Investigation of heavy metal and radionucilde mobility in soils based on soil characteristics and a critical evaluation of standard leaching tests

In the framework of impact assessment studies, two NORM sites were sampled. The first site is a Belgian NORM site consisting of an overgrown CaF2-sludge, contaminated with radionuclides and heavy metals, originating from local phosphate industry. On these samples the soil characteristics (density, field capacity, pH, soil texture and organic content) and the solid-liquid distribution coefficient (Kd) value of uranium were determined to be used in a model of a forest ecosystem. The activity within the soil samples was determined externally. Out of the determined soil characteristics and activity measurements a lower activity and density were seen in the top layer and that all samples classified as clay according to the USDA soil classification. The Kd-value was determined by a batch sorption test and ranged from 9767-22975 g cm-³. The second soil samples were taken from a historically contaminated site contaminated with heavy metals (e.g. As, Cd and Zn) and natural (238U, 226Ra, 210Pb, 210Po) and artificial (137Cs, Am, Pu) radionuclides. The aim was to test standard leach tests and assess the leaching of these elements and heavy metals (Zn, As, Cd and Pb) from the soil, but the acidification step in the procedures was overlooked. Other analyses performed were organic and inorganic carbon analysis (TOC and TIC), Energy Dispersive X-ray fluorescence (ED-XRF). Fourier Transform Infrared Spectroscopy (FTIR) on the solid soil samples potentially reveal mineralogical information of the soil, and UV-VIS spectroscopy on the soil leachates clearly show different humic acid behavior as function of pH.