On the natural enrichment of cadmium and molybdenum in the sediments of Ucluelet Inlet, British Columbia.
Cadmium concentrations in Ucluelet Inlet sediments are usually high compared with most marine environments, ranging up to 8 micrograms g-1. The distribution of the element is closely correlated with Mo, organic carbon and total nitrogen in depth profiles at three stations. Paradoxically, organic carbon concentrations are high in inlet sediments, reaching up to 9 wt.%, although the sedimentation rate determined from 210Pb measurements is low at all three sites (less than 0.03 to 0.28 cm year-1). C:N ratio data indicate a mixed marine-terrigenous provenance for the organic material and a relatively recent increase in the terrigenous proportion which probably represents wood debris associated with logging and log booming activity in the area. The complete absence of Mn enrichments in surface sediments, coupled with qualitative observations that H2S is present at very shallow depths, strongly suggest that the deposits are anoxic very near the sediment-water interface. The Cd and Mo enrichments are not due to anthropogenic inputs but are instead ascribed to diffusion of the dissolved metals from overlying seawater into the slowly-accumulating, organic-rich, anoxic sediments and their fixation in the solid phase as CdS and as a coprecipitate with FeS, respectively.
Pedersen
T F
TF
Department of Oceanography, University of British Columbia, Vancouver, Canada.
Waters
R D
RD
MacDonald
R W
RW
D001955:British Columbia; D002104:Cadmium / Q000032:analysis*; D002244:Carbon / Q000032:analysis; D008982:Molybdenum / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis; D012623:Seawater / Q000032:analysis*; D012987:Soil / Q000032:analysis*
D012987:Soil; D002104:Cadmium; D002244:Carbon; D008982:Molybdenum; D009584:Nitrogen