There are a number of water pollutants the aquatic environment has to deal with.
1. Organic pollutants:
Organic matters that require oxygen are major pollutants of water. These contain compounds that need bacterial activity for their degradation. This bacterial activity decreases the oxygen level in the water. Decaying organic water, overflowing sewage, animal excreta or excreta of an unwell person and nutrients of plants, are some of the organic compounds.
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Effects:
i. Humans can be infected with diseases like typhoid and dysentery.
ii. Pathogens found in sewage make it unfit for drinking.
iii. The decreased oxygen levels lead to a foul smell in water.
2. Inorganic pollutants:
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These are industrial wastes that are not soluble in water. Inorganic pollutants include inorganic salts, oils and surfactants, organometallic compounds, acids, heavy metals and trace elements.
Effects:
i. Water cannot be used for domestic purposes.
ii. Inorganic pollutants have a harmful effect on living organisms and have resulted in the extinction of a number of marine species.
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iii. Water is not able to self purify and this leads to degradation of the water.
iv. It changes the colour and smell of water.
v. Water becomes turbid and unsuitable for use.
3. Toxic organics:
Certain organic materials are harmful substances as well. These come from excessive use of pesticides and herbicides; spillage from economic activities; and overflow of septic tanks.
Effects:
i. Water becomes turbid due to suspended impurities, making it difficult to use.
ii. It does not remain fit for drinking.
iii. It cannot be used for domestic purposes.
4. Thermal pollutants:
Thermal pollutants are warm discharges from thermal and nuclear power plants, sewage, industries, and power plants that make use of coal as an input. Often, industries use water from surrounding water bodies for cooling and discharge the heated water back into the water bodies. This causes much harm to the water.
Effects:
i. They aggravate the activities of pathogens, which increase in population due to thermal wastes.
ii. It is difficult for marine plants and animals to survive in heated water.
iii. It changes the properties of water.
5. Sediment:
Sedimentation is primarily caused due to erosion of the land’s surface. Soil erosion happens due to rainfalls and water run-off from construction and mining activities. Sediments are also a result of illegal spillages and organic wastes such as plant remains and animal excreta. Sedimentation decreases the visibility in water and harms the natural processes of aquatic animals.
Effects:
i. Sediments does not allow sufficient light to filter into the water. This makes it difficult for water plants to undertake photosynthesis.
ii. They cause difficulty for water animals to breathe.
iii. The height of the waterbed increases due to sedimentation. This results in overflowing of water bodies like lakes and rivers.
6. Radioactive materials:
Radioactive material enters the water through nuclear power plants, nuclear tests, research for new medicines, spillage from industries and through mining of radioactive elements. When radioactive substances enter the water bodies, they cause severe harm to the marine ecosystems and even change the gene mechanism of living organisms.
Effects:
i. It spoils the gene system and cause deterioration of the immune system.
ii. It causes disruption of DNA in living organisms.
iii. It leads to life threatening diseases like cancer.