1. Air Pollution and Stratospheric Ozone Depletion
Chapter 15
Air Pollution and Stratospheric Ozone Depletion

2. Objectives
AP Standards: Air pollution sources—primary and secondary; major air pollutants; measurement units; smog; acid deposition—causes and effects; heat islands and temperature inversions; indoor air pollution; remediation and reduction strategies; Clean Air Act and other relevant laws
Identify major air pollutants and their sources
Explain how photochemical smog and acid deposition are formed, and describe the effects of eac
Examine various approaches to the control and prevention of outdoor air pollution
Explain the causes and effects of stratospheric ozone depletion
Hazards of indoor air pollution, especially in developing nations

3. Review of Earth’s Atmosphere
Troposphere- the layer closest to Earth's surface extending roughly 16 km (10 miles) above Earth.
Stratosphere- above the troposphere, this extends from roughly 16 to 50 km (10-31 miles).
DRAW FIGURE 4.1

4. Air Pollution
Air pollution- the introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings, or to alter ecosystems.
Refers to pollution in the troposphere
a.k.a. “Ground-level pollution”
Global system of air pollution
Inputs and outputs?
This false color image is a map of natural aerosols (green pixels), human pollution (red pixels), or a mixture of both (light brown pixels). Gray areas indicate a lack of usable data. This map covers pollution measured between January 2001 and July 2002.

5. China’s Air Pollution
JAN 2013 – Air pollution was “beyond index” limiting visibility to 100m. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite acquired this image of northeastern China on Jan The image shows an area about 150 miles wide. Beijing is located at the upper center of the picture, Tianjin at lower right

6. Major Air Pollutants Atmosphere is a global commons
1970 U.S. Clean Air Act identified 6 air pollutants that threaten organisms, ecosystems, and/or structures: sulfur dioxide, nitrogen oxides, carbon monoxide, particulate matter, ozone and lead
“criteria” air pollutants = EPA must specify allowable concentrations
Definition of pollution has undergone rapid change:
Sulfur oxides
1/3 of SO2 in the troposphere occurs naturally through the sulfur cycle
2/3 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.
Volcanoes and to a very small degree forest fires release

7. Major Air Pollutants Nitrogen Oxides (NOX)
Nitrogen oxide (NO) is a colorless, odorless gas that forms when nitrogen and oxygen gas in air react at high-combustion temperatures (e.g. automobile engines and coal-burning plants)
Anthropogenic sources: burning fossil fuels
Natural sources: forest fires, lightening, and certain soil bacteria
NO reacts with oxygen in the air to form NO2.
Nitrogen dioxide (NO2) is a pungent, reddish-brown gas that reacts with water vapor in the air to form nitric acid (HNO3) and nitrate salts (NO3-) which are components of acid deposition.
X = 1 or 2 oxygen atoms per N NO

8. Major Air Pollutants Carbon Oxides
Carbon monoxide (CO) is a highly toxic colorless, odorless gas that forms during the incomplete combustion of carbon-containing matter
Carbon dioxide (CO2) is a colorless, odorless gas that forms during the complete combustion of carbon-containing matter
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 currently regulated as a pollutant under the U.S. Clean Air Act.

9. Major Air Pollutants Particulate Matter (PM)
Solid particles and liquid droplets small and light enough to remain suspended in the air
Anthropogenic sources: combustion of wood, animal manure, other biofuels, fossil fuels, and from road dust and rock-crushing
Natural sources: forest fires, volcanoes, and dust storms
Most harmful PM’s are fine particles PM-10, with an average diameter < 10 micrometers and ultrafine particles PM-2.5
According to the EPA, PM is responsible for about 60,000 premature deaths a year in the U.S.
Scatters and absorbs sunlight
Haze (scattered light)
1816-large volcanic eruption in Java released more than 150 million metrics tons of PM

11. Major Air Pollutants Photochemical Oxidants
Class of air pollutants that form as a result of sunlight acting on oxides (nitrogen and sulfur)
Ozone (O3) is most abundant and frequently measured
Harmful to plant tissue, human respiratory tissue, and construction materials
Oxidants + PM = smog
Photochemical smog (a.k.a. LA smog or brown smog)
Dominated by oxidants like ozone
Sulfurous smog (a.k.a. London smog or gray smog)
Dominated by sulfur oxides
1816-large volcanic eruption in Java released more than 150 million metrics tons of PM

12. Major Air Pollutants Lead and other metals
Added to fuels to improve vehicle performance.
Phased out between in U.S.
Also present in older buildings with lead-based paints
Know your mercury facts!
Campaign to phase out lead globally is still underway

13. Major Air Pollutants Volatile organic compounds (VOCs)
Most are hydorcarbons that give off strong aroma
Anthropgenic sources: gasoline, lighter fluid, dry-cleaning fluid, oil- based paints, perfumes, and industrial solvents such as trichlorethylene (TCE), benzene, and vinyl chloride.
Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage.
Natural sources: emitted by the leaves of many plants and methane
About 2/3 of global methane emissions comes from human sources.
TCE is a degreaser, vinyl chlorides make PVC = sweet smelling
Benzene is used to make a lot of heavy chemicals including gasoline

14. MUST DRAW THIS

15. Primary and Secondary Pollutants
Primary pollutants- polluting compounds that come directly out of the smoke-stack, exhaust pip, or natural emission source
Examples: CO, CO2, SO2, NOX, and most suspended particulate matter
Secondary pollutants- pollutants that have undergone transformation in the presence of sunlight, water, oxygen, or other compounds
Examples: ozone, sulfate and nitrate
Stationary vs. mobile

16. Natural Sources of Air Pollution
Volcanoes – SO2, PM, CO, NOx
Lightning - NOx
Forest fires - PM, CO, NOx
Plants – VOCs (ethylenes and terpenes)
IPCC estimates natural sources contribute:
30% of sulfur oxides
44% of nitrogen oxides
89% of VOCs
Conifers and citrus = terpenes = are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers,[1] though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeteria. They are often strong smelling and thus may have had a protective function.
They are the major components of resin, and of turpentine produced from resin. The name "terpene" is derived from the word "turpentine". In addition to their roles as end-products in many organisms, terpenes are major biosynthetic building blocks within nearly every living creature. Steroids, for example, are derivatives of the triterpene squalene.
Ethylene = hydrocarbon with the formula C2H4 or H2C=CH2. It is a colorless flammable gas with a faint "sweet and musky" odor when pure.[3] It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds), and the simplest unsaturated hydrocarbon after acetylene (C2H2).
Ethylene is widely used in chemical industry, and its worldwide production (over 109 million tonnes in 2006) exceeds that of any other organic compound.[4][5] Ethylene is also an important natural plant hormone, used in agriculture to force the ripening of fruits

17. Anthropogenic Sources of Air Pollution
Emissions from human activity are monitored, regulated, and in many cases controlled
EPA periodically reports on criteria pollutants for U.S.
Clean Air Act requires the EPA establish standards to control pollutants that are harmful to “human health and welfare”
Specific concentration limits are determined through NAAQS
Human health = health of human population especially elderly, young and sensitive populations
Welfare = visibility, crop status, natural vegetation, ecosystems, and buildings
NAAQS = national ambient air quality standards

18. Photochemical Smog
Mixture of air pollutants formed by the reaction of nitrogen oxides and volatile organic hydrocarbons under the influence of sunlight
Produces harmful substances such O3 (causes breathing difficulties, headaches, fatigue), aldehydes and peroxyacetylnitrate (PAN - irritates eyes)
Formation requires the following conditions:
Still, sunny day
Thermal inversion:
relatively warm layer of air at mid-altitude covers a layer of cold, dense air below
warm inversion layer traps emissions that then accumulate beneath it
Originally used to describe smoke and fog.
Aldehydes=
PAN=mutagen and clastogen. Eye irritation and respiratory tract damage.

19. Descending warm air mass Decreasing temperature
Increasing altitude
Descending warm air mass
Warmer air
Inversion layer
Inversion layer
Figure 19.5
Natural capital degradation: two sets of topography and weather conditions that lead to prolonged temperature inversions, in which a warm air layer sits atop a cooler air layer. Air pollutants can build to harmful levels during an inversion. A temperature inversion can occur during cold, cloudy weather in a valley surrounded by mountains (left). Frequent and prolonged temperature inversions can also occur in an area with a sunny climate, light winds, mountains on three sides, and the ocean on the other (right). A layer of descending warm air from a high-pressure system prevents ocean-cooled air near the ground from ascending enough to disperse and dilute pollutants. Because of their topography, Los Angeles, California and Mexico City, Mexico (Figure 19-4) have frequent temperature inversions, many of them prolonged during the summer. QUESTION: Do you live in an area that suffers from fairly frequent thermal inversions?
Sea breeze
Decreasing temperature
Fig. 19-5, p. 447

20. Chemistry of Photochemical Smog
In the absence of VOCs, ozone will form during daylight hours and break down after sunset
In the presence of VOCs, ozone will form during daylight, then VOCs combine with N oxides which reduce the amount ozone that will break down later

21. Acid Deposition All rain is naturally slightly acidic (pH 5.6)
Acid deposition refers to rain, snow, dust or gas lower than pH 5.6
Nitrogen oxides, sulfur oxides, and particulates are released into the atmosphere and combine with atmospheric oxygen and water
These form the secondary pollutants nitric acid and sulfuric acid
Carbon dioxide in atmosphere lowers pH naturally
While acid rain is much less of a problem due to the Clean Air Act reducing emssions

22. Tall smokestacks reduce local air pollution but can increase regional air pollution.
pH measurements in relation to major coal-burning and industrial plants.

23. ACID DEPOSITION
Figure 19-8

24. Effects of Acid Deposition
Lowering the pH of lake water
Decreasing species diversity of aquatic organisms
Organisms can only survive in narrow pH range
AD increased substantially between

25. Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3)
Wind
Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3)
Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts
Wet acid depostion (droplets of H2SO4 and HNO3 dissolved in rain and snow)
Nitric oxide (NO)
Sulfur dioxide (SO2) and NO
Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts)
Figure 19.6
Natural capital degradation: acid deposition, which consists of rain, snow, dust, or gas with a pH lower than 5.6, is commonly called acid rain. Soils and lakes vary in their ability to buffer or remove excess acidity.
Acid fog
Farm
Lakes in shallow soil low in limestone become acidic
Ocean
Lakes in deep soil high in limestone are buffered

26. Effects of Acid Deposition
Damages statues, monuments, and buildings
Contributes to chronic respiratory disease
Causes leaching of toxic metals (such as lead and mercury) from soils and rocks into acidic lakes used as sources for drinking water
Can damage, weaken, or kill trees and pollute surface and groundwater
2000 year old Hadrian’s Arch in Greece

27. Emissions Lake Groundwater
SO2
NOx
Acid deposition
H2O2 O3
PANs
Others
Susceptibility to drought, extreme cold, insects, mosses, & disease organisms
Direct damage to leaves & bark
Reduced photo-synthesis and growth
Figure 19.9
Natural capital degradation: air pollution is one of several interacting stresses that can damage, weaken, or kill trees and pollute surface and groundwater.
Soil acidification
Tree death
Leaching of soil nutrients
Release of toxic metal ions
Root damage
Reduced nutrient & water uptake
Acids
Lake
Groundwater

28. Solutions Acid Deposition Prevention Cleanup
Reduce air pollution by improving energy efficiency
Add lime to neutralize acidified lakes
Reduce coal use
Add phosphate fertilizer to neutralize acidified lakes
Increase natural gas use
Figure 19.10
Solutions: methods for reducing acid deposition and its damage. QUESTION: Which two of these solutions do you think are the most important?
Increase use of renewable energy resources
Burn low-sulfur coal
Remove SO2 particulates & NOx from smokestack gases
Remove NOx from motor vehicular exhaust
Tax emissions of SO2
Fig , p. 452

29. Ways to Prevent Air Pollution
Best practice – avoid them in the 1st place
Control of Sulfur and Nitrogen Emissions
Removing sulfur dioxide from coal by fluidized bed combustion
Granulated coal is burned in close proximity to calcium carbonate which reduces sulfur emissions
Heated calcium carbonate absorbs sulfur dioxide and produces calcium sulfate, which can be used in the production of gypsum wallboard
Burn temps must be reduced and oxygen levels controlled to lower nitrogen oxide emissions
This process can create CO and reduces efficiency
Catalytic converters on cars
CTI Journal – Research how catalytic converters work and write ½ - 1 page summary in your journal

30. Baghouse filters
Allow gas to pass through but remove particulate matter

31. Electrostatic precipitators

32. Scrubbers on smoke stacks

33. Stratospheric Ozone
The stratospheric ozone layer exists roughly kilometers above the Earth.
Ozone has the ability to absorb ultraviolet radiation and protect life on Earth.

34. Formation and Breakdown of Ozone
First, UV-C radiation breaks the bonds holding together the oxygen molecule )2, leaving two free oxygen atoms: O2 + UV-C -> 2O
Sometimes the free oxygen atoms result in ozone: O2 + O -> O3
Ozone is broken down into O2 and free oxygen atoms when it absorbs both UV-C and UV-B ultraviolet light: O3 + UV-B or UV-C -> O2 + O

35. Anthropogenic Contributions to Ozone Destruction
Certain chemicals can break down ozone, particularly chlorine.
The major source of chlorine in the stratosphere is a compound known as chlorofluorocarbons (CFCs)
CFCs are used in refrigeration and air conditioning, as propellants in aerosol cans and as “blowing agents” to inject air into foam products like Styrofoam.

36. Anthropogenic Contributions to Ozone Destruction
When CFCs are released into the troposphere they make their way to the stratosphere.
The ultraviolet radiation present has enough energy to break the bond connecting chlorine to the CFC molecule.
which can then break apart the ozone molecules.

37. Anthropogenic Contributions to Ozone Destruction
First, chlorine breaks ozone’s bonds and pulls off one atom of oxygen, forming a chlorine monoxide molecule and O2: O3 + Cl -> ClO + O2
Next, a free oxygen atoms pulls the oxygen atom from ClO, liberating the chlorine and creating one oxygen molecule: ClO + O -> Cl + O2
One chlorine atom can catalyze the breakdown of as many as 100,000 ozone molecules before it leaves the stratosphere.

38. Depletion of the Ozone Layer
Global Ozone concentrations had decreased by more than 10%.
Depletion was greatest at the poles
Decreased stratospheric ozone has increased the amount of UV-B radiation that reaches the surface of Earth.

39. Indoor Air Pollutants
Wood, animal manure or coal used for cooking and heating in developing countries.
Asbestos
Carbon Monoxide
Radon
VOCs in home products