ACID PRECIPITATION

Table Of Contents  Introduction  What is Acid precipitation  Causes of Acid precipitation  Acid Deposition  Effects of Acid precipitation  Solutions to the problem of acid rain  A global problem

Introduction  Acid rain is one of the most dangerous and widespread forms of pollution. Sometimes called "the unseen plague," acid rain can go undetected in an area for years.  Technically, acid rain is rain that has a larger amount of acid in it than what is normal.  The acidity of rain in parts of Europe and North America has dramatically increased over the past few decades. It is now common in many places for rain to be ten to seventy times more acid than unpolluted rain.  Many living and non-living systems become harmed and damaged as a result of acid rain.

What is Acid Rain? The term "acid rain" is commonly used to mean the deposition of acidic components in rain, snow, fog, dew, or dry particles. The more accurate term is "acid precipitation." Acid rain is mostly caused by human emissions of sulphur and nitrogen compounds which react in the atmosphere to produce acids

Causes of Acid Precipitation Natural Phenomenon  The principal natural phenomenon that contribute acid- producing gases to the atmosphere are emissions from volcanoes and those from biological processes that occur on the land, in wetlands, and in the oceans.  The major biological source of sulfur containing compounds is dimethyl sulfide.  The effects of acidic deposits have been detected in glacial ice thousands of years old in remote parts of the globe.

Human Activity  The principal cause of acid rain is sulphuric and nitrogen compounds from human sources, such as electricity generation, factories and motor vehicles.  Coal power plants are one of the most polluting.  The gases can be carried hundreds of kilometres in the atmosphere before they are converted to acids and deposited.

Equations

Acid Deposition Wet deposition  Wet deposition of acids occurs when any form of precipitation (rain, snow, etc) removes acids from the atmosphere and delivers it to the Earth's surface.  This can result from the deposition of acids produced in the raindrops or by the precipitation removing the acids either in clouds or below clouds.

Dry deposition  Acid deposition also occurs via dry deposition in the absence of precipitation. This can be responsible for as much as 20 to 60% of total acid deposition. [8] This occurs when particles and gases stick to the ground, plants or other surfaces. [8]

Adverse Effects of Acid Rain Acid rain has been shown to have adverse impacts on forests, freshwaters and soils, killing off insect and aquatic lifeforms as well as causing damage to buildings and having possible impacts on human health.

The Effects of Acid Rain  The lower pH and higher aluminum concentrations in surface water that occur as a result of acid rain can cause damage to fish and other aquatic animals.  Soil biology can be seriously damaged by acid rain. The hydronium ions of acid rain also mobilize toxins and leach away essential nutrients and minerals.  Acid rain can slow the growth of vulnerable forests and cause leaves and needles to turn brown and fall off. [ High altitude forests are especially vulnerable as they are often surrounded by clouds and fog which are more acidic than rain. Also, acid Rain depletes minerals from the soil and then it stunts the growth of the plant. [

 Human Health- Fine particles a large fraction of which are formed from the same gases as acid rain (sulphur dioxide and nitrogen dioxide), have been shown to cause illness and premature deaths such as cancer and other deadly diseases. Visibility is also reduced by sulfate and nitrate in the atmosphere.  Acid rain can also cause damage to certain building materials and historical monuments.  This is because the sulfuric acid in the rain chemically reacts with the calcium compounds in the stones (limestone, sandstone, marble and granite) to create gypsum, which then flakes off. CaCO 3 (s) + H 2 SO 4 (aq) ⇌ CaSO 4 (aq) + CO 2 (g) + H 2 O (l)

Leaching Effects of Acid Rain

Practical andTechnical Solutions  Use less energy! When less energy is used, less coal is burnt, and as a result, there is less acid rain. Experts say that if energy was used more carefully, we could cut the amount of fuel burned in half!  Also, if coal was cleaned before it was burnt, the dangerous pollutants that cause acid rain would be cleaned away. If coal is crushed and washed in water, the sulfur washes out. However, this is a very costly method.  In the United States, many coal-burning power plants use Flue gas desulfurization(FGD) to remove sulphur- containing gases from their stack gases.  Automobile emissions control reduces emissions of nitrogen oxides from motor vehicles.

International treaties  A number of international treaties on the long range transport of atmospheric pollutants have been agreed e.g. Sulphur Emissions Reduction Protocol under the Convention on Long-Range Transboundary Air Pollution. Emissions trading  In this scheme, every current polluting facility is given an emissions license that becomes part of capital equipment. Operators can then install pollution control equipment, and sell parts of their emissions licenses. The intention of this is to give operators economic incentives to install pollution controls.

A Global Problem  Acid rain is truly global phenomenon that is causing problems for humans, plant and animal species and the environment. Here are a few of the major problems caused by acid rain around the world:  In Brazil,fish are dying in the reddish water due to acid deposition, trees are turning to skeletons, and human health has suffered immensely.  Poland is one of the most polluted in the world, and burns coal with much sulfur in it. There is much human illness in cities close to coal burning factories, and in Crakow, the golden roof of a chapel is quickly dissolving.

 In South Africa, There is lots of coal burning near Kruger National Park, and the park is currently facing the threat of acid rain.  In the country of Czechoslovakia, the sickness rate for children is quite high because of acid rain, especially in the form of breathing problems. Much of the fresh water there is too acidic to drink.  North America is a huge contributer to the world's pollution and acid rain. Back in 1982, in the United States and Canada alone, 51,000 people died from sulfur pollution (a number which has increased considerably ove r the years) In 1967, a bridge over the Ohio River collapsed due to corrosion from acid rain, and killed 46 people.