Examples of thermal pollution are; heat-induced dissolved oxygen depletion, aquatic population decline in nuclear power plant vicinity, combined sedimentary and thermal water pollution by stormwater runoff from urban areas, deforestation-induced solar exposure and overheating of water bodies, and localized thermal changes around water-immersed turbines of hydropower plants.
This article discusses the examples of thermal pollution, as follows;
1). Heat-Induced Oxygen Depletion (as one of the Examples of Thermal Pollution)
The depletion of oxygen in ecologic media is a classic example of the effects of thermal pollution.
In general, the temperature of water is inversely proportional to its dissolved oxygen (DO) content; so that cold water tends to contain more oxygen than warm water .
Because of how rapidly oxygen depletes as temperature rises, the phenomenon of heat-induced oxygen depletion can be described as one of the most instant environmental impacts associated with thermal pollution.
As already implied, the severity of oxygen-resource depletion in a given medium or environment due to thermal pollution, depends on the extent of temperature-change. This in turn varies with the source of thermal pollution involved; so that the more-active sources like industrial facilities (including power plants) may deplete more oxygen than the less-active ones like solar radiation.
Changes in biogeochemical nutrient distribution is also among the environmental issues associated with oxygen depletion, within the context of thermal pollution . These changes can severely affect aquatic organisms like fish.
An instance of this is the deficiency of Selenium (Se) in fish .
2). Aquatic Population Decline in Nuclear Power Plant Vicinity
An example of thermal pollution in aquatic ecosystems is induced decline of local populations in water bodies within the vicinity of nuclear power plants.
Thermal pollution affects aquatic plants by altering their enzymatic processes and the availability of nutrients which they require for metabolic activities. These alterations reduce the ability of the plants to perform photosynthesis, which defines their role as primary producers in the food chain and energy pyramid.
Excessive warming can also damage the parts of plants like roots and stems, and may reduce the efficiency of these components in their ecologic function.
Nuclear power plants cause thermal pollution through the production of large quantities of thermal energy in the process of electricity generation. Water that is used as a coolant to remove excessive waste heat from the reactor and turbine compartment, may subsequently be discharged into the external environment, including oceans, rivers and lakes.
In large water bodies with high biodiversity and species richness, this implies that the effects can occur across a significant portion of the ecosystem, and alter the living conditions of numerous organisms.
Aquatic animals like crustaceans, amphibians, some reptiles and fish; may experience decline in their local population size(s) due to thermal pollution.
This can occur by any of various mechanisms, including loss of nutrients and oxygen, changes in metabolic tendencies and reproductive capability/behavior; as well as mass migration to less-impacted zones.
Aquatic ecosystems that are in close proximity with nuclear power plants that have poor wastewater management practices; often see rapid loss of biodiversity till they are inhabited by only a few, adaptive and resilient species. Such an outcome affects the climate, biomass production rate, and carbon cycle, among others.
3). Combined Sedimentary and Thermal Water Pollution by Urban Stormwater Runoff (as one of the Examples of Thermal Pollution)
Thermal pollution by urban stormwater is a prominent and severe problem in several parts of the world .
Stormwater itself comes from rainfall and other forms of precipitation.
In order for this water to cause significant environmental degradation, it must contain a significant concentration of impurities. The process by which stormwater acquires these impurities is known as stormwater pollution.
Pollutants in urban stormwater runoff may include chemical waste, sewage, inorganic and organic materials from landfills, and sediments picked up and transported as a result of erosional action (where the stormwater acts as an agent of erosion).
Studies have linked the dynamics of stormwater runoff to increased rates of suspended-sediment transport in both rural and urban landscapes .
The risk of severe pollution by stormwater is often higher in urban areas because urbanization is accompanied by an increase in regional industrialization, which exposes stormwater to chemicals and refined energy resources like gasoline.
These toxic materials alongside sediments can do significant damage to the quality of any medium into which they are introduced.
Urban stormwater often has a relatively-warm temperature caused by the chemical and biochemical dynamics of its impurities. On flowing into water bodies, the stormwater tends to increase ambient temperature, with adverse consequences like dissolved oxygen (DO) decline .
4). Deforestation-Induced Solar Exposure and Overheating of Water Bodies
When vegetation surrounding a water body is lost to deforestation, the shade provided by this vegetation is lost as well. Such a scenario is relatively common in forests with freshwater sub-ecosystems like ponds and streams.
Loss of shade increases the solar exposure of water bodies in previously-forested areas, allowing the water to absorb more heat than usual, and resulting in increased temperature .
Overheating can be used to describe the scenario where water absorbs heat in a rapid and voluminous manner that exceeds healthy levels. Ripple effects of such phenomena include food chain disruption and loss of local aquatic life .
Examples of Thermal Pollution: Deforestation-Induced Solar Exposure and Overheating of Water Bodies (Credit: Dietmar Rabich 2016 .CC BY-SA 4.0.)
5). Localized Thermal Changes around Water-Immersed Turbines of Hydropower Plants (as one of the Examples of Thermal Pollution)
However, on a localized scale, hydro power plants can cause thermal enrichment of water bodies, with potential hazardous consequences.
Thermal pollution from hydroelectric systems occurs due to the dynamics of turbines, which may generate heat from frictional contact with surrounding water, as well as with adjoined components of the hydro system.
Flood water that is retained by hydroelectric dams may attain slightly-higher temperature than other parts of a given water body, due to both friction and zonal volumetric differences. This higher temperature may then be infused into colder zones as the retained water is released, thereby causing thermal change.
Examples of thermal pollution are;
1. Heat-Induced Oxygen Depletion
2. Aquatic Population Decline in Nuclear Power Plant Vicinity
3. Combined Sedimentary and Thermal Water Pollution by Urban Stormwater Runoff
4. Deforestation-Induced Solar Exposure and Overheating of Water Bodies
5. Localized Thermal Changes around Water-Immersed Turbines of Hydropower Plants
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