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AIR POLLUTION CHAPTER 15 Structure and Science of the Atmosphere • The atmosphere consists of several layers with different temperatures, pressures, and compositions. • The atmosphere’s innermost layer (troposphere) is made up mostly of nitrogen and oxygen, with smaller amounts of water vapor and CO2. • The ozone layer (stratosphere) filters out most of the sun’s UV radiation that is harmful to us and most other species. Structure and Science of the Atmosphere The density of air molecules decreases as altitude increases. (hence the term thin air high up in the mountains) So… air pollution is more a concern at the earth’s surface. Air contents: 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. Natural Sources of Air Pollution • • • • Volcanoes Lightning Forest fires Plants Anthropogenic Sources of Air Pollution • • • • On-road vehicles Power plants Industrial processes Waste disposal Primary Pollutants • • Primary pollutantspolluting 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 Air Quality Indicator - Lichens • Lichens can warn us of bad air because they absorb it as a source of nourishment. • Some lichen species are sensitive to specific air-polluting chemicals. • After Chernobyl, more than 70,000 reindeer had to be killed because they ate highly radioactive lichens. • Because lichens are widespread, long-lived, and anchored in place, they can help track pollution to its source. Major Air Pollutants • • • • • • • • Sulfur Dioxide Nitrogen Oxides Carbon Oxides Lead Mercury Particulate Matter Volatiles Organic Compounds Ozone Major Air Pollutants • Sulfur dioxide (SO2) and Sulfuric acid: • About one-third of SO2 in the troposphere occurs naturally through the sulfur cycle. • Two-thirds come from human sources, mostly combustion of sulfur-containing coal and from oil refining and smelting of sulfide ores. Primary Air Pollutant Secondary Air Pollutant Acid Rain Major Air Pollutants • Nitrogen Oxides and Nitric Acid: • Nitrogen oxide (NO) forms when nitrogen and oxygen gases in air react at the high-combustion temperatures in automobile engines and coal-burning plants. • NO can also form from lightening and certain soil bacteria. • NO reacts with oxygen to create NO2 with is a major component in… • Smog • Acid Rain • PANS (Peroxyacyl nitrates) (respiratory & eye irritants in smog) Major Air Pollutants • Carbon Oxides: • Carbon monoxide (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials. • Carbon dioxide (CO2) • 93% of carbon dioxide in the troposphere occurs as a result of the carbon cycle. (cellular respiration) • 7% of CO2 in the troposphere occurs as a result of human activities (mostly burning fossil fuels). Major Air Pollutants • Lead & Mercury • Lead is a powerful neurotoxin. • Was removed from gasoline over three decades ago • Concentrations in the air have declined precipitously • Mercury from coal fired power plants is now of greater concern than lead • Lead & Mercury are heavy metals. They cause human health concerns – they cause brain damage in infants and children. Major Air Pollutants • Suspended Particulate Matter (SPM): • Consists of a variety of solid particles and liquid droplets small and light enough to remain suspended in the air. • The most harmful forms of SPM: • Fine particles (PM-10) • meaning the average diameter < 10 micrometers • Ultrafine particles (PM-2.5) • According to the EPA, SPM is responsible for about 60,000 premature deaths a year in the U.S. Particulate Matter Major Air Pollutants Volatile Organic Compounds (VOCs): • These organic compounds have a high vapor pressure, which allows them to evaporate into atmosphere at room temperature. Most VOCs are… • Hydrocarbons • emitted by the leaves of many plants as scents and odors • Methane • About two thirds of global methane emissions comes from human sources (leakage from natural gas sources & livestock manure) • Atmospheric methane concentrations are of interest due to methane's impact on climate change, as it is one of the most potent greenhouse gases in Earth's atmosphere. Major Air Pollutants Volatile Organic Compounds (VOCs): • Some other VOCs include industrial solvents such as acetone, trichloroethylene (TCE), benzene, paints, vinyl chloride and fuels like gasoline. • Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage. Major Air Pollutants Ozone (O3): • Is a highly reactive gas that is a major component of photochemical smog. • It is a secondary air pollutant… it is created from sunlight & VOCs, NOx, CO • It can… • Damage plants, rubber in tires, fabrics, and paints. • Cause and aggravate respiratory illness. • Can aggravate heart disease. Major Air Pollutants Ozone (O3): SMOG Air Pollution– Chapter 15 What is smog? • Mexico City is one of the many cities in sunny, warm, dry climates with many motor vehicles that suffer from photochemical smog. • The primary component of smog is ozone. Secondary components are VOCs and sunlight. • Smog is also impacted by thermal inversions. Photochemical Smog Thermal Inversions • • Thermal Inversionwhen 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. Thermal Inversions Las Vegas NV Los Angeles CA • Cold, cloudy weather in a valley surrounded by mountains can trap air pollutants (left). • Areas with sunny climate, light winds, mountains on three sides and an ocean on the other (right) are susceptible to inversions. Smog & Thermal Inversions • During severe inversions that last over long periods, smog can cover entire metropolitan areas and cause respiratory problems for the inhabitants of those areas. London, England 2013 Factors Influencing Levels of Outdoor Air Pollution • Outdoor air pollution can be reduced by: • settling out • precipitation • sea spray • winds • chemical reactions • Outdoor air pollution can be increased by: • urban buildings (slow wind dispersal of pollutants) • mountains (promote temperature inversions) • high temperatures (promote photochemical reactions) ACID DEPOSITION Air Pollution – Chapter 15 Acid Deposition • Acid deposition consists of rain, snow, dust, or gas with a pH lower than 5.6. It exists in two forms: dry acid deposition and wet acid deposition (acid rain). 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 • • During the 1970’s and 1980’s, many lakes in Canada and the Northeastern U.S. lost all of their fish due to lowered pH levels Acid Deposition can release aluminum from lake sediments which, in turn, adversely affects the gills of fish Damaging statues, monuments, and buildings Emissions SO2 Acid H O 2 2 deposition PANs NOx O3 Others Reduced photosynthesis and growth Direct damage to leaves & bark Tree death Soil acidification Leaching of soil nutrients Acids Lake Groundwater Release of toxic metal ions Susceptibility to drought, extreme cold, insects, mosses, & disease organisms Root damage Reduced nutrient & water uptake Where is Acid Rain a problem? • In the US, the Appalachian forests from Maine to Georgia are particularly affected by acid rain. Trees usually don't die outright but are weakened and more susceptible to pathogens, insects, drought or extreme cold. • In Europe, acid rain was first found in Scandinavia in the late 1950's and at first it was thought to be a local problem, however, later it was discovered that the pollution was actually coming from Britain and Northern Europe. • Acid rain is an international problem because it is dispersed by winds. Solutions Acid Deposition Prevention Reduce air pollution by improving energy efficiency Cleanup Add lime to neutralize acidified lakes Reduce coal use Increase natural gas use Increase use of renewable energy resources Burn low-sulfur coal Remove SO2 particulates & NOx from smokestack gases Remove NOx from motor vehicular exhaust Tax emissions of SO2 Add phosphate fertilizer to neutralize acidified lakes OZONE LAYER DEPLETION Air Pollution – Chapter 15 Stratospheric Ozone • • Good Ozone Bad 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 of Ozone - Stratosphere Breakdown of Ozone - Stratosphere 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. Creating a chlorine atom, which then breaks apart the ozone molecules. 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. Effects of Ozone Depletion • Eye cataracts • Sunburn and cancer • Weaker immune systems • Interference with photosynthesis which leads to lower crop yields as growth is reduced • Plants suffer as they become more susceptible to disease • Plankton near the surface dies which disrupts food chains INDOOR AIR POLLUTION Air Pollution – Chapter 15 Indoor Air Pollution Indoor air pollution usually is a greater threat to human health than outdoor air pollution. •According to the EPA, the four most dangerous indoor air pollutants in developed countries are: • Tobacco smoke (second-hand smoke can cause lung cancer… especially in children) • Formaldehyde (wrinkle free shirts, particle board, carpets, nail polish) • Radioactive radon-222 gas (in rocks & soil… penetrates building materials… created from breakdown of uranium ore) • VOCs in home products (wood flooring and products) Indoor Air Pollution Other indoor air pollutants are: • Wood, animal manure or coal used for cooking and heating in developing countries. • Asbestos (heat resistant fiber in home insulation… used for fire-proofing) • Carbon Monoxide (from auto exhausts, central heating furnaces, space heaters) • Living things such as dust mites (mites feed on human skin.. Can cause asthma & allergies… they live in bedding and furniture fabrics) Structures with high levels of indoor air pollutants that make people ill are said to suffer from Sick Building Syndrome WAYS TO PREVENT AIR POLLUTION Air Pollution – Chapter 15 The Clean Air Acts of 1970 and 1990 greatly improved air quality in the United States Air Quality Index (AQI) The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air. EPA calculates the AQI for five major air pollutants regulated by the Clean Air Act: 1.ground-level ozone 2.particulate matter 3.carbon monoxide 4.sulfur dioxide 5.nitrogen dioxide Ways to Prevent Air Pollution Three techniques control particulate matter: 1.Scrubbers on smoke stacks – uses water 2.Electrostatic precipitators – uses an electric charge (+) and they stick to (-) charged plates 3.Baghouse filters – uses fabric filters *Drawback… All three types use electricity (additional energy) with require the use of more fuel and result in increased carbon dioxide emissions Preventing other types of air pollution: 4.Fluidized Bed Combustion - granulated coal is burned near calcium carbonate - (reduces sulfur dioxide emissions from coal) 5.Catalytic Converters on cars (controls particulate matter and nitrogen oxides) 1. Wet Scrubber • Can remove 98% of SO2 and particulate matter. • Not very effective in removing hazardous fine and ultrafine particles. 2. Electrostatic Precipitator • Can remove 99% of particulate matter • Does not remove hazardous ultrafine particles. • Produces toxic dust that must be safely disposed of. • Uses large amounts of electricity 3. Baghouse Filters Fabric filter are used to separate particulates from clean air. 4. Fluidized Bed Combustion Coal is burned with limestone (contains calcium carbonate) to help reduce acid-forming air pollutants 5. Catalytic Converters The job of the catalytic converter is to convert harmful pollutants into less harmful emissions before they ever leave the car's exhaust system. It uses a honeycomb like mesh coated with metals (platinum or palladium) that will react with the pollutants and produce cleaner gases (NO is reduced to O2 and N2) SOLUTIONS TO POLLUTION Air Pollution – Chapter 15 Solutions Air Pollution Outdoor Improve energy efficiency to reduce fossil fuel use Rely more on lower-polluting natural gas Rely more on renewable energy (especially solar cells, wind, & solar-produced hydrogen) Transfer technologies for latest energy efficiency, renewable energy, & pollution prevention to developing countries Indoor Reduce poverty Distribute cheap & efficient cookstoves or solar cookers to poor families in developing countries Reduce or ban indoor smoking Develop simple and cheap tests for indoor pollutants such as particulates, radon, and formaldehyde Solutions Indoor Air Pollution Prevention Cover ceiling tiles & lining of AC ducts to prevent release of mineral fibers Ban smoking or limit it to well ventilated areas Set stricter formaldehyde emissions standards for carpet, furniture, and building materials Prevent radon infiltration Use office machines in well ventilated areas Use less polluting substitutes for harmful cleaning agents, paints, and other products Cleanup or Dilution Use adjustable fresh air vents for work spaces Increase intake of outside air Change air more frequently Circulate a building’s air through rooftop green houses Use exhaust hoods for stoves and appliances burning natural gas Install efficient chimneys for woodburning stoves What Can You Do? Indoor Air Pollution • Test for radon and formaldehyde inside your home and take corrective measures as needed. • Do not buy furniture and other products containing formaldehyde. • Remove your shoes before entering your house to reduce inputs of dust, lead, and pesticides. • Test your house or workplace for asbestos fiber levels and for any crumbling asbestos materials if it was built before 1980. • Don't live in a pre-1980 house without having its indoor air tested for asbestos and lead. • Do not store gasoline, solvents, or other volatile hazardous chemicals inside a home or attached garage. • If you smoke, do it outside or in a closed room vented to the outside. • Make sure that wood-burning stoves, fireplaces, and kerosene- and gas-burning heaters are properly installed, vented, and maintained. • Install carbon monoxide detectors in all sleeping areas. Solutions Stationary Source Air Pollution Prevention Burn low-sulfur coal Remove sulfur from coal Convert coal to a liquid or gaseous fuel Shift to less polluting fuels Dispersion or Cleanup Disperse emissions above thermal inversion layer with tall smokestacks Remove pollutants after combustion Tax each unit of pollution produced Solutions Motor Vehicle Air Pollution Prevention Cleanup Mass transit Emission control devices Bicycles and walking Produce hybrid and electric cars Less polluting fuels Improve fuel efficiency Car exhaust inspections twice a year Get older, polluting cars off the road Give buyers large tax write-offs or rebates for buying low-polluting, energy efficient vehicles Stricter emission standards