Water Pollutant FAQ Frequently Asked Questions
The question library on water related issues
Many different chemicals are regarded as pollutants, ranging from simple inorganic ions to complex organic molecules.
There are many different types of organic pollutants, examples are:
Some inorganic pollutants are not particularly toxic, but are still a danger to the environment because they are used so extensively. These include fertilizers, such as nitrates and phosphates. Nitrates and phosphates cause algal blooms in surface water, which causes the oxygen level of the water to decline. This causes oxygen starvation because of the uptake of oxygen by microrganisms that brake down algae. This is called eutrophication.
The first class we will refer to here is metals. Metals are good conductors of electricity and generally enter chemical reactions as positive ions, known as cations. Metals are natural substances that have consisted through weathering of ore bodies, where they were deposited during volcanic action. They can be relocated into situations where they can cause serious environmental damage. Examples of metals are: lead, zinc, manganese, calcium and potassium. They can be found in surface waters in their stable ionic forms. Unnatural metals can be very dangerous, because they often come from man-made nuclear reactions and can be strongly radioactive.
The half-lives and the ways of decay of radioactive isotopes determine how dangerous they are to humans. Humans create all radioactive isotopes in the nuclear industry. There are still debates going on about whether the benefits of nuclear power exceed the dangers of radioactive radiation. When an atom of a radioactive substance decays, it can produce four kinds of particles: alpha, beta, gamma and neutrons.
Discharge of sewage water represents a mayor global source of pollution. Domestic and industrial wastes are discharged unto surface water through sewage systems. In some cases industrial waste is released directly unto surface water. The quality of sewage water that enters the surface water depends upon the pollutants that are present in the sewage water and the extend to which it is treated before it is brought in contact with surface water.
Pollutants can exist in water in different states. They can be dissolved or they can be in suspension, which means that they exist in the form of droplets or particles. Pollutants can also be dissolved in droplets or absorbed by particles. All states of pollutants can travel great distances through water in many different ways.
Physical processes determine the movement of chemicals within water; movement depends upon properties of the chemicals themselves and properties of the water. These processes will be overviewed here.
When pollution enters the body of an organism it causes a variety of changes. These changes can either serve to protect the organism against harmful effects or not.
Water pollutants can have many different effects on organisms, always depending on the pollutant and the organism in question. Here the general effects a pollutant can have are discussed.
Many compounds that enter the body of an organism are known to cause damage to DNA. These compounds are called genotoxins, due to their genotoxic effect.
Several pollutants are carcinogenic, which means they can induce cancer in the body of humans and animals. Carcinogenic pollutants are pollutants that play a role in one or more of the stages of cancer development in an organism.
The nervous system of organisms is very sensitive to toxic effects of chemicals, both naturally occurring and man-made. Chemicals that cause neurological effects are called neurotoxins. Examples of dangerous neurotoxins are insecticides.
Energy transformation in organisms is done through mitochondria systems in the cells. On the mitochondrion ATP-molecules are produced, which transfer energy through the body of an organism. When ATP production is disturbed the energy transfer will cease. This will make an organism tired and lifeless and unable to function normally.
Pollutants that cause reproductive failure due to damage to the reproductive organs are called endocrine disruptors. There are several ways in which a pollutant can act as an endocrine disruptor.
All behaviours are vulnerable to alteration by pollutants. Foraging levels can deplete, resulting in reduced production. Vulnerability to predators can increase, due to a depletion of vigilance. In these ways, effects of pollutants on behaviour result in lowered production and higher mortality rates.
Toxicity of chemicals in water can be tested with aquatic animals as indicators. Toxicity tests with aquatic animals are mainly concerned with direct uptake from water. The chemicals may be in solution, in suspension or both.
For toxicity testing and toxicity responses from aquatic life check out toxicity to aquatic organisms
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