ASSESSING PHYTOEXTRACTION POTENTIAL IN A RANGE OF HYBRID POPLAR

Tracy Punshon & Domy C. Adriano
University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802

INTRODUCTION

Successful field-scale phytoremediation is dependant upon several factors; screening for suitable species, site-specific sampling of the contaminant profile, monitoring potential long-term effects of the remediation effort, (e.g. food chain biomagnification of contaminants) and good environment base-line data.  The research project of which this screening study is an initial part aims to develop a core technology for the phytoremediation of mixed waste contaminated plumes and soils by covering all of these aspects.  The site chosen for eventual deployment of this technology, located on the Savannah River Site, is contaminated with elevated concentrations of nickel, a range of guest metals at lower concentrations and depleted uranium.  In addition, a large trichloroethylene plume is expected to emerge within the floodplain within the next 5 to 10 years.  Research efforts in phytoremediation have produced a database of plant species which are reported to have the ability to either extract or degrade single inorganic or organic contaminants, or to stabilize radiologically contaminated sediments.  This plant database was the starting point for choosing species for inclusion in the program.  Concurrent studies in the program include:  monitoring contaminant movement through successive trophie levels (base-line data from contaminated ecosystems prior to phytoremediation efforts) and the effect of TCE and Ni on enzyme systems (e.g. P450) within hybrid poplar to establish the integrity of degradation/tolerance mechanisms during mixed-contaminant phytoremediation.

Work on willows (Salix spp.) and hybrid poplar (Populus spp.) suggest that there is a great deal of potential for use of fast growing trees in phytoremediation.  However, screening for phytoremediators has in the past been largely random, and based on anecdotal evidence.  Screening must be more taxonomically structured, and based on relevant criteria, such as the presence of genetic variability which allows plants to occupy inhospitable soil niches.  Fast-growing trees within the genus Salix (willows and poplars) are highly adaptable to environmental change, hybridize rapidly, have valid economic uses and have been found to possess traits which make them ideal for phytoremediation testing.  Heavy metal tolerances, both natural and induced have been detected in willows, and the ability to degrade organic chemicals into less harmful by-products have been observed in poplars.  This investigation gives data on initial screening of several significant poplar clones (Populus deltoides 5 nigra (DN5); P. maximowiczii 5 nigra (NM6); P. trichocarpa 5 deltoides (TD) 58-280 and 56-273) to nickel in solution culture to establish their potential as phytoextractor species.