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Air Pollution Chapter 18 South Asia’s Massive Brown Cloud Asian Brown Cloud-2 miles thick Causes Chemical composition- dust, smoke, ash, Areas impacted (India, Bangladesh, and China) Reduced photosynthesis by about 7% Air pollution connects the world –LA 2 weeks to circle the globe Steps taken in China and India to reduce air pollution coal to natural gas Air Pollution in Shanghai, China, • • Intro video The Asian Brown Cloud 18.1 The Atmosphere Consists of Several Layers Divided into layers based on temperature changes from differences in absorption of incoming solar energy Atmosphere varies in Density-higher at sea level than top of mountain Atmospheric pressure -decreases with altitude –less gas molecules at higher altitudes Influenced by Gravity-pulls gas molecules towards Earth’s surface Air Movements in the Troposphere Play a Key Role in Earth’s Weather and Climate Troposphere 75–80% of the earth’s air mass Closest to the earth's surface 0-11 km above sea level Chemical composition of air Nitrogen 78% Oxygen 21% H20, CO2, trace amounts of others (Ar) Weather, climate and all life forms exist here Involved in chemical cycling Upper boundary = tropopause As altitude increases, temperature decreases The Stratosphere Is Our Global Sunscreen Stratosphere 11-50 km above Earth's surface Similar composition to the troposphere, with 2 exceptions Much less water (1/1000) O3, ozone layer As altitude increases, temperature increases Air motion is horizontal Airplanes fly here OZONE O3 – our global sunscreen Keeps 95 + % of UV rays from Earth's surface Allows humans and other life to exist on earth Helps protect humans from sunburn, cancer, cataracts and damage to the immune system 50-80 km Mesosphere As altitude increases, temperature decreases Very little O3 Middle atmosphere – Air thin, pressure low Need oxygen to live in this region. Air quite cold -90°C (-130°F) near the top of mesosphere Thermosphere Altitude increases, temperature increases “Hot layer” – oxygen molecules absorb energy from solar rays warming the air. Very few atoms and molecules in this region. Intense UV – breaks O2 and N2 bonds International Space Station is here Comparison of the lower atmosphere with the higher atmosphere Continuous mixing Constant, uniform chemical composition Fairly constant temp over a 24 hour period Still air – slow diffusion of gases Different composition at different heights Wide temperature variations The Earth’s Atmosphere Is a Dynamic System with Four Layers 18.2 What are the major outdoor air pollution problems? Air Pollution Comes from Natural Sources Air pollution: presence of chemicals in atmosphere in concentrations high enough to harm organisms Natural sources Dust blown by wind Pollutants from wildfires and volcanoes Volatile organics released by plants – mold and terpenes Air Pollution Comes from Human Sources (anthropogenic) Human sources: mostly in industrialized and/or urban areas Stationary sources - power and industrial plants Mobile sources - cars, buses Air Pollution in the Past: The Bad Old Days Discovery of fire-may have started air pollution problem Middle Ages-haze of wood smoke over densely populated urban areas Industrial Revolution-late 1700’s coal being burned for factories and homes-increase in respiratory diseases London, England 1850s 1952: yellow fog-lasted 5 days-killed over 4,000 Clean Air Act of 1956 The London Smog of 1952 London naturally has very calm air, and regularly experiences thick sea fog. The weather turned unusually cold, causing the residents to burn greater amounts of coal to heat their homes. This combined with a temperature inversion to create a thick smog of sulfur dioxide over the city. The number of fatalities is unknown, but estimated to be 4,000- 12,000. 16 United States 1948: Donora, PA; first U.S. air pollution disaster-coal burning factories, steel mills, zinc smelter and sulfuric acid trapped in fog 1963: New York City - killed 300 Global problem Air Pollution History The Donora Fluoride Fog of 1948 In late October, the town of Donora experienced a temperature inversion. The town is located along the Monongahela River south of Pittsburgh, within a small valley. The main employer of the town was a US Steel Zinc smelting plant. 18 Donora Fluoride Fog 19 Emissions of sulfur dioxide, nitrogen dioxide, and fluoride from the zinc smelting plant began to accumulate. The smog became so thick that driving was impossible. The plant itself did not cease operations until 4 days later. The smog finally broke up as a rainstorm entered the area after 5 days. Donora Fluoride Fog 20 A total of 20 residents died; About a third to a half of the town’s entire population of 14,000 became sickened. Donora experienced higher than normal mortality rates for 10 years afterwards. Noon in Donora Some Pollutants in the Atmosphere Combine to Form Other Pollutants Primary pollutants- chemical emitted directly into air Secondary pollutants- when primary pollutants react with each other to form new harmful chemicals – ozone, PANs, HNO3 Air quality improving in developed countries Much more needs to be done in developing countries Indoor pollution: big threat to the poor 1 in 6 live in area where air is bad Sources and Types of Air Pollutants polyacrylonitrile (PAN) What Are the Major Outdoor Air Pollutants? Carbon oxides Carbon monoxide (CO) – colorless, odorless, highly toxic-car exhaust, open fires, tobacco smoke Reduces body ability of blood to transport oxygen to Carbon dioxide (CO2) colorless, odorless Sources 93% from carbon cycle, rest from burning fossil fuels, clearing forests/grasslands Human health and environmental impactGlobal Warming What Are the Major Outdoor Air Pollutants? Nitrogen oxides (NO, NO2 and N2O) and nitric acid (HNO3) Sources-car engines and coal burning plants Acid deposition-reacting with water vapor Photochemical smog-sun and traffic Human health and environmental impact Sulfur dioxide (SO2) and sulfuric acid (H2SO4) Colorless, bad smell Sources – 1/3 from sulfur cycle, 2/3 humans-coal in electrical plants and industrial plants Human health and environmental impact-Asian Brown cloud What Are the Major Outdoor Air Pollutants? Particulates Suspended particulate matter (SPM) Fine Ultrafine Sources-dust, wild fires, sea salt (~62%) cars, tobacco smoke, coal burning (~38%) Human health and environmental impact Toxic particulates (Pb, PCBs and Cd) can cause reproductive problems, cancer, reduce visibility and corrode metals 60,000-70,000 premature deaths/year Small particles less than 10 micrometers in diameter pose the greatest problems, because they can get deep into the lungs, and some may even get into your bloodstream Fine particles (PM2.5) are the main cause of reduced visibility (haze) in parts of the United States, including many of our treasured national parks and wilderness areas. What Are the Major Outdoor Air Pollutants? Ozone (O3) – a secondary pollutant An unstable molecule that readily reacts to shed a single O2 atom Human and environmental impact Volatile organic compounds (VOCs) Organic compounds that exist as gas in atmosphere Hydrocarbons such as terpenes (C10H15 emitted by leaves of plants) and methane (CH4) Sources-mainly plants, wetlands and termites (natural) and human sources like oil wells, landfills, cows Other VOCs are benzene and vinyl chloride that are used as industrial solvents Human and environmental impact Leukemia, blood disorders, immune system damage Chemical Reactions That Form Major Outdoor Air Pollutants Detecting Air Pollutants Chemical instruments Satellites-Asian Brown Cloud Unmanned aircraft 2 miles thick, 1-3 miles above ground, covers much of India, Bangladesh and China- satellites tracked its movement- even across the Pacific Ocean to California! Nanotechnology-nanodetectors? Biological indicators Lichens-fungus and algae - are always absorbing air as a source of nourishment Natural Capital: Lichen Species, Vulnerability to Air Pollutants Old mans beard sickens in the presence of SO2 YellowEvernia also sickens in SO2 Lichen are sensitive to pollution because they lack root and act like sponges, taking in and retaining everything that is in the air and dissolved in rainwater. As pollutants reach a high level, the chlorophyll in the algal portions breaks down and photosynthesis stops Lead Is a Highly Toxic Pollutant Does not break down in the environment Sources-toys, paint, water pipes, red, long-lasting lipsticks Human health and environmental impact Most vulnerable – children under 6 and fetuses Neurotoxin-about 200 kids die per year Lead Is a Highly Toxic Pollutant Reduction of lead (Pb) Unleaded gasoline Unleaded paint Still problems 2007: toys with Pb paint recalled Older buildings- Pb- based paint peeling, Pb contaminated dust, water pipes/faucets Global bans on lead in gasoline and paint would be helpful- China just phased on leaded gasoline 5 years ao. Burning Coal Produces Industrial Smog (gray-air smog) Chemical composition = sulfur dioxide, suspended droplets of sulfuric acid (mostly from coal burning), suspended solid particles and droplets Carbon from coal and oil converted to CO and CO2 Unburned carbon ends up as particulate matter in air (soot) Reduction of this smog in urban cities of the United States China and Smog Each year 358,000 Chinese die from air pollution (some estimate as many as 750,000 including indoor air pollution) Relies heavily on coal burning 16 of world’s 20 most polluted cities are in China 62% of the cities suffer from industrial smog How Pollutants Are Formed from Burning Coal and Oil, Leading to Industrial Smog Sunlight Plus Cars Equal Photochemical Smog – brown air smog Requires sunlight and cars Morning traffic releases NOx and VOCs in the air UV radiation produces a series of reactions that form as many as 100 different compounds such as peroxyacyl nitrates (PANs) and aldehydes. Ozone is the most abundant. In sunlight, NO2 dissociates into O and NO. The O reacts with O2 to produce ozone Levels off pollutants peak around noon and drop during the late afternoon, then starts again the next morning. But NO drops as the sun gets higher as secondary pollutants form. PANs Peroxyacetyl nitrate causes eye irritations at very low concentrations of only a few parts per billion. It also irritates the respiratory system. It may cause emphysema, impaired breathing, acute pulmonary edema or lung lesions following inhalation exposure. People with heart and lung disease, children and the elderly are the most susceptible to air pollutants, including PAN. PAN inhibits the primary process of photosynthesis in various types of plants, which can stop or reduce their growth. Pan is more toxic to plants than ozone. Affected plants exhibit discolored leaves and leaves can fall off, which further reduces photosynthesis. The plant's ability to store food, grow and reproduce is reduced, and the plants also become more vulnerable to attacks by pests and diseases. Present in most cities – irritates eyes and respiratory tracts. The heat island effect makes the reactions worse.