2. General concepts on ACID RAIN Tareq Bin Azir Lecturer- Department of Chemistry Government Titumir College Dhaka tareqbinazir@yahoo.com Tareq Bin Azir Lecturer- Department of Chemistry Government Titumir College Dhaka tareqbinazir@yahoo.com

3. Definition Sources Formation Deposition Affected Areas Effects Preventive Measures

5. Definition of Acid Rain Rain water that has a pH of less than that of natural rainwater (<5.6) It is formed when 1. sulfur dioxide and sulfur trioxide (SO 2 ; SO 3 ) 2. nitrogen monoxide and nitrogen dioxide (No x ) gases in the atmosphere, combine with water vapor and precipitate as Sulfuric acid(H 2 SO 4 ) or Nitric acid(HNO 3 ) This acidic precipitation then falls to the earth as rain, snow or fog

6. pH Scale pH = -log[H + ]

7. pH & WATER Pure water is neutral Sea water is slightly basic Normal rainfall is slightly acidic due to carbon dioxide (CO 2 ) mixing with water vapor forming carbonic acid Acid rain is acidic

8. Sources of Acid Rain Natural Sources – – Emissions from volcanoes and biological processes that occur on the land, in wetlands and in the oceans contribute acid-producing gases to the atmosphere – Effects of acidic deposits have been detected in glacial ice thousands of years old in remote parts of the globe

9. Human Sources of Acid Rain Industrial factories, power-generating plants and vehicles Sulfur dioxide and oxides of nitrogen are released during the fuel burning process (i.e. combustion) Sulfur dioxide accounts for about 90 % of all acid rainfall

10. Formation of Acid Rain

11. Formation of Sulfuric Acid (H 2 SO 4 ) 2SO 2 (g) + O 2 (g)  2SO 3 (g) SO 3 (g) + H 2 O(l)  H 2 SO 4 (aq) 2NO(g) + O 2 (g)  2NO 2 (g) 4NO 2 (g) + 2H 2 O(l) + O 2 (g)  4HNO 3 (aq) Formation of Nitric Acid (HNO 3 )

12. Acid deposition Wet deposition Wet deposition of acids occurs when any form of precipitation (rain, snow and so on) 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. 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. This occurs when particles and gases stick to the ground, plants or other surfaces.

14. Effects of Acid Rain  Harmful on aquatic life Increased acidity in water bodies Stops eggs of certain organisms (e.g. fish) to stop hatching Changes population ratios Affects the ecosystem  Effects on Vegetation Harmful to vegetation Increased acidity in soil Leaches nutrients from soil, slowing plant growth Leaches toxins from soil, poisoning plants Creates brown spots in leaves of trees, impeding photosynthesis Allows organisms to infect through broken leaves

15.  Effects on Buildings and Structures Marble is particularly susceptible Accelerates weathering in metal and stone structures – Eg. Parthenon in Athens, Greece; Taj Mahal in Agra, India  Effects on Human Health Respiratory problems, asthma, dry coughs, headaches and throat irritations Brain damage, kidney problems, and Alzheimer's disease has been linked to people eating "toxic" animals/plants

16. Affected Areas – A cid rain is a problem in Eastern Canada and the Northeastern USA – Acid rain from power plants in the Midwest United States has also harmed the forests of England. – Industrial acid rain is a substantial problem in China, Taiwan, Eastern Europe, Russia and areas down-wind from them. – The effects of acid rain can spread over a large area, far from the source of the pollution

18. Prevention  Using alternative sources of electricity (i.e. nuclear power, hydro-electricity, wind energy and solar energy)  Minimize fossil fuel use in power plants, factories, vehicles etc.  Reduce the amount of electricity use  Energy Conservation & Change life style  Use catalytic converters in vehicle exhausts which remove the nitrogen oxides.  Limit the number of vehicles on the roads and increase public transport.

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