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URBAN AIR POLLUTION. Air Pollution Air pollution: presence of one or more chemicals in the atmosphere in concentrations high enough to affect climate and harm organisms and materials.
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Air Pollution Air pollution: presence of one or more chemicals in the atmosphere in concentrations high enough to affect climate and harm organisms and materials. An air pollutant is any substance in the air that can cause harm to humans or the environment. Pollutants may be natural or man-made and may take the form of solid particles, liquid droplets or gases. The 1990 Clean Air Act Amendments lists 188 toxic air pollutants that EPA is required to control. These pollutants are divided into various groups, including particulate matter, volatile organic compounds (VOCs) and halogen compounds. Also included are more commonly-known pollutants such as lead, mercury and asbestos (EPA).
There is 4 to 1000 times more dust in the cities than the surrounding suburban air. Lead in the dust is 3 times more in the inner city than the suburban area. City air also contains roughly 10 times as many microorganisms as the surrounding country air. What Are the Six Common Air Pollutants? • Particles: soots and acid aerosols • Sources: • diesel trucks, buses, factory and electric utility smoke stacks, car exhaust, burning wood, mining, and construction. • Impacts: • impair the function of lungs; mainly affect people with chronic respiratory illnesses such as asthma, bronchitis, and emphysema; Lung disease is the third leading cause of death in U.S. • EPA standard is 150 microgram per cubic meter of air. • PM10 (dust size particles): particular matters smaller than 10 micrometers; • PM2.5; have been linked to bronchitis, asthma, pneumonic, and pleurity in children (inflamation of pleura inside the lung).
State and Federal Ambient Air Quality Standards for Particulate Matter CA ARB Std PM10 Fed EPA Std PM10 Annual Average 20 µg/m3N/A 24-Hour Average 50 µg/m3150 µg/m3 CA ARB Std PM2.5 Fed. EPA Std PM2.5 Annual Average 12 15 24-Hour Average ---- 35
2. Carbon Monoxide (greatest emission from human activity): colorless, odorless, and tasteless gas from incomplete combustion of coal, fuel oil, and gasoline Source: mostly from automobiles Impact: when reach 100PPM, people develop headache and may become dizzy. Levels of 100PPM has been observed in some urban areas and concentrations of 370 PPM have been recorded inside vehicle trapped in traffic jams. Residence time: several days, and change to CO2
3. Sulfur compounds: SO2 is one of the major oxides of sulfur; it is heavy, pungent, colorless gas; forms from the combination of sulfur from emissions of coal burning industries and atmospheric oxygen. It ranges from 0.1 to 2 PPM, if reaches to 3PPM is regarded as dangerous. Source: 70% comes from the burning low-grade coal and petroleum in electric power plants (Ohio valley). Residence time: less than 10 days; highly reactive; much of them combines water vapor in atmosphere to form acid (acid rain) Impact: major irritant to eyes and respiratory system, and is lethal at a few parts per million. Sulfuric acid causes the leaves of plants to burn yellow, it dissolves limestone and marble; highly corrosive of iron and steel; reduce atmospheric visibility and blocks out sunlight; more dangerous than SO2; toxic chemicals are absorbed in soots, fogs form easily (<RH 90%),these insoluble particles enter the lungs, where they remain concentrated on small spots . • Another form is H2S; from organic decay where there is not enough oxygen present to oxidize the organic material. Smell like rotten eggs; Short residence time. • Source: swamp • Impact: darkens lead in oil-based house paint; tarnishes copper and silver.
4. N0X - nitric oxide (N0) and nitrogen dioxide (N02) -Natural component of the Earth's atmosphere. -Important in the formation of both acid precipitation and photochemical smog (ozone), and causes nitrogen loading. -Comes from the burning of biomass and fossil fuels. -30 to 50 million tons per year from human activities, and natural 10 to 20 million tons per year. -Average residence time in the atmosphere is days. -Has a role in reducing stratospheric ozone. N20 - nitrous oxide -Natural component of the Earth's atmosphere. -Important in the greenhouse effect and causes nitrogen loading. -Human inputs 6 million tons per year, and 19 million tons per year by nature. -Residence time in the atmosphere about 170 years. -1700 (285 parts per billion), 1990 (310 parts per billion), 2030 (340 parts per billion). -Comes from nitrogen based fertilizers, deforestation, and biomass burning.
5. Surface Ozone: colorless and odorless except at very high concentration. A major ingredient in smog Source: pollutants such as unburned petroleum hydrocarbons and nitrogen oxides from automobile exhausts and fossil fuel power plants react with sunlight. The chemical reaction is faster at higher temperature; Residence time: it usually to form at 10:00AM solar time and breaks down at night. High is Mississippi valley, California and Texas. Impact: respiratory problems for those who exercise outdoors; irritant to the lungs and air passages; cough, chest pain and shortness of breath.
Photochemical Smog Figure 2.26
6. Photochemical smog: a mixture of primary and secondary pollutants formed under the influence of sunlight. Example: ozone. • Brown-air smog: • Automobile engines, coal-burning power and industrial plants where high t cause N2 and O1 in air to form colorless nitric oxide (NO). Some of NO is converted to nitrogen dioxide (NO2), yellowish-brown gas with a choking odor, exposed to UV, BI2 reacts with hydrocarbons that produce photochemical smog. • Peak in later afternoon, hotter or sunnier, more. Irritating eyes and respiratory system. • Gray-air smog: industry smog • Sulfur dioxide, aerosols containing suspended droplets of sulfuric acid, and a variety of suspended solid particles that give the resulting smog a gray color. Heavy oil and coal burned in Power plants and factories, and heating and cooking of homes 50 years ago. Now influence in developing countries.
Natural sources: volcanic eruptions, hydrocarbons evaporating from some tree species, and human activities (motor vehicles, coal-burning power plants). . Primary pollutants: emitted directly into the troposphere in a potentially harmful form. ie soot, CO. Secondary pollutants: formed from primary pollutants react with one another or with the basic components of air
Others types of pollutants 1. Acid deposition or acid rain Mixture of dry deposition of acidic particles (2-3 days), and wet deposition of acidic rain, snow, fog and cloud vapor (4-14 and more distance downwind areas- as much as 1000 KM or 600 miles). It occurs when primary pollutants, sulfur dioxide, nitrogen dioxide transformed into secondary pollutants such as nitric acid vapor, sulfuric acid, and particles of acid-forming sulfate and nitrate salts. Natural precipitation has a PH value of 5.6; Acid rain has PH value of less than 5.6 Sources: coal burning electric power plants, industrial furnaces, and motor vehicles. Impacts: • 1. Harmful to human: respiratory diseases such as bronchitis and asthma, leach toxic metals (lead and copper) from water pipes into drinking water. Hospital admission to Asthma and pneumonic were significantly related to sulfur levels based on study in southern Ontario. • 2. Damages status, national monuments, buildings, metals, and car finishes. • 3. Reduce visibility and smoggy in national parks. • 4. ecological effects on aquatic system. Fish bone deformation, lost fertility, high mercury concentration, etc. • 5. affect forests and crops by leaching essential plant nutrients such as calcium and magnesium salts from soils. Or kill trees directly or weaken them and make them more susceptible to other stresses.
Stratospheric Ozone ant UV radiation Ozone mainly concentrated in a layer at 12 and 50 KM (7 and 30 miles) where it is continuously formed and removed. It absorbs radiation at wave length of 0.1-0.3 micrometers. Compound CFCs have a depleting effect on stratospheric ozone layer. They are artificial gases first synthesized in 1928, odorless, nonflammable, nontoxic, and chemically inert; Used in refrigerators, deodorants and hair sprays; in producing plastic foams, and in cleaning electronic parts; air conditioning in cars is the largest source, in 1993 models, cars are no longer use CFCs producing air conditionings. Residence time: 40-80 years for CFC-11; 80-120 years for CFC-12 (from cars). Antarctic Ozone Hole: loss of stratosphere ozone over Antarctic in September and October since the later 1970s. The lowest stratospheric ozone was recorded September 1987. UVB: 0.28-0.32 micrometer is most harmful to living organisms. It can damage DNA a genetic code in every living thing; Soybean yield drop 1% for each 1% drop in ozone; Sun tan and sun burn by UV. A single blistering sunburn in a person 20 to 30 years of age triples the risk of skin cancer.
Urban heat pollution Urban heat island: air temperature in the center of a city is 4-7º F higher than surrounding suburban. Causes: buildings and structures trap heat, high density population, traffic, and industries produce excessive heat Impact: Heat wave is more severe in the city, combined with high humidity, and did not get relieve during evening (stronger urban heat island effect), related to high mortality.
Human respiratory system protects body from air pollution • hairs in noise filter out large particles • sticky mucus in the lining of your upper respiratory tract captures smaller particles and dissolves some gaseous pollutants (not smallest ones) • sneezing and coughing expel contaminated air and mucus when pollutants irritate your respiratory system. • 100,00s of tiny mucus coated air-like structures called cilia line your upper respiratory tract. They wave back and forth and transport mucus that traps the pollutants to your throat.
COSTS/BENEFITS OF AIR POLLUTION CONTROL • Total direct cost $523 billion • Direct monetized benefits $5.6 to $49.4 trillion – average $22.2 trillion • Net financial benefit $21.7 trillion • 206,000 fewer deaths in 1990!
