Distribution of
Trace Elements in Sediments and Aquatic Biota in Streams of the Santee
River Basin and coastal drainages, North and South Carolina
Thomas
A. Abrahamsen
U.S.
Geological Survey, Stephenson Center, Suite 129, 720 Gracern Road Columbia,
South Carolina, 29210-7651, USA
Abstract
As part of
the National Water Quality Assessment (NAWQA) Program of the U.S.
Geological Survey, 26 sediment samples and 30 tissue samples were
collected from streams of the Santee River Basin and coastal drainages
(SANT) in North and South Carolina, during 1995-97. Samples were analyzed
for the concentrations of 43 elements in sediments and 21 elements
in tissues. Nine of the elements have been designated as priority
pollutants by the U.S. Environmental Protection Agency. Within the
SANT study area, there was a distinct concentration gradient for seven
of the nine elements. The concentrations of chromium, copper, nickel,
and zinc in sediments decreased from the Blue Ridge Ecoregion through
the Southeastern Plains to the Coastal Plains. In contrast, the concentrations
of cadmium, mercury, and selenium in sediments increased along the
same gradient. The concentrations of arsenic and lead in sediment
were not significantly different among ecoregions. Those elements
with the highest concentrations were zinc, chromium, and lead. None
of the elements in sediment exceeded the threshold concentration harmful
to aquatic life; they pose no threat to the biota in the steams.
Among the priority
pollutant trace elements in tissue, there was no significant ecoregion
distributional gradient. Copper and zinc were bioconcentrated more readily
by carp (Cyprinus carpio) than by Asiatic clams (Corbicula fluminea).
The clams concentrated selenium and mercury. Chromium, lead, and nickel
were not accumulated, or were rapidly eliminated by clams and carp. Mercury
was the sole element for which fish consumption advisories have been issued
by state regulators in the SANT study area. Mercury concentration in Asiatic
clams in one river was more than an order of magnitude greater than the
concentration in the sediments.
Scatter plots
of trace element data show that there was no significant correlation between
the concentrations of trace elements in sediments and biota. Patterns
of concentration in tissue and sediment imply that only a fraction of
the priority pollutant trace elements in sediment are being bioaccumulated,
and suggest that clams may be assimilating trace elements through routes
other than sediment contact.
--- March 1999
To order SANT NAWQA publications,
please email or call:
Celeste A. Journey
SANT NAWQA Project
Chief
cjourney@usgs.gov
(803) 750-6141
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