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Document Title:
Sediment Quality within the Impounded Reaches of Cape Fear River Locks and Dams
AUTHOR(S):
Tom Augspurger Christopher G. Ingersoll James L. Kunz Sara E. Ward N. E. Kemble
PAGES:
1 - 178
PUBLICATION DATE:
August 2007
ABSTRACT:
This report documents an evaluation of chemical contaminants in, and toxicity of, sediments
collected from impoundments created by locks and dams on the Cape Fear River in Bladen and
Cumberland Counties, North Carolina. Twelve whole-sediment samples from within the
impounded reaches of the three locks and dams were collected in November 2006. All samples
were analyzed for elemental contaminants and polycyclic aromatic hydrocarbons (PAHs), and a
subset of nine of the samples were used in toxicity tests. Whole sediments had no significant
effect on survival or growth in 28-d toxicity tests with Hyallela azteca (freshwater amphipod) or
in 10-d tests with Chironomus dilutus (freshwater midge). In 2-d sediment elutriate (waterextractable
fraction) tests with Ceriodaphnia dubia (freshwater cladoceran), statisticallysignificant
reductions in survival occurred in four of the nine exposures. Pairwise correlation
analyses indicated several whole-sediment and elutriate water chemistry variables were
significantly and negatively correlated with C. dubia survival. Of the correlated variables,
elutriate manganese had among the strongest correlation (r2 = 0.79, p = 0.0006) and the most
plausible biological association with reduced C. dubia survival because some elutriate
manganese concentrations exceeded published lethal concentrations for C. dubia in water
exposures. All elemental contaminants for which published freshwater whole-sediment
threshold effects concentrations (TECs, concentrations of contaminants in whole sediment below
which adverse effects to sensitive aquatic organisms are not expected to occur) are available
were less than their corresponding TECs and are therefore considered toxicologically
insignificant. Sediment PAHs with published freshwater whole-sediment TECs were in excess
of TECs at two of the 12 sampling stations (river mile 112.9 near Fayetteville and river mile 88.5
about 0.2 miles upstream of Tar Heel Landing Road). Five individual PAHs exceeded TECs at
these locations, but no samples exceeded the probable effects concentrations (PECs,
concentrations of contaminants in whole sediment above which adverse effects to sedimentdwelling
organisms may be expected). Based on review of existing data (Tier 1) and results of
sediment chemistry and toxicity tests (Tier 2 and 3), contamination in surface sediments behind
Cape Fear River locks and dams is unlikely to be a concern in-place. Mobilization of sediments
may be a short-term water column concern based on the elutriate toxicity test results. While
sediment re-suspension and contaminant release in the elutriate tests may be near a worst case
simulation of actual conditions following sediment disturbing activities, additional synthesis is
needed to characterize the nature and magnitude of this issue. In particular, data regarding the
modeled or measured sediment re-suspension caused by specific sediment disturbing activities
(e.g., dredging, dam alterations, etc.) will help put the elutriate test results in context for normal
sediment management practices. Sediment disturbing activities proposed for the Cape Fear
River would benefit from development of a sediment management plan to address these issues.
DOCUMENT LINK:
http://www.fws.gov/raleigh/pdfs/Cape_Fear_Sediment_Quality_August_2007_(with_appendices).pdf, 4 MB
ADDITIONAL LINKS:
U.S. Fish and Wildlife Service - Raliegh, North Carolina, Ecological Services Field Office
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