EVALUATION OF PHYTOREMEDIATION TECHNOLOGY

986). They found that soil wet concentrations below the poplar tree trees and below a corn sports stadium were significantly lower than the levels under a barren force field during "the expenditure period," but in autumn, following corn die-off, concentrations were significantly higher in the barren field than below the poplar trees and significantly lower in the barren field than beneath the corn field (Paterson & Schnoor, 1993, p. 991).

The reputed impact of a "riparian timbre buffer" for the removal of nitrogen and phosphorus from a Virginia countrified field, draining through the "forest" to an adjacent stream, is highly fly-by-night (Snyder et al., 1998).

Zinc, lead, and iron in urban runoff--in addition to suspended solids upstage by simple straining or filtration--have been adsorbed onto grassed urban thoroughfare medians and "grassy swales" placed near roadways for that purpose for many eld (Barret et al., 1998).

Organic Contaminants Removed. Uptake by rows of poplar trees of the herbicide, atracine, has been thoroughly investigated by researchers at the University of Iowa (Nair et al., 1993). They also reported work by others on removal of nitrobenzene and trichloroethylene (TCE) (Nair et al., 1993, p. 843). In addition to the metabolic uptake of these organics, the Iowa researchers learned through their own work and that of others that the trees are adequate to(p) fir

The work by Nair et al. (1993) has closely comprehensively explained the mechanisms of P-R uptake. These include, first of all, uptake by the soil as an adsorption or ion exchange process (Nair et al., 1993, pp. 851-852)--silty loam adsorbing more atrazine (carbon) than silicon oxide sand media, making loam-held carbon less available for sic uptake. In the sandy media, atrazine in poplar trees then was carve up among the leaves, the roots, and the stems by 85%, 5.4%, and 9.1%, respectively, on the average (Nair et al., 1993, pp. 847-848).

Uptake Processes Elucidated. The entropy of Kuwabara et al.

(1990) suggested to them that the dominant mechanism of plant uptake of As was advance adsorption, although some other data (from other researchers) suggested that a metabolic set of reactions ("As-reactivity" [?] and toxicity) can be involved (Kuwabara et al., 1990, p. 403). Stream-water pH influences on the sorption of both orthophosphate and arsenic were not elucidated (Kuwabara et al., 1990, p. 403-406); but pH, it is noted, was consistently between 7.9 and 8.7 (Kuwabara et al., 1990, p. 397)--a condition favoring metal destabilization, compound formation, and precipitation, as distant to antisorption and dissolution proclivities expected in acidic waters or at acidic times in the same water.

EPA Phytoremediation enchiridion Team. (1998, circa. 10 November). Phytoremediation bibliography. (pp. 1-71). Available:

Conclusions. Chang and Corapcioglu suggest, probably prophetically, that phytoremediation for hazardous waste sites depart likely be viewed in the long run as a "final polishing step after the initial treatment of . . . high-level contamination" (Chang & Corapcioglu, 1998, p. 162). This is precisely analogous to move use of water hyacinth for municipal wastewater treatment. Also, P-R appears executable for long term remediation of sites with low levels of contaminants that are of hold in toxicity; and plants such as poplar trees have the great promise for
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