Uptake and transformation of TNT by hybrid poplar trees

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-C-14]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.