? 1—What is Pollution? 32 Environmental Pathways
Small particles of sand, soil, clay, and other miner-als
are washed into rivers, lakes and streams from
the land. Often these come from construction proj-ects
or paved areas, but they can also come from
natural runoff or erosion. Stream channels and
harbors that have been filled with sediment often
need to be dredged. Sediment can harm wildlife
by covering nests of fish or by clogging the gills of
fish and shellfish.
Petroleum (gas/oil) Products
Oil spills, such as the Exxon Valdez spill, kill fish,
seabirds, shellfish, and aquatic plants. However,
there are many other ways that petroleum prod-ucts
(such as oil, gasoline, and kerosene) can
contaminate water. They can seep into groundwa-ter
from damaged or corroded underground stor-age
tanks, be washed into waterways from drive-ways,
streets or service stations, or be released
from ships, refineries, or drills. Petroleum products
are poisonous to many animals. Additionally,
waterbirds cannot fly if they get oil on their feath-ers.
Heated or Cooled Water
Electric power plants generate large amounts of
heated water. This warm water can’t carry as
much oxygen as cooler water. If oxygen cannot be
returned to the water, fish and other aquatic ani-mals
can be harmed. Cooler water is sometimes
released by deep dams; this too can damage
aquatic animals and plants that require warmer
temperatures to survive.
Other organic wastes can also get into the water.
These include natural animal and plant products
such as wood pulp or food by-products. These
products also contain nutrients for bacteria and
algae. The concentration of bacteria will increase
if too much organic waste gets into the water.
These bacteria will then use up the oxygen in the
water, and fish will die.
Untreated sewage and runoff from farms, stock-yards,
and barns can contain viruses and bacteria
that are very danger-ous
to humans. People
can contract cholera,
typhoid fever, dysen-tery,
other diseases if they
drink or come into con-tact
with water that has
been polluted this way,
or if they eat fish or shellfish from polluted water.
Human and animal wastes also contain nutrients
and act as a fertilizer in water. Bacteria feed on
the nutrients and use up all of the oxygen in the
water. This kills many aquatic animals and plants.
Detergents, pesticides, herbicides, salts, mineral
compounds, and other inorganic compounds are
harmful to water ways. They come from factories,
mines, agriculture, factories, households, and
sometimes from natural sources as well. Many of
these chemicals are poisonous to fish and other
animals or cause damage to structures, such as
boats or water purification equipment.
Runoff from farms, gardens, lawns and golf cours-es
sometimes contains excess fertilizers. When
high concentrations of these fertilizers get into
water, they cause large amounts of algae to grow.
The algae feed on the nutrients in the fertilizer,
just as crops would; once they use up all of the
nutrients, the algae die and are themselves eaten
by bacteria. The bacteria use up all the oxygen in
the water, which makes the water unsuitable for
fish, shellfish, and other animals.
Normal water is not usually acidic. However,
plants and animals can be harmed or killed by
water that has been made acidic by inorganic
Types of Water Pollutants Handout
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