Air Pollution and Stratospheric Ozone Depletion

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Air Pollution and Stratospheric Ozone Depletion

• Chapter 15

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Air Pollution

• introduction of chemicals, particulate matter
  (PM), or microorganisms into the atmosphere at
  concentrations high enough to harm plants,
  animals, and materials such as buildings or alter
  ecosystems
• pollution of troposphere or ground-level
  pollution

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• Sources
• a. natural
• - volcanoes
• - forest fires
• - plants
• b. anthropogenic
• - on-road vehicles (largest source of CO
  and NOx)
• - industry
• - power plants

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Major Air Pollutants

• Six pollutants (criteria) U.S. Clean Air Act
• a. SO2
• b. NOx
• c. CO
• d. PM
• e. tropospheric ozone
• f. lead

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• Sulfur Dioxide (SO2)
• a. corrosive gas
• b. combustion of fossil fuels (coal and oil)
• c. respiratory irritant
• d. released from volcanoes and forest fires

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• Nitrogen Oxides
• a. NOx (NO or NO2)
• b. NO
• 1. colorless, odorless gas
• c. NO2
• 1. pungent, reddish-brown gas
• d. nitrogen (N2)
• 1. makes up 78 of atmosphere

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• Carbon Oxides
• a. CO
• 1. colorless, odorless gas
• 2. vehicle exhaust
• b. CO2
• 1. colorless, odorless gas
• 2. photosynthesis/cellular respiration
• 3. burning of fossil fuels

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• Particulate Matter (PM)
• a. solid or liquid particles suspended in the
  air
• b. sizes
• 1. ranges 0.001 micrometer to 100
  micrometer
• 2. larger than 10
• - can be filtered out by nose and
  throat
• 3. PM10 not filtered and deposited in
• respiratory tract
• 4. PM2.5 BIG health concern
• c. scatter and absorb sunlight

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• Photochemical Oxidants
• a. sunlight acting on NOx and SO2
• b. main focus O3 (ozone)
• 1. most abundant in troposphere
• 2. respiratory inflammation
• 3. reacts with NOx and sulfur to form
  smog
• - photochemical
• LA type, brown
• - sulfurous
• London type, gray
• - atmospheric brown cloud
• seen in Asia

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• Lead (Pb)
• a. occurs naturally in rocks and soil
• b. has been added to gasoline
• c. persistent
• Mercury (Hg)
• a. coal and oil released into atmosphere
• b. toxic to CNS

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• VOCs (volatile organic compounds)
• a. become vapors at typical atmospheric
• temperatures
• b. hydrocarbons
• c. gasoline, lighter-fluid, oil-based paints
• d. strong aromas
• e. lead to ozone formation

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Primary and Secondary Pollutants

• Primary
• a. direct source
• b. CO, CO2, SO2, NOx, most PM and VOCs
• Secondary
• a. product of primary pollutant undergoing a
• reaction
• ex) ozone (O3)

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Photochemical Smog

• Smog
• a. originally smoke, fog, and sometimes SO2
  
• due to burning of
  coal
• b. today brown smog still a problem
• c. typically urban areas, but some rural
  (trees and
• shrubs, forest fires)
• d. atmospheric conditions (higher
  temperatures)
• 1. emission of VOCs
• 2. NOx emissions from electric utilities

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• c. no VOCs or photochemical oxidants
• 1. ozone (O3) forms during the day and breaks
  
• down at night
• 2. little to no photochemical smog
• d. VOCs present
• 1. VOCs combines with NOx
• 2. NOx no longer available to recombine with
• O3 in atmosphere, therefore the O3
• accumulates over time

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• e. Thermal inversion
• 1. warm layer of air at mid-altitude covers
• a layer of cold, dense air below
• 2. warm inversion layer
• - traps emissions causing severe
  pollution
• - vehicle exhaust and industrial emissions

http//news.bbc.co.uk/2/hi/uk_news/magazine/753260
3.stm
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Acid Deposition

• Formation
• a. NOx and SOx released into atmosphere
• (primary) ? nitric acid and sulfuric acid
• (secondary) ? nitrate, sulfate, and
  hydrogen
• ions (generate acidity in acid deposition
• b. fall as wet or dry deposition
• c. reduced in US due to Clean Air Act

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• Effects
• a. lowers pH of water
• b. detrimental to aquatic organisms
• c. decrease in species diversity
• d. erode statues, monuments, and buildings
• e. harm tree species (Red Spruce in NE US)

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Stratospheric Ozone
Tropospheric Ozone Stratospheric Ozone
Oxidant that harms respiratory systems Protective shield against radiation from Sun (UV-B)
Air pollutant damaging lung tissue and plants Critically important to life
ground-level ozone global sunscreen
UV-A reaches this layer Absorbs UV-B and UV-C
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• Formation and Breakdown of Ozone
• - occurs in closed loop cycle
• a. O2 UV-C ? 2O
• b. O2 O ? O3
• c. O3 UV-B or UV-C ? O2 O
• Ozone continuously formed/broken down in presence
  of sunlight

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• Anthropogenic Contributions to Ozone Destruction
• a. Chlorine
• 1. major source CFCs
• 2. O3 CL ? ClO O2
• ClO O ? Cl O2
• O3 O ? 2 O2
• 3. catalyst, does not get used up
• 4. ozone no longer able to absorb UV-B

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• Depletion of Ozone layer
• a. greatest at the poles since 1970
• b. ozone hole in Antarctica
• 1. seasonal depletion
• 2. cold weather
• - build up of ice crystals mix with
  NO
• - accumulation of Cl
• 3. sunny weather
• - UV breaks down more Cl catalyzing
• ozone destruction

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• Effort to reduce ozone depletion
• a. Montreal Protocol on Substances that
• Deplete the Ozone Layer
• - reduce CFC production 50 by 2000

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Indoor Air Pollution

• Causes more deaths each year than outdoor air
  pollution
• Developing v. developed

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• Asbestos
• a. insulating properties
• b. respiratory diseases (lung cancer)
• c. not dangerous until disturbed

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• Carbon Monoxide
• a. malfunctioning exhaust system
• - typically natural gas
• b. binds with hemoglobin more efficiently
• than O2
• c. lead to oxygen deprivation in brain

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• Radon
• a. Radon-222, decay of uranium
• b. exists in bedrock
• c. seep through crack in foundation
• d. second leading cause of lung cancer

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• VOCs in home products
• a. strong aroma
• b. glues, paints, formaldehyde
• c. burning sensation of eyes, throat

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• Sick Building Syndrome
• a. high levels of VOCs and other pollutants
• b. headaches, sore throat, fatigue
• c. sources
• - mold, pollen
• - cleaning agents