Fig. 4

ATR-FTIR spectra of (a) groundwater colloids before injection of remedial solution (week-zero); b groundwater colloids after 22.5 weeks of remedial solution injection; c three-meter soil core taken before injection of the remedial solution (week-zero); d three-meter soil core taken after 22.5 weeks of remedial solution injection. The three-meter soil core was taken \(\sim\)14.2 m from the injection point of the remedial solution, adjacent to one of the monitoring wells from which colloids were sampled