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

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.

Major Air Pollutants Sulfur Dioxide Nitrogen Oxides Carbon Oxides Particulate Matter Volatiles Organic Compounds Ozone Lead Mercury

Primary Pollutants Primary pollutants- polluting compounds that come directly out of the smoke-stack, exhaust pipe, or natural emission source. Examples: CO, CO2, SO2, NOx, and most suspended particulate matter.

Secondary Pollutants Secondary pollutants- pollutants that have undergone transformation in the presence of sunlight, water, oxygen, or other compounds. Examples: ozone, sulfate and nitrate

Natural Sources of Air Pollution Volcanoes Lightning Forest fires Plants

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

Photochemical Smog

Thermal Inversions 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.

Acid Deposition

Acid Deposition 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.

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

Ways to Prevent Air Pollution Removing sulfur dioxide from coal by fluidized bed combustion Catalytic converters on cars Scrubbers on smoke stacks Baghouse filters Electrostatic precipitators

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 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

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.

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.

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.

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.

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

A pungent reddish brown gas often associated with photochemical smog CO CH4 NO2 SO2 PM10

A corrosive gas from burning coal often associated with industrial smog CH4 NO2 SO2 PM10

A dangerous indoor air pollutant CO CH4 NO2 SO2 PM10

Emitted from both diesel and burning wood CO CH4 NO2 SO2 PM10

All of the following are examples of primary air pollutants except (a) sulfur dioxide. (b) carbon dioxide. (c) tropospheric ozone. (d) nitrogen oxide. (e) particulates.

The greatest emission of sulfur dioxide comes from (a) on-road vehicles. (b) biofuels. (c) industrial processes. (d) electricity generation. (e) fires.

The least amount of nitrogen oxide emissions comes from (a) on-road vehicles. (b) fossil fuel combustion. (c) industrial processes. (d) electricity generation. (e) fires.

The accumulation of tropospheric ozone at night depends mainly upon the atmospheric concentration of (a) nitrogen dioxide. (b) volatile organics. (c) chlorofluorocarbons. (d) sulfates and nitrates. (e) nitric acid.

Under natural conditions the pH of rainfall is closest to (a) 8. 5 Under natural conditions the pH of rainfall is closest to (a) 8.5. (b) 7.1. (c) 5.6. (d) 4.5. (e) 3.1.

The effects of acid deposition include all of the following except (a) mobilization of metal ions from the soil into surface water. (b) increased numbers of salamanders in ponds and streams. (c) lower food sources for aquatic organisms. (d) erosion of marble buildings and statues. (e) erosion of painted automobile finishes and metals.

The World Health Organization estimates that over half of the deaths worldwide due to indoor air pollution occur among (a) children less than 5 years old. (b) elderly people over 65 years of age. (c) people who work in office buildings. (d) workers in the smelting industry. (e) workers who manufacture asbestos.

Two major factors involved in the conversion of primary pollutants into secondary pollutants are (a) sunlight and water. (b) sulfates and sunlight. (c) water and volatile organics. (d) nitrogen oxides and sulfates. (e) sulfur dioxide and sulfuric acid

The pollutant least likely to be emitted from a smokestack would be (a) carbon monoxide. (b) carbon dioxide. (c) ozone. (d) sulfur dioxide. (e) particulates.

The EPA identifies all of the following as reasons for sick building syndrome except (a) faulty ventilation systems. (b) emissions from carpets and furniture. (c) contamination from outdoor air. (d) contamination from molds and pollen. (e) high levels of radon in the basement.

Which statement regarding the decreased levels of stratospheric ozone is correct? (a) Increased photosynthetic activity has been measured in the phytoplankton around Antarctica. (b) The largest decrease in the level of stratospheric ozone over the Arctic region occurs between January and April. (c) Although the Montreal Protocol led to a reduction in the use of CFCs, it will have little effect on stratospheric ozone levels in the long term. (d) There is no correlation between the incidence of cataracts and skin cancers and the lower levels of stratospheric ozone. (e) The global crop yields of wheat, rice, and corn have increased since the reduction in CFC use.

The type(s) of ultraviolet radiation most strongly absorbed by ozone in the stratosphere is/are (a) UV-A. (b) UV-B. (c) UV-C. (d) UV-B and UV-C. (e) UV-A and UV-B.

Natural sources of air pollution include all of the following except (a) forest fires. (b) volcanic eruptions. (c) waterfalls. (d) dust storms. (e) conifer trees.

A thermal inversion (a) rarely occurs in cities but is common in rural areas. (b) helps remove pollutants from the atmosphere. (c) leads to decreased amounts of ground- level smog. (d) occurs when a warm air layer overlies a cooler layer. (e) occurs when a cool air layer overlies a warmer layer.

Examine the following ambient air data collected for Pittsburgh, Pennsylvania, and answer the following questions. (a) Based on the National Ambient Air Quality Standards (NAAQS), the 2008 standard for ozone states that the average ozone levels are not to exceed 0.075 ppm (75 ppb) in any 8-hour period. Is Pittsburgh in compliance with this standard? Discuss how this NAAQS may not truly reflect the overall air quality. (2 points) (b) Ozone is classified as a secondary pollutant. Identify the primary pollutants necessary for its formation and describe how tropospheric ozone is formed. (2 points) (c) Identify two relationships between the data presented. Apply these relationships to your answer in (b) to explain the pattern of ozone levels in Pittsburgh. (4 points) (d) Explain how the same ozone that is harmful in the troposphere is beneficial in the stratosphere. (2 points)