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GECH 119 Acid Rain

GECH 119 Acid Rain. Dr. Ralph C. Gatrone Department of Chemistry and Physics Virginia State University. Acid Rain Chapter Objectives. What is acid rain? Historical perspective Consequences Potential solutions. What is acid rain?. Water dissolves CO 2 in air Forms carbonic acid

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GECH 119 Acid Rain

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  1. GECH 119Acid Rain Dr. Ralph C. Gatrone Department of Chemistry and Physics Virginia State University

  2. Acid RainChapter Objectives • What is acid rain? • Historical perspective • Consequences • Potential solutions

  3. What is acid rain? • Water dissolves CO2 in air • Forms carbonic acid • Lowers the pH • Rainwater is naturally acidic • If acid is present in air from industrial or natural processes • Described as acid rain

  4. Acid Rain • Acidic rain, snow, sleet, small droplets • Fall to Earth • Acid deposition • Respiratory disease • Lower pH in streams and lakes • Tree damage • Weathering of buildings and monuments

  5. Causes of Acid Rain • Industrial manufacturing • Generation of electric power • Personal automobile use • Traces of HCl • Sulfur oxides • Nitrogen oxides

  6. Sulfur Oxides • Combustion of high sulfur coal • Products are carbon dioxide and sulfur oxides • Smelting of sulfur containing ores • Roasting Metal sulfides produces metal oxide • Sulfur oxides are the other product • SOx + H2O H2SOx

  7. Sulfuric Acid • Sulfur oxides produce sulfuric acid • when mixed with water • Many metals are more soluble in acidic medium than water • Al – leached from soil into acid solutions • Interferes with plants ability to collect nutrients from soil • Synergistic effect upon other plant problems • Temperature extremes, insects, air pollution • Deforestation

  8. Nitrogen Oxides • Burning gasoline in auto engine • Tremendous heat • Sufficient heat to react N2 with O2 • Produces NOx • NOx + H2O HNOx • Nitric Acid (x = 3)

  9. Acid Rain is not New • 1661 • pollution exchange between England and France • 1727 • rain contains salt, sulfur, acid • 1734 • acid rain corrodes Earth preventing plant growth • 1852 • burning coal effect amount of acid in rain • 1872 • phrase acid rain was used • 1896 • corrosion due to pollution noted in United States • proposed scrubbing effluent gases

  10. Consequences of Acid Rain • Lakes and Streams • Drop of pH by one unit impacts animal life • Acid neutralizing ability is provided by limestone rocks • Northeast primarily granite rocks – can’t neutralize much acid • Harmful metal ions leached into acidic water • Al, Cd, Hg, Pb – common, toxic metal ions • Impacts lower end of food chain • Contamination spreads from bottom up • Algae to fish to humans

  11. Consequences of Acid Rain • Deforestation • Tree decline due to soil damage • Accelerating over last 20 years • 1984 – 84% of pine showed damage • Damage is very clear in Europe and US • Causes of deforestation are complex

  12. Causes of Deforestation • Acid rain is definitely involved • Increase in ground level ozone • Interrupts photosynthesis • Synergistic with acid rain present • Excessive nitrogen fertilization • Nitrogen needed, excess requires other nutrients to present in larger amounts • Toxic metals – increased by acid rain • Natural cycle of life and death • Synergistic combination

  13. Consequences of Acid Rain • Building decay • Mortar, marble, limestone • Calcium carbonate – major component • Reacts with acidic solutions • Products are somewhat soluble in water • Buildings are washing away

  14. Consequences of Acid Rain • Human health • Multiple causes • Respiratory illnesses • Atmospheric Sulfur dioxide • 100 ppb (near large cities) • Increase of Asthma by 20% • Pb in residential water wells • Brain damage • Inconclusive data

  15. Consequences of Acid Rain • Economic • Critical factor • Financial beneficiaries not the suffers • Technology? • Cost? • Price of inaction?

  16. Consequences of Acid Rain • Reduction from 1978 dollars of 60% • Savings of $40 Billion/year • Inaction • Environmental impact is incalculable • Benefit to pollution control companies • $800 Billion spent 1980 - 1991

  17. The Future • Chemical methods are available • Not enacted • The Chemistry • Flue gas desulfurization (remove sulfur oxides) • Successful in US, Japan, Germany • Process contributes to Greenhouse effect • Reduces power plan efficiency • Does not impact nitrogen oxides

  18. Removal of Nitrogen Oxides • Fluidized bed combustion • Coal and air are mixed and burned • Lowers the temperature of coal burning • Reduces nitrogen oxide formation • Limestone is added to remove sulfur oxides • ½ of power plants have no pollution control • Installation is very expensive • Consumer ultimately pays

  19. A Difficult Problem • Political issue • State versus federal • Economic • Who pays? Who benefits? • Social • Who is affected? • Chemical • Strategies are available

  20. Acid Rain and Air Quality • Acid Rain • One factor involved in Air Quality • There are other factors as well

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