Acid rain 2

What is acid rain? Acid rain is caused by emissions of sulphur dioxide and nitrogen oxides. Although natural sources of sulphur oxides and nitrogen oxides do exist, more than 90% of the sulphur and 95% of the nitrogen emissions occurring in eastern North America come from human origin. These primary air pollutants come from the use of coal in the production of electricity, from base-metal smelting, and from fuel combustion in vehicles. Once released into the atmosphere, they can be converted chemically into such secondary pollutants as nitric acid and sulfuric acid, both of which dissolve easily in water. The resulting acidic water droplets can be carried long distances by very strong winds, returning to Earth as acid rain, snow, or fog.
Who is affected? Basically every one who comes in contact with acid rain is affected. Among one of the serious side effects of acid pollution on humans is respiratory problems. The SO2 and NO2 emmisions give rise to respitory problems such as asthma, dry coughs, headaches, eye, nose and throat irritations. An indirect effect of acid rain on humans is that the toxic metals dissolved in the water are absorbed in fruits, vegetables and in the tissues of animals. Even though these toxic metals do not directly affect the animals, they have serious effects on humans when they are being eaten.

How did it happen? One of the main causes of acid rain is sulphur dioxide. Natural sources thatlet out this gas are volcanoes, sea spray , rotting vegetation and plankton. However, the burning of fossil fuels, such as coal and oil, are largely to be blamed for about half of the emissions of this gas in the world. When sulphur dioxide gets in the atmosphere, it oxidizes to first form a sulphate ion. It then becomes sulphuric acid as it joins with hydrogen atoms in the air and falls back down to earth in the form of acid rain, snow, or fog. Oxidation occurs the most in clouds and especially in heavily polluted air where other compounds such as ammonia and ozone help to speed up the reaction, changing more sulphur dioxide to sulphuric acid.

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When did it start? Since acid rain is emmited from natural sources such as volcanoes, sea spray, rotting vegetation and degasing plankton, acid rain has always been around. Although the first recorded acid rain “storm” was in 1944 when readings of pH 2.4(as acidic as vinegar) were recorded during storms in New England.
Where is the problem? Acid pollution ranges everywhere from the U.S.(the world’s biggest producer of sulfur dioxide) to the Arctic(the world smallest producer of sulfur dioxide). Because of prevailing winds acidic water droplets can be carried long distance, returning to earth as acid rain, snow or fog. Canada, for example, produces about half of it’s own acid rain and imports the rest from the U.S.

There are 4 ways to reduce gases(which contain sulphur dioxide and nitrogen oxides) from power plants. The first and probably best way is energy conservation. This means using less energy. Less energy means less coal burned in power plants. Burning less coal means less acid in the air.
Burning low-sulfur coal is the second step. There is a difference between high-sulfur coal and low-sulfur coal. High-sulfur coal will give off more sulfur in the air when it is burned. Burning low-sulfur coal will give off less sulfur which means less acid will enter the air. However, high- sulfur costs two thirds the price of low-sulfur coal.
Then there are smokestack scrubbers. Scrubbers capture sulfur from smoke before it enters the air. The captured sulfur is mixed with other things, such as lime. This creates a semiliquid which looks like wet cement. This also becomes a problem. The captured sulfur has nowhere to go. One power plant can capture an amount of 400 tons of sulfur mixture a day.
Then there’s the last way-search for alternate energy sources. One alternate source is nuclear power, but some believe this source may create problems even worse than acid rain. Other sources include solar power (power from the sun) and wind power. These two sources have hardly ever been tried.

Acid Rain

Acid rain is rain that is more acidic than normal. Acid rain is a complicated problem. Caused by air pollution, acid rain’s spread and damage involves weather, chemistry, soil, and the life cycles of plants and animals on the land and from acid rain in the water.
Scientists have discovered that air pollution from the burning of fossil fuels is the major cause of acid rain. Power plants and factories burn coal and oil. Power plants use that coal and oil to produce the electricity we need to heat and light our homes and to run our electric appliances. We also burn natural gas, coal, and oil to heat our homes.
The smoke and fumes from burning fossil fuels rise into the atmosphere and combine with the moisture in the air to form acid rain. The main chemicals in air pollution that create acid rain are sulfur dioxide and nitrogen oxides. Acid rain usually forms high in the clouds where sulfur dioxide and nitrogen oxides react with water, oxygen, and oxidants. This forms a mild solution of sulfuric acid and nitric acid. Sunlight increases the rate of most of these reactions. Rainwater, snow, fog, and other forms of precipitation containing those mild solutions of sulfuric and nitric acids fall to the earth as acid rain.
Water moves through every living plant and animal, streams, lakes, and oceans in the hydrologic cycle. In that cycle, water evaporates from the land and sea into the atmosphere. Water in the atmosphere then condenses to form clouds. Clouds release the water back to the earth as rain, snow, or fog. When water droplets form and fall to the earth they pick up particles and chemicals that float in the air. Even clean, unpolluted air has some particles such as dust or pollen. Clean air also contains naturally occurring gases such as carbon dioxide. The interaction between the water droplets and the carbon dioxide in the atmosphere, and to a lesser extent, from chlorine which is derived from the salt in the sea, gives rain an average pH of about 5.6, making even clean rain slightly acidic. Other natural sources of acids and bases in the atmosphere may lower or raise the pH of unpolluted rain. However, when rain contains pollutants, especially sulfur dioxide and nitrogen oxides, the rain water can become very acidic.
Acid rain does not account for all of the acidity that falls back to earth from pollutants. About half the acidity in the atmosphere falls back to the earth through dry deposition as gases and dry particles. The wind blows these acidic particles and gases onto buildings, cars, homes and trees. In some instances, these gases and particles can eat away the things on which they settle. Dry deposited gases and particles are sometimes washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than the falling rain alone. The combination of acid rain plus dry deposited acid is called acid deposition.
The chemical reactions that change air pollution to acid rain can take from several hours to several days. Years ago, when smokestacks were only a few stories high, pollution from smokestacks usually stayed near the ground and settled on land nearby. This caused unhealthy conditions for plants and animals near the smokestacks. To reduce this pollution, the government passed a law permitting the construction of very tall smokestacks. At that time, people thought that if the pollution were sent high into the air it would no longer be a problem. Scientists now know that this is incorrect. Sending pollution high into the sky increases the time that the pollution stays in the air. The longer the pollution is in the air, the greater are the chances that the pollutants will form acid rain. In addition, the wind can carry these pollutants for hundreds of miles before they become joined with water droplets to form acid rain. For that reason, acid rain can also be a problem in areas far from the polluting smokestacks. Dry deposition is usually more abundant near the cities and industrial areas where the pollutants are released.
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