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بحث عن التلوث باللغه الانجليزيه

بحث عن التلوث باللغه الانجليزيه


بحث عن التلوث باللغه الانجليزيه 
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What is pollution?



Pollution is the presence of a substance or substances that would not normally be found or that are not present in normal amounts. Pollutants can be in solid, liquid or gaseous form.



The consequences of pollution can be direct, by the toxic effect of a substance. For example, an accidental spill of a pesticide spilled into a river may very well have an immediate effect and be very harmful to aquatic life. The consequences of pollution can be indirect. Nitrogen and phosphorus are essential for plant growth, but excessive growth of plants can be dangerous for water. For example, phosphorus levels in improved surface waters (which adequately contain nitrogen) can stimulate excessive growth of algae. Over time, the decomposition process of algae reduces the oxygen available in the water, fish and harms aquatic life.



Our use of water can cause pollution, not only because of the substances we accidentally or deliberately put into the water, but also because of intensive use of water and groundwater. Therefore, the reduction of water pollution is based not only on the prevention of potentially polluting substances, but also on reducing the amount of water we use.



Before going further you can consult our soil pollution diagnosis page.

Some useful definitions related to pollution 
Pollutants - a contaminant present in the environment or entering the environment which, because of its properties or the quantity or concentration, causes harm.
Contaminant - substance, material or agent that is undesirable in the environment.
Risk - the combination of the probability of occurrence of damage and the severity of damage.
Dose - the amount received by the receiver: this is an essential consideration "the dose makes the poison".

Nature of pollution sources 
Pollution is often described as a point or diffuse source of pollution.
Point pollution on a body of water or at a specific location, it is usually easily identifiable. Potential point sources of pollution are effluent discharges from wastewater treatment plants and industrial sites, power plants, landfills, fish farming and oil spills via a pipeline of industrial sites for example.
Point pollution is usually easily avoided as it is possible to identify the source. Polluters can take preventive action through immediate corrective action, or long-term investments in treatment and control facilities.
Diffuse pollution occurs when substances are widely used and dispersed over an area as a result of intensive land use, such as urban development, agriculture and forestry.

These activities may be recent or have been conducted in the past. It is often difficult to identify specific sources of pollution and therefore take immediate action to prevent it, since prevention often requires major changes to land use and management practices.
Examples of diffuse pollution are leaching into surface water and groundwater from roads, fertilizers, nutrients and pesticides used in agriculture and forestry, atmospheric deposition of contaminants from industry. A special case arises when, for example, a power plant emits sulfur dioxide and nitrous oxide into the air. Although it is a point source, the deposition (fallout) will result in a large area of ​​diffuse pollution.

Substances that can cause pollution 
Some of the main substances that can cause pollution are described below.
nutrients
The main potentially polluting nutrients in water are nitrogen, ammonia (a gas containing nitrogen and hydrogen), phosphorus and sulfur. They come from the natural decomposition of crop residues and soil organic matter, precipitation, fertilizer, urine and manure, landfills, industrial effluents and effluents, electricity generation and other fuel activities.
For example, nutrients are the main cause of eutrophication which is the enrichment of lakes, rivers and the marine environment that leads to plant growth. This has the effect of increasing the appearance of algae.

pesticides 
These include herbicides, insecticides and fungicides that are used in gardens, agriculture, roadsides and on the ground (railway) and in parks and golf courses.

Heavy metals 
Heavy metals are commonly used ingredients for chemical compounds in the industry. Contaminated industrial land can be a source of leaching of heavy metals into the environment. They also exist naturally in low concentration soils. They can be present in fuels, chemicals, waste and batteries. At high concentrations, they are toxic to humans, animals, fish and plants.

Suspended solids 
Suspended solids are inorganic or organic particles that remain in suspension in water. They sink very slowly or are easily resuspended by the turbulence of the water. Suspended matter can erode the soil. Wastewater from sewage treatment plants and industry can also transport suspended solids into the water. Solids suspended in water also reduce light levels. The murky waters can also be a sign of pollution, pesticides and metals can be attached to suspended particles.

Pathogens 
They are present in faeces of human and animal origin, including wildlife. They can enter the water due to poor wastewater management or improper handling of manure, slurry and other agricultural waste. They can also be spread directly on the fields during heavy rains or on water bodies.

Temperature 
Temperature is not strictly a pollutant in the general sense of the word, but is included here because it can affect the health of the aquatic environment. Shallow water tends to be warmer than deep water because it is heated more easily by the sun. Treated effluents from wastewater treatment and industry and cooling water from power plants are generally warmer than the receiving waters in which they are discharged, which can lead to temperature stress as well as stress due to reduced oxygen content in the water because hot water has less oxygen than cold water.

hydrocarbons 
These include vegetable and mineral oils (including gasoline, diesel, white spirit, heating and lubricating oil) and chlorinated solvents such as dry cleaning fluids.

Persistent organic pollutants   (POP)
These are chemicals that are able to be transported over long distances. They accumulate in human and animal tissues, and have a significant impact on human health and the environment, even at low concentrations. They include substances such as dioxins and PCBs.

More details on some sources of pollution

Landfills 
Landfills can be a source of pollution in the aquatic environment through several mechanisms. Waste containing water releases the polluting substances during the run-off process after landfilling. The landfill directive requires that the amount of unstabilized organic waste sent to landfill must be significantly reduced in order to reduce the risk of water pollution and emissions of methane, which is a significant greenhouse gas. However, it will take time to be fully effective and there are many older landfills that continue to generate leachate for many years. Otherwise the leachate (residual liquid that comes from the percolation of water through a material) can be partially treated on site and then discharged into a sewer for further treatment in a sewage treatment plant.

Contaminated land 
Contaminated land is largely a legacy of historic industrial activity, when there was little, if any, environmental regulation. The nature of the contamination can vary considerably. Contamination of water from these sites occurs mainly due to rain, contaminated sediment and dissolved compounds run down to streams or groundwater beneath a site and groundwater. Contamination of groundwater and surface water can also occur when there is poor storage and when handling chemicals such as solvents or spill oils.

Mining 
The main source of water contamination from mining is acid mine drainage. For example, rock layers contain pyrite (iron sulphide) which oxidizes in contact with air and in the presence of bacteria to form sulfuric acid. Therefore, the drainage of a mine has a very low pH (acidity) and contains high concentrations of sulfur, iron and a range of heavy metals such as arsenic and cadmium. This process also depletes the water of its oxygen, this has an impact on the fishing and the life of the insects.

fish farming 
Fish farming is the intensive production of fish in a small area. It can be carried out in specifically constructed basins, or in cages in sheltered lakes and coastal waters.
Fish farming can have a variety of effects on the marine environment, through the release of nutrients, solid waste, drugs. Nitrogen and phosphorus from fish feed released into the marine environment in a soluble form can enhance the growth of marine plants and algae. Food waste can be deposited on the seabed under the fish cages. This increase in organic matter can have an impact on the environment, which affects the nature and chemistry of sediments, and can reduce the diversity of animals that live there.
Intensive fish farming can increase the disease because of the proximity of a large number of fish. As a result, a number of drugs are used in fish farms to maintain fish health. Farmed salmon is susceptible to pest infestations that cause considerable stress. Sea lice on farmed fish can potentially be transferred to wild salmon and sea trout by reducing the health of the wild stock. Treatment chemicals may be toxic to marine invertebrates, although the use of antibiotics to treat bacterial diseases has declined in recent years because of effective vaccination programs.
Fish farming is monitored and regulated by the authorities, supported by good practice guides. For example, the manual of the Scottish Environmental Protection Fish Farming Agency provides advice on legislation, policies and procedures relevant to the marine cage farming industry.

Road and runoff, urban stormwater discharges 
Roads and car parks produce runoff in urban areas. This runoff is often contaminated by sediment, oil, gasoline and toxic metals from motor vehicles. These contaminants are flowing in sewers and nearby waterways. Most surface water is directly connected to streams, so any spills of chemicals tend to drain into rivers.
Unit sewage systems transport both wastewater and runoff. Unit sewers are common in urban areas. Normally, the entire flow goes to a wastewater treatment plant, but during a heavy rainstorm the flow into the sewers may be greater than it can accommodate and the excess flow must be redirected to a receiving watercourse via an overflow (called overflow of combined sewers) to avoid severe flooding near urban areas and the treatment plant.
Sustainable urban drainage systems are increasingly adopted to ensure that urban areas behave more like natural basins through the use of porous pavement surfaces and by diverting potentially polluted water from rivers . The goal is to reduce the risk of pollution caused by direct runoff and reduce the volume of water flowing through the drainage system, thus avoiding flooding and sewer overflows.



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