Air Pollution

1. Air Pollution

2. The Atmosphere • This is our protective blanket of gasses. • 78% Nitrogen • 21% Oxygen • .03% Carbon Dioxide CO2 • .01% Ozone 03

3. Atmospheric Gases

4. Atmospheric pressure (millibars) Temperature Pressure Thermosphere Mesopause Heating via ozone Mesosphere Altitude (kilometers) Altitude (miles) Stratopause Stratosphere Tropopause Ozone “layer” Heating from the earth Troposphere Pressure = 1,000 millibars at ground level (Sea level) Temperature (˚C) Fig. 19-2, p. 440

5. The Atmosphere - Layers • Troposphere • Layer in which we live • Most weather occurs here • 90% of the gasses are here • 78% nitrogen, 21% oxygen • 0-6 mile above N and S Pole • Mount Everest is 5.3 miles tall • 0-10 miles above equator • Temperature decreases with altitude until the next layer is reached • Stratosphere • 6-31 miles in altitude • Calm • Air traffic due to lack of weather • Temperature increases with altitude • Ozone layer (oxygen is converted to O3 by lightning and/or sunlight) • 99% of ultraviolet radiation (especially UV-B) is absorbed by the stratosphere

6. The Atmosphere - Layers • Mesosphere • 30 to 50 miles in altitude • Temperature decreases with increasing altitude • Temperatures in the mesopause (top of the mesosphere) are the coldest on Earth – approx. -100˚C (-148˚F) • Above airplane heights and below orbital heights, thus it is poorly understood • Thermosphere • 50 to 310 miles in altitude • Biggest of all layers • Temperature increases with altitude • Very high temperatures 1,500 °C (2,730 °F) to 2,500 °C (4,530 °F) but little heat is transferred because of the space between the gas particles • International Space Station flies in this layer

7. The Atmosphere - Layers • Exosphere • 310 miles to space • Upper most layer of the atmosphere • Only light elements exist here, mainly Hydrogen To the right is a scale representation of the atmospheric layers: • Purple = Exosphere • Blue = Thermosphere • Green = Mesosphere • Yellow = Stratosphere • Red = Troposphere

8. Ozone • How much of our atmosphere is ozone? • Ozone that surrounds the earth 12-35 miles above the earth is our first line of defense of the sun’s ultraviolet radiation. • This radiation can cause sunburn, skin cancer, cataracts, … • Ozone is constantly created and destroyed

9. What Happens to Solar Energy Reaching the Earth? • Solar energy flowing through the biosphere warms the atmosphere, evaporates and recycles water, generates winds and supports plant growth. Figure 3-8

10. The Natural Greenhouse Effect • Three major factors shape the earth’s climate: • The sun. • Greenhouse effect that warms the earth’s lower troposphere and surface because of the presence of greenhouse gases. • Oceans store CO2 and heat, evaporate and receive water, move stored heat to other parts of the world. • Natural cooling process through water vapor in the troposphere (heat rises).

11. Greenhouse Effect • This “greenhouse effect” is vital for our survival. Without heat trapping gasses our planet would be cold and lifeless. • The gasses act like a car that gets hot inside.

12. Major Greenhouse Gases • The major greenhouse gases in the lower atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, ozone, and CFCs. • These gases have always been present in the earth’s troposphere in varying concentrations. • Fluctuations in these gases, plus changes in solar output are the major factors causing the changes in tropospheric temperature over the past 400,000 years.

13. Major Greenhouse Gases • Increases in average concentrations of three greenhouse gases in the troposphere between 1860 and 2004, mostly due to fossil fuel burning, deforestation, and agriculture. Figure 20-5

14. PAST CLIMATE AND THE GREENHOUSE EFFECT • Over the past 900,000 years, the troposphere has experienced prolonged periods of global cooling and global warming. • For the past 1,000 years, temperatures have remained fairly stable but began to rise during the last century.

15. PAST CLIMATE AND THE GREENHOUSE EFFECT Figure 20-2

16. How Do We Know What Temperatures Were in the Past? • Scientists analyze tiny air bubbles trapped in ice cores learn about past: • troposphere composition. • temperature trends. • greenhouse gas concentrations. • Solar output,snowfall, and forest fire activity. Figure 20-3

17. How Do We Know What Temperatures Were in the Past? • In 2005, an ice core showed that CO2 levels in the troposphere are the highest they have been in 650,000 years. Figure 20-4

19. Greenhouse Effect • If the gasses in the atmosphere become increased beyond “normal” the temperature of the earth can increase. • An increase in temperature can change the climate cycles. • Ice caps melt, drought, floods, change in temperature… • Effects the environment as well • What are some effects if the above happens?

20. Controversy • CO2 levels are increasing due to human activity – no controversy • What does that mean? - controversy • 97% of climate scientists agree that this leads to global warming • 53% of Americans believe global warming is real • 87% of Europeans believe global warming is a serious concern

22. Data can be manipulated

23. From NOAA

24. EFFECTS OF GLOBAL WARMING • Between 1979 and 2005, average Arctic sea ice dropped 20% (as shown in blue hues above). Figure 20-8

25. Rising Sea Levels • During this century rising seas levels are projected to flood low-lying urban areas, coastal estuaries, wetlands, coral reefs, and barrier islands and beaches. Figure 20-10

26. Rising Sea Levels • If seas levels rise by 9-88cm during this century, most of the Maldives islands and their coral reefs will be flooded. Figure 20-11

27. Changing Ocean Currents • Global warming could alter ocean currents and cause both excessive warming and severe cooling. Figure 20-12

28. CLIMATE CHANGE AND HUMAN ACTIVITIES • Evidence that the earth’s troposphere is warming, mostly because of human actions: • The 20th century was the hottest century in the past 1000 years. • Since 1900, the earth’s average tropospheric temperature has risen 0.6 C°. • Over the past 50 years, Arctic temperatures have risen almost twice as fast as those in the rest of the world. • Glaciers and floating sea ice are melting and shrinking at increasing rates.

30. EFFECTS OF GLOBAL WARMING • A warmer troposphere can decrease the ability of the ocean to remove and store CO2 by decreasing the nutrient supply for phytoplankton and increasing the acidity of ocean water. • Global warming will lead to prolonged heat waves and droughts in some areas and prolonged heavy rains and increased flooding in other areas.

31. EFFECTS OF GLOBAL WARMING • In a warmer world, agricultural productivity may increase in some areas and decrease in others. • Crop and fish production in some areas could be reduced by rising sea levels that would flood river deltas. • Global warming will increase deaths from: • Heat and disruption of food supply. • Spread of tropical diseases to temperate regions. • Increase the number of environmental refugees.

32. DEALING WITH GLOBAL WARMING • Climate change is such a difficult problem to deal with because: • The problem is global. • The effects will last a long time. • The problem is a long-term political issue. • The harmful and beneficial impacts of climate change are not spread evenly. • Many actions that might reduce the threat are controversial because they can impact economies and lifestyles.

33. Air Pollution • Air Pollutant is defined as any substance in the air that is concentrated enough to harm living things or do damage to man-made objects. • The EPA regulates (tries) pollution emissions from combustion by factories and machines.

34. Human Actions and Our Environment • When the human population was low, there was very little impact to the environment. • Wind, rain, and time were the natural air cleaners. • As the human population increased, time could not clean the air fast enough.

35. Human Actions and Our Environment • The human impact has changed three major ecosystem cycles. • The chemical cycles • Carbon Cycle • Nitrogen Cycle • Sulfur Cycle • By adding more chemicals we slow down the cycle

36. Human Actions and Our Environment 2. The energy cycles • Conservation of energy • Energy from fossil fuels is used faster that replaced 3. Biodiversity is reduced • Farms reduce the plant biodiversity with a single crop, and kill animals with chemicals

37. Air Pollution • Primary pollutants – released directly into the atmosphere • Ex) nitrogen oxides (NOx), sulfur oxides (SOx), methane (CH4), dust, Chlorofluorocarbons (CFCs) • Causes of Primary Pollutants – factories, cars, wind and soil, volcanoes, forest fires, pollen, decaying plants, salt particles from the sea, and refrigerants.

38. Air Pollution • Secondary pollutants – Form when primary pollutants react. • Ex) ozone, smog, and acid rain

39. Air Pollutants – Carbon Oxides • Carbon monoxide (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials. • 93% of carbon dioxide (CO2) in the troposphere occurs as a result of the carbon cycle. • 7% of CO2 in the troposphere occurs as a result of human activities (mostly burning fossil fuels). • It is not regulated as a pollutant under the U.S. Clean Air Act.

41. Carbon Cycle • The ocean is the largest carbon sink. • The process of CO2 being removed from the atmosphere and stored by a sink is called sequestration.

42. Ocean Acidification • Dissolving CO2 in seawater increases the hydrogen ion (H+) concentration in the ocean, and thus decreases ocean pH. • Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.25 to 8.14, representing an increase of approaching 30% in acidity.

43. The Nitrogen Cycle:

44. Steps in Nitrogen Cycle • Nitrogen Fixation • Lightning (N2  NO3) • Bacteria (N2  NH4+) • Nitrification(NH4+ NO2- (nitrite)  NO3-(nitrates)) • Assimilation (NO3-(nitrates) converted to amino acids, DNA, chlorophyll) • Ammoniafication(wastes and decaying organisms broken down into NH4+) • Denitrification(nitrites are changed to N2 by anaerobic bacteria)

45. Air Pollutants – Nitrogen Oxides • The atmosphere is the largest nitrogen sink, storing nitrogen in the form of N2. • NO2 reacts with water vapor in the air to form nitric acid (HNO3) and nitrate salts (NO3-) which are components of acid deposition.

46. Human Influence on Nitrogen Cycle • Fossil fuel combustion, • Use of artificial nitrogen fertilizers, • Release of nitrogen in wastewater • At high temps, N2 reacts with O2 to form NOx. • Gives brown color to smog • Photochemical smog – nitrogen and light form “bad” ozone.

47. Air Pollutants – Sulfur Oxides • Naturally occurring • Volcanoes • Burning of coal, oil, gasoline • Cause Lung damage, asthma, and bronchitis • Sulfur can be removed from smoke by wet scrubbers in factories • Largest sulfur sink is sedimentary rocks

48. Air Pollutants – Sulfur Oxides • Sulfur dioxide (SO2)andsulfuric acid: • About one-third of SO2 in the troposphere occurs naturally through the sulfur cycle. • Two-thirds come from human sources, mostly combustion (S+ O2 SO2) of sulfur-containing coal and from oil refining and smelting of sulfide ores. • SO2 in the atmosphere can be converted to sulfuric acid (H2SO4) and sulfate salts (SO42-) that return to earth as a component of acid deposition.

49. The Sulfur Cycle Figure 3-32

50. Air Pollutants - VOCs • Volatile organic compounds (VOCs): • Organic compounds (mostly hydrocarbons) that exist as gases in the air • Ex) incomplete combustion of gasoline, methane • About two thirds of global methane emissions comes from human sources. • Can be natural (methane and terpenes) or man-made (trichlorethylene (TCE), benzene, CFCs and vinyl chloride). • Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage.