The aim of this study was to analyse and compare the heavy metal retention of different embankment soils. It should be examined whether the infiltration of road runoff into stable embankments leads to an exceedance of the trigger values of the Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV) in soil solution or not. In a first step metal retention of seven different embankment constructions was analyzed in column experiments. Based on the obtained results three different embankment constructions were chosen to be investigated in a field study. A lysimeter site was constructed at the BAB A115 highway in order to determine heavy metal retention of embankment constructions from road runoff. The following materials were analysed for heavy metal retention capacity: a topsoil (OB), a base course material (BS), a mixture of base course material (BS) and topsoil (OB), containing 15% topsoil (OB15). The variants BS and OB15 have a sufficient bearing capacity, the OB was used as a non-stable reference. Additionally, three further lysimeters were installed to collect the road runoff. The mean solute concentration in the soil solution of all variants are do not exceed the trigger values of the BBodSchV (except for Cu at OB). Since the BS variant has the highest infiltration capacity (5,5*10-6 m*s-1) a higher rate of road runoff infiltrates compared to the other variants. Even though metal concentrations are lowest, this leads to higher metal loads. The predictions of the numerical modelling performed also indicate that the OB15 is the most appropriate variant for metal retention from road runoff. Based on the previous results it can be assumed that stable embankment constructions provide a sufficient heavy metal retention capacity. It is recommended to define a minimum share of fine soil material for materials used for stable embankment constructions to reduce heavy metal loads in the embankment area. (Author/publisher)
Samenvatting