# Case Study on Secondary Building Materials
## 3 Results
### Assessment of PAH-Containing Soil-like Material  
The amended German Federal Soil Protection and Contaminated Sites Decree [21], which will be enforced from August 2023 onwards, contains new requirements regarding the application of soil-like material outside of a rootable soil layer. It is intended to enable the utilization of soil-like materials containing regulated substances in concentrations between the single and double precautionary values, provided that the limit values for the eluate are complied with. The aim of a research project by [PERSON] et al. [26] was to fill data deficits for soil-like materials that meet the aforementioned criteria to promote circular economy and the conservation of natural resources. Different soil-like material types containing PAHs were investigated (see Section 2.2). A major challenge in sample acquisition was the relatively narrow target range of the PAH content, which was between 3 and 6 mg/kg of dry matter (concentration between precautionary limit value and its double value)--considering a high measurement uncertainty at this concentration level mainly caused by the laborious sample preparation steps before analysis [28]. Finally, twelve of the twenty-three investigated materials had a total PAH content in the desired range (see Table 1 and Figure 4). From the twelve soil-like materials inside of the desired PAH content range, only one material from an urban source (STB12) failed the to achieve the leaching limit value for PAH, meaning that further utilization of the material is excluded. This could be due to fire exposure, as indicated by the distribution pattern of PAHs in urban soil. Comparing column and batch tests, larger differences for the eluate concentrations of the sum of PAHs occurred only for materials whose total content was above the target content range (i.e., above 6 mg/kg, see Figure 4). Consideration of the additional inorganic parameters measured (limit values for metals) led to the exclusion of another five materials regarding the recovery potential (Table 1). For sulfate, only a limit value for the eluate has to be taken into account. All materials which exceeded the limit value for sulfate (BAG 5 to 8, STB 3 and 14, UB/STB 1, 2, and 5) exhibited other exceedances for metals already (see Table 1). Figure 4: Graphical overview of the utilization potential of the soil-like materials investigated, considering PAHs (PLV = precautionary limit value for total content). Overall, as expected, the single PAH compounds with medium molecular sizes (phenanthrene to chrysene) were the most abundant compounds in the eluates for almost all soil-like materials, which is related to the lower stability of compounds with smaller molecules and lower solubility of compounds with larger molecules (Figure 5). Fluoranthene and pyrene most frequently had the highest individual concentrations in the eluates. Higher naphthalene concentrations were observed, particularly in eluates from alluvial soils (AUE) and materials containing tailings (BER). The eluate value for naphthalene was never exceeded for the materials in the target range for the total content of PAH. In the dredged materials (BAG), volatile PAHs were hardly present in the eluates. In the eluates obtained from banquet peeling materials (BSG), the more sparingly soluble PAHs, starting with benzo[b]fluoranthene, were proportionally more released compared to other materials. The benzo[a]pyrene concentrations in the eluates tested were very low and mostly below the analytical limit of quantitation.