Transport of Tritium and Heavy Metals in Unsaturated Soils.

Infiltration column experiments were performed to assess the reactivity and mobility of As, Cd, Cu, Ni, and Zn under unsaturated flow conditions in soil. A mixed solution of As, Ni, and Zn was introduced into a 30-cm air-dry Commerce silt loam packed column.  The heavy metal pulse was followed by a pulse of phosphate solution. Breakthrough results indicated early arrival of As in the effluent solutions when compared to Ni and Zn. The recoveries of applied As, Ni, and Zn were of 91%, 105%, and 71%, respectively. These results strongly indicate that, application of P pulse resulted in increased As mobility. In contrast, application of P pulse resulted in reduced mobility of Ni and Zn. In a second soil column, tritium, as a tracer, was mixed with the heavy metal solution of Cd, Cu, and Ni.  This mixed pulse also followed by a pulse of phosphate solution. Complete recoveries of applied Cd and Ni were obtained whereas 51% of Cu was recovered in the effluent. Earlier arrivals of Cd and Ni in the effluent solutions were observed when compared to Cu. Infiltration was characterized based on wetting front and tritium measurements. Multireaction approaches were used to describe the transport results and amount sorbed vs. soil column depth for all heavy metals used.