Lead Mobility in Calcareous Soils

Abstract

The mobility and reactivity of heavy metals such as Pb, Cd, and Cu in the soil system is of great significance because of their potential influences on their concentration levels in the soil solution as well as water in streams and lakes. In this study, surface and subsurface soil samples were collected from an area near Bustan in the northwestern desert of Egypt. Soils were used to investigate Pb mobility in a calcareous soil and the subsequent influence of Cd and Cu on Pb release. Miscible displacement column experiments indicated that Pb was strongly sorbed (99.5%), with less than 0.5% recovery of Pb mobility in the effluent solution. The influence of subsequent Cd and Cu pulse applications did not result in Pb release from both surface and subsurface Bustan soils. Distribution of the amount of heavy metals retained versus depth in the soil column indicated that more than 85 to 93% of Pb applied was retained in the surface 2 cm. In addition, Pb was mainly associated with oxidizable as well as the carbonate and oxide fractions. Based on effluent results, the surface and subsurface soil exhibited affinity in the order of Pb > Cu > Cd. Lead exhibited high mobility when applied to the reference sand, and the amounts retained by each reference sand column were similar regardless of Pb concentration of the input pulse. Therefore, we conclude that sorption capacity for Pb in this reference sand material was attained.