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back to 6. Results                   6.1. Outdoor experiments              

6.1.6 Pollutant retarding effect of trees

In the initial establishment phase, less the soil leaching rates, than above all TNT degradation and TNT binding to organic soil matter and/or to clay minerals overlay and mask the dendroremediation.

Dendroremediation is slowly beginning with the soil permeation by tree roots and dendroremediation increases when tree transpiration becomes effective.

So, dendroremediation effects are first observable after termination of the initial establishment phase. These effects are clearly recognizably as "tree-caused" decrease of the leaching rates. This decrease of pollutant leaching  is thereby not (only) due to enhanced tree transpiration.

The TNT/ADNT retarding effect occurs faster at lower TNT soil concentrations, which also permit a more rapid tree establishment. Under contamination conditions, which inhibit the growth of the trees, however no dendroremediation effects are possible.

Winter retardation !

Remarkably is, that the tree-mediated  TNT/ADNT retardation is clearly provable even in "winter leachate"  for willows, poplar and birch.

Tree-mediated Winter retardation of soil pollutants is above all very important, because in the winter phase the bulk of  groundwater formation takes place and the risk of  pollutant entry is the highest in Winter.