Government Approved Pollution
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What's Polluting Our Waters
Missouri Botanical Gardens
Water pollution occurs when a body of water is adversely affected due to the addition of large amounts of
materials to the water. The sources of water pollution are categorized as being a point source or a
non-source point of pollution. Point sources of pollution occur when the polluting substance is emitted
directly into the waterway. A pipe spewing toxic chemicals directly into a river is an example. A non-point
source occurs when there is runoff of pollutants into a waterway, for instance when fertilizer from a
field is carried into a stream by surface runoff.
Specific Sources of Water Pollution
- Farms often use large amounts of herbicides and pesticides, both of which are toxic pollutants.
These substances are particularly dangerous to life in rivers, streams and lakes, where toxic substances
can build up over a period of time.
- Farms also frequently use large amounts of chemical fertilizers that are washed into the waterways and
damage the water supply and the life within it. Fertilizers can increase the amounts of nitrates and
phosphates in the water, which can lead to the process of eutrophication.
- Allowing livestock to graze near water sources often results in organic waste products being washed
into the waterways. This sudden introduction of organic material increaces the amount of nitrogen in the
water, and can also lead to eutrophication.
- Four hundred million tons of soil are carried by the Mississippi River to the Gulf of Mexico each year.
A great deal of this siltation is due to runoff from the exposed soil of agricultural fields. Excessive
amounts of sediment in waterways can block sunlight, preventing aquatic plants from photosynthesizing,
and can suffocate fish by clogging their gills.
- Clearing of land can lead to erosion of soil into the river.
- Waste and sewage generated by industry can get into the water supply, introducing large organic pollutants
into the ecosystem.
- Many industrial and power plants use rivers, streams and lakes to despose of waste heat. The resulting
hot water can cause thermal pollution. Thermal pollution can have a disasterous effect on life in an
aquatic ecosystem as temperature increaces decreace the amount of oxygen in the water, thereby reducing
the number of animals that can survive there.
- Water can become contaminated with toxic or radioactive materials from industry, mine sites and
abandoned hazardous waste sites.
- Acid precipitation is caused when the burning of fossil fuels emits sulfur dioxide into the
atmosphere. The sulfur dioxide reacts with the water in the atmosphere, creating rainfall which contains
sulfuric acid. As acid precipitation falls into lakes, streams and ponds it can lower the overall pH
of the waterway, killing vital plant life, thereby affecting the whole food chain. It can also leach
heavy metals from the soil into the water, killing fish and other aquatic organisms. Because of this,
air pollution is potentially one of the most threatening forms of pollution to aquatic ecosystems.
- Sewage generated by houses or runoff from septic tanks into nearby waterways, introduce organic
pollutants that can cause eutrophication.
- Fertilizers, herbicides and pesticides used for lawn care can runoff and contaminate the waterway.
As with agriculteral fertilizers, home fertilizers can lead to the eutrophication of lakes and rivers.
- Improper disposal of hazardous chemicals down the drain itroduce toxic materials into to the ecosystem,
contaminating the water supplies in a way that can harm aquatic organisms.
- Leaks of oil and antifreeze from a car on a driveway can be washed off by the rain into nearby waterways,