Contaminants
are introduced into the Sound from sewage effluent, disposal of dredged
material, industrial discharge, urban and agricultural runoff, atmospheric
deposition, and combined input from major rivers. In the ocean, many contaminants
stick to sediment particles and are deposited on the seafloor. The sediments,
and the contaminants associated with them, accumulate on the sea floor over
time and provide a record of past events. In addition, contaminant distributions
can be used to identify rates and patterns of modern sediment movement.
Knowledge of the magnitude of contaminant concentration in sediments is
important for regulation of contaminant discharges as well as management
of the natural resources throughout the Long Island Sound watershed. |
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Figure 1. Contaminants have entered the
Sound from three hundred years of population growth and industrial activity.
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Sediments are composed of small particles
of soil, clays, and sand that are carried to the ocean by rivers and wind,
or are eroded from rocks. These materials sink to the seafloor and become
part of the sedimentary record along with the remains of marine plants
and animals that have died. The sediment particles may be composed of
many different minerals and organic substances. Some particles, such as
clays, iron-oxide minerals, and complex carbon molecules interact chemically
with pollutants and hold them in the sediments. Tiny shells from marine
organisms can remain intact for thousands of years and can be used to
identify past environmental conditions.
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Figure 2. Scanning electron
microscopy image that shows Clostridium perfringens bacteria in
a matrix of fine sediment particles found in a sediment core sample collected
in Long Island Sound.
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Figure 3. Concentration map of the distribution
of Clostridium perfringens in Long Island Sound sediments.
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Clostridium perfringens
Link to Clostridium perfringens results
in USGS
Open-File Report 00-304 and in the Journal
of Coastal Research.
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Figure 4. The distribution of lead (Pb)
concentrations in the surface sediments (0-2cm) of Long Island Sound.
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Surficial Metal Contamination
Link to Surficial Metal Contamination
results in USGS
Open-File Report 00-304 and the Journal
of Coastal Research.
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Figure 5. Mercury concentrations in sediment
cores record a history of contamination from population and industrial
centers.
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Mercury Enrichment
Link to Mercury results in USGS
Open-File Report 00-304 and in the Journal
of Coastal Research.
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Figure 6. Distribution of
total organic carbon in the sediments of Long Island Sound. Contours are
in weight percent. Block diagrams explain map units.
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Total Organic Carbon
Link to Total Organic Carbon
results in USGS
Open-File Report 00-304 and the Journal of
Coastal Research.
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U.S. Department of the Interior |
U.S. Geological Survey
