Geochemical Partitioning of Pb, Zn, Cu, Fe, and Mn Across the Sediment-Water Interface in Large Lakes

摘要

The early diagenetic remobilization of Mn, Fe, Zn, Cu, and Pb was evaluated by studying the geochemical partitioning of the metals among hydromorphic phases (as operationally defined by sequential-chemical extractions) in interfacial sediment (fluff) and in the sediment column at a site in the Caribou sub-basin, Lake Superior. The fluff was collected with a vacuum/filtration system developed for the submersible Johnson Sea-Link II and the sediment column by gravity coring. The results show that: Pb, Cu, and Zn exhibit sediment profiles in which their concentrations decrease with depth for total metal and some of the hydromorphic phases; Mn and Fe profiles are the result of early diagenesis; each of the metals is uniquely partitioned among the phases and the partitioning changes from the fluff to the sediment column and with depth; and the concentrations of Zn, Cu, and Pb in the fluff are higher than those in the sediment column and in some instances, appear to be an exponential extrapolations of the latter. The results are interpreted to indicate that the metals are remobilized during early diagenesis and that the fluff may be chemically unique compared to the sediment column, perhaps being similar to interfacial sediments identified in deep marine environments.