## 2 Experimental
### Flushing of Soils with Oil-in-Water Emulsions
There were some fluctuations in the results, which can be attributed to inhomogeneities in the sample. The trials were performed at room temperature and ambient pressure. A agitation was performed for 30 min. As Table 4 shows, the initial hydrocarbon contamination of the clay was as high as 12,100 ppm. Flushing with milk yielded a very low reduction. Likewise, pure rapeseed oil did not wash out much of the hydrocarbons. Coconut milk was better in this matrix, and the best result was achieved with a rapeseed-oil-in-water emulsion (50%). The residual hydrocarbon contamination was 2090 ppm, which means that 83% of the contamination was washed out. In the next step, it was investigated how much plant oil remains in the soil after flushing (see Table 5). \begin{table}
\begin{tabular}{c c c c} \hline \multicolumn{4}{c}{**Clay, Untreated**} \\ \hline \multicolumn{4}{c}{Clay, extracted with pure rapeseed oil} \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 97.8 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 7820 \\ \hline \multicolumn{4}{c}{Clay, extracted with pure coconut milk (19\% fat)} \\ \hline Parameter & Method & Unit & Value \\ \hline Dry matter & EN 14346:2006 & \% & 69.4 \\ \hline Hydrocarbons (C10–C40) & EN 14039:2004 & mg/kg & 4860 \\ \hline \end{tabular}
\end{table} 
Table 4: _Cont._ \begin{table}
\begin{tabular}{c c c c} \hline \hline Medium & Solvent [g] & Captured [\%] & Captured after flushing w. water once [\%] & Captured after flushing w. water twice [\%] \\ \hline Pebbles & Water/oil & 84 & 91.37 & 97.64 \\ \cline{2-4}  & 900/100 & & \\ \hline Pebbles & Water/oil & 90.85 & 99.35 & 99.71 \\ \cline{2-4}  & 900/100 & & \\ \hline Medium & Solvent [g] & Captured [\%] & Captured after flushing w. water once [\%] & Captured after flushing w. water twice [\%] \\ \hline Coarse sand & Water/oil & 63.15 & 71.67 & 78.75 \\ \cline{2-4}  & 900/100 & & \\ \hline Coarse sand & Water/oil & 57.77 & 71.21 & 76.77 \\ \hline Medium & Solvent [g] & Captured [\%] & Captured after flushing w. water once [\%] & Captured after flushing w. water twice [\%] \\ \hline Clay & Water/oil & 56.11 & 73.26 & 79.83 \\ \cline{2-4}  & 900/100 & & \\ \hline Clay & Water/oil & 53.9 & 67.82 & 74.67 \\ \cline{2-4}  & 900/100 & & \\ \hline Medium & Solvent & Captured [\%] & Captured after flushing w. water once [\%] & Captured after flushing w. water twice [\%] \\ \hline Clay & Oil & 81.5 & 86.37 & 89.7 \\ \hline (Clay & Oil & 80.89 & 87.56 & 89.61 \\ \hline \end{tabular}
\end{table} 
Table 5: How much plant oil stays in the ground after flushing with the emulsion?As Table 5 shows, the experiments were performed with three model matrix materials: pebbles, coarse sand and clay. The clay was tested dry and wet. A quantity of 10% of rapeseed oil in water was added to the solids, and the amount of oil that could be captured after passage through a column on a net was determined. Additionally, the flushing of that column with water (same mass as the solids) was performed once and twice in order to further reduce the amount of rapeseed oil in the material. It can be seen that by the washing activity, the residual oil is reduced. Additionally, it can be seen that dry clay retains more plant oil than wet. With a very coarse ground (pebbles), almost all plant oil can be extracted, whereas clay will retain approx. 10-20% of the plant oil. In Figure 6, one can see an IBC from the field trials in Droesing with two phases: groundwater with a layer of mixed plant oil, and mineral oil floating on top. The main experiments carried out in the non-saturated zone during the field trials are tabulated in Table 6:  
The following summary can be given for the non-saturated zone:  
* Approx. 50-85% of mineral hydrocarbons from the soil can be washed out in one passage with 10% plant oil in water;
* The method is suitable for permeable soil (gravel, sand), but not for clay;
* Max. 15-50% of the plant oil will remain in the soil, which can be reduced to 10-30% and sometimes 5% by washing with water.