Locations

General information about the sites

The two main research sites are the Tiergarten park in the centre of Berlin and the former sewage fields at the northern city limit. The Tiergarten park is an example for an highly frequented park and recreation area in the urban environment. On the former sewage fields rapid ecological adaptation processes due to the change in land can be suited. This site is indicative for the problems of a commercial strongly used and polluted site.

Sewage fields Berlin Buch

From the late 19th century to the 80ies untreated wastewater was applied on 13 000 ha of sewage farm land around Berlin. The wastewater emanated from industrial and domestic sources. First, the sewage farms were used for agricultural production. The rising amount of wastewater caused a change of the infiltration regime. Up to 10000 mm•a-1 were applied.. With the waste water a lot of organic compounds and heavy metals on the fields. With the construction of wastewater treatment plants the sewage farms lost their relevance, infiltration on that sites stopped. In 1985 the wastewater application on the sewage farm Buch was stopped, the soil surface was levelled and an effort was made to afforest the fields. Most of the trees died, mainly due to water shortage during summer time, nutrient deficiencies and heavy metal contamination.

Today, dry grasslands (mainly couch grass: Agropyron repens) can be found. Rapid turnover processes of organic matter occur, and an increased leaching of heavy metals and nitrate were measured.

Perennial investigations show continual exceeding of limit values for heavy metals in groundwater nearby the surface, especially for cadmium, lead, copper, zinc, sulphate and nitrate.

To the leaching of heavy metals maley material (>10% loam and calcareous) was mixed with the topsoil on a pilot area of 80 hectares to raise the pH and stabilise the organic matter and fix the heavy metals.

The expected benefits are:

Formation of stable heavy metal minerals in the soil as well as reducing of heavy metal dislocation (WILKE et al. 1996, HOFFMANN & RENGER 1998)
Decrease of toxicological potential and a decrease of ill effects on plants and microorganisms (KANDELER et al. 1998).
Long-term increase of nutrient storage ability as well as a release of nutrients from mineral weathering which serve as mineral fertilizer for tree-crops.
Facilitation of reforestation by increasing silt and clay content (improving water storage capacity) (SCHLENTHER et al. 1996).
Reduction of groundwater formation and absorption of mobile heavy metals with soil water (effective slowdown of pollutant dislocation) due to fast clay and silt inputs on healthy forest-crops.
Displacement of the dominant couch grass ( Agropyron repens) by covering it with loam for at least four month and thus enabling other soil-borne seeds to germinate.
Formation of more stable soil aggregates by increased clay content and thereby reduced mass transfer by leaching.

Tiergarten

The study-site Tiergarten serves for documentation of long-term development proceedings in inner -city locations. The Tiergarten soils are characterized by small-scale heterogeneities due to different natural and anthropogenic applied substrates, damages due to intensive use like compaction of soil and treaded down vegetation.