Feasibility of using forage grasses and legumes for phytoremediation of organic pollutants

Selected forage and soil conservation grasses and legumes were evaluated in the greenhouse for their abilities to stimulate dissipation of PCB, TNT, and pyrene in a soil. The grasses tested were tall fescue (Festuca arundinacea Schreb), reed canarygrass( Phalaris arundinacea L.), switchgrass ( Panicum variegatum L.), and deertongue (Panicum clandestinum L.). The legumes were alfalfa (Medicago sativa L.), crownvetch (Coronilla varia L.), sericea lespedeza (Lespedeza cuneata Dum-Cours.), and flatpea (Wagner pea) ( Lathyrus sylvestris L). The plants were grown in 13.5x15.0 cm pots containing soils that were fortified with 100 mg/kg nominal concentrations of the respective compounds and aged in the laboratory. After six months, 51% or less of an initial 100 mg/kg dose of aroclor 1248 was recovered from soils planted with reed canarygrass, switchgrass, and flatpea. Between 64-70% of the initial dose was recovered from soils planted with tall fescue, deer tongue, and sericea lespedeza, and about 80 % or more was recovered from soils that were planted with alfalfa and crownvetch as well as soil that was left unplanted. During the same period, <0.5% of the initial dose of TNT and <3% of pyrene were recovered from soils that were fortified with those compounds, including unplanted controls. Laboratory flask experiments that compared the dissipation of TNT and pyrene in natural soils and soils containing microbial inhibitor suggested that microbial transformation accounted for a major portion of the loss of TNT and pyrene in this soil. A comparison of the dissipation of TNT and pyrene in two different soils reinforces previously well-documented strong role of organic matter in the overall fate of TNT and pyrene in soil.