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June 10-14, 2002 - Victoria, British Columbia, Canada
Ephemeral mud deposits in the Mississippi River Delta: Evidence from down-core trace metal profiles.
Presenters: Peter W. Swarzenski and Pamela L. Sutton
The Mississippi River, which traverses one of the most industrialized corridors of the world, exhibits very low concentrations of many classes of dissolved contaminants. Profiles of trace metal concentrations in sediment cores were determined during a high-flood stage condition in the Mississippi River delta region. The observed increased water discharge in the lower Mississippi River effectively scoured the riverbed, thus resuspending fine-grained sediments back into the water column. Clear evidence of such resuspension and remobilization is observed in the solid phase metal profiles from sediment cores. In these ephemeral mud deposits, the down core distribution of trace metals is variable to a depth of about 60cm. In contrast, below 60cm the sediments are less susceptible to scouring and remobilization. Such dynamic transport processes across the sediment-water interface may play an important role in the fluvial delivery of Mississippi River sediment and associated chemical constituents to the Gulf of Mexico.
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