A watershed is a geographic area that includes all of the land and waterways that drain into a body...
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A watershed is a geographic area that includes all of the land and waterways that drain into a body of water. Sometimes a watershed is called a drainage
A watershed is a geographic area that includes all of the land
and waterways that drain into a body of water. Sometimes a
watershed is called a drainage Basin.
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The definition of food chain is a series of plants and animals,
each of which depends on the one below it for food. A food chain
usually forms part of a much larger food web. The definition of
food web is all of the feeding relationships within an ecosystem.
Each living thing in a food web provides food energy to other
living things within that ecosystem.
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Point-source pollution is water pollution from a single place,
such as discharge pipe at a plant that treats sewage. Non-point
source pollution is pollution that does not come from a single
location, but rather from many sources such as runoff from
farms.
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This silt-laden runoff from a residential area contains not
only soil and clay particles from nearby construction, but also is
likely to contain small amounts of lawn chemicals, oil, grease,
gasoline, and even residues from recent highway de-icing. These are
all examples of pollutants released from nonpoint sources.nonpoint
sources
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Atmospheric pollution Atmospheric pollution (or air deposition)
is another form of nonpoint source pollution, though instead of
polluting via runoff, the pollution falls from the sky. As water
moves through the hydrologic cycle, it falls as rain or snow and
then evaporates into the air from land and surface water.
Pollutants emitted into the air, such as through smoke stacks,
follow this same path, and can be carried through the atmosphere
and deposited into waterways hundreds of miles away from its
source. Acid rain is the most well-known form of atmospheric
pollution. The major sources of atmospheric pollution include coal-
burning energy plants and waste incinerators. The combustion of
fossil fuels and waste (such as from hospitals) produces large
amounts of mercury in the air, a toxic chemical that is fatal to
humans and animals in large quantities. Phosphorus and
polychlorinated biphenyls (PCBs) are also transported to waterways
via air deposition.polychlorinated biphenyls (PCBs)
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PCBs are synthetic (human-made) chemicals first produced in the
late 1920s. They were used as cooling fluids in electrical
equipment and machinery because of their durability and resistance
to fire. DDT was developed as an insecticide in the 1940s, and was
widely used during World War II to combat insect-borne diseases.
DDTs effectiveness, persistence, and low cost made it popular for
agricultural and commercial uses. More than a billion pounds were
used in the U.S. over a 30-year period.
