A Laboratory Study of the Turbidity Generation Potential of Sediments to be Dredged.
ABCOR INC WILMINGTON MA WALDEN DIV
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In order to understand the effects of physical and chemical factors which control particle settling rates and thereby develop the means to predict the extent of dredging-related turbidity, a series of laboratory jar tests was performed. The turbidity of suspensions of three pure clay samples and eight natural sediments was monitored as a function of time in waters of various salinity, hardness, and pH. The results were statistically analyzed to relate specific sediment and water compositional factors to observed settling rates and to evaluate their relative importance. Additional experiments were performed to characterize the nature of turbidity. While turbidity was found to be extremely persistent in soft fresh waters, hardness 200 mgl and particularly salinity 1-5 ppt induced flocculation and consequently rapid settling. The organics content was the principal sediment component affecting turbidity, with higher organics levels correlated with more rapid settling in salt water. No significant segregation of sediment components was observed during settling, with the exception of coarser silt particles, which settled independently of clay-organic aggregates. A turbidity plume model was developed which accounts for flocculation in suspensions of dredged material.
- Hydrology, Limnology and Potamology
- Civil Engineering