Fate, Transport and Tranformation of Toxic Substances: Significance of Suspended Sediment and Fluid Mud

Nichols, Maynard
Harris, Richard
Thompson, Galen
Nelson, Bruce
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This research aimed to determine the distribution of selected metals in suspended material and fluid mud, to identify potential zones of toxic accumulation, and to trace their transport routes. Observations of flow,salinity, suspended maierial, pH, and dissolved oxygen were accomplished in Bay-wide longitudinal sections and at four anchor stations in the ncrthern Bay between March 1979 apd April 1980 The observations cover a range of conditions, including seasonal high-low river discharge. sediment influx, neap spring tide range, and oxygenated-anoxic water. Samples of suspended material, fluid mud, and bed sediment were analyzed for their particle size, organic matter, and metal content. Metal concentrations of As, Cu. Mn, Ni, Pb Sn, and Zr, in fluid mud and bed sediment per gram of material decrease seaward from a maximum in the Baltimore-Susquehanna Rtver Area. The metals Mn, Pb, and Zn are four to six times greater than Fe-corrected average shale, indicating major human input and significant accumulation in this zone. Metal concentrations rf Cd, Cu, Pb. Ni, and Zn are maximal in surface suspended material from the Central Bay. They are higher than landward near potential sources and they exceed concentrations in bed sediment 2 to 80 times The enrichment is not natural compared to average shale or plankton, it is most likely created by bio-accumulation. Transport of particle-associated metals from major sources follows either hydrodynamic pathways leading to particle accumulations by the estuarine circulation, or bio-ecological routes leading to bio-accumulation. Management and monitoring strategies are provided to reduce potentially toxic metals to acceptable levels and warn management agencies of toxic hazards.
Toxics , Transformation , Suspended Sediment , Fluid Mud