Water Pollution: Eutrophication, Oil Spills, and Aquifer Contamination

Item 12: Impacts on the Hydrosphere

Effects of Water Pollution

Eutrophication

Eutrophication is defined as the excessive supply of nutrients in a body of water, leading to a depletion of oxygen. When large amounts of organic matter reach a poorly oxygenated body of water, such as a lake or reservoir, microbial decomposition consumes the available oxygen while releasing phosphates and nitrates.

The surface layers lose transparency and take on a greenish color because algae reproduce in the waters close to the surface, consuming the phosphates and nitrates. The oxygen produced by the algae through photosynthesis escapes into the air, further decreasing the oxygen available for other organisms, which are subsequently harmed.

• Causes: Wastewater containing detergents, fecal waste, industrial discharge, etc.
• Measures: Limit or prohibit domestic and agricultural effluents in aquatic ecosystems, treat wastewater before returning it to nature, and reduce the use of polyphosphate-containing detergents.

Black Tide (Oil Spills)

The sea is the primary sink for pollutants emitted by humans. A very significant source of pollution is oil, hence the name "black tide" or oil spill.

• Negative Effects: Lack of oxygen due to the film of oil floating on the sea's surface, and death of living organisms due to intoxication or fouling of feathers, as is the case with birds, both caused by the viscous petroleum.
• Minimizing the Impact: To minimize the impact caused by an oil spill, the oil slick must be removed. Various methods are employed, such as mechanical collection, combustion, the use of detergents, sinking the oil, and even biodegradation to degrade the petroleum components.

Pollution Resulting from Overexploitation of Aquifers

This involves the mobilization of groundwater that is contaminated when it reaches unintended places. Two situations are discussed:

• Saline Intrusion: The high water demand that occurs in coastal populations, due to intensive tourism, often leads to the overexploitation of underground water reserves.
• Mobilization of Contaminated Water: The concentration of pollutants during exploitation means "less water = higher concentration," increasing the possibility that a volume of contaminated water will move toward the well being exploited.