Dilution curves will be completed for dredged material discharge, similar to
those already generated for waste disposal techniques. John Proni, AOML
Dilution curves for discharged dredged material have been obtained for
dredged material discharged in the New York/New Jersey mud dump site coordinator
location and in the western boundary region of the Florida Current (Gulfstream) off
Miami, Florida. These curves were obtained using water sample measurements of total
suspended material (TSS) and acoustical backscatter (IB). In both cases the dilution
curves differed above and below the shallow pycnocline.
Shown in Figure 1 is a plot of IB as a function of
distance and time for three discharge events at the New York Bight mud dump site.
All data points were gathered at a depth below the pycnocline. Shown in Figure 2A
and 2B are plots of IB for the 19 meter depth
horizon as a function of time and the 8 meter depth
horizon as a function of time, respectively. Shown in Figure
3 is the total suspended
solids, TSS, as a function of time corresponding to figure 2. Background
TSS levels
at the mud dump site during the study appear to be in the range 5-10 mg/l while at
the Miami discharge site they were 1 mg/l or less.
These curves provide a measure of reduction of concentration of discharged
dredged material for use in exposure and toher studies. While all the scattering
mechanisms contributing to the backscattered sound have not been fully evaluated,
there appears to be a significant correlation between relative reduction in IR and in
TSS over a broad variety of discharge situations.