Abstract
Monitoring of contaminant accumulation in
fish has been conducted in East Fork Poplar Creek (EFPC)
in Oak Ridge, Tennessee since 1985. Bioaccumulation
trends are examined over a twenty year period coinciding
with major pollution abatement actions by a Department of
Energy facility at the stream’s headwaters. Although EFPC
is enriched in many contaminants relative to other local
streams, only polychlorinated biphenyls (PCBs) and mercury
(Hg) were found to accumulate in the edible portions
of fish to levels of human health concern. Mercury concentrations
in redbreast sunfish were found to vary with
season of collection, sex and size of individual fish. Over
the course of the monitoring, waterborne Hg concentrations
were reduced[80%; however, this did not translate into a
comparable decrease in Hg bioaccumulation at most sites.
Mercury bioaccumulation in fish did respond to decreased
inputs in the industrialized headwater reach, but paradoxically
increased in the lowermost reach of EFPC. As a
result, the downstream pattern of Hg concentration in fish
changed from one resembling dilution of a headwater point
source in the 1980s to a uniform distribution in the 2000s.
The reason for this remains unknown, but is hypothesized
to involve changes in the chemical form and reactivity of
waterborne Hg associated with the removal of residual
chlorine and the addition of suspended particulates to the
streamflow. PCB concentrations in fish varied greatly from
year-to-year, but always exhibited a pronounced downstream
decrease, and appeared to respond to management
practices that limited episodic inputs from legacy sources
within the facility.
