This paper examines the potential for using hybrid poplar trees to remediate sites contaminated with the high explosive 2,4,6-trinitrotoluene (TNT). Laboratory experiments assessed the uptake of [U-14C]TNT from both hydroponic and soil systems. TNT is strongly bound and transformed by root tissues, and it only translocates slightly to the leaves of poplar cuttings. TNT was more bioavailable in the hydroponic system, but this did not affect the distribution of radiolabel among root, stem, or leaf tissues. The translocation of TNT was found to be similar to that reported for other plant species with up to 75% of the explosive uptaken remaining in root tissues and up to 10% eventually being translocated to the leaves. The majority of TNT was not extractable from plant tissues, and less than 10 percent of the applied label was identifiable by HPLC/radiochromatograph. TNT was transformed by the tree to 4-amino-2,6-dinitrotoluene (4-ADNT), 2-amino-4,6-dinitrotoluene (2-ADNT), and to a number of unidentified compounds which are more polar than TNT. Phytoremediation efforts must consider the fate and toxicity of these metabolites.

This article evaluates the translocation of the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in hybrid poplar trees (Populus deltoides ϫ nigra, DN34) grown in hydroponic solutions. Mass balances with [U-14 C]RDX were used to assess RDX translocation. Up to 60% of the RDX uptaken by the tree accumulated in leaf tissues. Analysis of plant extracts by highperformance liquid chromatography equipped with radiochemical detection indicated that RDX was not significantly transformed during exposure periods of up to 7 d. The bioaccumulation of RDX may be an important concern for phytoremediation efforts.

This article discusses the effects of various concentrations of the explosive 2,4,6‐trinitrotoluene (TNT) on the transpiration of hybrid poplar trees growing in hydroponic media. Transpiration was measured daily by gravimetric means. The rapid removal of TNT from hydroponic solutions was a result of plant uptake and required a daily dosage of TNT to ensure a relatively constant exposure over time. Transpiration decreased with increasing TNT concentrations ≥5 mg/L. Decreases in transpiration were accompanied by leaf chlorosis and abscission. A comparison between a laboratory study and a pilot‐scale experiment showed good scale‐up potential.

Abstract-This article evaluates the translocation of the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in hybrid poplar trees (Populus deltoides ϫ nigra, DN34) grown in hydroponic solutions. Mass balances with [U-14 C]RDX were used to assess RDX translocation. Up to 60% of the RDX uptaken by the tree accumulated in leaf tissues. Analysis of plant extracts by highperformance liquid chromatography equipped with radiochemical detection indicated that RDX was not significantly transformed during exposure periods of up to 7 d. The bioaccumulation of RDX may be an important concern for phytoremediation efforts.

Abstract-This article discusses the effects of various concentrations of the explosive 2,4,6-trinitrotoluene (TNT) on the transpiration of hybrid poplar trees growing in hydroponic media. Transpiration was measured daily by gravimetric means. The rapid removal of TNT from hydroponic solutions was a result of plant uptake and required a daily dosage of TNT to ensure a relatively constant exposure over time. Transpiration decreased with increasing TNT concentrations Ն5 mg/L. Decreases in transpiration were accompanied by leaf chlorosis and abscission. A comparison between a laboratory study and a pilot-scale experiment showed good scaleup potential.