Understanding the partitioning processes of mobile lead in soakaway sediments using sequential extraction and isotope analysis

Lead (Pb) isotopic data were used in this study to first distinguish the partitioning of anthropogenic and natural lead in different fractions, obtained by BCR sequential extraction, and then to anticipate their mixing process in the soakaway sediment of artificial infiltration facilities (AIF). Total metal content was found higher in soakaway sediment samples than that of soil. The lowest Pb-206/Pb-207 ratios were mostly observed in exchangeable fractions of soil and sediment samples, while residual fractions mostly showed the highest Pb-206/Pb-207 and Pb-208/Pb-207 ratios than those of other fractions. In general, both ratios were higher in the soil than those of sediments. Further among soil samples, residual fraction of bottom soil exhibited higher ratios than surface soil indicating higher contribution of natural lead with depth. In addition, the difference in Pb content, partitioning and its isotope signature among four sediment samples were also investigated considering their sampling locations. The plot of Pb-206/Pb-207 versus Pb-208/Pb-207 showed two well demarcated cluster formations by soil and sediments samples that describe the partitioning between anthropogenic and natural lead; and some points falling in between soil and sediment samples pertinently illustrated the mixing processes between these two different pools of lead.