Phytoremediation of Trichloroethylene with Hybrid Poplars

Abstract

We tested the ability of hybrid poplar to absorb trichloroethylene (TCE) from groundwater. Initial studies used axenic tumor cultures of H11 -11 grown in the presence of 14 C-TCE. These cells metabolized the TCE to produce trichloroethanol, di-and trichloroacetic acid. Some of the TCE was incorporated into insoluble, non-extractable cell residue, and small amounts were mineralized to 14 C-CO 2 . Rooted poplar cuttings grown in PVC pipes produced the same metabolites when exposed to TCE. Mass balance studies indicate that the poplars also transpire TCE. In addition we are conducting one of the first controlled field trials for this technology. Trees were planted in cells lined with high density polyethylene and dosed with TCE via an underground water stream during the growing season. Cells containing trees had significantly reduced TCE levels in the effluent water stream compared to control cells containing only soil. These results show that significant TCE uptake and degradation occur in poplars, which bodes well for the future use of poplars for in situ remediation of TCE.Trichloroethylene (TCE) has been widely used since its discovery in the midnineteenth century (1) for a variety of purposes: as an anesthetic, a dry cleaning agent and, until recently, in enormous quantities as a degreasing agent. While most TCE is of anthropomorphic origin, TCE has recently been found to be produced by marine algae (2). It has contaminated ground water at many localities, and is now the most commonly found volatile organic contaminant at many of these sites (3).The fact that TCE is a suspected carcinogen (4) has lent urgency to clean-up efforts. The stability, persistence and accumulation ofTCE in non-miscible underground pools, "DNAPLs", that are not easily found or accessible render attempts at remediation

Enhanced metabolism of halogenated hydrocarbons in transgenic plants containing mammalian cytochrome P450 2E1

“…Plants have been shown to take up and, in some cases, to metabolize organic pollutants (6), excess nutrients (6, 7), 2,4,6-trinitrotoluene (TNT) (8,9), and metals (10,11). Work in our laboratory has demonstrated that poplar trees are able to take up and metabolize TCE both under laboratory conditions and in a field test (12)(13)(14).…”

Poplar Metal Tolerance Protein 1 Confers Zinc Tolerance and Is an Oligomeric Vacuolar Zinc Transporter with an Essential Leucine Zipper Motif

“…The use of larger plants that are not currently classified as hyperaccumulators can compensate for somewhat lower accumulation factors in aboveground organs with greater biomass production and high transpiration rates. Poplar, which has emerged as a model system for genomic approaches to wood formation and tree physiology (Sterky et al, 1998;Taylor, 2002;Kohler et al, 2003), also is a good candidate for phytoremediation purposes (Gordon et al, 1998;Rugh et al, 1998;Pilon-Smits and Pilon, 2002;Stanton et al, 2002;Di Baccio et al, 2003). Thus, an ideal plant for phytoremediation purposes would combine high biomass production and superior capacity for pollutant accumulation and tolerance.…”

Enhanced Attenuation: A Reference Guide On Approaches To Increase The Natural Treatment Capacity Of A System

“…Others have demonstrated similar uptake rates. For example, Gordon et al (1997) reported that a stand of 5 year old poplars could cause a 140 cm/year draw-down in the water table when grown at a density of 1,750 trees/ha in the warm, arid conditions of eastern Washington state.…”