Presentation on theme: "Contents Review of pH Definition of acid rain Pollutants that create acid rain: a. sulfur dioxide b. nitrogen oxide c. ammonia IV. Acid rain ecosystem."— Presentation transcript:
4Contents Review of pH Definition of acid rain Pollutants that create acid rain:a. sulfur dioxideb. nitrogen oxidec. ammoniaIV. Acid rain ecosystem impactsV. Other impactsVI. Legislation and technologyVII. Trends over time
5I. Review of pHpH 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
61.Review of pH Water is converted into hydrogen and hydroxyl ions. H2O H OH-water hydrogen ion hydroxyl ionWhen 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.
71.Review of pHBecause 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.
81.Review of pHIn 1997, the pH of wet deposition at HBEF was 4.2; today it is 4.5.From Acid Rain Revisited, page 5
9II. Definition of Acid Rain pH levels found in precipitationAcid rainAverage pH of rain at Hubbard Brook Experimental Forest in 2007< 5.24.5Acid Rain 101
10Acid rain isn’t just RAIN- 2. Definition of Acid RainAcid 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 fogThe terms “acid deposition” and “acid precipitation” are more descriptive, but “acid rain” is widely used and accepted.
11III. Pollutants that Cause Acid Rain What creates acid rain?- sulfur dioxide- nitrogen oxides- ammoniaAcid Rain 101
123. Pollutants that cause acid rain Sulfur dioxide, emitted mainly from combustion of coal and oil in factories and powerplants.
13Chemical reactions: sulfur dioxide 3. Pollutants that cause acid rainChemical reactions: sulfur dioxideCoal 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 SO2 (sulfur dioxide)Processes found in chemical and petroleumindustries also release sulfur into the air.
143. Pollutants that cause acid rain Chemical reactions: sulfur dioxideSO H2O → H2SO4sulfur dioxide water → sulfuric acidH2SO4 ↔ H HSO4- ↔ 2H SO42-sulfuric acid ↔ hydrogen ions + sulfateSulfur dioxide reacts with water in the atmosphere to create sulfuric acid, which dissociates into sulfate and hydrogen ions.Hydrogen ions make a solution acidic.
153. Pollutants that cause acid rain Nitrogen oxides from electric utilitiesautomobilesLightening (to a much smaller degree)
163. Pollutants that cause acid rain Major sources of Nitrogen oxides:Transportation≈ 54% nationally- Uses nitrogen found in atmosphereElectric Utilities≈ 30% nationally- Use nitrogen found in coal and oilThe 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
17Nitrogen oxides 3. Pollutants that cause acid rain Energy + N2 + O2 2NOEnergy + 2NO + O2 2NO2The 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.
18Chemical reactions: nitrogen oxides 3. Pollutants that cause acid rainChemical reactions: nitrogen oxidesNOx H2O → HNO3nitrogen oxides water → nitric acidHNO ↔ H NO3-nitric acid ↔ hydrogen ion + nitrateNitrogen oxides react with water in the atmosphere to create nitric acid, which dissociates into nitrate and hydrogen ions.Hydrogen ions make a solution acidic.
193. Pollutants that cause acid rain Ammonia (NH3) is produced mainly through agriculture:livestock and poultrymanurefertilizer application
20Chemical reactions: Ammonia 3. Pollutants that cause acid rainChemical reactions: AmmoniaAmmonia gas reacts with sulfuric and nitric acids to form ammonium aerosols.Example: NH NO3- NH4NO3ammonium nitrate ammonium nitrateWhen aerosols are deposited to the ground they react with oxygen in a process called nitrification.NH4NO O2 2H NO H2Oammonium nitrate oxygen hydrogen ions nitrate waterThis process releases H+ ions, which lowers the pH (creates more acidic conditions).
21From emissions to acid deposition: From Acid Rain Revisited, pg. 4
22IV. Acid rain ecosystem impacts 1. Acid rain causes increasedloss of base cations from soilthis causesDecrease 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
23How does acid rain affect soils? 4.a. Impacts on terrestrial ecosystems2. Inorganic aluminum is dissolved from minerals and accumulates in the soil.this causesThe 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 alsotoxic to animals thatlive in the soilsuch as frogs,salamanders and larvalstages of insects.
244.a. Impacts on terrestrial ecosystems From Acid Rain Revisited, pg. 10
25Is it a big problem in terrestrial ecosystems? 4.a. Impacts on terrestrial ecosystemsIs 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.
26Changes 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
274.b. Impacts on aquatic ecosystems 1. Chemical effects on aquatic systemsInorganic 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.
284.b. Impacts on aquatic ecosystems 1. Chemical effects on aquatic systemsIt 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
294.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.
30From http://www.epa.gov/acidrain/effects/surface_water.html 4.b. Impacts on aquatic ecosystems2. 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
314.b. Impacts on aquatic ecosystems ≈ 8% of lakes in Adirondacks≈ 15% of lakes in New Englandand≈ 8.5% of streams in the northern Appalachian Plateauare considered acidic, which means ANC is less than zero.Acid Rain 101
32V. Other Impacts from acid rain 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.Acid Rain 101
335. Other impacts from acid rain Causes an increased rate of oxidation for iron.Visibility is reduced by sulfate and nitrate in the atmosphere.
34What has been done to remedy the problem of acid rain? VI. Legislation and technologyWhat 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
356. 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 monoxideSulfur dioxideOzoneNitrogen dioxideLeadParticulate matter** With size of particle less than or equal to 10 micrometers
36Title IV of the Clean Air Act Amendments of 1990 6. Legislation and technologyTitle IV of the Clean Air Act Amendments of 1990Targeted 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
37Some strategies used to reduce sulfur and nitrogen oxides emissions: 6. Legislation and technologySome strategies used to reduce sulfur and nitrogen oxides emissions:‘cap,’ or limit, the amount of SO2 that can be emitted by electric utilitiesuse of trade allowances for SO2use of catalytic converters in automobiles
38Some strategies used to reduce sulfur and nitrogen oxides emissions: 6. Legislation and technologySome 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
39How 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
40How 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.
41To date there is no legislation to: 6. Legislation and technologyTo date there is no legislation to:‘cap’ NOx emissions from electric utilities, which will likely increase as electric generation from power plants increasesset standards for ammonia emissions.Have the CAA and CAAA helped to reduce SO2 and NOx pollution?
42Change in SO2 emissions in the U.S. over time VI. Legislation and technologyChange in SO2 emissions in the U.S. over timeTotal SO2 emissions (US)1940: 20 million tons1970: 28 million tons2002: 19 million tonsSO2 emissions from utilities (US)1980: million tons2002: million tonsAcid Rain 101
446. Trends over timeConcentration of Sulfate in Precipitation at the Hubbard Brook Experimental ForestData provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation.
45Change in NOx emissions in the U.S. over time 6. Trends over timeChange in NOx emissions in the U.S. over timeNOx emissions from utilities (US)1990: 5.5 million tons2001: 4.7 million tonsAcid Rain 101
476. Trends over timeConcentration of Nitrate in Precipitation at the Hubbard Brook Experimental ForestData provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation.
496. Trends over timeConcentration of Ammonium in Precipitation at the Hubbard Brook Experimental ForestData provided by G.E. Likens through funding from the National Science Foundation and The A.W. Mellon Foundation.
506. Trends over timeHave reductions in SO2 and NOX affected the acidity, or pH of precipitation?
526. Trends over timepH of Stream Water and Precipitation at the Hubbard Brook Experimental ForestNote: 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.
53Overall… 6. Trends over time 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.
54A complex, tricky problem… 6. Trends over timeA complex, tricky problem…Sulfur and nitrogen compounds can travel thousands of kilometers from their original source, thereforeAir 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.
55Clean Air Interstate Rule 6. Trends over timeClean Air Interstate RuleDesigned to reduce air pollution that moves across state boundariesWill 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
56States Covered by Clean Air Interstate Rule 6. Trends over timeStates covered by Clean Air Interstate RuleFrom
57World-wide 6. Trends over time Acid rain is a substantial problem wherever there is concentrated industry, particularly in-People’s Republic of China-Eastern Europe-RussiaA number of international treaties dealing with the long-range transport of atmospheric pollutants have been signed.Sulfur Emissions Reduction ProtocolConvention on Long-Range Transboundary Air Pollution
58The Hubbard Brook Acid Rain Story 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 StoryPart 1: The Discovery