SUITMA 2005 Cairo - Ecological properties of paved urban soils
SUITMA 2005 Cairo
| This abstract is about one of the papers of the Cycling of city fluids and solid refuse theme of the SUITMA 2005 symposium. |
| Gerd Wessolek,i | Thomas Nehls.i |
- i - Department of Soil Conservation, Technical University of Berlin, Berlin, Germany.
To judge sealing of soil and interventions in locations in the framework of city and water management planning quantitative data relating to soil properties, climate and water cycles are required. The assessment of substances gains increasingly in importance; notably if impacts by emissions, motor traffic or by abandoned polluted sites have to be considered.
By sealing notably the natural water cycle is remarkably changed. The actual evapotranspiration is essentially reduced by sealing measures to the benefit of surface runoff (canalizing). Infiltration, i.e., deep percolation rate reaches still orders of magnitude as below areas covered by vegetation. Also the heat balance has extremely changed in the urban area: the higher the building density will be the greater will be heating up in summer.
The accumulation of different, mostly airborne substances and particles alters the ecological functions of the seam filling material of freshly constructed pavements in only a few years. We conducted several studies concerning the biological, physical and chemical features of that material. Although the site characteristics include extreme dryness and temperatures up to 60°C we found very high biological activities, even higher than in "natural" soils. Thereby the heavy metal contents are significantly increased compared to background levels of German soils. This seam material furthermore exhibits some very interesting soil physical features such as increased available water capacity. By the increased pollutant load in urban space and a frequently concentrated infiltration of rainwater into unsealed and partly sealed areas often comparatively high pollutant concentrations occur in the topsoil and joint materials. All these features, which are connected to the incorporation of urban inputs lead to immobilization of the investigated soil pollutants. Therefore the investigated material can fulfill some important ecological functions.
