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 living things and materials, or alter ecosystems

Major Air Pollutants Sulfur dioxide (SO 2 ) Nitrogen oxides (NO x ) Carbon oxides Particulate matter (PM) Volatile Organic Compounds (VOCs) Ozone (O 3 ) Lead Mercury

Particulate Matter (PM)

Smog Portmanteau of smoke + fog – Ex: “Brangelina” – Ex: “Tomkat” – Ex: “Strogiana Lima”

Photochemical (Brown) Smog NO x + VOCs + sunlight = photochemical smog Found in areas with a lot of cars (Los Angeles, New York, Sydney, etc.)

Sulfurous (Gray) Smog SO x + PM + fog = sulfurous smog Found in areas with a lot of coal burning (Victorian London)

Primary Pollutants Primary pollutants: polluting compounds that come directly out of the smokestack, exhaust pipe, or natural emission source – Ex: CO, CO 2, SO 2, NO x, and most suspended particulate matter

Secondary Pollutants Secondary pollutants: pollutants that have undergone transformation in the presence of sunlight, water, oxygen, or other compounds – Ex: ozone (O 3 ), sulfate (SO 4 2- ), and nitrate (NO 3 - )

Natural Sources of Air Pollution Volcanoes Lightning Forest fires Plants

Anthropogenic Sources of Air Pollution Vehicles Power plants Industrial processes Waste disposal

History of Air Pollution in the U.S.

What are some examples of standards? Every student must achieve a minimum score in the Keystone Exams before graduating high school in Pennsylvania There may not be more than 2 rodent hairs per 100 grams of peanut butter Adriana Lima refuses to date Mr. Strogen because she has “standards”

Clean Air Act Since 1970, the goal of the Clean Air Act has been to reduce the amount of pollution in America’s air The Act created the National Ambient Air Quality Standards (NAAQS), which sets a maximum level of pollution allowed per pollutant Six major “criteria” pollutants are regulated: – NO 2 – SO 2 – Ozone – CO – Lead – Particulate Matter (PM)

Regulation The Environmental Protection Agency (EPA) has regulatory authority over the air standards Each state is obligated by law to meet the NAAQS Areas that do not meet the standards are called “non-attainment”

Percent Change in Air Quality Pollutant1990 vs Carbon Monoxide-68% Ozone-14% Lead-78% Nitrogen Dioxide-35% PM % Sulfur Dioxide-59%

Comparison of Growth Areas and Emissions,

Number of People Living in Counties with Air Quality Concentrations Above the Level of the NAAQS in 2008

Photochemical Smog Fig p. 424

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Photochemical Smog

Nitric oxides VOCs Ozone A.M.NoonP.M. Time Parts per million

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 are released into the atmosphere and combine with atmospheric oxygen and water, forming 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

Effects of Acid Deposition rain-eating-washington-dc.html rain-eating-washington-dc.html

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

Catalytic Converter SV0tY SV0tY

Wet Scrubber

Baghouse Filter

Electrostatic Precipator

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

Ozone

Formation & 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 result in ozone: O 2 + O O 3 Ozone is broken down into O 2 and free oxygen atoms when it absorbs both UV-C and UV-B ultraviolet light: O 3 + UV-B or UV-C O 2 + 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 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 O 2 : O 3 + Cl ClO + O 2 Next, a free oxygen atoms pulls the oxygen atom from ClO, liberating the chlorine and creating one oxygen molecule: ClO + O Cl + O 2 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

Depletion of the Ozone Layer Destruction is seasonal: Mid-spring at poles is low O 3 concentration point During winter ice clouds concentrate Cl atoms They are released during spring, destroying ozone By summer production is greater than depletion

Indoor Air Pollutants SOURCERISKREMEDIATION Indoor cooking fuel Asbestos Carbon Monoxide Radon VOCs in home products

Sick Building Syndrome Due to insulation and prevention of drafts Caused by high concentrations of VOCs, hydrocarbons, allergens Present if symptoms start upon entry and are relieved 20 minutes after exiting EPA - four reasons: faulty ventilation, chemical contamination from inside or outside, and biological contamination