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Air Pollution. Chapter 18. Outline:. Natural Sources Human-Caused Air Pollution Conventional Pollutants Unconventional Pollutants Indoor Air Pollution Climate and Topography Effects of Air Pollution Air Pollution Control Clean Air Legislation. THE AIR AROUND US.
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Air Pollution Chapter 18 Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Outline: • Natural Sources • Human-Caused Air Pollution • Conventional Pollutants • Unconventional Pollutants • Indoor Air Pollution • Climate and Topography • Effects of Air Pollution • Air Pollution Control • Clean Air Legislation Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
THE AIR AROUND US • Approximately 14 million metric tons of air pollution are released annually into the atmosphere in the US by human activities. • Worldwide emissions total around 2 billion metric tons. • Developed countries have been improving air quality, while air quality in developing world is getting worse. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
NATURAL SOURCES OF AIR POLLUTION • Natural Fires - Smoke • Volcanoes - Ash and Acid components • Sea Spray - Sulfur • Vegetation - Volatile organic compounds • Bacterial Metabolism - Methane • Dust • Pollen • Viruses and Bacteria Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
HUMAN-CAUSED AIR POLLUTION • Primary Pollutants - Released directly from the source. • Secondary Pollutants - Modified to a hazardous form after entering the air and mixing with other environmental components. • Fugitive Emissions - Do not go through smokestack. • Dust from human-activities. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants • US Clean Air Act designated seven major (conventional or criteria) pollutants for which maximum ambient air levels are mandated. • Sulfur Dioxide • Carbon Monoxide • Particulates • Hydrocarbons • Nitrogen Oxides • Photochemical Oxidants • Lead Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants • Sulfur Compounds • Natural sources of sulfur in the atmosphere include evaporation from sea spray, volcanic fumes, and organic compounds. • Predominant form of anthropogenic sulfur is sulfur-dioxide from fossil-fuel combustion. • Annual Emissions: 114 million metric tons Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Sulfur Compounds Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants • Nitrogen Compounds • Nitrogen oxides are reactive gases formed when nitrogen is heated above 650o C in the presence of oxygen, or when nitrogen compounds are oxidized. • Annual Emissions: 230 million metric tons Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Nitrogen Compounds Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants • Carbon Oxides • Predominant form of carbon in the air is carbon dioxide. • Increasing levels due to human activities. • Annual Emissions: 8-10 billion metric tons • Carbon monoxide is a colorless, odorless, toxic gas produced by incomplete fuel combustion. • Annual Emissions: 1 billion metric tons Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants • Metals • Many toxic metals occur as trace elements in fuel. • Lead Emissions: 2 million metric tons. • Mercury • Bioaccumulation in aquatic ecosystems. • Nickel, beryllium, cadmiuym, arsenic… • Halogens (Fluorine, Chlorine, Bromine) • CFC’s Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants • Particulate Matter • Atmospheric aerosols (solid or liquid) • Respirable particles smaller than 2.5 micrometers are among most dangerous. • Volatile Organic Compounds • Organic chemicals • Generally oxidized to CO and CO2. • Of 188 air toxics listed in Clean Air Act, two-thirds are VOC’s. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants • Photochemical Oxidants • Products of secondary atmospheric reactions driven by solar energy. • Ozone formed by splitting nitrogen dioxide. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Unconventional Pollutants • EPA sets emissions standards for unconventional or non-criteria pollutants that are considered especially hazardous. • Asbestos, benzene, beryllium, etc. • Most have no natural source in the environment. • Aesthetic Degradation • Noise, odor, light pollution. • Reduce quality of life. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Indoor Air Pollution • EPA found indoor concentrations of toxic air pollutants are often higher than outdoor. • People generally spend more time indoors. • Smoking is the most important air pollutant in the US. • 400,000 die annually from a disease related to smoking. • Associated costs are estimated at $100 billion annually. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Indoor Air Pollution • Less Developed Countries also suffer from indoor air pollution. • Organic fuels make up majority of household energy. • Often burned in smoky, poorly ventilated heating and cooking fires. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
CLIMATE AND TOPOGRAPHY • Inversions • Temperature inversions occur when a stable layer of warm air overlays cooler air, reversing the normal temperature decline with increasing height, and preventing convection currents from dispersing pollutants. • Cold front slides under warm air mass. • Cool air subsides down slope. • Rapid nighttime cooling in a basin. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Inversions Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Dust Domes and Heat Islands • Sparse vegetation and large amounts of concrete and glass create warm, stable air masses, heat islands, over large cities. • Concentrates pollutants in a “dust dome”. • Rural areas downwind from major industrial areas often have significantly decreased visibility and increased rainfall. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Long-Range Transport • Fine aerosols can be carried great distances by the wind. • Increasingly, sensitive monitoring equipment has begun to reveal industrial contaminants in places usually considered among the cleanest in the world. • Contaminants trapped by winds at the north pole, concentrate at high latitudes and eventually fall out as snow and ice and enter the food chain. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Long-Range Transport Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Stratospheric Ozone • Discovered in 1985 that stratospheric ozone levels were dropping rapidly during September and October. • Occurring since at least 1960. • At ground-level, ozone is a pollutant, but in the stratosphere it screens UV radiation. • A 1% decrease in ozone results in a 2% increase in UV rays reaching the earth. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Stratospheric Ozone • Circumpolar vortex isolates Antarctic air and allows stratospheric temperatures to drop and create ice crystals at high altitudes. • Absorb ozone and chlorine molecules. • When sun returns in the spring, energy liberates the chlorine allowing the depletion process to proceed rapidly. • CFC’s believed to be main culprit. • Persist for decades. • Production eliminated in 1996. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
CFC Production Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
EFFECTS OF AIR POLLUTION • Human Health • EPA estimates each year 50,000 people die prematurely from illnesses related to air pollution. • Likelihood of suffering ill health is related to intensity and duration of exposure. • Inhalation is the most common route, but absorption through the skin and consumption via food can also occur. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Human Health • Bronchitis • Persistent inflammation of airways in the lung that causes mucus build-up and muscle spasms constricting airways. • Can lead to emphysema - irreversible obstructive lung disease in which airways become permanently constricted and alveoli are damaged or destroyed. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Plant Pathology • Chemical pollutants can directly damage plants, or can cause indirect damage by disrupting normal growth and development patterns. • Certain environmental factors have synergistic effects in which the injury caused by the combination is more than the sum of the individual exposures. • Pollutant levels too low to cause visible effects may still be damaging. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Acid Deposition • pH and Atmospheric Acidity • pH scale ranges from 0-14. • 7 = Neutral; <7 = Acidic; >7 = Basic • Unpolluted rain generally has ph of 5.6. • Carbonic acid from atmospheric CO2. • In industrialized areas, anthropogenic acids in the air often outweigh natural sources of acid. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Acid Deposition Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Acid Deposition • Aquatic Effects • Thin, acidic soils and oligotrophic lakes of southern Norway and Sweden have been severely affected by acid deposition. • Generally, reproduction is the most sensitive stage in fish life cycles. • In early 1970’s, evidence began to accumulate suggesting air pollutants are acidifying many NA lakes. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Acid Deposition • Forest Damage • Air pollution and depositions of atmospheric acids are believed to be important causes of forest destruction in many areas. • Buildings and Monuments • Limestone and marble are destroyed by air pollution at an alarming rate. • Corroding steel in reinforced concrete weakens buildings, roads, and bridges. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
AIR POLLUTION CONTROL • Particulate Removal • Remove particles physically by trapping them in a porous mesh which allows air to pass through but holds back solids. • Electrostatic Precipitators - Fly ash particles pick up electrostatic charge as they pass between large electrodes in waste stream, and accumulate on collecting plate. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Sulfur Removal • Fuel Switching • Switch from soft coal with a high sulfur content to low sulfur coal. • Change to another fuel (natural gas). • Limestone Injection • Can reduce sulfur emissions by 90% by mixing crushed limestone with coal before it is fed into a boiler. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Sulfur Removal • Flue Gas Desulfurization • Inject crushed limestone into stack gas stream to remove sulfur after combustion. • Dry Alkali Injection • Sulfur Recovery Process • Use catalytic converters to oxidize or reduce sulfur and create chemical compounds that can be collected and sold. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Air Pollution Control • Nitrogen Oxide Control • Best method is to prevent creation. • Staged Burners • Selective Catalysts • Hydrocarbon Control • Use closed systems to prevent escape of fugitive emissions. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
CLEAN AIR LEGISLATION • Clean Air Act (1963) - First national air pollution control. • Clean Air Act (1970) rewrote original Act. • Identified critical pollutants. • Established ambient air quality standards. • Primary Standards - Human health • Secondary Standards - Materials, environment, aesthetic and comfort. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Clean Air Act • Revision (1990) - Included provision for: • Acid Rain • Urban Smog • Toxic Air Pollutants • Ozone Protection • Marketing Pollution Rights • Volatile Organic Compounds • Lead • Revision (1997) - Stricter standards Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
CURRENT AND FUTURE CONDITIONS • In the United States, air quality has improved dramatically in the last decade in terms of major large-volume pollutants. • Cities where pollution is largely from traffic still have serious air quality problems. • Major metropolitan areas of many developing countries are growing at explosive rates, and environmental quality is very poor. Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Summary: • Natural Sources • Human-Caused Air Pollution • Conventional Pollutants • Unconventional Pollutants • Indoor Air Pollution • Climate and Topography • Effects of Air Pollution • Air Pollution Control • Clean Air Legislation Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.