(Table 5) Experimental hydrodynamic parameters for different soil types obtained in the Lüchow-Dannenberg district, Lower Saxony

In three typical sandy soils of Northern Germany the mobility of radioactive fission products of technetium, iodine, ruthenium and zirconium have been investigated in dependence of the hydrodynamic and physico-chemical soil properties. The laboratory experiments, which simulated fall-out events, used soil columns (1 m length, 30 cm diameter) taken as undisturbed as possible. By measurements of the breakthrough curves in the percolate and of the depth distribution of radionuclides in the soil columns after 6 months the average transport velocity could be determined. These values could be compared with the average water velocity measured by 3H tagging. Three qualitative mobility relations were observed: Ranker: Tc > Ru > I > Zr; Podsol: Tc > Ru > I > Zr; Brown forest soil: Tc = Ru > I > Zr. Relations between some physico-chemical soil properties and the retardation of radionuclides due to adsorption could be observed (eg. retardation of iodine and technetium by organic substances). The average retardation factors of the radionuclides and the hydrodynamic soil parameters are used in a model which gives a quantitative assessment of the hazard of groundwater contamination by a fall-out event in areas covered with comparable soils.

(Table 1) Physical properties of basalts from DSDP Holes 69-504B and 70-504B

A detailed study of physical properties was made on core samples from Deep Sea Drilling Project Hole 504B. The measured properties are density, porosity, sonic velocity, electrical resistivity, and fluid permeability. Basalts from this young oceanic crust have higher density and sonic velocity than the average DSDP basalts. Porosity (and temperature) dependences of physical properties are given by V = Vo - a-phi; roo = roo-0 exp(E*/RT)phi**-q; k = k0' phi**2q-1; where V is the sonic velocity (km/s), Vo = 6.45 (km/s), a = 0.111 (km/s %), phi is the porosity (%), roo is the electrical resistivity (ohm m), roo-0 = 0.002 (ohm m), E* = 2.7 (Kcal/mol) for fresh basalts, RT has its usual meaning, q = 1.67 ± 0.27, k is the permeability, k0' = (1 to about 10) x 10**-12 (cm**2). Porosity distribution in the crust in this area is estimated by combining the seismic velocity distribution and velocity-porosity relation. Because of the rapid decrease in porosity with depth, resistivity increases and permeability decreases rapidly with depth. The decreasing rate of permeability with increasing depth is approximately given by k(cm**2) = 2 x 10**-10 exp(-z (km)/0.3).