Artificial groundwater recharge in Stockholm III. An experimental study of chemicalprocesses in the unsaturated zone

Untreated water from a eutrophic lake (pH 7.0 – 7.5) was infiltrated into columns (diameters 0.3 m; height 4 m) filled with coarse soil material, to test the retention capacity with respect to dissolved organic matter. After 8 months the retention was not more than 15% (initial TOC concentration 5.7 – 6.5 mg C/l). There are indications of a selective retention of hydrophobic and hydrophilic acids.