomass production and metal accumulation between pre-selected tobacco clones, sunflower mutants, and experimental poplar and willow clones, as well as variations throughout different years where possible
For 2012, the plants with the highest metal concentrations of Zn and Pb were the clones with the lowest biomass

Summary

Introduction

In the northeast of Belgium, an area of about 280 km is historically polluted by mainly cadmium (Cd), zinc (Zn) and lead (Pb) (Vangronsveld et al, 1995; Hogervorst et al, 2007). Cultivating non-food high biomass crops with moderate metal accumulation capacity is promising for this area as these crops result in both a gradual soil depollution by extracting metals as well as in an alternative income for the farmers Woody plants such as willow and poplar have been the topic of research over the past years for soil trace metal remediation (Mench et al, 2010; Courchesne et al, 2016). They are fast growing tree species often grown in short rotation coppice (SRC) for bioenergy production (Mola-Yudego et al, 2015). To account for these site-specific effects and to discriminate which are some of the most influential factors, knowledge can only be gained through more field studies

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