1. Case Studies of Scientific and Technological Issues Nature and Development of Science and Technology

2. Acid Rain and its Effects

3. Concepts of Acidity

4. Acidity of some everyday objects on the pH scale Normal rainwater shows pH of about 5.6 because of the reaction of carbon dioxide with water to form a weak carbonic acid.

5. What is Acid Rain?

6. Basically, rain water is considered as acidic when it’s pH value lower than 5.6 What is Acid Rain?

7. Causes of Acid Rain?

8. Sulphur Dioxide and Nitrogen Oxides… …the pollutants hiding behind Acid Rain

9. Sulphur Dioxide  Sulphur occurs widely in nature, in all animal and plants, and in the fossil fuels  When fossil fuels are burned to generate energy the sulphur combines with the oxygen in the atmosphere to form sulphur dioxide.  When fossil fuels are burned to generate energy the sulphur combines with the oxygen in the atmosphere to form sulphur dioxide.  In many urban and industrial areas human activity may account for around 90 percent of the SO2 in the air.  Sulfur dioxide oxidizes in the atmosphere and reacts with water to produce sulfuric acid which eventually falls as acid rain

10. Sulphur Dioxide About 20 million tons of sulfur dioxide are emitted into the atmosphere from the United States each year

11. Nitrogen Oxides  A number of different kinds of nitrogen oxides exist in the atmosphere. Collectively they are given the name NOx.  A number of different kinds of nitrogen oxides exist in the atmosphere. Collectively they are given the name NOx.  In industrial areas, the vast majority are produced when fossil fuels are burned.  In industrial areas, the vast majority are produced when fossil fuels are burned.  The nitrogen present in the fuel and in the atmosphere combines with oxygen to produce several different types of NOx.  The nitrogen present in the fuel and in the atmosphere combines with oxygen to produce several different types of NOx.  Coal-burning power stations and transport are the major sources.  Nitric oxides also oxidize in the atmosphere and react with water to produce nitric acid which eventually falls as acid rain

12. Nitrogen Oxides About 25 million tons of nitrogen oxides are emitted into the atmosphere from the United States each year

13. Acid rain forms when pollutants (e.g. SO 2 and NO x ) combine with water in the atmosphere and fall to the earth as rain

14. Acid Rain in Hong Kong

15. From the fading view across Victoria Harbour to the poor quality of the air we breathe, air pollution is having a growing impact on our lives……. (Environment Hong Kong 1999)

16. MingPao News 24 June 1999