Chapter 15Air Pollution

A bowl is formed by the Appalachian Mountains and this makes it more susceptible to pollution, much like Boise inversions. Dense smog gets trapped and cannot rise above the mountains

• Air pollution: chemicals, particulate matter, or microorganisms found in the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings or to alter ecosystems

Air pollutants are found throughout the entire global system. Air Pollution is

the 5th largest killer in India.

China, India, Africa

Major Air Pollutants

• Sulfur dioxide SO2

• Nitrogen oxides NO or NO2 (NOx)

• Carbon oxides CO, CO2 (COx)• Early air pollution legislation didn’t care about CO2,

• Particulate matter (ash, dust, combustion of gas or diesel black smoke)

CO

• Prevents O2 from attaching to hemoglobin in blood.

• Odorless, Colorless, • It is created by

incomplete combustion of gas and is found in car emissions

Particulate Matter (PM)

PM ranges in size from .01μm to PM10. PM2.5, is of great concern, because nose hair does not filter it out and it can become embedded in the lungs. Asbestos.

PM can also scatter light.

Particulate Matter

PM can create what is called a haze or smog.

Amazon has haze from slash and burning of rainforest

Major Air Pollutants

• Volatile organic compounds (VOC)

• Ozone in troposphere

• Lead

• Mercury

Sulfates are considered to be secondary pollutants because they are transformed from primary pollutants.

Gas can become a VOC because it evaporates at room temperature, leaving a strong smell, is a hydrocarbon that can leave PM,

The combustion of coal is the primary cause of mercury in the air.

Dry cleaner fluid, spilled gas lighter fluid are additional VOC.

Primary Pollutants

• Primary pollutants: polluting compounds coming directly out of smoke-stacks, exhaust pipes, or natural emission source

• E.g., CO, CO2, SO2, NOx, and most suspended particulate matter

Secondary Pollutants

• Secondary pollutants: pollutants transformed in the presence of sunlight, water, oxygen or other compounds

• E.g., ozone, sulfate, and nitrate

Air pollution comes from both natural and

human sources.

Natural Sources of Air Pollution

• Volcanoes

• Lightning

• Forest fires

• Plants

Anthropogenic Sources of Air Pollution

Anthropogenic: From the Greek,

• Anthropos, “human”

• -genesis, “created”

• Meaning anything caused or created by human activity

Anthropogenic Sources of Air Pollution

• On-road vehicles

• Power plants

• Industrial processes

• Waste disposal

Photochemical smog is still an environmental problem in the United

States.

Smog Formation

• Smog forms when sunlight, nitrogen oxides (Nox), and volatile organic compounds (VOCs) are present.

California smog is mostly due to ozone and called brown smog. London has SO2 smog and is called tea and crumpets smog. Ok, I made that up, it is gray smog.

Smog Formation

• The secondary pollutant ozone is a major component of photochemical smog.

• Sulfur is the main ingredient in sulfurous smog.

Photochemical Smog

Thermal Inversions

• Thermal Inversion: a relatively warm layer of air at mid-altitude covers a layer of cold, dense air below.

• The warm inversion layer traps emissions (pollutants) that then accumulate beneath it.

Acid Deposition

• These secondary pollutants further break down into nitrate and sulfate, which create the acid in acid deposition.

Acid Deposition• Acid deposition: nitrogen oxides and sulfur

oxides released into the atmosphere combine with atmospheric oxygen and water.

• These become the secondary pollutants nitric acid and sulfuric acid.

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Acid Deposition

Metamorphic differences due to acid rain during development and pollution in the soil.

Effects of Acid Deposition

• Lowers the pH of lake water

• Decreases species diversity in aquatic ecosystems

• Mobilizes metals found in soils and releases these into surface waters

• Damages statues, monuments, and buildings and other structures

Pollution control includes prevention, technology,

and innovation.

Nitrates are produced in combustion of coal and gas. By reducing the temperature of burning the coal and gas, less NOx is produced

Ways to Prevent Air Pollution

• Removing sulfur dioxide from coal by fluidized bed combustion

• Catalytic converters on cars A catalytic converter is a vehicle emissions control device that converts toxic pollutants in exhaust gas to less toxic pollutants, by catalyzing a redox reaction (oxidation or reduction). Catalytic converters are used in internal combustion engines fueled by either gasoline or diesel—including lean burn  engines.

• Scrubbers on smoke stacks

• Baghouse filters

• Electrostatic precipitators

Why is there no leaded-gasoline anymore?The metals in the catalytic converter (platinum and palladium) cannot be exposed to lead to work properly. This lead to less lead and CO, NO in atm.

Baghouse filter removes particles by using a series of filters. It is the most common means of removing particle pollution.

Particles given a negative charge, after attaching to plate, it is disposed of.

Particles are scrubbed from the exhaust stream by water

droplets. The sludge is collected and disposed

of.

All three filters requires additional energy and emit heat pollution. They are very expensive to prevent PM air pollution

The stratospheric ozone layer provides protection from ultraviolet radiation.

Ultra Violet has 3 sub wavelengths of energy

UV-A passes through atm. w/o being absorbed and can cause skin cancer.

UV-B, UV-C can cause severe tissue damage, DNA damage,

Ozone blocks 99% of UV-B and UV-C

Stratospheric Ozone

• The stratospheric ozone layer exists roughly 45-60 kilometers above the Earth.

• Ozone has the ability to absorb ultraviolet radiation and protect life on Earth.

Formation and Breakdown of Ozone

• UV-C radiation breaks the bonds holding together the oxygen molecule, leaving two free oxygen atoms: O2 + UV-C → 2 O

• Sometimes these free oxygen atoms produce ozone: O2 + O → O3

• Ozone breaks down into O2 and free oxygen atoms when it absorbs both UV-C and UV-B light: O3 + UV-B + UV-C → O2 + O

Anthropogenic Contributions to Ozone Destruction

• Certain chemicals can break down ozone, particularly chlorine.

• The major sources of chlorine in the stratosphere are compounds 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.

Anthropogenic Contributions to Ozone

Destruction

• CFCs released into the troposphere disperse into the stratosphere.

Anthropogenic Contributions to Ozone

Destruction• In the stratosphere, UV radiation has enough energy to

break the bond connecting chlorine to the CFC molecule, producing Cl atoms.

• The Cl atoms act as catalysts and can break apart the ozone molecules.

Anthropogenic Contributions to Ozone

Destruction• Initially, 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 atom and creating one oxygen molecule:

ClO + O → Cl + O2

Anthropogenic Contributions to Ozone

Destruction

• One chlorine atom can catalyze the breakdown of as many as 100,000 ozone molecules before it leaves the stratosphere.

• This depletes the ozone layer.

Depletion of the Ozone Layer

• Global ozone concentrations have decreased by more than 10%.

• Depletion is greatest at the poles.

• Decreased stratospheric ozone has increased the amount of UV-B radiation that reaches the surface of Earth.

Indoor air pollution is a significant hazard, particularly in developing countries.

More die from indoor air pollution than out door air pollution

(2nd hand smoke)90% of deaths attributed to indoor pollution are in

developing countries. 56% of those deaths are children under 5

Indoor Air Pollutants

• Wood, animal manure or coal used for cooking and heating in developing countries.

• Lack of indoor ventilation can lead to carbon monoxide (CO) poisoning and increase in particulates in the air.

• This increases the risk for respiratory diseases such as infections and even cancer.

Indoor Air Pollutants

• In developed countries, people are spending more time inside.

• Houses are sealed more tightly for better insulation.

• This results in increased exposure to a number of indoor air pollutants.

Indoor Air Pollutants

• Asbestos: insulating mineral fiber found in older buildings, which must be removed by professionals.

• Carbon Monoxide: CO detectors should be installed where natural gas or wood stoves are used, as CO is odorless.

Indoor Air Pollutants

• Radon: radioactive gas released by some rocks into the soil, and migrates into homes in certain areas of the country.

• VOCs: many home products can give off these solvent fumes, such as building materials, plastics, and fabrics and carpets.

Review Questions

1. Define air pollution.

2. What are several types of major air pollutants?

3. What is carbon monoxide, and why is it so dangerous?

4. What is smog?

Review Questions

5. What is the difference between a primary and a secondary pollutant?

1. What are some natural sources of air pollution?

2. Give some examples of anthropogenic air pollution.

Review Questions1. How do thermal inversions form?

Why are they important in air pollution events?

2. How does smog form?

3. Define acid deposition.

4. Describe some effects of acid deposition.

5. What are some methods used to reduce air pollution?

Review Questions

1. What is the stratospheric ozone layer? How does it form?

2. Why is this layer important to humans and other organisms?

3. What are some indoor air pollution problems in (a) developing and (b) developed countries?