Everything about Thermal Pollution totally explained
Thermal pollution is a
temperature change in natural water bodies caused by human influence. The temperature change can be upwards or downwards. In the Northern Hemisphere, a common cause of
thermal pollution is the use of water as a
coolant, especially in
power plants. Water used as a coolant is returned to the natural environment at a higher temperature. Increases in water temperature can impact on
aquatic organisms by (a) decreasing
oxygen supply, (b) killing fish juveniles which are vulnerable to small fluctuations in temperature, and (c) affecting
ecosystem composition. In the Southern Hemisphere, thermal pollution is commonly caused by the release of very cold water from the base of reservoirs, with severe affects on fish (particularly eggs and larvae), macroinvertebrates and river productivity.
Ecological effects — warm water
Warm water typically decreases the level of dissolved oxygen in the water. The decrease in levels of
dissolved oxygen can harm aquatic animals such as fish,
amphibians and
copepods. Thermal pollution may also increase the
metabolic rate of aquatic animals, as
enzyme activity, resulting in these organisms consuming more food in a shorter time than if their environment were not changed. An increased metabolic rate may result in food source shortages, causing a sharp decrease in a population. Changes in the environment may also result in a migration of organisms to another, more suitable environment, and to in-migration of organisms that normally only live in warmer waters elsewhere. This leads to competition for fewer resources; the more adapted organisms moving in may have an advantage over organisms that are not used to the warmer temperature. As a result one has the problem of compromising
food chains of the old and new environments.
Biodiversity can be decreased as a result.
It is known that temperature changes of even one to two degrees
Celsius can cause significant changes in organism metabolism and other adverse
cellular biology effects. Principal adverse changes can include rendering cell walls less permeable to necessary
osmosis, coagulation of cell
proteins, and alteration of
enzyme metabolism. These cellular level effects can adversely affect
mortality and
reproduction.
Primary producers are affected by warm water because higher water temperature increases plant growth rates, resulting in a shorter lifespan and species overpopulation. This can cause an
algae bloom which reduces the oxygen levels in the water. The higher plant density leads to an increased plant
respiration rate because the reduced light intensity decreases
photosynthesis. This is similar to the
eutrophication that occurs when watercourses are polluted with
leached agricultural inorganic fertilizers.
A large increase in temperature can lead to the denaturing of life-supporting enzymes by breaking down
hydrogen- and
disulphide bonds within the quaternary structure of the enzymes. Decreased enzyme activity in aquatic organisms can cause problems such as the inability to break down
lipids, which leads to
malnutrition.
In limited cases, warm water has little deleterious effect and may even lead to improved function of the receiving aquatic ecosystem. This phenomenon is seen especially in seasonal waters and is known as thermal enrichment. An extreme case is derived from the aggregational habits of the
manatee, which often uses power plant discharge sites during winter. Projections suggest that manatee populations would decline upon the removal of these discharges.
The added heat lowers the dissolved oxygen content and may cause serious problems for the plants and animals living there. In extreme cases, major fish kills can result. Warm water may also increase the metabolic rate of aquatic animals, as enzyme activity, meaning that these organisms will consume more food in a shorter time than if their environment wasn't changed.
Ecological effects — cold water
Releases of unnaturally cold water from reservoirs can dramatically change the fish and macro invertebrate fauna of rivers, and reduce river productivity. In Australia, where many rivers have warmer temperature regimes, native fish species have been eliminated, and macro invertebrate faunas have been drastically altered and impoverished.
Computer modeling of thermal pollution
In the 1970s there was considerable activity from scientists in quantifying effects of thermal pollution.
Hydrologists,
physicists,
meteorologists, and
computer scientists combined their skills in one of the first
interdisciplinary pursuits of the modern
environmental science era.
First came the application of
gaussian function dispersal modeling that forecasts how a thermal
plume is formed from a thermal
point source and predicts the distribution of aquatic temperatures.
The ultimate model was developed by the
U.S. Environmental Protection Agency introducing the statistical variations in meteorology to predict the resulting plume from a thermal
outfall.
Further Information
Get more info on 'Thermal Pollution'.
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