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Contents I.Review of pH II.Definition of acid rain III.Pollutants that create acid rain: a. sulfur dioxide b. nitrogen oxide c. ammonia IV.Acid rain.

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Presentation on theme: "Contents I.Review of pH II.Definition of acid rain III.Pollutants that create acid rain: a. sulfur dioxide b. nitrogen oxide c. ammonia IV.Acid rain."— Presentation transcript:

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4 Contents I.Review of pH II.Definition of acid rain III.Pollutants that create acid rain: a. sulfur dioxide b. nitrogen oxide c. ammonia IV.Acid rain ecosystem impacts V. Other impacts VI. Legislation and technology VII.Trends over time

5 pH is a measure of the activity of hydrogen ions (H+) in a solution. pH is shorthand: - pH = -log10 [H+] - a small p is used in place of writing -log10 - H represents the concentration of hydrogen ions ([H+]) I. Review of pH Acid Rain 101

6 Water is converted into hydrogen and hydroxyl ions. H 2 O  H + + OH - water hydrogen ionhydroxyl ion When the activity of these ions is equal, water is neither acidic or alkaline and is said to be neutral, represented by a pH value of 7. When the activity of hydrogen ions is greater, a solution is said to be acidic and is represented by a range of pH values from 0-6. When the activity of hydroxyl ions is greater, a solution is said to b alkaline and is represented by a range of pH values from Review of pH

7 Because pH is a logarithmic function, there are tenfold differences between each pH value. Examples: - A pH value of 6 is ten times more acidic than a pH value of 7. - A pH value of 5 is one hundred times more acidic than a pH value of 7. 1.Review of pH

8 From Acid Rain Revisited, page 5 In 1997, the pH of wet deposition at HBEF was 4.2; today it is Review of pH

9 Acid rain Average pH of rain at Hubbard Brook Experimental Forest in 2007 < pH levels found in precipitation II. Definition of Acid Rain Acid Rain 101

10 Acid rain isn’t just RAIN- It includes everything that falls from the atmosphere (with a pH < 5.2): - Wet precipitation (rain, snow, etc.) - Dry dust and gases (dry deposition) - Clouds and fog The terms “acid deposition” and “acid precipitation” are more descriptive, but “acid rain” is widely used and accepted. 2. Definition of Acid Rain

11 What creates acid rain? - sulfur dioxide - nitrogen oxides - ammonia III. Pollutants that Cause Acid Rain Acid Rain 101

12 Sulfur dioxide, emitted mainly from combustion of coal and oil in factories and powerplants. 3. Pollutants that cause acid rain

13 Chemical reactions: sulfur dioxide Coal and oil contain sulfur. When burned in factories and powerplants, the sulfur combines with oxygen in the air and is emitted from smokestacks and chimneys. S + O 2  SO 2 (sulfur dioxide) Processes found in chemical and petroleum industries also release sulfur into the air. 3. Pollutants that cause acid rain

14 SO 2 + H 2 O → H 2 SO 4 sulfur dioxide + water →sulfuric acid H 2 SO 4 ↔ H + + HSO 4 - ↔ 2H + + SO 4 2- sulfuric acid ↔ hydrogen ions + sulfate Hydrogen ions make a solution acidic. Sulfur dioxide reacts with water in the atmosphere to create sulfuric acid, which dissociates into sulfate and hydrogen ions. Chemical reactions: sulfur dioxide 3. Pollutants that cause acid rain

15 Nitrogen oxides from electric utilitiesautomobiles Lightening (to a much smaller degree) 3. Pollutants that cause acid rain

16 Transportation ≈ 54% nationally - Uses nitrogen found in atmosphere Electric Utilities ≈ 30% nationally - Use nitrogen found in coal and oil The high temperature of the internal combustion engine- used in autos, airplanes, electric utility boilers, etc.- releases energy that causes a reaction between nitrogen and oxygen. Major sources of Nitrogen oxides: 3. Pollutants that cause acid rain Acid Rain 101

17 Nitrogen oxides Energy + N 2 + O 2  2NO Energy + 2NO + O 2  2NO 2 The transportation sector (cars, trucks, etc..,) is the leading source of nitrogen oxides in the atmosphere. Electricity generation, which still largely relies on combustion, is the second leading source. The energy released by the lightning also creates a reaction between oxygen and nitrogen, so it is a natural source of nitrogen oxides to the atmosphere. 3. Pollutants that cause acid rain

18 Chemical reactions: nitrogen oxides NO x + H 2 O → HNO 3 nitrogen oxides + water → nitric acid HNO 3 ↔ H + + NO 3 - nitric acid ↔ hydrogen ion + nitrate Nitrogen oxides react with water in the atmosphere to create nitric acid, which dissociates into nitrate and hydrogen ions. Hydrogen ions make a solution acidic. 3. Pollutants that cause acid rain

19 Ammonia (NH 3 ) is produced mainly through agriculture: livestock and poultry manure fertilizer application 3. Pollutants that cause acid rain

20 Chemical reactions: Ammonia Ammonia gas reacts with sulfuric and nitric acids to form ammonium aerosols. Example: NH NO 3 -  NH 4 NO 3 ammonium nitrateammonium nitrate When aerosols are deposited to the ground they react with oxygen in a process called nitrification. NH 4 NO 3 + 2O 2  2H + + 2NO H 2 O ammonium nitrateoxygen hydrogen ions nitrate water This process releases H + ions, which lowers the pH (creates more acidic conditions). 3. Pollutants that cause acid rain

21 From emissions to acid deposition: From Acid Rain Revisited, pg. 4

22 1. Acid rain causes increased loss of base cations from soil Decrease in acid neutralizing capacity (ANC) of soils (reduced ability to buffer the incoming acids) Lower fertility of soils (base cations are nutrients necessary for tree growth) this causes IV. Acid rain ecosystem impacts Acid Rain 101

23 How does acid rain affect soils? 2. Inorganic aluminum is dissolved from minerals and accumulates in the soil. The presence of dissolved inorganic aluminum in soil is harmful to plants as it can damage root tips and affect the way plants take up nutrients. Dissolved inorganic aluminum is also toxic to animals that live in the soil such as frogs, salamanders and larval stages of insects. this causes 4.a. Impacts on terrestrial ecosystems

24 From Acid Rain Revisited, pg a. Impacts on terrestrial ecosystems

25 Is it a big problem in terrestrial ecosystems? It depends on the soil of the ecosystem. Soils with limestone bedrock, for example, are able to buffer incoming acids. Soils with a low acid neutralizing capacity (ANC), such as granitic bedrock, are not and are called acid-sensitive soils. 4.a. Impacts on terrestrial ecosystems

26 Changes in the calcium cycle at the Hubbard Brook Experimental Forest between From Acid Rain Revisited, pg. 10 The amount of available calcium in the soil at the HBEF appears to have declined more than 50 percent between the years 1950 – 1995.

27 Inorganic aluminum dissolves out of minerals at acidic pH levels, and is toxic to living things. Inorganic aluminum is 1,000 times more soluble in water with a pH of 4.6 than in water with a pH of Chemical effects on aquatic systems 4.b. Impacts on aquatic ecosystems

28 Acid Rain 101 It can reduce the acid neutralizing capacity of water. Acidic waters are defined as having an ANC of less than zero (i.e., no buffering capacity in the water). 1. Chemical effects on aquatic systems 4.b. Impacts on aquatic ecosystems

29 Animals all along the food chain are affected: zooplankton, invertebrates and fish can be harmed. Aluminum clogs fish gills by forming lesions that obstruct a fish’s ability to take oxygen from water. 2. Biological effects: 4.b. Impacts on aquatic ecosystems

30 Different organisms can tolerate different pH levels. For example, frogs are the only organisms included on this chart that can tolerate a pH of Biological effects on animals: From 4.b. Impacts on aquatic ecosystems

31 Acid Rain 101 ≈ 8% of lakes in Adirondacks ≈ 15% of lakes in New England and ≈ 8.5% of streams in the northern Appalachian Plateau are considered acidic, which means ANC is less than zero. 4.b. Impacts on aquatic ecosystems

32 Acid Rain 101 Causes damage to certain building materials, historical monuments, ancient statues and gravestones. Sulfuric acid in the rain chemically reacts with calcium compounds in the stones (limestone, sandstone, marble and granite) to create gypsum, which then flakes off. V. Other Impacts from acid rain

33 Visibility is reduced by sulfate and nitrate in the atmosphere. Causes an increased rate of oxidation for iron. 5. Other impacts from acid rain

34 Acid Rain 101 What has been done to remedy the problem of acid rain? In the past 30 years, the U.S. Congress has enacted several laws to promote clean air. Two important laws were the Clean Air Act of 1970 and the Clean Air Act Amendments of VI. Legislation and technology

35 The Clean Air Act of 1970 Was not written to reduce acid rain, but to reduce pollutants in the air in general. Identified six major pollutants as harmful to human health and environment: Carbon monoxideSulfur dioxide OzoneNitrogen dioxide LeadParticulate matter* * With size of particle less than or equal to 10 micrometers 6. Legislation and technology

36 Title IV of the Clean Air Act Amendments of 1990 Targeted the emissions of electric utilities, which accounted for 70% of sulfur and 30% of nitrogen emissions. Goals: - reduce SO 2 by 10 million tons, or 40% - reduce NO x by 2 million tons, or 10% compared to 1980 levels 6. Legislation and technology

37 Some strategies used to reduce sulfur and nitrogen oxides emissions: ‘cap,’ or limit, the amount of SO 2 that can be emitted by electric utilities use of trade allowances for SO 2 use of catalytic converters in automobiles 6. Legislation and technology

38 Some strategies used to reduce sulfur and nitrogen oxides emissions: use of ‘clean coal technology’ (use of low sulfur coal in factories and electric utility plants) Installation of scrubbers in smokestacks 6. Legislation and technology

39 A type of scrubber called ‘Counter Current Packed Tower’, sold by Ceilcote Air Pollution Control Generally, a scrubber is tower equipped with a fan that extracts gases from the power plant into the tower. A limestone slurry is injected into tower to mix with these gases. Calcium carbonate of the limestone produces pH-neutral calcium sulfate that is physically removed from scrubber. How do scrubbers work?

40 How do catalytic converters work? Catalytic converters treat exhaust before it leaves the car and remove a lot of the pollution. US car manufacturers were required to reduce the amount of emissions coming from vehicles by installing catalytic converters.

41 ‘cap’ NO x emissions from electric utilities, which will likely increase as electric generation from power plants increases set standards for ammonia emissions. To date there is no legislation to: 6. Legislation and technology Have the CAA and CAAA helped to reduce SO 2 and NO x pollution?

42 Acid Rain 101 Change in SO 2 emissions in the U.S. over time Total SO 2 emissions (US) 1940: 20 million tons 1970: 28 million tons 2002: 19 million tons SO 2 emissions from utilities (US) 1980: 17.5 million tons 2002: 10.3 million tons VI. Legislation and technology

43 Sulfate 6. Trends over time

44 Concentration of Sulfate in Precipitation at the Hubbard Brook Experimental Forest Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation. 6. Trends over time

45 Change in NO x emissions in the U.S. over time 1990: 5.5 million tons 2001: 4.7 million tons NO x emissions from utilities (US) 6. Trends over time Acid Rain 101

46 Nitrate 6. Trends over time

47 Concentration of Nitrate in Precipitation at the Hubbard Brook Experimental Forest Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation. 6. Trends over time

48 Ammonium 6. Trends over time

49 Concentration of Ammonium in Precipitation at the Hubbard Brook Experimental Forest Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation. 6. Trends over time

50 Have reductions in SO 2 and NO X affected the acidity, or pH of precipitation? 6. Trends over time

51 Acidity (pH) 6. Trends over time

52 pH of Stream Water and Precipitation at the Hubbard Brook Experimental Forest Note: An increase in pH indicates a decrease in acidity. Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation. 6. Trends over time

53 Overall… Sulfur dioxide regulation has been fairly successful. However, emissions remain high compared to background (pre- industrial) conditions. Although emissions of NO x and ammonia have not been fully addressed, nitrogen deposition has declined significantly over the past decade as electric utility regulations take effect. 6. Trends over time

54 A complex, tricky problem… Sulfur and nitrogen compounds can travel thousands of kilometers from their original source, therefore Air pollution crosses state and national boundaries. (ie: Pollutants from power plants in Michigan or New Jersey can travel to the forests of New Hampshire and Vermont.) Taller smokestacks have improved air quality in industrialized areas, but now pollutants are blown great distances by wind and affect much larger areas. 6. Trends over time

55 Clean Air Interstate Rule Designed to reduce air pollution that moves across state boundaries Will cap SO 2 and NOx emissions across 28 eastern states and the District of Columbia. When fully implemented… -will reduce SOx by 70% from 2003 levels -will reduce NOx by 60% from 2003 levels 6. Trends over time

56 St ate s Co ver ed by Cl ea n Air Int ers tat e Ru le States covered by Clean Air Interstate Rule From 6. Trends over time

57 A number of international treaties dealing with the long- range transport of atmospheric pollutants have been signed. Sulfur Emissions Reduction Protocol Convention on Long-Range Transboundary Air Pollution World-wide Acid rain is a substantial problem wherever there is concentrated industry, particularly in -People’s Republic of China -Eastern Europe -Russia 6. Trends over time

58 The Hubbard Brook Acid Rain Story Part 1: The Discovery For more information on the role of the Hubbard Brook Ecosystem Study in acid rain research, please view the next slideshow.


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