I. I. Review of ph. Acid Rain 101

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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 I. I. Review of ph 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+]) Acid Rain 101

6 1.Review of ph Water is converted into hydrogen and hydroxyl ions. H 2 O H + + OH - water hydrogen ion hydroxyl 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 7-14.

7 1.Review of ph 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.

8 1.Review of ph In 1997, the ph of wet deposition at HBEF was 4.2; today it is 4.5. From Acid Rain Revisited, page 5

9 II. Definition of Acid Rain ph levels found in precipitation Acid rain < 5.2 Average ph of rain at Hubbard Brook Experimental Forest in Acid Rain 101

10 2. Definition of Acid Rain 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.

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

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

13 3. Pollutants that cause acid rain 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.

14 3. Pollutants that cause acid rain Chemical reactions: sulfur dioxide 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 Sulfur dioxide reacts with water in the atmosphere to create sulfuric acid, which dissociates into sulfate and hydrogen ions. Hydrogen ions make a solution acidic.

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

16 3. Pollutants that cause acid rain Major sources of Nitrogen oxides: 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 engineused in autos, airplanes, electric utility boilers, etc.- releases energy that causes a reaction between nitrogen and oxygen. Acid Rain 101

17 3. Pollutants that cause acid rain 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.

18 3. Pollutants that cause acid rain 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.

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

20 3. Pollutants that cause acid rain Chemical reactions: Ammonia Ammonia gas reacts with sulfuric and nitric acids to form ammonium aerosols. Example: NH NO 3 - NH 4 NO 3 ammonium nitrate ammonium 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 nitrate oxygen hydrogen ions nitrate water This process releases H + ions, which lowers the ph (creates more acidic conditions).

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

22 IV. Acid rain ecosystem impacts 1. Acid rain causes increased loss of base cations from soil this causes 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) Acid Rain 101

23 4.a. Impacts on terrestrial ecosystems How does acid rain affect soils? 2. Inorganic aluminum is dissolved from minerals and accumulates in the soil. this causes 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.

24 4.a. Impacts on terrestrial ecosystems From Acid Rain Revisited, pg. 10

25 4.a. Impacts on terrestrial ecosystems 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.

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

27 4.b. Impacts on aquatic ecosystems 1. Chemical effects on aquatic systems 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 5.6.

28 4.b. Impacts on aquatic ecosystems 1. Chemical effects on aquatic systems 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). Acid Rain 101

29 4.b. Impacts on aquatic ecosystems 2. Biological effects: 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.

30 4.b. Impacts on aquatic ecosystems 2. Biological effects on animals: Different organisms can tolerate different ph levels. For example, frogs are the only organisms included on this chart that can tolerate a ph of 4.0. From

31 4.b. Impacts on aquatic ecosystems 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. Acid Rain 101

32 V. Other Impacts from acid rain 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.

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

34 VI. Legislation and technology 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 Acid Rain 101

35 6. Legislation and technology 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 monoxide Ozone Lead Sulfur dioxide Nitrogen dioxide Particulate matter* * With size of particle less than or equal to 10 micrometers

36 6. Legislation and technology 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

37 6. Legislation and technology 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

38 6. Legislation and technology 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

39 How do scrubbers work? 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. A type of scrubber called Counter Current Packed Tower, sold by Ceilcote Air Pollution Control

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

42 VI. Legislation and technology 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 Acid Rain 101

43 6. Trends over time Sulfate

44 6. Trends over time Concentration of Sulfate in Precipitation at the Hubbard Brook Experimental Forest 100 Concentration (µeq/l) Sulfate Water Year Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation.

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

46 6. Trends over time Nitrate

47 6. Trends over time Concentration of Nitrate in Precipitation at the Hubbard Brook Experimental Forest 50 Concentration (µeq/l) Nitrate Water Year Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation.

48 6. Trends over time Ammonium

49 6. Trends over time Concentration of Ammonium in Precipitation at the Hubbard Brook Experimental Forest 50 Concentration (µeq/l) Ammonium Water Year Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation.

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

51 6. Trends over time Acidity (ph)

52 6. Trends over time ph of Stream Water and Precipitation at the Hubbard Brook Experimental Forest Streamwater ph 4.8 ph Precipitation ph 1984 (slope of line becomes significant) Water Year 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.

53 6. Trends over time Overall Sulfur dioxide regulation has been fairly successful. However, emissions remain high compared to background (preindustrial) 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.

54 6. Trends over time 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.

55 6. Trends over time 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

56 6. Trends over time States covered by Clean Air Interstate Rule From

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

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