EVALUATION OF PHYTOREMEDIATION TECHNOLOGY FOR
Introduction. Phytoremediation is "the use of plants to remove, contain or render harmless environmental contaminants in water, soil and sediments" (BIOMINET, 1998a, p. 2). It is fairly new as an attempt to treat hazardous waste sites, although it has been used for decades for wastewater polishing or the straining of pollutants from urban runoff through grass buffer areas.
Inorganic Contaminants Removed. Kuwabara et al. (1990) studied the uptake of arsenic from mine tailings by algae and attached aquatic plants ("submerged macrophytes") in a 57-km stretch of a South Dakota stream (Kuwabara et al., 1990, p. 395). The uptake of arsenic was affected by an apparent preferential uptake of phosphorus, if present in the water, principally in the orthophosphate form (Kuwabara et al., 1990, p. 403).
Cadmium in an embayment of the Hudson River estuary, resulting from 1953-71 discharges of wastes from a nickel-cadmium battery plant, was identified by Thomann et al. (1993) to be influenced by several biological forms (blue crab and benthic worms), but aquatic plant species were not identified as being significant influencers of cadmium in either the sediments or the overlying water column (Thomann et al., 1993, p. 424).
Driven by a concern that 18% of Iowa's rural wells show nitrate-N concentrations exceeding Federal standards (10 mg/L NO3-N), Paterson and Schnoor (1993) studied the uptake of nitrate by plants (poplar trees) from the upper, unsaturated soil zone below and beside (fertilized) agricultural fields (Paterson & Schnoor, 1993, p. 986). They found that soil water concentrations below the poplar trees and below a corn field were significantly lower than the levels beneath a barren field during "the uptake 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 barre...