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Major Contaminants of Sediments
Five major types of pollutants are found in sediments:
- Nutrients, including phosphorous and
nitrogen compounds such as ammonia. Elevated levels of phosphorous
can promote the unwanted growth of algae. This can lead
to the amount of oxygen in the water being lowered when
the algae die and decay. High concentrations of ammonia
can be toxic to benthic organisms.
- Bulk Organics, a class of hydrocarbons
that includes oil and grease.
- Halogenated Hydrocarbons or
Persistent Organics, a group of chemicals that
are very resistant to decay. DDT and PCBs are in this category.
- Polycyclic Aromatic Hydrocarbons (PAHs),
a group of organic chemicals that includes several petroleum
products and byproducts.
- Metals, including iron, manganese, lead,
cadmium, zinc, and mercury, and metalloids
such as arsenic and selenium.
Metals, PAHs, and organics listed above are toxic to various
plants and animals, including people. These contaminants tend
to biomagnify as they travel up the food chain. All have been
linked to health problems in people.
Sources of Contaminants
The origins of sediment contamination can be divided into
point and nonpoint sources
of pollution. Point source pollution comes from a specific,
identifiable source such as a pipe. Nonpoint source pollution
cannot be traced to a specific spot.
Point sources include municipal sewage treatment plants,
overflows from combined sanitary and storm sewers, stormwater
discharges from municipal and industrial facilities, and waste
discharges from industry.
Nonpoint sources include stormwater runoff from hazardous
and solid-waste sites; runoff from croplands, livestock pens,
mining and manufacturing operations, and storage sites. Atmospheric
deposition is another source of nonpoint pollution.
contaminated sediment home |
sources |
locating contaminated sediments
species affected |
protecting sediments from contamination
management options |
preventing contaminated sediment
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