Acid Rain III

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

I.I. ReviewReview ofof pHpH

• 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 1.Review of pH

• Water is converted into hydrogen and hydroxyl ions. + - H2O Æ 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. 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. 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 II.II. DefinitionDefinition ofof AcidAcid RainRain

pH levels found in precipitation

Acid rain < 5.2

Average pH of rain at 4.5 Hubbard Brook Experimental Forest in 2007

Acid Rain 101 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. III.III. PollutantsPollutants thatthat CauseCause AcidAcid RainRain

What creates acid rain?

- sulfur dioxide - nitrogen oxides - ammonia

Acid Rain 101 3. Pollutants that cause acid rain

•Sulfur dioxide, emitted mainly from combustion of coal and oil in factories and powerplants.

www.FreeFoto.com 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 + O2 Æ SO2 (sulfur dioxide) http://en.wikipedia.org/wiki/Image:Gavin_Plant.JPG • Processes found in chemical and petroleum industries also release sulfur into the air. 3. Pollutants that cause acid rain

Chemical reactions: sulfur dioxide

SO2 +H2O → H2SO4 sulfur dioxide + water → sulfuric acid

+ - + 2- H2SO4 ↔ H + HSO4 ↔ 2H + SO4 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. 3. Pollutants that cause acid rain Nitrogen oxides from

electric utilities automobiles

www.FreeFoto.com Lightening (to a much smaller degree) 3. Pollutants that cause acid rain Major sources of Nitrogen oxides:

Transportation Electric Utilities ≈ 54% nationally ≈ 30% nationally - Use nitrogen found - Uses nitrogen found in in coal and oil atmosphere 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.

Acid Rain 101 3. Pollutants that cause acid rain Nitrogen oxides

Energy + N2 + O2 Æ 2NO Energy + 2NO + O2 Æ 2NO2 • 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

Chemical reactions: nitrogen oxides

NOx + H2O → HNO3 nitrogen oxides + water → nitric acid + - HNO3 ↔ H + NO3

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

Ammonia (NH3) is produced mainly through agriculture: • livestock and poultry • manure • fertilizer application

www.FreeFoto.com 3. Pollutants that cause acid rain Chemical reactions: Ammonia • Ammonia gas reacts with sulfuric and nitric acids to form ammonium aerosols. + - Example: NH4 + NO3 Æ NH4NO3

ammonium nitrate ammonium nitrate • When aerosols are deposited to the ground they react with oxygen in a process called nitrification. + - NH4NO3 + 2O2 Æ 2H + 2NO3 + H2O ammonium nitrate oxygen hydrogen ions nitrate water

• This process releases H+ ions, which lowers the pH (creates more acidic conditions). From emissions to acid deposition:

From Acid Rain Revisited, pg. 4 IV.IV. AcidAcid rainrain ecosystemecosystem impactsimpacts

1. Acid rain causes increased loss of base cations from soil

this causes

Decrease in acid neutralizing Lower fertility of soils capacity (ANC) of soils (base cations are nutrients (reduced ability to buffer the necessary for tree growth) incoming acids)

Acid Rain 101 4.a.How Impacts does onacid terrestrial rain affect ecosystems soils? 2. Inorganic aluminum is dissolved from minerals and accumulates in the soil.

this causes

The presence of Dissolved inorganic dissolved inorganic aluminum is also aluminum in soil is toxic to animals that harmful to plants as it can live in the soil damage root tips and such as frogs, affect the way plants take salamanders and larval up nutrients. stages of insects. 4.a. Impacts on terrestrial ecosystems

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

Is it a big problem in terrestrial ecosystems?

www.FreeFoto.com

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. Changes in the calcium cycle at the Hubbard Brook Experimental Forest between 1950-1995

The amount of available calcium in the soil at the HBEF appears to have declined more than 50 percent between the years 1950 – 1995.

From Acid Rain Revisited, pg. 10 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. 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 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 www.FreeFoto.com from water. 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 http://www.epa.gov/acidrain/effects/surface_water.html 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 lessAcid Rainthan 101 zero. V.V. OtherOther ImpactsImpacts fromfrom acidacid rainrain

•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. www.Free.Foto.com

Acid Rain 101 5. Other impacts from acid rain • Causes an • Visibility is reduced by increased rate of sulfate and nitrate in oxidation for iron. the atmosphere.

www.FreeFoto,com www.FreeFoto.com VI.VI. LegislationLegislation andand technologytechnology

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 1990.

Acid Rain 101 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 Sulfur dioxide

Ozone Nitrogen dioxide

Lead Particulate matter*

* With size of particle less than or equal to 10 micrometers 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 SO2 by 10 million tons, or 40%

- reduce NOx by 2 million tons, or 10% compared to 1980 levels 6. Legislation and technology

Some strategies used to reduce sulfur and nitrogen oxides emissions:

• ‘cap,’ or limit, the amount of SO2 that can be emitted by electric utilities

• use of trade allowances for SO2 • use of catalytic converters in automobiles

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

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 A type of scrubber limestone produces pH-neutral called ‘Counter Current Packed Tower’, sold by calcium sulfate that is physically Ceilcote Air Pollution removed from scrubber. Control

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. 6. Legislation and technology To date there is no legislation to:

• ‘cap’ NOx 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 SO2 and NOx pollution?

VI.VI. LegislationLegislation andand technologytechnology

Change in SO2 emissions in the U.S. over time

Total SO2 emissions (US) •1940: 20 million tons •1970: 28 million tons •2002: 19 million tons

SO2 emissions from utilities (US)

•1980: 17.5 million tons •2002: 10.3 million tons

Acid Rain 101 6. Trends over time Sulfate

1994 2005 6. Trends over time Concentration of Sulfate in Precipitation at the Hubbard Brook Experimental Forest 100 Sulfate 80

Concentration (µeq/L) 20

0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Water Year Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation. 6. Trends over time

Change in NOx emissions in the U.S. over time

NOx emissions from utilities (US)

• 1990: 5.5 million tons • 2001: 4.7 million tons

Acid Rain 101 6. Trends over time Nitrate

1994 2005 6. Trends over time Concentration of Nitrate in Precipitation at the Hubbard Brook Experimental Forest

50 Nitrate 40

Concentration (µeq/L) 10

0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Water Year

Data provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation. 6. Trends over time Ammonium

1994 2005 6. Trends over time Concentration of Ammonium in Precipitation at the Hubbard Brook Experimental Forest

50 Ammonium 40

Concentration (µeq/L) 10

Have reductions in SO2 and NOX affected the acidity, or pH of precipitation? 6. Trends over time Acidity (pH)

1994 2005 6. Trends over time pH of Stream Water and Precipitation at the Hubbard Brook Experimental Forest 5.2 Streamwater pH 5.0

4.8 1984 (slope of line becomes significant) 4.6 pH 4.4 Precipitation pH 4.2

4.0

3.8 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 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. 6. Trends over time Overall… • Sulfur dioxide regulation has been fairly successful. However, emissions remain high compared to background (pre- industrial) conditions.

• Although emissions of NOx 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 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 Clean Air Interstate Rule

• Designed to reduce air pollution that moves across state boundaries

• Will cap SO2 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 States covered by Clean Air Interstate Rule

From www.epa.gov 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 long- range transport of atmospheric pollutants have been signed. • Sulfur Emissions Reduction Protocol • Convention on Long-Range Transboundary Air Pollution

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