Evaluation of Phytoremediation Technology For Hazardous Materials

986). They found that soil water system concentrations below the poplar tree trees and below a corn theme were importantly lower than the levels below a barren sphere of influence during "the use of goods and services 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 woodland buffer" for the removal of nitrogen and phosphorus from a Virginia uncouth field, draining through the "forest" to an adjacent stream, is highly peculiar (Snyder et al., 1998).

Zinc, lead, and iron in urban runoff--in addition to suspended solids remote by simple straining or filtration--have been adsorbed onto grassed urban bridle-path medians and "grassy swales" placed near roadways for that purpose for many geezerhood (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 ar

Paterson and Schnoor (1993) found in Iowa that corn die-off in the after-harvest autumn, leads to decomposition reaction of the seed material, first releasing organic nitrogen, after which nitrifying bacterium in the soil convert that to nitrate (Paterson & Schnoor, 1993, p. 989-991). This (predictable) nonpermanent removal and link of contaminating constituents will be the major mechanism militating against wide-spread applicability of phytoremediation to truly dangerous hazardous waste sites.

Uptake Processes Elucidated. The info of Kuwabara et al. (1990) suggested to them that the dominant mechanism of plant uptake of As was rebel 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 systematically between 7.9 and 8.7 (Kuwabara et al., 1990, p. 397)--a condition favoring metal destabilization, compound formation, and precipitation, as debate to antisorption and dissolution proclivities expected in acidic waters or at acidic times in the same water.

Barrett, M. E., Walsh, P. M., Malina, J. F., Jr., & Charbeneau, R. J. (1998). executing of vegetative controls for treating highway runoff. ASCE Journal of Environmental Engineering, 124, 1121-1129.

Nair, D. R., Burken, J. G., Licht, L. A., & Schnoor, J. L. (1993). Mineralization and uptake of triazine pesticide in soil-plant systems. ASCE Journal of Environmental Engineering, 119, 842-854.

Burken, J. G., & Schnoor, J. L. (1996). Phytoremediation: plant uptake of atrazine and role of root exudates. ASCE Journal of Environmental Engineering, 122, 958-963.

Probably the best known P-R operation by environmental engineers has been the use (since 1970) of a hardy ruinous weed, the water hyacinth, placed in man-made greenhous
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