SPECIES-DEPENDENT UPTAKE AND TOLERANCE OF NITROAROMATIC COMPOUNDS BY HIGHER-PLANTS

Eleven plant species (five dicotyledonous, six monocotyledonous specie s) were cultivated for eight weeks in standard soil under identical co nditions in the greenhouse. The soil was contaminated with 10, 100 or 500 mg TNT/kg, respectively. Plant roots were extracted using dichloro methane with acid hydrolysis followed by alkalinisation. The main TNT- metabolites measured by GC-ECD were 2-aminodinitrotoluene and 4-aminod initrotoluene. There was a positive correlation between soil contamina tion and the concentrations of extractable nitroaromatics in the roots . A species-dependent contamination level of extractable nitroaromatic s was shown. In soil supplemented with 10 mg TNT/kg, the highest conce ntration of all species tested in this soil was found in the roots of Medicago sativa (2.7 mu g NAC/g d. wt.). Medicago sativa was not able to grow in soil contaminated with 100 mg TNT/kg, where Triticum aestiv um and Phaseolus vulgaris can develop and their roots contain high lev els of TNT-metabolites (98 mu g NAC/g d. wt, and 91 mu g NAC/g d. wt., respectively). In the same soil the lowest level of nitroaromatics wa s detected in the root extract of Lupinus angustifolius (14 mu g/g d. wt.). Only Phaseolus vulgaris was able to grow in the presence of 500 mg TNT/kg soil with very high levels of NACs in the roots (460 mu g/g d wt.). General differences between dicotyledonous and monocotyledonou s plants in quality or quantity of nitroaromatic compounds were not no ticed. Uptake and/or sequestration of nitroaromatics by plants reduce the level of extractable nitroaromatics in the immediate environment o f the root (rhizosphere soil). Several cultivars of Triticum aestivum were cultivated in TNT contaminated soil (50 mg TNT/kg) from a former ammunition site. Four of the six cultivars were able to reduce signifi cantly the TNT concentration in the rhizosphere soil.