Subproject Soil
Water and solute transport of heterogeneous urban sites
Prof. Dr. Gerd Wessolek, Dr. Heiner Stoffregen
Aim of the project is the analysis of the water movement and solute dynamics of heterogeneous urban areas.
The main foci are:
- the combination of soil physical and geophysical methods for the determination of spatial water movement and its temporal variability of these heterogeneous areas and
- the numerical simulations of water and solute movement on this heterogeneous site, which show water repellent phenomena.
Phase II (2004-2007):
In the second phase the focus is on the following topics:
- including the variables for hydrophobic properties in numeric models for water flow in the vadose zone (HYDRUS 1D, 2D und 3D)
- based on this updated model a risk analysis, validated by the measured data, of solute transport on these highly heterogeneous areas
- monitoring three dimensional temporal dynamics and spatial heterogeneity of the water flow using soil physical and geophysical methods
- determination of the temporal and spatial changes in the flow domain
Phase I (2001-2004):
The focus was on the soil physical and –chemical characterisation of the sites as well as on the installation of the intensive measuring areas. The main measurement sites are the Tiergarten Park in the centre of Berlin and the former sewage farm Berlin/Buch. Both places show high small scale heterogeneity in soil chemical and physical properties (fig. 1).
fig.1: soil block (0.8m x 0.8m) sampling at Berlin Buch, organic matter content (%)left and heavy metal Zn (mg/kg-1) right, layers in 20, 35, 50 cm depth
The spatial distribution of the hydraulic functions (saturated/unsaturated conductivity) and bulk density were analysed, as well as the availability of heavy metals and nutrients, pH, organic matter content, the desorption characteristics and water repellency. The experiments were complemented by the detailed chemical and biological analysis of the other subprojects. Measuring areas equipped with automated TDR-probes devices and tensiometers provided us continuously with water content and tension. Water movement through the soils can be observed with high spatial resolution. This made it possible to observe the water movement through the soil with high spatial resolution.
fig.2: soil moisture pattern in 20 cm depth, Berlin Buch, Oct. 2001
The water movement is strongly influenced by water repellency (fig. 2), a phenomenon which can be observed throughout the year. The water repellency occurs mainly in the topsoil, forming structures 10-20 cm in diameter. The improvement of non-destructive soil physical and geophysical methods, such as GPR (fig. 3), geoelectrics and NMR, to detect and observe these water repellent dry spots is one of our main tasks.
fig3.: GPR measurement in the Tiergarten park
Staff:
Dr. Heiner Stoffregen
Karsten Täumer
Christine Ehrlicher
Leif Ikels
Heiko Wonglorz