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BW, Pestemer W 2004: Dendroremediation of trinitrotoluene (TNT). Part 2: Fate of Radio-labelled TNT in Trees. ESPR - Environmental Science & Pollution Research 11(5), 331-339 ESPR - Abstract <www.scientificjournals.com/sj/espr/abstract/ArtikelId/6667> Full text (pdf): www.dendroremediation.de/2004publi/TNT-fate-low-resolut.pdf (250 KB) Full text (pdf): www.dendroremediation.de/2004publi/TNT-fate-high-resolut.pdf (789 KB) |
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The qualitatively most important results of the project were obtained by the radiotracer investigations with uniform ring-labeled [14C]-2,4,6-trinitrotoluene.
TNT was applied to four years old, lignified mature deciduous and coniferous trees (hybrid willow Salix EW-20 and Picea abies). Radiotracer incubation systems were pots with glass fibre wick based basal water supply with different application variants.
Trees were pre-cultivated for five month in the illustrated incubation systems and than selected to uniform growth and equal transpiration rates. Monitoring of transpiration was also used as vitality indicator during the experiments.
In all application variants, [14C]-TNT was applied as a short pulse, avoiding a permanent TNT delivery.
No substantial differences between basal and substrate application mode were detected. That's why for all dendrotoxicity experiments, the basal pollutant supply was applied.
Within the first five days after application, radioactivity appeared in the apical tree portions (leaves, spring needles and branch tips).
After 60 days the compartment distribution of the applied [14C]-TNT-radioactivity was determined in an biological Oxidizer.
Up to three quarters of the initial radioactivity were found within the trees.
Approx. 90% of this tree-located TNT radioactivity are, both in willow and in spruces, in the tree roots.
Approx. 10% of plant 14C arrived in aboveground tree parts.
In the aboveground portions of spruces the older needles (approx. 50 %) are the predominant deposition sites of 14C.
In willows, however, maximal aboveground radioactivity was found in the bark-free wood of the stems (approx. 50%) and in the branches (25%).
In the quantitatively most important root compartment at least three quarters of the root-located radioactivity are not extractable. Even with the most successful, acetic acid extraction only 25% (spruce roots) and 18% (willow roots) are extractable. Similar low extraction efficiencies are found in the aboveground tree parts.
Obviously, an intensive metabolisation happened in the tree roots. The small, still extractable portion of the TNT derived radioactivity is likewise metabolized. After thin layer chromatographic (TLC) separation of the root extracts, neither TNT, nor the known TNT metabolites aminodinitrotoluenes (ADNT) or diaminonitrotoluenes (DANT) were found. Only strong polar and polar TNT derivatives are provable in the extractable portion.
Radiotracer balances using [14C]-TNT are known from experiments of Thompson et al. 1998 [# Lit. 9]. After [14C]-TNT application to juvenile poplar cuttings, besides a polar radioactive fraction in the tissue extracts, the authors still found the known TNT metabolites aminodinitrotoluenes (ADNT) and diaminonitrotoluenes (DANT).
The role of mycorrhiza in juvenile trees of Populus tremula and Pinus sylvestris seedlings in [14C]-TNT degradation processes was investigated in our partner project at UFT Bremen by Ingo Dobner.
It was the first time that a complete [14C]-TNT incorporation and TNT degradation to still unknown metabolites could be demonstrated in mature woody plants, in both, deciduous trees and conifers. Moreover we could firstly show a differential compartment distribution of the fate of [14C]-TNT in older trees. The tree compartments included spring needles, older needles (leaves respectively for willow), branches, bark of stems, bark-free wood of stems and roots.
last update: 08.12.04 19:16
by Bernd Schoenmuth@yahoo.de
Web date: June 2002
