Acid Rain

Educational Objectives To understand how the pH level of an environment affects living organisms. To understand the relationship between the pH level and CO 2 concentration of distilled water.

What is Acid Rain ? Acid Rain is any form of rain that is more acidic than normal Generally, rain water has a pH value of a little less than 7 Pure water has a pH of 7 Any rainfall that has a pH value less than 5.6 ( about ) is defined as acid rain. Northeastern United States pH in range of 4.

History of Pollution From Industrial Revolution to the Space Age, humans have produced inventions that use many of the earth’s varied energy resources to make living easier. Often, energy comes from fossil fuels - coal, oil and natural gas ! These inventions and using fossil fuels lead to pollution !

How does Acid Rain Form ? Gas pollutants e.g. carbon dioxide, sulphur dioxide, or nitrogen dioxide dissolve in rain water. Acids are formed when gases, such as CO 2, SO 2 and NO 2 react with the water in the atmosphere

Pollutants Nitrogen oxides can also be produced naturally by lightning strikes Sulfur dioxide is produced by volcanic eruptions. Human activities ( burning fossil fuels – Carbon dioxide )such as electricity generation, factories, and motor vehicles also release lots of acid vapour into the atmosphere.

How does Acid Rain form ? Smoke and fumes from burning fossil fuels rise into the atmosphere and combine with the moisture in the air to form acid rain. Acid rain usually forms high in the clouds Sunlight increases the rate of these acid forming reactions. Rainwater, snow, fog, and other forms of precipitation containing acids fall to earth as acid rain.

Pollution The chemical reactions that change air pollution to acid rain can take from several hours to several days. Many years ago, smokestacks were only a few stories high, pollution stayed near the ground causing unhealthy conditions for plants and animals

Pollution To reduce this pollution, government passed a law permitting construction of very tall smokestacks However, sending pollution high into the sky, increases the time that pollution stays in the air The longer the pollution is in the air, the greater the chances that pollutants can form acid rain. In addition, wind can carry pollutants for hundreds of miles before they combine with water droplets and form acid rain.

What is Acid Rain ? –CO 2 + H 2 O  H 2 CO 3 (carbonic acid) –SO 2 + H 2 O  H 2 SO 3 (sulphorous acid) –NO 2 + H 2 O  HNO 2 (nitrous acid) + HNO 3 (nitric acid) The pH of Rain drops

Examples When CO 2 reacts with water, carbonic acid is formed. CO 2 (g)+H 2 O(l)-  H 2 CO 3 (aq) When SO 2 reacts with water, sulfurous acid is formed. SO 2 (g)+H 2 O(l)-  H 2 SO 3 (aq) When NO 2 reacts with water, nitric acid and nitric acid is formed. 2NO 2 (g)+H 2 O(l)-  HNO 2 (aq)+HNO 3 (aq)

Causes of Acid Rain

How does Acid Rain effect us ? Harmful effects on plants, aquatic animals and human beings. It kills micro-organisms It poisons plants It damages metals and limestone It kills fish

Effects of Acid Rain harmful to plants – acid rain destroys the nutrients in the soil which the plants need to survive.

Effects of Acid Rain harmful to aquatic animals - fish eggs will not hatch and adult fishes will die when acid rain enters lakes or rivers

Effects of Acid Rain harmful to human beings, although the acid in the rainwater is too dilute to have direct effect on us humans, increased amount of sulfur dioxide and nitrogen oxides in the air do contribute to heart and lung problems including asthma and bronchitis.

Effects of Acid Rain Urban areas of cities – acid rain affects buildings, statues, monuments, and cars. Chemicals found in acid rain can cause paint to peel and stone statues to begin to appear old and worn down, which reduces their value and beauty.

Effects of Acid Rain Most building materials made of limestone and marble. The acid rain water mainly sulphuric acid will react with calcium carbonate from limestone and marble to form calcium sulphate.

Acid Rain on Earth Region of Continental US most affected by acid rain is Northeast ( pH levels between ) Most rapid increase in acid precipitation in US seems to be Southeast. West of Mississippi rain neutral or alkaline. Exceptions : Colorado, Los Angeles Basin, San Francisco Bay area, Tucson, Spokane, Portland ( pH 4-5 )