Acid Rain

Environmental StudiesUnit:3

Air is becoming increasingly polluted Acid Rain -- sulfur dioxide (also nitrogen

oxides) from coal burning sources + rain = ACID RAIN

Acid rainAcid rain is rain consisting of water droplets that are

unusually acidic because of atmospheric pollution - most notably the excessive amounts of sulfur and nitrogen released by cars and industrial processes. Acid rain is also called acid deposition because this term includes other forms of acidic precipitation such as snow.

Acidic deposition occurs in two ways: wet and dry. Wet deposition is any form of precipitation that removes acids from the atmosphere and deposits them on the Earth’s surface. Dry deposition polluting particles and gases stick to the ground via dust and smoke in the absence of precipitation.

Causes of Acid RainAcid deposition can occur via natural sources like

volcanoes but it is mainly caused by the release of sulfur dioxide and nitrogen oxide during fossil fuel combustion.

When these gases are discharged into the atmosphere they react with the water, oxygen, and other gases already present there to form sulfuric acid, ammonium nitrate, and nitric acid. These acids then disperse over large areas because of wind patterns and fall back to the ground as acid rain or other forms of precipitation.

The gases responsible for acid deposition are normally a byproduct of electric power generation and the burning of coal.

Effects of Acid RainThere are several important impacts of acid deposition

on both natural and man-made environments. Aquatic settings are the most clearly impacted by acid deposition though because acidic precipitation falls directly into them. Both dry and wet deposition also runs off of forests, fields, and roads and flows into lakes, rivers, and streams.

As this acidic liquid flows into larger bodies of water, it is diluted but over time, acids can accrue and lower the overall pH of the body. Acid deposition also causes clay soils to release aluminum and magnesium further lowering the pH in some areas. If the pH of a lake drops below 4.8, its plants and animals risk death

Effects of Acid RainAcid deposition can significantly impact forests. As acid rain

falls on trees, it can make them lose their leaves, damage their bark, and stunt their growth. By damaging these parts of the tree, it makes them vulnerable to disease, extreme weather, and insects. Acid falling on a forest’s soil is also harmful because it disrupts soil nutrients, kills microorganisms in the soil, and can sometimes cause a calcium deficiency.

Finally, acid deposition also has an impact on architecture and art because of its ability to corrode certain materials. As acid lands on buildings (especially those constructed with limestone) it reacts with minerals in the stones sometimes causing it to disintegrate and wash away. Acid deposition can also corrode modern buildings, cars, railroad tracks, airplanes, steel bridges, and pipes above and below ground.

Problems from Acid Rain:

• Destruction of limestone and marble monuments due to increased chemical weathering

• Acidification of aquatic ecosystems destroying the life in them and of animals depending on them.

• Damage forests and other plants in a variety of ways

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Ozone Depletion• Losing Earth's Protective Layer

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The ozone layer is a belt of naturally occurring ozone gas that sits 9.3 to 18.6 miles (15 to 30 kilometers) above Earth and serves as a shield from the harmful ultraviolet B radiation emitted by the sun.

Ozone is a highly reactive molecule that contains three oxygen atoms. It is constantly being formed and broken down in the high atmosphere

Today, there is widespread concern that the ozone layer is deteriorating due to the release of pollution containing the chemicals chlorine and bromine. Such deterioration allows large amounts of ultraviolet B rays to reach Earth, which can cause skin cancer and cataracts in humans and harm animals as well.

Causes:Scientific evidence indicates that stratospheric

ozone is being destroyed by a group of manufactured chemicals, containing chlorine and/or bromine. These chemicals are called "ozone-depleting substances" (ODS).

The primary cause of ozone depletion is the presence of chlorine-containing source gases (primarily CFCs and related halocarbons).

In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction.

• The main ODS are chlorofluorocarbons (CFCs), hydrochlorofluorcarbons (HCFCs), carbon tetrachloride and methyl chloroform.

• Halons (brominated fluorocarbons) also play a large role. Their application is quite limited: they're used in specialized fire extinguishers. But the problem with halons is they can destroy up to 10 times as much ozone as CFCs can.

Effects:Increased UV: Ozone, while a minority constituent in Earth's

atmosphere, is responsible for most of the absorption of UVB radiation. Its depletion causes increased UV radiation.

Biological effects Ozone layer depletion is expected to increase surface UVB levels,

which could lead to damage, including increase in skin cancer and cataract (eye damage) in human beings.

Increased tropospheric ozone: Increased surface UV leads to increased tropospheric ozone. Ground-level ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties. The risks are particularly high for young children, the elderly, and those with asthma or other respiratory difficulties.

Effects on crops:An increase of UV radiation

would be expected to affect crops. A number of economically important species of plants, such as rice, depend on cyanobacteria residing on their roots for the retention of nitrogen. Cyanobacteria are sensitive to UV radiation and would be affected by its increase. Thus crop growth will be affected. NASA projections of

stratospheric ozone concentrations if chlorofluorocarbons had not been banned.

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Global warming

Global warming is the unequivocal and continuing rise in the average temperature of Earth's climate system.

Since 1971, 90% of the warming has occurred in the oceans. Despite the oceans' dominant role in energy storage, the term "global warming" is also used to refer to increases in average temperature of the air and sea at Earth's surface.

• Scientists were more than 90% certain that most of global warming was being caused by increasing concentrations of greenhouse gases produced by human activities.

Greenhouse gases• The greenhouse effect is the process by

which absorption and emission of infrared radiation by gases in a planet's atmosphere warm its lower atmosphere and surface.

• On earth, naturally occurring amounts of greenhouse gases have a mean warming effect of about 33 °C

• The major greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect; carbon dioxide (CO2), which causes 9–26%;methane (CH4), which causes 4–9%; and ozone (O3), which causes 3–7%.

• Changes in the concentration of greenhouse gases, which occur both naturally and as a result of human activities, also influence Earth’s climate.

Increasing greenhouse gases trap more heat

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• Earth’s surface absorbs heat from the sun and then re-radiates it back into the atmosphere and to space.

• Much of this heat is absorbed by greenhouse gases, which then send the heat back to the surface, to other greenhouse gas molecules, or out to space. Though only 1% of atmospheric gases are greenhouse gases, they are extremely powerful heat trappers.

• By burning fossil fuels faster and faster, humans are effectively piling on more blankets, heating the planet so much and so quickly that it’s hard for Mother Nature and human societies to adapt.

CO2 comes from a variety of sources. For example, plants take up carbon dioxide in the air to make wood, stems, and leaves, and then release it back into the air when the leaves fall or the plants die. The concern today is that fossil fuel use is putting huge amounts of CO2 in the atmosphere at a rate faster than the climate system can adapt to.

• Certainly, past temperatures past have been lower than today, and CO2 concentrations have also varied.

• Large global swings were probably caused by such things as changes in Earth’s orbit, which changed the distribution of sunlight over the planet. When this caused warming, more CO2 and other greenhouse gases were released, producing additional warming.

• Earth is getting warmer by virtually every measure we know, and the temperature has been well above normal for more than 25 years. Although increases of 1.0-1.6°F (0.6-0.9°C) over the last century or so may not sound very threatening, remember that’s a global average.

• The warming is stronger over land than over oceans and in the higher latitudes than in the tropics.

Sea-level rise projections : a few inches to a few feet

•2 ft: U.S. would lose 10,000 square miles•3 ft: Would inundate Miami•Affects erosion, loss of wetlands, freshwater supplies•Half of the world’s population lives along coasts•Big question: Ice sheets

Why should we care?

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• Global average temperatures are expected to increase by about 2-13°F (1-7°C) by the end of the century. That may not sound like a lot, so what’s the big deal? The problem is that small changes in global average temperature can lead to really large changes in the environment. Let’s look at some of the expected changes.

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• There will always be natural variability, and some places and some years will be warmer or cooler than average. In general, however, summers will get hotter, not only because of higher temperatures but also because humidities will increase. That means that heat waves, like the one that killed 35,000 people in Europe in 2003, will become more common.

• On the plus side, winters will be warmer in many places, reducing heating bills. And the number of days with frosts is likely to decrease.

References/Sources1. https://lh3.ggpht.com/VpghZaXZE2No81LCRdJwvYvZ8y9h7ld51Q4vTZXK

PT2bHRSKclZa71nFBIkpvEQQNNZy=s1062. https://lh3.ggpht.com/xNtvJ_BaQS5k6uYGiLK5FpE8i08-

NKGIVDGyrla0xZ3CPhwvXJRAiW8ZXAzIWzcMXMr4NxM=s1133. https://lh3.ggpht.com/

OuxQWgnPi4ND_Ix7PfjEU9o6ahjFnXwz1skcMc9fCLw47lAzCh49h8a6V78Aid7pQO-3CQ=s119

4. https://lh6.ggpht.com/McSsK4-mfj0DMKcmNPVOHz4Ucc24kWsF-B0wL89M982Bp_r61vlmGRvL0IIr73yiuiqhZg=s113

5. https://lh5.ggpht.com/jymlJFxrbl9SwM0NMsr_1Qh4Vmd6yC4ty9zd7B2-Njdv338-Cjh4n_druUdZYK24FOtIQQ=s170

6. https://lh6.ggpht.com/pm95_mJWfD-XDQl8x4JP88dtd767HkF7DOaPtkllk3v5zlzG2aBgsMeHYBlzuQIvccIc=s115

Book/Web Resources• Environmental Pollution: Causes, Effects & Control by K.C Agarawal