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The Atmosphere and Air Pollution. a. Origin of Modern Atmosphere. original atmosphere surrounded the homogenous planet Earth and probably was composed of H and He second atmosphere evolved from gases from molten Earth H 2 O, CO 2 , SO 2 , CO, S 2 , Cl 2 , N 2 , H 2 , NH 3 , and CH 4
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Origin of Modern Atmosphere • original atmosphere surrounded the homogenousplanet Earth and probably was composed of H and He • second atmosphere evolved from gases from molten Earth • H2O, CO2, SO2, CO, S2, Cl2, N2, H2, NH3, and CH4 • allowed formation of oceans and earliest life • modern Atmosphere • evolved after Cyanobacteria started photosynthesizing • oxygen produced did not reach modern levels until about 400 million years ago
Earth’s Atmosphere • compared to the size of the Earth (104 km), the atmosphere is a thin shell (120 km). http://www.gsfc.nasa.gov/gsfc/earth/pinatuboimages.htm
AtmosphereLayers • Exosphere • Thermosphere • (Ionosphere) • Mesosphere • Stratosphere • Troposphere
Troposphere • 8 to 14.5 kilometers high (5 to 9 miles) • most dense • the temperature drops from about 17 to -52 degrees Celsius • almost all weather is in this region
Stratosphere • extends to 50 kilometers (31 miles) high • dry and less dense • temperature in this region increases gradually to -3 degrees Celsius, due to the absorption of ultraviolet radiation • ozone layer absorbs and scatters the solar ultraviolet radiation • ninety-nine percent of "air" is located in first two layers • every 1000-m 11% less air pressure
Composition • Nitrogen (N2, 78%) • Oxygen (O2, 21%) • Argon (Ar, 1%) • myriad of other very influential components are also present which include the Water (H2O, 0 - 7%), "greenhouse" gases or Ozone (O3, 0 - 0.01%), Carbon Dioxide (CO2, 0.01-0.1%),
Importance of the Atmosphere • Physicists • physical properties and processes that take place between the radiant energy and atmospheric gases • Chemists • behavior of the chemical materials in the atmosphere • the ways in which lightning causes the formation of substances • chemistry of the ozone layer and of chemicals introduced from industrial processes
Astronomers and space scientists • the layer through which they must peer before entering the realms of space • Meteorologists, climatologists and geographers • lower layers of the atmosphere • predicting the weather • investigating climatic regions • examine the effects of climate and weather on human society
Primary Pollutants CO CO2 Secondary Pollutants SO2 NO NO2 SO3 Most hydrocarbons HNO3 H2SO4 Most suspended particles H2O2 O3 PANs 2 – NO3 and salts SO4 Most – Natural Sources Stationary Mobile
Major Sources of Primary Pollutants Stationary Sources • Combustion of fuels for power and heat – Power Plants • Other burning such as Wood & crop burning or forest fires • Industrial/ commercial processes • Solvents and aerosols Mobile Sources • Highway: cars, trucks, buses and motorcycles • Off-highway: aircraft, boats, locomotives, farm equipment, RVs, construction machinery, and lawn mowers
Human Impact on Atmosphere • Adds CO2 and O3 to troposphere • Global Warming • Altering Climates • Produces Acid Rain • Releases NO, NO2, N2O, and NH3 into troposphere • Produces acid rain • Releases SO2 into troposphere • Releases toxic heavy metals (Pb, Cd, and As) into troposphere • Burning Fossil Fuels • Using Nitrogen fertilizers and burning fossil fuels • Refining petroleum and burning fossil fuels • Manufacturing www.dr4.cnrs.fr/gif-2000/ air/products.html
Criteria Air Pollutants EPA uses six "criteria pollutants" as indicators of air quality • Nitrogen Dioxide: NO2 • Ozone: ground level O3 • Carbon monoxide: CO • Lead: Pb • Particulate Matter: PM10 (PM 2.5) • Sulfur Dioxide: SO2 • Volatile Organic Compounds: (VOCs) EPA established for each concentrations above which adverse effects on health may occur
Nitrogen Dioxide (NO2) • Properties: reddish brown gas, formed as fuel burnt in car, strong oxidizing agent, forms Nitric acid in air • Effects: acid rain, lung and heart problems, decreased visibility (yellow haze), suppresses plant growth • Sources: fossil fuels combustion, power plants, forest fires, volcanoes, bacteria in soil • Class: Nitrogen oxides (NOx) • EPAStandard: 0.053 ppm
Ozone (O3) • Properties: colorless, unpleasant odor, major part of photochemical smog • Effects: lung irritant, damages plants, rubber, fabric, eyes, 0.1 ppm can lower PSN by 50%, • Sources: Created by sunlight acting on NOx and VOC , photocopiers, cars, industry, gas vapors, chemical solvents, incomplete fuel combustion products • Class: photochemical oxidants
Ozone (O3) • 10,000 to 15,000 people in US admitted to hospitals each year due to ozone-related illness • Children more susceptible • Airways narrower • More time spent outdoors
Carbon Monoxide (CO) • Properties:colorless, odorless, heavier than air, 0.0036% of atmosphere • Effects:binds tighter to Hb than O2, mental functions and visual acuity, even at low levels • Sources:incomplete combustion of fossil fuels 60 - 95% from auto exhaust • Class:carbon oxides (CO2, CO) • EPAStandard:9 ppm • 5.5 billion tons enter atmosphere/year
Lead (Pb) • Properties: grayish metal • Effects: accumulates in tissue; affects kidneys, liver and nervous system (children most susceptible); mental retardation; possible carcinogen; 20% of inner city kids have [high] • Sources: particulates, smelters, batteries • Class:toxic or heavy metals • EPAStandard: 1.5 ug/m3 • 2 million tons enter atmosphere/year
Suspended Particulate Matter (PM10) • Properties: particles suspended in air (<10 um) • Effects: lung damage, mutagenic, carcinogenic, teratogenic • Sources:burning coal or diesel, volcanoes, factories, unpaved roads, plowing, lint, pollen, spores, burning fields • Class: SPM: dust, soot, asbestos, lead, PCBs, dioxins, pesticides • EPA Standard: 50 ug/m3 (annual mean)
Sulfur Dioxide (SO2) • Properties: colorless gas with irritating odor • Effects: produces acid rain (H2SO4), breathing difficulties, eutrophication due to sulfate formation, lichen and moss are indicators • Sources:burning high sulfur coal or oil, smelting or metals, paper manufacture • Class: sulfur oxides • EPA Standard: 0.3 ppm (annual mean) • Combines with water and NH4 to increase soil fertility
VOCs (Volatile Organic Compounds) • Properties: organic compounds (hydrocarbons) that evaporate easily, usually aromatic • Effects: eye and respiratory irritants; carcinogenic; liver, CNS, or kidney damage; damages plants; lowered visibility due to brown haze; global warming • Sources:vehicles(largest source),evaporation of solvents or fossil fuels, aerosols, paint thinners, dry cleaning • Class: HAPs (Hazardous Air Pollutants) • Methane • Benzene • Chlorofluorocarbons (CFCs), etc. • Concentrations indoors up to 1000x outdoors • 600 million tons of CFCs
Other Air Pollutants • Carbon dioxide • ChloroFluoroCarbons • Formaldehyde • Benzene • Asbestos • Manganese • Dioxins • Cadmium • Others not yet fully characterized
Factors that increase and/or decrease pollution • Local climate (inversions, air pressure, temperature, humidity) • Topography (hills and mountains) • Population density • Amount of industry • Fuels used by population and industry for heating, manufacturing, transportation, power • Weather: rain, snow,wind • Buildings (slow wind speed) • Mass transit used • Economics
Thermal Inversion cool air Pollutants cool air warm air (inversion layer) warm air • surface heated by sun • warm air rises (incl. pollutants) • cools off, mixes with air of equal density & disperses • surface cools rapidly (night) • a layer of warm air overlays surface • polluted surface air rises but cannot disperse ⇒ remains trapped
Smog Forms ...when polluted air is stagnant (weather conditions, geographic location) Los Angeles, CA
Pollution • The term “Smog” (smoke and fog) was first used in 1905 to describe sulfur dioxide emission • In 1952, severe pollution took the lives of 5000 people in London • “It isn’t pollution that’s harming the environment. It’s the impurities in our air and water that are doing it.” FormerU.S. Vice President Dan Quayle www.aqmd.gov/pubinfo/ 97annual.html
Photochemical Smog UV radiation H2O + O2 Primary Pollutants NO2 + Hydrocarbons Secondary Pollutants HNO3 O3 nitric acid ozone Photochemical Smog Auto Emissions
Solar radiation Photochemical Smog Ultraviolet radiation NO Nitric oxide O Atomic oxygen O2 Molecular oxygen NO2 Nitrogen dioxide H2O Water Hydrocarbons PANs Peroxyacyl nitrates Aldehydes (e.g., formaldehyde) O3 Ozone HNO3 Nitric acid P h o t o c h e m i c a l S m o g
Why is indoor air quality important? • 70 to 90% of time spent indoors, mostly at home • Many significant pollution sources in the home (e.g. gas cookers, paints and glues) • Personal exposure to many common pollutants is driven by indoor exposure • Especially important for susceptible groups – e.g. the sick, old and very young
Exposure • Time spent in various environments in US and less-developed countries
House of Commons Select Committee Enquiry on Indoor Air Pollution (1991) • “[There is] evidence that 3 million people have asthma in the UK… and this is increasing by 5% per annum.” • “Overall there appears to be a worryingly large number of health problems which could be connected with indoor pollution and which affect very large numbers of the population.” • [The Committee recommends that the Government] “develop guidelines and codes of practice for indoor air quality in buildings which specifically identify exposure limits for an extended list of pollutants…”
Sources of Indoor Air Pollutants • Building materials • Furniture • Furnishings and fabrics • Glues • Cleaning products • Other consumer products • Combustion appliances (cookers and heaters) • Open fires • Tobacco smoking • Cooking • House dust mites, bacteria and moulds • Outdoor air
Important Indoor Air pollutants • Nitrogen dioxide • Carbon monoxide • Formaldehyde • Volatile Organic Compounds (VOCs) • House dust mites (and other allergens, e.g. from pets) • Environmental tobacco smoke • Fine particles • Chlorinated organic compounds (e.g. pesticides) • Asbestos and man-made mineral fibres • Radon
Health Effects Nitrogen dioxide • Respiratory irritant • Elevated risk of respiratory illness in children, perhaps resulting from increased susceptibility to respiratory infection; inconsistent evidence for effects in adults • Concentrations in kitchens can readily exceed WHO and EPA standards
Health Effects Carbon monoxide • An asphyxiant and toxicant • Hazard of acute intoxication, mostly from malfunctioning fuel-burning appliances and inadequate or blocked flues • Possibility of chronic effects of long-term exposure to non- lethal concentrations, particularly amongst susceptible groups
Health Effects Formaldehyde • Sensory and respiratory irritant and sensitizer • Possible increased risk of asthma and chronic bronchitis in children at higher exposure levels • Individual differences in sensory and other transient responses • Caution over rising indoor concentrations
Health Effects Volatile Organic Compounds (VOCs) • Occur in complex and variable mixtures • Main health effects relate to comfort and well-being, but benzene (and other VOCs) are carcinogenic • Concern about possible role of VOCs in the aetiology of multiple chemical sensitivity; also implicated in sick building syndrome
Health Effects House dust mites • House dust mites produce Der p1 allergen, a potent sensitizer • Good evidence of increased risk of sensitization with increasing allergen exposure, but this does not necessarily lead to asthma • Small reductions in exposure will not necessarily lead to reduced incidence and/or symptoms • Indoor humidity is important
Health Effects Fungi and bacteria • Dampness and mould-growth linked to self-reported respiratory conditions, but little convincing evidence for association between measured airborne fungi and respiratory disease • Insufficient data to relate exposure to (non-pathogenic) bacteria to health effects in the indoor environment
Health Effects Environmental tobacco smoke (ETS) • Sudden infant death syndrome • Lower respiratory tract illness • Middle ear disease • Asthma 12 million children exposed to secondhand smoke in homes
Health Effects Fine particles • Consistent evidence that exposure to small airborne particles (e.g. PM10) in ambient air can impact on human health; mechanisms uncertain • Chronic Obstructive Pulmonary Disease and Cardiovascular Disease patients and asthmatics probably at extra risk • Relative importance of indoor sources is unknown
Health Effects Radon • Can cause lung cancer • Estimated that 7,000 to 30,000 Americans die each year from radon-induced lung cancer • Only smoking causes more lung cancer deaths • Smokers more at risk than non-smokers