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§ The rate of addition of water-solved TNT and other nitroaromatic substances to the soil and to the tree root system is limited by the rate of tree transpiration.

§ The dendrotoxicity is rather dependent on the transpiration velocity, thus depending on the relation between supply and  degradation rate, than on the absolutely supplied pollutant mass. 

§ The tolerance of the dendroremediation systems to water-solved NAC-pollutants can be assessed with the used experimental designs.

§ This opportunity of tree-specific pre-assessment of dendrotoxicity is very important for: 

	the utilization of tree based waste water purification systems
	the "hydraulic control" of contaminated ground water with trees
	run-off effects (heavy rain events, snow melt water in spring)
	the controlled introduction of contaminated water into forest stands

§ As tolerance limit, concentration values of 15 mg/l should be regarded. Besides the exception of 2,4-DNT, this concentration limit is valid for all tested nitroaromatics. 

§ Although, with the concentration of 15 mg/l, a slight relative growth reduction in relation to the control occurs, growth and transpiration remain at an acceptable level.

§ TNT applications to wick supplied tree trays showed, that TNT-induced growth inhibition is reversible in Salix EW-13.

Also the new growth of Salix EW-13, if pruning the branches after temporary DNT treatment is independent of the pretreatment concentration.

last update: 14.02.04 18:06 by  Bernd Schoenmuth     Web date: June 2002