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

2. 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.
Why is air pollution considered a global system?
Earth’s atmosphere is a global commons or worldwide public resource.

3. Major Air Pollutants Sulfur Dioxide Nitrogen Oxides Carbon Monoxide
Particulate Matter
Lead
Volatiles Organic Compounds
Ozone
Mercury
Carbon Dioxide
Of the pollutants above what are the criteria pollutants? What does criteria stand for?

4. Criteria Pollutants vs Primary Pollutants
Criteria Pollutants are controlled by the Clean Air Act. The EPA is required to set National Ambient Air Quality Standards (NAAQS) for the six common air pollutants. These commonly found air pollutants (also known as "criteria pollutants") are found all over the United States.
Primary pollutants are direct products of combustion and evaporation and can lead to secondary pollutants.
On your chart notes mark the primary pollutants.

5. Criteria Air Pollutants
Compound
Symbol
Anthropogenic Cause
Effects/ Impacts
Criteria Air Pollutants
Sulfur Dioxide
Nitrogen Oxide
Carbon Monoxide
Particulate Matter
Lead
Ozone
Other Air Pollutants
Volatile Organic Compounds
Mercury
Carbon Dioxide
Primary
Primary
Primary
Primary
Primary
Primary
Primary

6. Examples of Sources for the Six Criteria Pollutants
O3 – Ozone
Ozone: Formed by the interaction of sunlight with other other pollutants: NO, CO, and Volatile Organic Compounds (VOCs)
NO2 – Nitrogen Dioxide
Car exhaust and Electricity Generation produce NO during combustion, which gets converted into NO2 in the atmosphere
CO – Carbon Monoxide
All combustion processes such as car exhaust and Electricity Generation
The common sources of three of the priority pollutants are listed here.  There are no significant human emissions of ozone; as we will learn in more detail, ozone (O3) is formed in the reaction of sunlight with a carbon source and oxides of nitrogen.  All three ingredients are necessary to make ozone at ground level.
Similarly, there are no large anthropogenic sources of nitrogen dioxide (NO2).  All combustion sources (burning of fuels such as gasoline, coal and natural gas) produce nitric oxide (NO), which reacts in the atmosphere with ozone and other oxidants (peroxy free radicals, RO2, ultimately derived from ozone) to form NO2.  Nitrogen dioxide is the crieria pollutant that is regulated, rather than NO, because it as orders of magnitude more toxic than NO.  In fact, NO is used in inhalation therapy to treat premature babies, and in that application there is a huge concern for removing any NO2 impurity from the source gas.
Carbon monoxide (CO) is a toxic gas because it competes with oxygen for binding to hemoglobin in red blood cells.  It is an odorless gas (unlike ozone) and can reach dangerous concentrations without being noticed.  For this reason, people are urged to have CO detectors in their homes if the home is heated by a natural gas or heating oil furnace.  Carbon dioxide can be a serious problem in tunnels where auto exhaust accumulates and cause accidents by making the driver sleepy.  Carbon monoxide is produced when fuels are not burned efficiently so that not all of the carbon is oxidized all the way to CO2.  For example, if automobile engines are adjusted to be "fuel rich", they will produce larger amounts of CO, and the car will have poor fuel efficiency since not all of the energy can be derived from the fuel combustion is released.  Because of the economic incentive to be as efficient as possible, CO emissions from electrical power plants, which burn either coal or natural gas, kept very low.   1 2 3
O3, NO2, and CO will be discussed further in Lesson 2
Lesson 1: Air Pollution Basics

7. Examples of Sources for the Six Criteria Pollutants
PM2.5,10 – Particulate Matter
Car Exhaust, Electricity Generation, Fires, and Road dust
Pb – Lead
Iron smelters and other industrial processes.
Before it was banned, leaded gasoline was a major contributor to lead in the atmosphere.
SO2 – Sulfur Dioxide
Electricity Generation from burning of coal.
The principal sources of the remaining three criteria pollutants are given here.  Particulate matter (PM) is measured as PM2.5 and PM10.  The subscripted numbers refer to the sizes of the particles.  Originally, only PM10, which refers to the mass of particles in a cubic meter of air having sizes less than 10 micrometers (µm) in diameter, was measured and regulated.  (By comparison, a red blood cell has a diameter of ~5 µm.)  However, the health effects of particulate matter depend on the particles being inhaled into the lungs.  The nose and throat remove nearly all particles larger than 10 µm ("course particles") and a large fraction of the particle larger than 2.5 µm.  The fine particles smaller than 2.5 µm are correlated with the adverse health effects associated with pulmonary diseases such as asthma and COPD (Chronic Obstructive Pulmonary Disease).  Particulate matter also is responsible for reduced visibility and the "brown cloud" that often hangs over cities.  Short wavelengths of light (e.g., blue light) are more strongly scattered by small particles than are long wavelengths (e.g., red light), causing the pollution layer to appear brown in color.
Lead (Pb) is a highly toxic element that affects the heart, bones, intestines, kidneys, reproductive organs and nervous system.  Lead poisoning has been a problem for thousands of years; the Romans sweetened their wine with lead salts, for example, and it is thought that this led to insanity of some of the Roman emperors.  Lead is of particular concern for children because it interferes with the development of the brain, causing permanent learning and behavioral disorders -- and even death.  Lead levels in blood have been correlated with reduced IQ and an increase in violent criminal behavior.  Lead poisoning of children, especially in poor neighborhoods, was at one time a very serious problem due to ingestion (pica) of paint flakes from houses painted prior to World War II when leaded paint widely used.  Lead smelters, which release lead in aerosol form, have been a large source of dangerous air pollution throughout the world.  The use of tetraethyl lead as an anti-knock agent in gasoline was developed in the 1920s and became widely used throughout the world.  It was discovered in the 1960s that burning leaded gasoline was poisoning our population, and leaded gasoline was finally banned for automobiles in the U.S. in the 1970s, although it is still used in light aircraft.  Also, many countries throughout the world still use leaded gasoline.
The main source of sulfur dioxide (SO2) to the atmosphere is burning of sulfur-containing coal.  Sulfur dioxide is a toxic gas like ozone and NO2, but it also reacts in the atmosphere to form sulfuric acid.  "Acid rain" contains both sulfuric acid and nitric acid formed from oxides of nitrogen.  Unlike lakes with limestone floors which can neutralize acid rain, the pH is lowered by acid rain for lakes with granite floors -- and in those lakes fish cannot live and reproduce.  The effects of acid rain on lakes, forests and other natural ecosystems led the EPA to regulate emissions of power plants through a "cap and trade" program beginning in the 1990s.  This led to installation of scrubbers on the smokestacks of coal-fired power plants and has greatly reduced the atmospheric levels of sulfur dioxide in the U.S. over the past two decades.  However, sulfur dioxide remains a serious air pollutant throughout much of the word, especially in rapidly developing countries.  4 5 6
O3, NO2, and CO will be discussed further in Lesson 2
Lesson 1: Air Pollution Basics

9. **Page 412

10. Primary and Secondary Pollutants
Primary Pollutants are emitted directly from various sources and cause harm in their emitted state.
Examples of Primary Pollutants: NO, SO2, CO, CO2
Secondary Pollutants result from chemical transformations in the atmosphere.
Examples of Secondary Pollutants: O3, H2O2, HNO3, H2SO4, Nitrate and Sulfate Particles
Some of the principal pollutants emitted directly to the atmosphere include NO, CO, CO2 SO2, volatile organic compounds (VOCs) and some particulate matter such as soot.  The pollutants are sometimes referred to as "primary pollutants".
Ground level ozone, the pollutant of greatest interest to this course, is a "secondary pollutant" because there are no significant anthropogenic sources of ozone to the atmosphere.  Some other examples of secondary pollutants are hydrogen peroxide (H2O2), nitric acid (HNO3), sulfuric acid (H2SO4) and nitrate and sulfate particles formed from these acids.  Nitrogen dioxide is mostly a secondary pollutant, since combustion sources emit almost entirely NO as the only oxide of nitrogen.  Many oxidized products of hydrocarbons are secondary pollutants as well; for example, formaldehyde, acetaldehyde, formic acid, acetic acid, and many, many others.
Lesson 1: Air Pollution Basics

11. What is the difference between a primary and a secondary pollutant?
Primary causes secondary.
If society controls primary then secondary pollution will reduce.

12. Natural Sources of Air Pollution
Volcanoes
Lightning
Forest fires
Plants

13. Anthropogenic Sources of Air Pollution
On-road vehicles
Airplanes
Power plants
Industrial processes
Waste disposal

14. How does the Clean Air Act regulate anthropogenic emissions?
In developing the Clean Air Act of 1970 and subsequent amendments:
The Clean Air Act (CAA) is the comprehensive federal law that regulates air emissions from stationary and mobile sources. Among other things, this law authorizes EPA to establish National Ambient Air Quality Standards (NAAQS) to protect public health and public welfare and to regulate emissions of hazardous air pollutants.

15. Lesson 1: Air Pollution Basics
Air Quality Index
Levels of Health Concern
The Air Quality Index is color coded from green (good) through orange (unhealthy for sensitive groups), red (unhealthy for everyone) and purple (hazardous), as seen in this chart.  The AQI is based on the single priority pollutant that is the most unhealthy on that day and does not take into account any synergistic effects of high concentrations of multiple pollutants.  In the U.S., AQI typically is based on PM2.5 during the winter or either PM2.5 or ozone during the summer.  The other four criteria pollutants (CO, Pb, NO2, SO2) seldom contribute to the calculated API.
The current value of the AQI is provided by the EPA's AIRNow website and provided by many weather sources as well.
A daily measure of the quality of the air generally published along with weather reports based on the amount of the six criteria pollutants in the air.
Lesson 1: Air Pollution Basics

16. What is photochemical smog and how does it form?
Key Components:
Sunlight
NO2
Oxygen
VOC’s
Ozone
Photochemical smog in Denver!

17. Photochemical Smog

18. Thermal Inversions: How does an inversion layer influence air pollution events?
Thermal Inversion when a relatively warm layer of air at mid-altitude covers a layer of cold, dense air below.
The warm inversion layer traps emissions that then accumulate beneath it.

19. Acid Deposition What is acid deposition
Acid Deposition What is acid deposition? What are the 2 primary pollutants?
Acid deposition- occurs when nitrogen oxides and sulfur oxides are released into the atmosphere and combine with atmospheric oxygen and water. These form the secondary pollutants nitric acid and sulfuric acid.
These secondary pollutants further break down into nitrate and sulfate which cause the acid in acid deposition.

20. How does acid deposition have a negative effect on Earth’s surface?
Lowering the pH of lake water
Decreasing species diversity of aquatic organisms
Mobilizing metals that are found in soils and releasing these into surface waters
Damaging statues, monuments, and buildings

21. Acid Deposition

22. Ways to Prevent Air Pollution Pollution control methods for SO2, NOx, and particulates.
Removing sulfur dioxide from coal by fluidized bed combustion
Better combustion of fuels to reduce NOx
Catalytic converters on cars (NOx )
Scrubbers on smoke stacks
Baghouse filters
Electrostatic precipitators

23. Baghouse filters- most efficient
A fabric-filter dust collector can remove very nearly 100 percent of particles as small as 1 μm and a significant fraction of particles as small as 0.01 μm.
(Britannica.com)

24. Electrostatic precipitators
An electrostatic precipitator can remove particulates as small as 1 μm with an efficiency exceeding 99 percent. The effectiveness of electrostatic precipitators in removing fly ash from the combustion gases of fossil-fuel furnaces accounts for their high frequency of use at power stations.

25. Scrubbers on smoke stacks
Spray-tower scrubbers can remove 90 percent of particulates larger than about 8 μm.

26. Catalytic Converter
an automobile exhaust-system component containing a catalyst that causes conversion of harmful gases (as carbon monoxide and uncombusted hydrocarbons) into mostly harmless products (as water and carbon dioxide)

27. Good vs Bad Ozone
Even # Tables: Good ozone (blue poster) pages 52-55, Odd # Tables: Bad ozone (orange poster) pages 415,

28. Good Ozone: Formation and Breakdown of Ozone How does the stratospheric ozone layer form and why is it beneficial?
First, UV-C radiation breaks the bonds holding together the oxygen molecule, leaving two free oxygen atoms: ) O2 + UV-C -> 2O
Sometimes the free oxygen atoms result in ozone:
2) 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

30. Breakdown of the Good Ozone How does the stratospheric ozone layer deteriorates?
Reducing our Good Ozone
4) O3 + Cl -> ClO + O2
5) ClO + O -> Cl + O2
6) O3 + O -> 2O2

31. Stratospheric Ozone Ozone = good up high, bad near by!!!
The stratospheric ozone layer exists roughly kilometers above the Earth.
Ozone has the ability to absorb ultraviolet radiation and protect life on Earth.
Ozone = good up high, bad near by!!!

32. Anthropogenic Contributions to Ozone Destruction What causes the depletion of the ozone layer?
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.

33. 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.

34. 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.

35. Depletion of the Ozone Layer Steps taken to reduce ozone?
Montreal Protocol on Substances That Deplete the Ozone Layer in 1987: reduce CFCs by 50% by the year 2000.
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.

36. Indoor Air Pollutants
Main sources of indoor pollution for developing countries?
Wood, animal manure or coal used for cooking and heating in developing countries.
Main sources of indoor pollution for developed world?
Asbestos
Carbon Monoxide
Radon
VOCs in home products
Sick building syndrome?
The buildup of toxic compounds and pollutants in an airtight space; seen in newer buildings with good insulation and tight seals against air leaks.