Large-scale field experiments on the mobility of heavy metals (As, Cd, Co, Cr, Cu, Ng, Ni, Pb, Sb, Se, Zn) in groundwater

To understand and assess the effect of accidental spillages and diffuse contaminant sources on groundwater, understanding of the transport behaviour of contaminants is required. Therefore tracer experiments using various contaminants combined with non-reactive tracers were carried out under natural hydrogeological conditions at a GSF test area in Bavaria, southern Germany. This paper deals with the results of heavy metal (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Sr, Zn), DOC (dissolved organic carbon) and EDTA (ethylenediamine-tetraacetic acid) experiments. DOC and EDTA were used for mobilization experiments on the effectively immobile portion of heavy metals. The mobility of heavy metals differs because elements like Cr, Cd, Cu, Pb and Sb are nearly immobile, but the mobility of As, Co, Hg, Ni, Se, Zn is higher and decreases in the order As > Se > Ni > Hg > Zn > Co > Cr. The immobile elements (Cd, Cu, Pb) can be readily remobilized by EDTA, and to a lesser extent so can the mobile elements Co and Ni. Cr and Sb cannot be remobilized by EDTA or DOG. Since heavy metals have become fixed in most river sediments, and EDTA and DOC have become more common in the environment, water supplies based on bank filtration might become contaminated through the remobilization processes.