Chapter 18: Air Pollution
18.1 What Is the Nature of the Atmosphere?
The Atmosphere Consists of Several Layers
- Density varies→ Decreases with altitude
- Atmospheric pressure→ Decreases with altitude
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
- Chemical composition of air
- Rising and falling air currents
- weather and climate
- Involved in chemical cycling
The Stratosphere Is Our Global Sunscreen
- Stratosphere: Similar composition to the troposphere, with 2 exceptions
- Much less water
- O3, ozone layer
- Ozone layer: Filters 95% of harmful UV radiation and allows us and other life to exist on land
18.2 What Are the Major Outdoor Pollution Problems?
What is Air Pollution?
- Air pollution: Concentrations high enough to harm human health or alter the climate
- Natural sources
- Dust blew by the wind
- Pollutants from wildfires and volcanoes
- Volatile organics released by plants
- Pollutants mix in the air to form industrial smog
- Primarily as a result of burning coal and photochemical smog
- Caused by emissions from motor vehicles, industrial facilities, and power plants
Air Pollution Comes from Natural and Human Sources
- Human sources: mostly in industrialized and/or urban areas
- Stationary sources: power plants and industrial facilities
- Mobile sources: motor vehicles
Some Pollutants in the Atmosphere Combine to Form Other Pollutants
- Primary pollutants: Emitted directly into the air
- Secondary pollutants: From reactions of primary pollutants
- Air quality improving in developed countries
- Less-developed countries face big problems
- Indoor pollution: a big threat to the poor
Human Impact on the Atmosphere
- Burning Fossil Fuels
- Adds CO2 and O3 to troposphere
- Global Warming
- Altering Climates
- Produces Acid Rain
- Using Nitrogen fertilizers and burning fossil fuels
- Releases NO, NO2, N2O, and NH3 into troposphere
- Produces acid rain
- Refining petroleum and burning fossil fuels
- Releases SO2 into troposphere
- Manufacturing
- Releases toxic heavy metals (Pb, Cd, and As) into the troposphere
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 concentration above which adverse effects on health may occur
Carbon Monoxide (CO)
- Properties of carbon monoxide: colorless, odorless, heavier than air, 0.0036% of the atmosphere
- Effects of carbon monoxide: binds tighter to Hb than O2, mental functions, and visual acuity, even at low levels
- Sources of carbon monoxide: incomplete combustion of fossil fuels 60 - 95% from auto exhaust
- Class of carbon monoxide: carbon oxides (CO2, CO)
- EPA Standard of carbon monoxide: 9 ppm
- 5.5 billion tons enter the atmosphere/per year
Nitrogen Dioxide (NO2)
- Properties of nitrogen dioxide: reddish brown gas, formed as fuel burnt in the car, potent oxidizing agent, include Nitric acid in the air
- Effects of nitrogen dioxide: acid rain, lung and heart problems, decreased visibility (yellow haze), suppresses plant growth
- Sources of nitrogen dioxide: fossil fuels combustion @ higher temperatures, power plants, forest fires, volcanoes, bacteria in soil
- Class of nitrogen dioxide: Nitrogen oxides (NOx)
- EPA Standard of nitrogen dioxide: 0.053 ppm
Sulfur Dioxide (SO2)
- Properties of sulfur dioxide: colorless gas with an irritating odor
- Effects of sulfur dioxide: produces acid rain (H2SO4), breathing difficulties, eutrophication due to sulfate formation, lichen and moss are indicators
- Sources of sulfur dioxide: burning high sulfur coal or oil, smelting or metals, paper manufacture
- Class of sulfur dioxide: sulfur oxides
- EPA Standard of sulfur dioxide: 0.3 ppm (annual mean)
- Combines with water and NH4 to increase soil fertility Suspend
Suspended Particulate Matter (PM10)
- Properties of particulate matter: particles suspended in air (<10 um)
- Effects of particulate matter: lung damage, mutagenic, carcinogenic, teratogenic
- Sources of particulate matter: burning coal or diesel, volcanoes, factories, unpaved roads, plowing, lint, pollen, spores, burning fields
- Class of particulate matter: dust, soot, asbestos, lead, PCBs, dioxins, pesticides
- EPA Standard of particulate matter: 50 ug/m3 (annual mean)
Ozone
- Properties of ozone: colorless, unpleasant odor, a major part of photochemical smog
- Effects of ozone: lung irritant, damages plants, rubber, fabric, and eyes, 0.1 ppm can lower PSN by 50%,
- Sources of ozone: Created by sunlight acting on NOx and VOC, photocopiers, cars, industry, gas vapors, chemical solvents, incomplete fuel combustion products
- Class of ozone: photochemical oxidants
Volatile Organic Compounds (VOC)
- Properties of VOCs: organic compounds (hydrocarbons) that evaporate easily, usually aromatic
- Effects of VOCs: eye and respiratory irritants; carcinogenic; liver, CNS, or kidney damage; damages plants; lowered visibility due to brown haze; global warming
- Sources of VOCs: vehicles (largest source), evaporation of solvents or fossil fuels, aerosols, paint thinners, dry cleaning
- Class of VOCs: HAPs (Hazardous Air Pollutants)
- Methane
- Benzene
- Chlorofluorocarbons (CFCs), etc.
- Concentrations indoors up to 1000x outdoors
- 600 million tons of CFCs
Lead (Pb)
- Properties of lead: grayish metal
- Effects of lead: accumulates in tissue; affects kidneys, liver, and nervous system (children most susceptible); mental retardation; possible carcinogen; 20% of inner city kids have [high]
- Sources of lead: particulates, smelters, batteries
- Class of lead: toxic or heavy metals
- EPA Standard of lead: 1.5 ug/m3 • 2 million tons enter the atmosphere/per year
Chemical Reactions That Form Major Outdoor Air Pollutants
- Carbon monoxide: 2C + O2 → 2CO
- Carbon dioxide: C + O2 → CO2
- Nitric oxide: N2 + O2 → 2NO
- Nitrogen dioxide: 2NO + O2 → 2NO2
- Sulfur dioxide: S + O2 → SO2
Types of Smog
- Smog: A mixture between smoke and fog that produces unhealthy urban air
- Two Types
- Sulfurous Smog / Industrial Smog / Fossil Fuels
- Photochemical Smog / Sunlight & Pollutants
Sunlight Plus Cars Equal Photochemical Smog
- Photochemical Smog
- Chemical composition
- Sources
- VOCs + NOx + Heat + Sunlight yields
- Ground-level O3 and other photochemical oxidants
- Aldehydes
- Other secondary pollutants
Several Factors Can Decrease or Increase Outdoor Air Pollution
Outdoor air pollution may be decreased by
- Settling of particles due to gravity
- Rain and snow
- Salty sea spray from the ocean
- Winds
- Chemical reactions
Outdoor air pollution may be increased by
Urban buildings
Hills and mountains
High temperatures
Emissions of VOCs from certain trees and plants
Grasshopper effect
Temperature inversions
- Warm air above cool air prevents mixing
18.3 What Is Acid Deposition and Why Is It a Problem?
Acid Disposition Is a Serious Regional Air Pollution Problem
- Acid deposition, acid rain
- Chemical sources
- Formation
- Local versus regional problems
- Effects of prevailing winds
- Buffers
Effects of Acid Deposition
- Leaching of soil nutrients
- Lower crop yields
- Forest damage
18.4 What Are the Major Indoor Air Pollution Problems?
Indoor Air Pollution Developing Countries
- Developing countries: Indoor burning of wood, charcoal, dung, crop residues, coal
- Poor suffer the greatest risk
- Who is at greatest risk from indoor air pollution?
- Children under 5 and the elderly
- Sick
- Pregnant women
- People with respiratory disorders or heart problems
- Smokers
- Factory workers
- Four most dangerous indoor air pollutants
- Tobacco smoke
- Formaldehyde
- Radioactive radon-222 gas
- Very small particles
Indoor Air Pollution Is a Serious Problem
- Other possible indoor air pollutants
- Pesticide residue
- Pb particles
- Living organisms and their excrements
- E.g., Dust mites and cockroach droppings
- Airborne spores of molds and mildews
18.5 What Are the Health Effects of Air Pollution?
Your Body’s Natural Defenses against Air Pollution Can Be Overwhelmed
- Respiratory system protection from air pollutants
- Role of cilia, mucus, sneezing, and coughing
- Effect of smoking and prolonged air pollution exposure
- Chronic bronchitis
- Emphysema
Air Pollution Is a Big Killer
- 2.4 million deaths per year world-wide
- Mostly in Asia; 750,000 in China
- 150,000 to 350,000 in the United States
- Role of coal-burning power plants
- EPA: proposed stricter emission standards for diesel-powered vehicles
- 125,000 die in the U.S. each year from diesel fumes
- Emissions from one truck = 150 cars
18.6 How Should We Deal with Air Pollution?
Laws and Regulations Can Reduce Outdoor Air Pollution
- United States
- Clean Air Acts: 1970, 1977, and 1990 created regulations enforced by states and cities
- EPA
- National ambient air quality standards for 6 outdoor pollutants
- NAPs: National emission standards for 188 hazardous air pollutants
- TRI: Toxic Release Inventory
The Clean Air Act
- Congress found
- Most people now live in urban areas
- Growth results in air pollution
- Air pollution endangers living things
- It decided
- Prevention and control at the source were appropriate
- Such efforts are the responsibility of states and local authorities
- Federal funds and leadership are essential for the development of effective programs
- 1990 version
- Acid rain, urban smog, toxic air pollutants, ozone depletion, marketing pollution rights, VOC’s
- 1997 version→ Reduced ambient ozone levels
- Cost $15 billion/year -> save 15,000 lives
- Reduce bronchitis cases by 60,000 per year
- Reduce hospital respiratory admission 9000/year
Solutions for Stationary Source Air Pollution
- Prevention
- Burn low sulfur coal or remove sulfur from coal
- Convert coal to a liquid or gaseous fuel
- Phase out coal use
- Reduction or disposal
- Disperse emissions (which can increase downwind pollution)with smokestacks
- Remove pollutants from smokestack gases
- Tax each unit of pollution produced
Solutions for Motor Vehicle Air Pollution
- Prevention
- Walk, bike, or use mass transit
- Improve fuel efficiency
- Get older, polluting cars off the road
- Cleanup
- Require emission control devices
- Inspect car exhaust systems twice a year
- Set strict emission standards