Testing contaminant mobility in soils and waste materials

Contaminant mobility in soils and waste materials is usually tested by standardized leaching procedures. In Germany, batch experiments are run for 24 h at a liquid/solid ratio of 10.1 (w/w). While the mobilities of metal(loid)s and hydrophilic organic compounds (e.g. phenols) can adequately be tested by automatic titration stands, working at constant pH values (e.g. pH 4 or 10), the mobility of hydrophobic organic chemicals like polycyclic aromatic hydrocarbons (PAHs) or polychlorinated biphenyls (PCBs) is more difficult to determine. Natural solubilizing agents have to be considered, when testing the mobility of hydrophobic organic chemicals. Several leaching experiments utilizing natural and synthetic leaching solutions are presented. Experimental results show that sodium dodecyl sulfate (SDS) is a suitable reference leaching solution. The solubilizing potential of SDS is comparable to the one of the most potent natural leaching solutions (e.g. compost water), and thus represents a worst case. Future leaching tests of the environmental mobility of hydrophobic contaminants should incorporate the solubilizing effects of amphiphilic substances. (C) 1998 Elsevier Science B.V. All rights reserved.