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.

6 Criteria Air Pollutants Carbon Monoxide (CO) Nitrogen Dioxide (NO 2 ) Sulfur Dioxide (SO 2 ) Suspended Particulate Matter (aerosols) Ozone (O 3 ) Lead (Pb) Know health effects of each p 438

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

Photochemical smog a) mix of primary and secondary pollutants influenced by sunlight NOx + VOC’s + light + heat -----> O 3 + aldehydes + PAN’s + HNO 3 Note: formaldehyde: H - C = O I H PAN’s: peroxyacyl nitrates b) NO ---> NO 2 <--- brown, so brown-air smog

Photochemical oxidants NO 2, O 3, PAN’s - b/c they are strong oxidizers (take electrons away) 1. common in warm, sunny climate with lots of cars - NO,NO 2 concentrations increase as traffic builds and unburned hydrocarbons rise and react, in sunlight, to produce photochemical smog (peaks in afternoon)

Industrial Smog 1. Combo of SO 2, H 2 SO 4 droplets, suspended particles 2. Burning coal, oil S + O 2 ---> SO 2 SO 2 + O 2 ---> SO 3 SO 3 + H 2 O---> H 2 SO 4 NH 3 + H 2 SO 4 ---> (NH 4 ) 2 SO 4, a particulate solid Combo of (NH 4 ) 2 SO 4 and soot, C, produces gray-air 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.

Temperature Inversion Warm air mass gets trapped above cooler air mass (acts as a lid), so surface air can‘t rise and dilute pollutants in cleaner air Early morning surface air is cool, clouds block sun so ground stays cool, upper air is warmer so there is no convection current Tends to happen in cities located in a valley (like Los Angeles)

Warmer air Inversion layer Cool layer Mountain Valley Decreasing temperature Increasing altitude

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

Wind Transformation to sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) Nitric oxide (NO) Acid fog Ocean Sulfur dioxide (SO 2 ) and NO Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Farm Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic Wet acid deposition (droplets of H 2 SO 4 and HNO 3 dissolved in rain and snow) Limestone in soil buffers acid deposition Limestone is sometimes added to lakes Adding phosphate to lakes can raise pH.

Acid Deposition and Humans  Respiratory diseases  Toxic metal leaching  Decreased visibility  Damage to structures, especially containing calcium carbonate  Decreased productivity and profitability of fisheries, forests, and farms

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

Atmosphere 1. troposphere (surface - 11mi): 78% N 2, 21% O 2, <1% Ar,.036% CO 2, % H 2 O a) tropopause: temperature abruptly rises b) each layer ends when temp gradient reverses) 2. stratosphere (11-30 mi) 1000x less water, 1000x more O 3 3O 2 + UV ----> 2O 3

3. mesosphere ( mi) 4. thermosphere ( mi) 5. human impact on nutrient cycle a) we add 1/4 as much CO 2 to atm as nature does b) we add 3x as much NOx (from fossil fuels, fertilizer) c) SO 2 from fossil fuels

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 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 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 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.

Montreal Protocol Highly successful international agreement In stages, all industrialized countries (180) have stopped the production of CFC’s, since 1996 Manufacturers gave up a significant market

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

Indoor air pollution 1. sick building syndrome- def: 20% of occupants get better when they go outside (coughing, dizziness, flu-like symptons) 2. most dangerous indoor pollutants: cigarette smoke, formaldehyde, radon- 222, very fine particles 3. Radon enters through cracks in foundation and openings around pipes, inhaled into lungs a. Reading Prong

Outlet vents for furnaces and dryers Slab joints Wood stove Cracks in floor Clothes dryer Furnace Radon-222 gas Slab Soil Uranium-238 Sump pump Cracks in wall Open window Openings around pipes Openings around pipes

Asbestos 1) best to wrap it 2) 1998, foam invented that binds fibers together, nontoxic, still fireproof

radon ) produced by radioactive decay of U ) outside diperses, indoors collects 3) radon is 55% of radiation dose in US 4) acceptable dose? picocuries/L NOTE: 1 Ci = 3.7 x disintegrations/s a 1g sample of radium has this activity 1 rad is the absorption of joule per gram of tissue

Effects of air pollution on living organisms A. Humans 1. CO takes up receptor site in hemoglobin so molecule cannot transport O study by World Bank and WHO says 2.7 million people die each year from air pollution (2.2 million from indoor pollution) B. Plants 1. air pollution (esp O 3 ) can break down waxy coating on leaves a) water loss, loss of protection from pests and frost, etc

Effects of air pollution on living organisms D. Materials 1. soot and grit ---> cleaning costs a) paint, roofs b) marble statues, historic buildings c) damage to buildings = $5 billion in US

Natural Defense Soil containing Ca 2+, Mg 2+ salts (buffering ions) can neutralize acid rain to a certain extent Limestone, CaCO 3 deposits

Solutions 1. Laws: Clean Air Acts of 1970, 1977, 1990 have led to federal regulations a) clean air act requires EPA to set national emission standards for toxic air pollutants (302) compounds) standards not met b) stricter car emission standards by 2002 c) required cleaner burning fuel (oxygenated) in 9 cities, including Philadelphia

Market Place a) 110 power plants in 20 states may buy and sell SO 2 emission rights b) SO 2 credits may be sold and used in the future c) b/w SO 2 emissions dropped by 30% d) emission credits are also proposed for NOx