Bài giảng Environmental Sciences - Chapter 21 Air Pollution

Ch. 21 Air PollutionAir pollutants consist of chemicals in the atmosphere that have harmful effects on living organisms and/or inanimate objects.Why Do We Care? (humans)We inhale 20,000 liters of air each dayCauses 150,000 premature deaths in the world each year (53,000 in U.S.); aggravates other diseasesU.S. human health costs from outdoor air pollution range from $40 to $50 billion per year (CDC)Health impacts - acute – pollutants bring on life-threatening reactions w/in a period of hours or days; causes headache, nausea, irritation - Chronic – pollutants cause gradual deterioration of health over years and low exposure - Carcinogenic – pollutions that causes cancer e.g. benzeneWhy Do We Care? (not human)Damage to Plants - Agriculture – crops loss ~$5 billion/year - Forests – significant damage to Jeffrey and Ponderosa Pine along Sierra Nevada; tree growth declined 75% in San Bernardino Mountains - suspected to increase plant diseases and pests Damages buildings, bridges, statues, booksAesthetics: It looks ugly. We all try to avoid living in polluted areas (admit it)Major Outdoor Air PollutantsPrimary – direct products of combustion and evaporationSecondary – when primary pollutants undergo further reactions in atmosphereSuspended particulate matter (primary)Volatile Organic Compounds (secondary)Carbon Monoxide (primary)Nitrogen Oxides (can be both)Sulfur Oxides(primary from combustion of coal)Ozone and other photochemical oxidants (secondary)Acid DepositionAcidic precipitation and dry falloutAcids and BasespH-log of hydrogen ions in a solution. Therefore each number higher on the pH scale is 10X more basicBasic- OH- (hydroxyl ions) over 7 on the pH scaleAcidic-H+ ions under 7 on the pH scaleNeutral- pure water is 7 on the pH scaleNormal rain is slightly acidic-pH 6.4Acid rain is defined as less than a pH of 5.5Deposition pictureSourcesNatural: a. Sulfur: Volcanoes, sea spray, microbialb. Nitrogen oxides: lightening, forest fires, microbialAnthropogenic (human caused) a. Sulfur oxides: coal burning plants, industry, fossil fuels.b. Nitrogen oxides: power plants, industrial fuel combustion, transportationc. Effect areas hundreds of miles from the source of emissions, generally not the whole globed. Both sulfur oxides and nitrogen oxides are primary components of acid rain.Indoor Air Pollutants1. Types: benzene, formaldehyde, radon, cigarette smoke2. Sources: off gassing from furniture, rugs and building materials, dry cleaning, cleaning fluids, disinfectants, pesticides, heaters3. Buildings with too many indoor air pollutants are called “sick buildings” because more than 20% of the people are sick due to occupying the building.Solutions: Reducing EmissionsBest way = Conservation, just use less!Input Control (pollution prevention)Cleaner burning gasoline and coal with low-sulfurincreased fuel efficiency and appliance efficiencyalternative modes of transportation -Mass transit, Walking, Bicycling, Electric vehiclesd. Switch to renewable forms of energyReducing Emissions (input control)d. catalytic converter- complete oxidation of hydrocarbons (VOCs) and carbon monoxide to CO2 and H2OOutput Pollution ControlCoal washing-using large amount of H2O to leach out the sulfurFluidized bed combustion-produces a waste ash that must be disposed ofOutput Control TechnologiesScrubbers are “liquid filters” The exhaust from burning fossil fuels runs through a spray of H2O containing lime (CaCO3)SO2 + CaCO3  CaSO3 + O2Required since 1977