Trace-metal geochemistry of sediments from Baffin Bay

Abstract

The major- (Si, Al, Ti, Fe, Mn, Ca, Mg) and trace-metal (Zn, Cu, Pb, Co, Ni, Cr, V, Li, Cd, Hg) compositions of surficial sediments from Baffin Bay and the sounds (Lancaster, Jones, Smith) leading into the Arctic Ocean have been determined. The sediment composition varies regionally and in response to textural variations and the heavy-metal concentrations are at or near natural levels in relation to their source rocks and other uncontaminated shelf and oceanic sediments.Chemical partition indicates that most of the heavy-metal concentrations (80–99%) except for Cd (27–71%) are derived from various sulphide, oxide, and silicate minerals. The host minerals are predominantly fine grained and have accumulated at the same rate as other detrital clastic material of comparable grain size. As a result, the highest trace-metal concentrations occur in the fine-grained sediments occupying the deepest parts of the sounds and Baffin Bay. Although most of the metals have reached their depositional site by water transport, a small but significant amount has probably been ice rafted to the offshore areas, especially in the northern part of the bay. Only small amounts of the total metal concentrations (1–20%) except Cd (29–73%) are present in the nondetrital fraction. Although difficult to locate exactly, the metals in this fraction appear to reside in ion-exchange positions and in amorphous iron grain coatings and are weakly bound to fine-grained organic matter.Overall, the physical–chemical sedimentological conditions including ice movements are responsible for the dispersal and deposition of fine-grained inorganic and organic matter and for the control of the abundance and distribution of trace metals in this part of the eastern Canadian Arctic.