Summary:
Problem
In
contrast to many phytoremediation results using herbaceous plants, little is known about the “dendroremediation”
potential of trees for explosives. Especially mass balances of the explosives
in the soil/tree system are rather
rare.
Goal
The
goal was to search for methods of remediation control utilizing the
dendroremediation potential of deciduous and coniferous trees for
sanitation purposes of contaminated soils. Soils polluted with the explosive
2,4,6-trinitrotoluene (TNT) and TNT side
products, e.g. dinitrotoluenes (DNT),
aminodinitrotoluenes (ADNT),
diamino-mononitrotoluenes (DANT)
and trinitrobenzene (TNB)
were investigated.
Methods
Trees
tested were hybrid willow (Salix spec.), hybrid poplar (Populus
spec.), birch (Betula pendula), spruce (Picea abies , Picea
glauca) and pine (Pinus sylvestris).
The fate of TNT
was
estimated in outdoor experiments with tree planted soils, obtained
from a former ammunition plant (AP-soils) in 72 lysimeter
pots in a two-factorial plot design.
Monitoring
parameters were: nitroaromatics content
of soil and plants, leachate load, and bioindication by measurements of growth
and tree yield.
Soil
based dendrotoxicity experiments using newly developed glass fiber wick
application systems allowed continuous measurements of transpiration
and growth.
Radiotracer mass balances of [14C]-TNT in older
trees, plant analysis of trees growing on a former ammunition site and
biomass measurements in the unpolluted field were conducted.
Results
and conclusions
Dendroremediation
could be proven for all trees tested by monitoring bioindication of
tree growth and leachate monitoring.
Analysis of soil samples was not
providing representative results and is not suited for phytoremediation
control in field trials.
The dendroremediation potential of juvenile and
adult trees by measurements of dendrotoxicity (growth and transpiration), TNT
fate and residual soil toxicity in cress tests is only assessable when
TNT application is definably.
It
was the first time that a complete [14C]-TNT incorporation and
TNT degradation to still unknown metabolites could be
demonstrated in both, mature deciduous trees and mature conifers. Moreover we could show the distribution of
TNT-derived [14C] in morphological compartments of these trees.
Basing
on the dendrotoxicity experiments, radiotracer results and yield
measurements in the field we were able to calculate both, the
dendroremediation capacity of newly planted trees and the natural
attenuation potential of adult trees growing in forests of former military
sites.
Concluding
from our project results we made proposals for the use of trees for
sanitation purposes and for the enhancement of natural attenuation.
