Nonpoint Source Pollution
Pollutants from Nonpoint Sources: Pesticides and Toxic Chemicals |
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![Pesticides applied to agricultural fields and lawns Pesticides applied to agricultural fields and lawns](media/pol012a_240.jpg) |
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Pesticides
applied to agricultural fields
and lawns can end up in a waterbody
as a result of “spray
drift”. |
![](https://webarchive.library.unt.edu/eot2008/20090508083856im_/http://oceanservice.noaa.gov/siteart/imagebar.jpg) |
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Pesticides typically enter a waterbody through surface water runoff, often from a farm field or from neighborhoods where they are applied on lawns. Pesticides can also enter a waterbody as a result of “spray
drift.” This occurs when the pesticide is sprayed over an area,
and the wind blows some of the spray into a
nearby waterbody.
Pesticides are designed to be toxic to a target
organism, but they often kill other organisms as well. The insecticide
azinphos-methyl, for example, is used to control insects such as biting
mites and aphids. It is also very toxic to fish and birds, however.
For the most part, today's pesticides do not build up in the tissues
of animals -- a process called bioaccumulation -- to the extent that
older compounds like DDT did. On the other hand, many of the compounds
used today are toxic at very low concentrations.
Toxic
chemicals, such as spilled oils and fuels
in cities, are often washed off streets, down
storm drains, and into waterbodies. Combustion
of fuels in automobiles and factories introduces
hydrocarbons and metals into the environment.
They eventually end up in the water through
atmospheric deposition or runoff. Industrial
facilities without the proper means to control
runoff can also contribute toxic chemicals
to the aquatic environment. The type of chemical that is released depends
on the type of manufacturing done at a facility. Other chemicals, such
as solvents, paints, cleaning solutions and others, originate from
marinas and boating activities.
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![warning sign warning sign](media/pol012c_240.jpg) |
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Spilled
oil that originates from cities and streets
or that is poured down storm drains,
can soak and kill aquatic organisms,
such as these crabs. Click on
image for
larger view. |
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Despite efforts
to control it, contaminated runoff still
results in conditions unhealthy for humans
and aquatic organisms alike, requiring
authorities to close beaches and fisheries. Click
on image for
larger view. |
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