5 Examples of Thermal Pollution and Characteristics Explained
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.
Oxygen depletion with temperature change, is most common in aquatic ecosystems; which include marine zones like oceans and freshwater biomes like rivers, ponds and lakes.
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 [2].
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.
Heat-induced oxygen depletion can impact the ecosystem severely in terms of the natural trends of the oxygen cycle, and the interaction between abiotic and biotic components.
Changes in biogeochemical nutrient distribution is also among the environmental issues associated with oxygen depletion, within the context of thermal pollution [8]. These changes can severely affect aquatic organisms like fish.
An instance of this is the deficiency of Selenium (Se) in fish [4].
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.
Both plants and animals in aquatic biomes around such plants can be affected adversely by the unnatural temperature changes accompanying thermal pollution.
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.
Studies have shown that the thermal discharge of nuclear energy facilities may have effects that span across a wide area of several kilometers from the main outlet [6].
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 [7].
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.
Like other cases of water pollution, the presence of polluted stormwater-runoff in urban areas is an indication of inadequate management of water resources; or poor water conservation approach.
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 [5].
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 [9].
4). Deforestation-Induced Solar Exposure and Overheating of Water Bodies
Deforestation causes thermal pollution through an indirect mechanism of increased exposure and passive solar heat absorption.
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 [1].
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 [3].
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)
Hydro energy is one of the most sustainable, clean energy resources as of the twenty-first century. Its use is not associated with significant changes to soil, water or air quality.
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.
Conclusion
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
References
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2). Dowling, D. C.; Wiley, M. J. (1986). "The Effects of Dissolved Oxygen, Temperature, and Low Stream Flow on Fishes: A Literature Review." Available at: https://www.researchgate.net/publication/32964040_The_Effects_of_Dissolved_Oxygen_Temperature_and_Low_Stream_Flow_on_Fishes_A_Literature_Review. (Accessed 16 May 2023).
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5). Herb, W. R.; Janke, B.; Mohseni, O.; Stefan, H. G. (2008). "Thermal Pollution of Streams by Runoff From Paved Surfaces." Hydrological Processes 22(7):987 - 999. Available at: https://doi.org/10.1002/hyp.6986. (Accessed 16 May 2023).
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7). Li, J.; Gong, Y.; Li, X.; Yin, D.; Shi, H. (2018). "Urban stormwater runoff thermal characteristics and mitigation effect of low impact development measures." Journal of Water and Climate Change 10(1):jwc2018145. Available at: https://doi.org/10.2166/wcc.2018.145. (Accessed 16 May 2023).
8). Råman, V. L.; Wuest, A.; Bouffard, D. (2017). "Physical effects of thermal pollution in lakes." Water Resources Research 53(5). Available at: https://doi.org/10.1002/2016WR019686. (Accessed 16 May 2023).
9). Simpson, M.; Winston, R. J. (2022). "Effects of land use on thermal enrichment of urban stormwater and potential mitigation of runoff temperature by watershed-scale stormwater control measures." Elsevier, Ecological Engineering, Volume 184, November 2022, 106792. Available at: https://doi.org/10.1016/j.ecoleng.2022.106792. (Accessed 16 May 2023).
