## 2 Experimental
### Flushing of Soils with Oil-in-Water Emulsions  
The oil-in-water emulsions prepared as described above were tested in various soils in order to flush them and remove the contained mineral hydrocarbons. In Figure 5, a lab experiment is shown where water and emulsions were allowed to travel through glass columns (250 cm) to determine the k\({}_{I}\) values. Figure 4: Setup of the field trials. **Left**: 300 L stainless steel mixer. **Right**: Close-up of the emulsion. It was colored for better visibility. Figure 5: Lab trials to determine the speed with which water and emulsions travel through the soil. Sand from the brownfield N77 was used as a substrate. It was compressed in the glass columns to obtain comparable conditions. The three curves are the first, second and third passages, with dry and wetted sand. The insert shows the experimental setup. Emu = emulsion; The * stands for trials where the sand was wet. From Figure 5, the following k\({}_{\rm f}\) values can be read: 4.6 \(\times\) 10\({}^{-4}\) m/s for water and 3.2 \(\times\) 10\({}^{-4}\) m/s to 2.1 \(\times\) 10\({}^{-4}\) m/s for oil-in-water emulsions. For clay, virtually no permeability of either water or emulsion could be measured, with estimated k\({}_{\rm f}\) values on the order of 10\({}^{-9}\) m/s. In the next step, the maximum extraction yields of the soil flushing were estimated by lab experiments. A total of 500 g of soil were intensely mixed with 500 g of solvent (water and emulsions). Table 3 presents the results for sand, and Table 4 for clay. \begin{table}
\begin{tabular}{c c c c} \hline \multicolumn{4}{c}{**Clay, Untreated**} \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 97.7 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 12,100 \\ \hline Clay, extracted with milk (3.6\% fat) & & \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 82.4 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 10,800 \\ \hline Clay, extracted with emulsion (50\% rapeseed oil in water) & & \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 88.1 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 2090 \\ \hline \end{tabular}
\end{table} 
Table 4: Extraction experiments with clay from Droesing. \begin{table}
\begin{tabular}{c c c c} \hline \multicolumn{4}{c}{**Sand, Untreated**} \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 96.9 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 1020 \\ \hline \multicolumn{4}{c}{Sand, extracted with milk (3.6\% fat)} \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 92.3 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 1050 \\ \hline \multicolumn{4}{c}{Sand, extracted with emulsion (50\% rapeseed oil in water)} \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 87.9 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 468 \\ \hline \multicolumn{4}{c}{Sand, extracted with pure rapeseed oil} \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 98.2 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 820 \\ \hline \multicolumn{4}{c}{Sand, extracted with pure coconut milk (19\% fat)} \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 89.9 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 704 \\ \hline \end{tabular}
\end{table} 
Table 3: Extraction experiments with sand from Droesing. The experiments were repeated three times and the results were averaged. The sand sample contained 1020 ppm of hydrocarbons prior to the flushing experiments. With milk, no reduction could be achieved, and with pure rapeseed oil and coconut milk there was hardly a reduction in the hydrocarbon content of the sand. The emulsion of 50% rapeseed oil in water, however, yielded a reduction to 468 ppm, which is a flushing of 54%.