[ Home Engl ] [ Top ] [ 6.1.1 Performance ] [ 6.1.2 Bioindication ] [ 6.1.3 Leachates ] [ 6.1.4 Soil analysis ] [ 6.1.5 Phase separation ] [ 6.1.6 Pollutant retardation ] [ 6.1.7 Balance lack ] [ 6.18 Evaluation ] [ 6.1.9 Alternatives ]

back to 6. Results         6.1. Outdoor experiments                       

6.1.1 Performance of outdoor experiments

The outdoor experiments were performed in lysimeter pots (20-liter Mitscherlich tubs) with TNT/ADNT-containing former ammunition plant soils (AP-soils) from the site Stadtallendorf (The State of Hesse, Germany), obtained from the HIM GmbH (Hessian Industrial Waste GmbH).

Four degrees of soil contamination  were used in the following range : 0,06; 1,3; 36,7 and 152,5 mg TNT/kg dry soil. Referring to their increasing TNT content the AP-soils were named SA1, SA2, SA3 and SA4.

Each contamination stage was combined with six types of planting  (hybrid Salix EW-13, hybrid Salix EW-20, hybrid Populus ZP-007, Betula pendula, Picea abies and the respective unplanted control variant.)

The outdoor experimental design is comparable with an in situ an area with varying contamination degrees. The 72 lysimeter pots represent the monitoring points. 

Since the soils were homogenized prior to pot filling, the experimental conditions are comparable with those, using mechanical in situ soil homogenization in combination with tree planting.

In contrast to most in situ investigations, the use of  lysimeter pots  offered  the additional opportunity of leachate quantification of the entire soil cylinder. Interfering lateral pollutant migration could be excluded in this manner and thus we were able to make an attempt of realistic outdoor pollutant balance.

All monitoring parameters for dendroremediation success control are illustrated in the figure. 

In addition to leachate control and measurements of initial and final soil nitroaromatics content, repeated measurements of branch elongation and tree yield were performed. 

Prior and during the dendroremediation, tree growth quantification at appropriate time intervals served as bioindication parameter of soil contamination decrease of the whole soil body 

For confirmation purposes, growth was monitored simultaneously in trials using tree planted 1-m³-lysimeters filled with the identical four soil types.