Chapter 15 Air Pollution and Stratospheric Ozone Depletion

Air Pollution Air pollution is a global issue that transcends national boarders. Increases death rate and lowers general health of the population.

1. Air pollutants are found through the entire global system 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

Air Pollution Decreasing in the United States since late 1970’s = Successful environmental story!

Major Air Pollutants Sulfur Dioxide Nitrogen Oxides Carbon Monoxide Particulate Matter Tropospheric Ozone Lead Mercury Volatiles Organic Compounds Carbon Dioxide *First 6 listed are the original “criteria” air pollutants in the Clean Air Act (1970)

Primary Air Pollutants Primary Pollutant- Polluting compound that come directly from a source – i.e. smokestack, exhaust pipe Examples: CO, CO 2, SO 2, NO x, many VOCs

Primary Air Pollutants 1. Sulfur Dioxide (SO 2 ) - Produced when sulfur-containing fossil fuels (primarily coal and oil) are combusted Natural sources: volcanic eruptions, forest fires Causes respiratory problems such as asthma

Primary Air Pollutants 2. Nitrogen Oxides (NO x ) NO or NO 2 - Formed when combustion takes place in the air Main sources: automobile engines, fossil fuel combustion Natural sources: forest fires, lightning Respiratory irritant

Primary Air Pollutants 3. Carbon Oxides – CO - Produced when organic materials are incompletely burned Main source: automobile Binds to hemoglobin in blood and makes it less able to carry oxygen Cigarette smoking an important source

Primary Air Pollutants 3. Carbon Oxides – CO 2 - Produced during complete combustion of fossil fuels and most matter Increased concentrations in the atmosphere cause it to become a pollutant Greenhouse gas; traps heat

Primary Air Pollutants 4. Particulate Matter - Minute pieces of solid (and sometimes liquid) materials suspended in air Produced from combustion of wood, manure, coal, oil, gasoline as well as road dust, volcanoes, forest fires, dust storms Can accumulate in lungs and interfere with the ability of lungs to exchange gases Can be carcinogenic Can scatter (causing haze) and absorb sunlight and affect photosynthesis Caused by travel on highways & roads, construction sites, campfires

Primary Air Pollutants 5. Volatile Organic Compounds (VOC) Become vapors at typical atmospheric temperatures Many are hydrocarbons from gasoline, lighter fluid, dry-cleaning fluid, perfumes that have a strong odor Evaporated from automobile fuel or remnants of fuel incompletely burned

Primary Air Pollutants 6. Lead Lead can enter the body through breathing airborne particles or consuming lead deposited on surfaces Leaded gasoline was primary source Can cause mental retardation & kidney damage

Primary Air Pollutants

Mercury From burning coal and oil Particles can land in water Toxic to nervous system

Secondary Air Pollutants - Form under reaction of primary pollutants and water, sunlight, or oxygen

Secondary Air Pollutants Reactions happen fastest during the day in wet environments Air Now

Secondary Air Pollutants SO 2  H 2 SO 4 Sulfuric acid &/or SO 4 2- Sulfate NO x  HNO 3 Nitric acid &/or NO 3 - Nitrate

2. Air pollution comes from both natural and human sources Natural Sources –Volcanoes –Forest fires –Lightning –Biogeochemical cycles

On-road vehicles – largest source of CO and NO x Power plants – largest source of SO 2 Industrial processes Waste disposal Anthropogenic Sources of Air Pollution

3. Photochemical smog is still an environmental problem in the United States

Tropospheric Ozone

Ozone (O 3 ) is a molecule of three oxygen atoms bonded to one another. Ground Level Ozone: VOC + NOx + Sunlight = Ozone

Tropospheric Ozone Primary Pollutants Secondary Pollutants

Tropospheric Ozone Extremely reactive secondary pollutant Permanent lung damage Damages plants by destroying chlorophyll

Photochemical Smog A mixture of primary and secondary pollutants Forms when primary pollutants interact under the influence of sunlight Only type of air pollution that has not decreased Ozone + nitrogen oxides + volatile organic compounds + sunlight + warm temperatures = Photochemical Smog

Name: London smog (New York smog, gray smog) Photochemical smog (L.A. smog, Denver smog, brown smog) Weather: cool, dampsunny Content: particulates, *SOx*NO x, ozone, hydrocarbons. Sources: coal, etc.gasoline, combustion. Secondary Air Pollutant

Thermal Inversions 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

Thermal Inversions

4. Acid deposition is much less of a problem than it used to be

Acid Deposition Pollution + Redox reaction  Acid Rain

Effects of Acid Deposition 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 1 2 3

Effects of Acid Deposition

5. Pollution control includes prevention, technology, and innovation Removing sulfur dioxide from coal by fluidized bed combustion Catalytic converters on cars Scrubbers on smoke stacks Baghouse filters Electrostatic precipitators

Bag House Filter

Electrostatic Precipitator

Scrubber

6. The stratospheric ozone layer provides protection from ultraviolet solar radiation The stratospheric ozone layer exists roughly kilometers above the Earth. Ozone has the ability to absorb ultraviolet radiation and protect life on Earth.

Formation and Breakdown of Ozone First, UV-C radiation breaks the bonds holding together the oxygen molecule (O 2 ), leaving two free oxygen atoms: O 2 + UV-C  2O Sometimes the free oxygen atoms react with other O 2 molecules and result in ozone: O 2 + O  O 3 If the ozone absorbs either UV-C or UV-B radiation, it will cause the reaction to reverse: O 3 + UV-B or UV-C  O 2 + O

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. Chlorine is a catalyst for the reaction (not used up). One chlorine atom can catalyze the breakdown of as many as 100,000 ozone molecules before it leaves the stratosphere.

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.

Depletion of the Ozone Layer Global Ozone concentrations continue to decrease about 4% per decade Depletion is greatest at the poles Decreased stratospheric ozone has increased the amount of UV-B radiation that reaches the surface of Earth NASA study showing strength of long wave energy around the poles, which affects temperature. Stronger long waves results in more circulation, warming the poles and spreading precipitation so that there is not a build up of ozone-destroying particles in the atmosphere. From

7. Indoor air pollution is a significant hazard, particularly in developing countries Indoor air pollutants include: Wood, animal manure, or coal (used for cooking and heating in developing countries). VOCs in home products Asbestos Carbon Monoxide Radon Indoor air pollutants also present a significant threat to human health, particularly in developing countries.

Review Questions 1. Describe natural and human sources of particulate matter. 2. Explain the different between primary and secondary air pollutants. 3. How does photochemical smog form? 4. Explain the chemical reaction that leads to acid deposition. 5. What are the two different locations of ozone? Why is one good and one bad? 6. How have humans affected the amount of stratospheric ozone?