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Water Pollution
Thirsty?Thirsty?
Water PollutionWater PollutionWater PollutionWater Pollution is is
the addition of any the addition of any substance that has substance that has a a negativenegative effect effect on water or the on water or the living things that living things that depend on water. depend on water.
The substances The substances that cause water that cause water pollution are called pollution are called pollutantspollutants..
Point source pollution
Sources of pollution are classified, in part, by how they enter a body of water.
Point source pollution is a specific source of pollution that can be identified.
Example: A pipe gushing colored water into a river
Nonpoint source pollution
A widely spread source of pollution that can’t be tied to a specific point of origin is called nonpoint source pollution.
Example: Runoff from a farm field, a street, or a construction site
Effects of PollutantsEffects of Pollutants
Some pollutants can build up in the bodies of living things.
Pesticides are chemicals intended to kill insects and other organisms that damage crops.
An example of a pesticide is DDT.
A very small amount of DDT in water can build up to harmful
levels in living things
Major Sources of Water Major Sources of Water PollutionPollution
The three major sources of The three major sources of water pollution are water pollution are human human wastes, wastes, industrialindustrial wastes, wastes, and and chemical runoffchemical runoff..
Human Waste
Sewage in citiesDuring heavy rains or floods,
sanitary sewers sometimes overflow and can pollute the surface water.
If this happens, people are often told to boil water for drinking and cooking after a flood.
The boiling kills many disease-causing organisms.
Sewage in Rural AreasSewage in Rural Areas
In rural areas, people must be careful where they locate septic tanks.
If a tank is too near a stream or on a hill, wastewater can leak into the stream or flow downhill to the area of a well.
Leaking septic tank
Sewage in Rural Areas
Wastes from cattle, pigs, and chickens can also be a problem in rural areas.
Animal wastes can run off from pastures and barnyards and pass disease-causing bacteria and other kinds of pollution into bodies of water.
Industrial WastesIndustrial Wastes
ChemicalsChemicals, , smokesmoke , and , and heatedheated water are three types water are three types of pollutants produced by of pollutants produced by factories, mines, and other factories, mines, and other industries. industries.
ChemicalsChemicals
Many factory processes Many factory processes involve toxic chemicals involve toxic chemicals and strong acids. and strong acids.
Other toxic wastes are Other toxic wastes are produced as a result of produced as a result of manufacturing and mining manufacturing and mining processes.processes.
Although Although lawslaws control control many many point sourcespoint sources of of chemical pollution, some chemical pollution, some factories still release toxic factories still release toxic chemicals directly into chemicals directly into nearby rivers and lakes. nearby rivers and lakes.
ChemicalsChemicals
Another problem is pollution Another problem is pollution caused by caused by nonpoint sourcesnonpoint sources. .
In the past, many industries In the past, many industries stored toxic wastes in stored toxic wastes in barrelsbarrels or or other containers buried other containers buried underground. underground.
Over the years, however, many of Over the years, however, many of these containers rusted or broke. these containers rusted or broke.
The chemicals leaked out, The chemicals leaked out, polluting both the soil and the polluting both the soil and the groundwater. groundwater.
Barrels of nuclear waste found in an abandoned
German salt mine
Smoke and ExhaustSmoke and ExhaustMany power plants and factories burn Many power plants and factories burn coalcoal
or or oiloil to fuel their processes. to fuel their processes.
The engines of millions of cars, trucks, The engines of millions of cars, trucks, and buses burn and buses burn gasolinegasoline. .
SmokeSmoke and and exhaust exhaust from these sources from these sources pour into the air, especially around large pour into the air, especially around large cities. cities.
Smoke and ExhaustWhen coal, oil, and
gasoline are burned, the gases sulfur dioxide and nitrogen oxide are released into the atmosphere.
The sulfur and nitrogen react with water, forming sulfuric and nitric acids.
The result is acid rain.
Acid RainAcid Rain
Acid rain is rain or another form of precipitation that is more acidic than normal.
Acid rain can affect fish, harm trees, and eat away the stone of buildings and statues.
Heat PollutionHeat Pollution Much of the water in
factories is used to cool machinery or metal objects.
The warm water alone can act as a pollutant.
Many water organisms can live in only a narrow range of temperatures.
Warm water released by factory into a nearby river or pond raises the temperature of the water, sometimes enough to harm the living things there.
Chemical RunoffChemical Runoff
Farmers spread or spray fertilizing chemicals on their fields to produce better crops.
When rain falls on the fields, it washes some of the chemicals away as runoff.
Water used for irrigation also creates runoff.
The fertilizers in the runoff are a nonpoint source of pollution.
Examples of runoff
Runoff from farmsRunoff from farms
With the addition of fertilizers running off into ponds and lakes, the process of eutrophication speeds up.
Runoff and irrigation water carry away pollutants from farm fields such as pesticides and fertilizers.
Runoff from farms
Runoff from roads When it rains, runoff carries oil into rivers
and lakes, or underground and into the groundwater.
During winter, runoff also picks up salt that is spread on roads and sidewalks to melt ice.
Gasoline, oil, and salt are nonpoint sources that pollute rivers and lakes.
They can also seep underground and pollute wells and aquifers.
Water Pollution Solutions
Solving pollution problems involves cleaning up existing problems as well as preventing new ones.
Cleanup Many pollutants are removed from fresh
water through natural cleanup processes. Living things in lakes, streams, and wetlands
help reduce pollution by filtering out and breaking down waste materials.
Living things helping cleanup pollution
Examples Plant roots filter larger particles from the
water. Certain bacteria consume oil and have been
used to cleanup oil spills. Natural and artificial wetlands can be used to
clean up water pollution. Wetlands have been built near coal mines to
treat acidic mining runoff before it returns to the environment.
Prevention Many industries have found that recycling
techniques that conserve water also reduce pollution. For example, factories cool the water used to cool
machinery and reuse it instead of releasing it into a river.
Another example is when farmers collect and reuse the runoff water from their pasture as water for irrigation.
Farmers can also plant fields of grasses that filter out pollutants before the water reaches a river or pond.
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