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.  Ground level pollution is also called tropospheric pollution.

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

Sulfur Dioxide (SO 2 )  A corrosive gas that comes primarily from combustion of coal and oil.  Respiratory irritant  Also released during volcanic eruptions and forest fires. S + O  SO 2

Nitrogen Oxide (NO x )  Can be either:  NO Nitrogen oxide: a colorless odorless gas  NO2 Nitrogen dioxide: pungent, reddish-brown gas  Primary anthropogenic sources- motor vehicles and stationary fossil fuel combustion.  Natural sources: Forest fires, lightning, microbial action in soil.

Carbon Oxides  Carbon monoxide (CO): colorless, odorless gas formed in the incomplete combustion of most matter  Ex. Vehicle exhaust, natural gas heaters, cooking with charcoal or kerosene  Carbon dioxide (CO2): colorless odorless gas that forms during the complete combustion of most matter, including fossil fuels and biomass

Particulate Matter Particulate Matter (PM): solid or liquid particles suspended in air. Also called particulates or particles.  Produced from the combustion of wood, animal manure, coal, oil, gasoline, volcanoes, road dust, rock crushing, forest fires and dust storms.  Diesel vehicles give off more black smoke than do gasoline vehicles.  Particulate matter smaller than 10  m (PM 10 )are not filtered by the nose and can be deposited in the respiratory tract.  Particulate matter 2.5  m or smaller (PM 2.5 ) are of deep concern, they deposit deeper in the respiratory tract and are composed of more toxic substance.

Haze: reduced visibility caused primarily when particulate matter from air pollution scatters light.

Photochemical Oxidants Photochemical oxidants are a class of air pollutants formed as a result of sunlight acting on compounds such as nitrogen oxides and sulfur dioxide.  Oxides remove electrons from other substances.  harmful to plant tissue, human respiratory tissue  Smog: mixture of oxidants and particulates

Photochemical Oxidants Photochemical smog: dominated by ozone  also called Los Angeles-type smog or brown smog  Occurs when sunlight acts on vehicle pollutants

Photochemical Oxidants Sulfurous smog dominated by sulfur dioxide and sulfate compounds  also called London-type smog or gray smog.  Occurs where coal is burned and the atmosphere is humid.

Volatile Organic Compounds VOC’s are organic compounds that become vapors at typical atmospheric temperatures. Anthropogenic o Emissions (Hydrocarbons) o Industrial solvents: trichlorethylene (TCE), benzene and vinyl chloride Natural o Ethylene, terpene

Primary 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  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

Check 1: _________________ are the largest source of carbon monoxide and nitrogen oxides. Vehicles (transportation)

Check 2: Electricity generation is almost 50% fueled by ________. Coal

Check 3: Electricity generation is the major source of anthropogenic ______________. Sulfur dioxide

Check 4: What is the difference between a primary and a secondary pollutant? Primary- come directly from the source. Transformation to secondary requires sunlight, water and/or temp.

Check 5: Identify 4 primary pollutants? CO, CO 2, SO 2, NO x, VOC’s

Check 6: Identify 2 secondary pollutants? Ozone, SO 3, H 2 SO 4, HNO 3, H 2 O 2

Check 7: What are the major natural sources of air pollution? Volcanoes, lightning, forest fires, plants (living and dead)

Check 8: Identify the pollutants released by a volcano. SO 2, particulate matter, CO, NO x

Check 9: Identify the pollutants created by lightning. NO x

Check 10: Identify the pollutants released by forest fires. particulate matter, CO and NO x

Check 11: Identify the VOC’s released by living plants. Ethylene, turpene These can give rise to smog and photochemical oxidant pollution… hence the name Smoky Mountains.

Check 12: Identify an anthropogenic source of particulate matter. Road dust, industrial processes, farming, combustion of coal, oil and gasoline.

Check 13: Identify the number 1 source of anthropogenic CO On-road vehicles

Check 14: Identify the number 1 source of anthropogenic NOx On-road vehicles

Check 15: Identify the number 1 source of anthropogenic SO 2 Electricity generation

Check 16: Identify two compounds that bioaccumulate DDT and mercury

Check 17: Identify a point source of CO. Vehicle emissions

Check 18: Identify a point source pollution of SOx. Volcanic eruptions, forest fires, car exhaust

Check 19: Identify point source pollution of NOx. motor vehicles, stationary fossil fuel combustion, Forest fires, lightning, microbial action in soil.

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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- occurs when nitrogen oxides and sulfur oxides 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… acid rain eats through stone and metal

Acid Deposition

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

Fluidized bed combustion  Removes sulfur dioxide from coal exhaust during combustion.  Coal is burned in close proximity to calcium carbonate (CaCO 3 )  CaCO 3 absorbs SO2 producing calcium sulfate (CaSO 4 )  CaSO 4 is used to make gypsum wallboard (sheetrock)

Control of NO x emissions  Reduce burn temperatures and control amount of oxygen can reduce NOx… can result in less complete combustion, more CO and particulates produced.  Catalytic converters on cars reduce NO and CO, as well as unleaded gas.

Control of Particulate Matter  A common means of pollution control  Each uses energy, generating additional pollution  Baghouse filter  Electrostatic precipitator  Scrubber

Baghouse filter  Fabric filter  Can remove almost 100% of PM emissions.

Electrostatic Precipitator  Uses an electric charge to make particles coalesce

Scrubber  Uses water and air to separate and remove particles.

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.

Formation and Breakdown of Ozone  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: 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