Bioaccumulation monitoring

In Mitchell Branch, the mean PCB concentrations in redbreast sunfish increased steadily from less than 1 ppm in 1993 to near 4 ppm in 1998 (Figure 1). It is unlikely that the recent remediation activities in Mitchell Branch were the cause of the increase observed in 1998, because the fish were collected in January prior to remedial activities. 
Caged clam monitoring results suggest that the observed increase was associated with SD190, because PCB levels in clams increased substantially over the last five year in clams placed below the SD190 discharge and near the weir in Mitchell Branch, but not upstream of these sites.
In the K1007-P1 pond, PCB concentrations in largemouth bass also increased over 1993-1998 period. Sampling of caged clams at various flow inputs to the pond clearly indicated continuing inputs of PCBs; SD100 continued to be the most contaminated outfall entering the pond.

Figure 1. Mean PCB concentrations (g/g, wet wt.) in fish from Mitchell Branch 1993-1998 (6 fish per site/year).

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Last Modified: April 17, 2001